Dorothy Davis Locanthi

Dorothy Nell Davis Locanthi (April 19, 1913 – September 27, 1999) was an American astronomer.
Early life.
Dorothy Nell Davis Locanthi (née Davis) was born in East St. Louis, Illinois, the daughter of Gordon Z. Davis and Nellie Thoma Davis. She was an athletic teen; her height (over six feet) was an advantage in her field event, the standing broad jump.
She graduated from high school at age 15. She attended Vassar College, where she majored in physics and took astronomy courses from Caroline Furness and Maud Makemson. She graduated from Vassar in 1933. Locanthi taught at Mills College in Oakland for a year, accessing Lick Observatory and the University of California, and earned a master's degree. Her master’s thesis was on S-Type long period variables. She pursued doctoral studies at the University of California and worked with C. Donald Shane there. She was awarded a Lick Observatory Fellowship in 1936, and completed her dissertation on the spectrum of the red supergiant star Antares in 1937.
Career.
After gaining her Ph.D. at age 24, Davis taught briefly at Smith College and at Vassar College. She did further work on stellar spectra at Mount Wilson Observatory on an AAUW Postdoctoral Fellowship. She worked as a researcher at Princeton University in 1940, assisting Henry Norris Russell to study ionized europium. In her last year at Princeton, 1942, Davis’s mother broke her ankle and Davis went home to St. Louis to help her. East St. Louis High School did not have anyone to teach physics because the former physics teacher had left to do work for the war, so she ended up teaching physics there for a period. Henry Russel visited Davis and her mother at her mother’s home in St. Louis to encourage Davis to come back to Princeton as soon as possible so she could continue her astronomy work there. She attended the International Astronomical Union meeting in Stockholm in 1938.
During World War II, she was involved in a rocket project at California Institute of Technology (Caltech), and at Ray Control Company in Pasadena. After the war, Davis worked at Beckman Laboratory in Pasadena, while her husband completed his education at Caltech. In 1950 she worked with astronomer Franklin E. Roach of the Naval Ordnance Test Station in Inyokern, California.
She returned to astronomy in 1962, working with Jesse L. Greenstein at Caltech on spectrometry projects until 1969. In 1972, she started working at the Jet Propulsion Laboratory. She was a life member of the Astronomical Society of the Pacific. She retired in 1985.
Personal life.
Davis married Bart N. Locanthi, an acoustical engineer, in 1943. They had two daughters and a son. She was widowed in 1994, and died in 1999, aged 86 years, in Glendale, California. An oral history interview she gave to David DeVorkin in 1977 is included in the American Institute of Physics' International Catalog of Sources for History of Physics and Allied Sciences. The American Institute of Physics also holds a collection of photographs taken by Dorothy Davis Locanthi.


Museum of Arts and Sciences (Macon, Georgia)

The Museum of Arts and Sciences in Macon is a community museum in the U.S. state of Georgia. The facility includes four galleries with frequently changing exhibitions, the Discovery House with hands-on activities, live animal habitats, the Mark Smith Planetarium, nature trail, garden, store, auditorium, and classrooms. New exhibitions on fine arts, science topics, and the humanities are presented for periods of four to six months. The museum is open to the public daily and offers programs to schools and groups. The museum is a member of the American Alliance of Museums as of July 2019.
History.
The museum first opened in 1956 and started as a room in the Wesleyan Conservatory with a few activities for children. In 1964, the museum moved locations with the construction of a gallery and workshop. A year later, a planetarium would be added as a new wing of the museum. A 1980 addition included most of the museum's infrastructure. The Discovery House, a new lobby, and classrooms were added in 2001. In 2018, an additional building was added which provides a view of the peach orchard behind the building. Planned additions to the museum, including a bat cave and amphitheater, were approved in March 2019 and are expected to be complete by the end of the year.
Exhibitions.
Art Gallery.
The Museum of Arts and Science's art gallery is a mixture of permanent gallery pieces and temporary exhibit pieces. The gallery is typically divided into three sections, with one section being for the permanent fixtures and the other two for the exhibits. Exhibitions shown include "Fired by Genius: The Ceramics of Pablo Picasso", "Sunlight and Shadow:" "American Impressionism", and "The Art of Tiffany".
Mark Smith Planetarium.
The Mark Smith Planetarium is an observatory built in 1965 and located to the southwest of the main entrance. The planetarium runs shows over various topics in astronomy, with two daily shows. The shows switch astronomical topics every two months. In addition to the shows, the planetarium is able to produce a virtual skyline with over 4,000 stars available for viewing. The size of the dome is 12.2 meters, and the planetarium can seat up to 118 people.
Mini-Zoo.
The Mini-Zoo is a wing of the facility that houses animals, located to the left of the Discovery House. It has housed numerous kinds of animals, including monkeys, birds, snakes, and an alligator. The exhibit is designed to simulate a jungle environment, and has two stories for visitors to view the animals from. The animals are also part of auditorium shows, led by the museum's animal caregivers.
Discovery House.
The Discovery House is a three story wing, making it the largest exhibit in the museum. It is preceded by "Gesturing Woman", a piece by Viola Frey. Each floor is focused on a different area of study; The upper floor is focused on visual art, including activities that allow for children to create their own art such as paper dolls and a light box; The base level floor focuses on the humanities, providing activities intended to promote well-rounded education on the world such as poetry writing and a map room; The bottom floor focuses on science, with activities such as fossil digging and simple experiments in weather and magnetism. This section of the museum includes "Ziggy", a 40 million year old whale fossil, as well as a taxidermy adult polar bear.
Outdoor Spaces.
The Museum of Arts and Sciences' grounds include an amphitheater, a pavilion, raptor retreat, bat cave, and walking trails.


2025 Nortia


Carl Theodor Albrecht

Carl Theodor Albrecht (August 30, 1843, Dresden, Kingdom of Saxony – August 31, 1915) was a German astronomer.
He studied mathematics and natural sciences at the TU Dresden and the Universität Berlin. During his time in Dresden, he helped founding "Polyhymnia", the fraternity that later became the German Student Corps Altsachsen.
He specialized in geodesy, to which he devoted much of his career. He also worked on the problem of variation of latitude, building upon the work of Seth Carlo Chandler who discovered the variation, known as the Chandler wobble. In 1882, Carl Theodor Albrecht was elected as member of the German Academy of Sciences Leopoldina.


Solar eclipse of February 5, 2046

An annular solar eclipse will occur on February 5, 2046. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide.
Images.
Animated path


Keeble Observatory

Keeble Observatory is an astronomical observatory owned and operated by Randolph-Macon College. It is located in Ashland, Virginia (USA), named for Dr. William Houston Keeble, distinguished Professor of Physics at Randolph-Macon College from 1919 until his retirement in 1952. He was a member of Phi Beta Kappa, the American Physical Society, the American Association of Physics Teachers, the American Astronomical Society, and was a fellow of the American Association for the Advancement of Science.
The first structure was opened in 1963 and housed a 12-inch Newtonian telescope. This building was razed in 2016. A new taller structure went into service the following year and houses a 40cm Ritchey-Chretien.


Catherine Wolfe Bruce

Catherine Wolfe Bruce (January 22, 1816, New York – March 13, 1900, New York) was a noted American philanthropist and patron of astronomy.
Early life.
Bruce was born on January 22, 1816. She was the daughter of the George Bruce (1781–1866), a famous type founder who was born in Edinburgh, and Catherine Wolfe (1785–1861), the daughter of David Wolfe (1748–1836) of New York City. Her brother was David Wolfe Bruce (1824–1895), who, along with David Wolfe Bishop, inherited the fortune of their cousin, Catharine Lorillard Wolfe.
Career.
She studied painting, learned Latin, German, French and Italian, and was familiar with the literature of those languages.
In 1890, she wrote and published a translation of the ""Dies Irae"."
Personal life.
Due to an ever-increasing illness, she was confined to her home and died on March 13, 1900 at 810 Fifth Avenue in New York City.
Philanthropy.
In 1877, she donated $50,000 for the construction of a library building and the purchase of books in memory of her father. The library, known as "The George Bruce Library" was completed in 1888 and was located at 226 West 42nd Street and designed by G. E. Harney. The building was sold in 1913 and the proceeds were used to build the current George Bruce library located on 125th Street in Harlem and designed by Carrère & Hastings.
As an amateur astronomer, she turned to philanthropy in this field at the age of 73, only after reading an article by Simon Newcomb claiming all the major discoveries in astronomy have occurred. Bruce turned to telescope maker Alvan Graham Clark to see how she can support research in astronomy.
Bruce made over 54 gifts to astronomy, totaling over $275,000, between 1889 and 1899. She donated funds to the Harvard College Observatory (U.S.A.), Yerkes Observatory (U.S.A.) and Landessternwarte Heidelberg-Königstuhl (Germany), run by Max Wolf at the time, to buy new telescopes at each of those institutes.
In 1887, she donated the "George Bruce Free Library".
Bruce established the Bruce Medal of the Astronomical Society of the Pacific in recognition of lifetime achievements and contributions to astrophysics, and is one of the prestigious awards in the field.
Honors.
Asteroid 323 Brucia, discovered by Max Wolf is named after her, as well as the crater "Bruce" on the Moon.
She received a gold medal by the Grand Duke of Baden.
Astronomer Johann Palisa gave her the honor of naming 313 Chaldaea as a token for the gratitude of astronomers.


Steven Balbus

Steven Andrew Balbus FRS (born 23 November 1953) is an American-born astrophysicist who is the Savilian Professor of Astronomy at the University of Oxford and a professorial fellow at New College, Oxford. In 2013, he shared the Shaw Prize for Astronomy with John F. Hawley.
Early life and education.
Balbus was born in 1953 in Philadelphia, Pennsylvania. He attended the William Penn Charter School, received S.B. degrees in mathematics and
in physics from the Massachusetts Institute of Technology (MIT) in 1975, and a PhD in theoretical astrophysics from the University of California, Berkeley in 1981.
Research and career.
Following his PhD, Balbus held postdoctoral research appointments at MIT and Princeton University. In 1985, Balbus joined the faculty of the University of Virginia. In 2004, he was appointed Professeur des Universités in the Physics Department of the École Normale Supérieure de Paris. He remained
in Paris until 2012, when he moved to Oxford as the Savilian Professor of Astronomy. At Oxford, he teaches astrophysical gas dynamics and supervises postdoctoral researchers
and students.
Balbus' research is in theoretical astrophysics. He has made discoveries related to gravitational instability in the interstellar medium and several contributions to the theory of thermal processes in magnetised dilute plasmas. He is best known for a 1991 paper, published with former colleague John F. Hawley, describing what is now known as magnetorotational instability (MRI). Most recently, Balbus has been working on a theory of the Sun's internal rotation. As of 2016, Balbus has also been lecturing an undergraduate course in general relativity at the University of Oxford; with several lectures coinciding with the discovery of gravitational waves in February 2016.
Awards and honours.
Balbus was awarded a Chaire d'excellence in 2004 by the French Ministry of Higher Education. In 2013, he shared the Shaw Prize in Astronomy with Hawley for their work on the MRI. Considered one of the highest honours in astronomy, the prize included a US$1 million cash award. According to the Shaw selection committee the "discovery and elucidation of the magnetorotational instability (MRI)" solved the previously "elusive" problem of accretion, a widespread phenomenon in astrophysics and "provides what to this day remains the only viable mechanism for the outward transfer of angular momentum in accretion disks".
Balbus is the recipient of a Royal Society Wolfson Research Merit Award, and has held visiting faculty positions at Princeton University (Bohdan Paczynski Visitor and Spitzer Lecturer, 2011) and the University of California, Berkeley (Visiting Miller Professor, 2012). In April 2015, Balbus was elected to the US National Academy of Sciences. He was elected a Fellow of the Royal Society (FRS) in 2016. In 2020 he was awarded the Eddington Medal of the Royal Astronomical Society.


Rainwater Observatory and Planetarium

Rainwater Observatory and Planetarium is an educational astronomical observatory and Planetarium run as an educational ministry of French Camp Academy. It is located near French Camp, Mississippi, United States. It is the largest observatory in Mississippi with 16+ telescopes, with the largest instruments including a 32-inch Dobsonian telescope and 14-inch Celestron catadioptric telescope. Rainwater is currently awaiting delivery of the Sollee Telescope, a 25-inch research-grade telescope. When installed in the two-story observatory building already constructed in the observatory complex, the Sollee Telescope will be suitable for serious astronomical studies, in the last remaining "dark spot" in Mississippi on the U.S. Dark Skies photograph.
Rainwater Observatory and Planetarium is the site for the annual Midsouth Star Gaze. This gathering of amateur astronomers is held in late March or early April each year on the weekend closest to New Moon (to allow for the maximum night-time observing for deep-sky objects such as galaxies and nebulae). The planetarium/activities complex includes one main building with a 30-foot dome and Spitz planetarium projector, combined with a computer/activities room. A meeting room and exhibition space building next door includes dormitory space and male/female group bathrooms with showers. Up the hill from the activity buildings is the cluster of observatory buildings for all the reflector, refractor, and catadioptric telescopes. Various astronomical exhibits such as markers showing the arrangement of the Stonehenge standing stones with their annual rise and set points, a multitude of sundials, and a walking trail that demonstrates the relative distances between the Sun and all its planets, cover the distance between the activities complex and the hilltop cluster of observatory buildings.
Rainwater Observatory has a video astronomy van for astronomy education outreach. This consists of large LCD monitors which can present both objects visible in the van's telescope plus PowerPoint presentations describing what the telescope is pointed to. The video astronomy van is available for visits within approximately a 100-mile radius of French Camp.


Lyudmila Chernykh

Lyudmila Ivanovna Chernykh (, June 13, 1935 in Shuya, Ivanovo Oblast – July 28, 2017) was a Russian-born Soviet astronomer, wife and colleague of Nikolai Stepanovich Chernykh, and a prolific discoverer of minor planets.
Professional career.
In 1959 she graduated from Irkutsk State Pedagogical Institute (now Pedagogical Institute of Irkutsk State University). Between 1959 and 1963 she worked in the Time and Frequency Laboratory of the All-Union Research Institute of Physico-Technical and Radiotechnical Measurements in Irkutsk, where she did astrometrical observations for the Time Service.
Between 1964 and 1998 she was a scientific worker at the Institute of Theoretical Astronomy of the USSR Academy of Sciences (Russian Academy of Science since 1991), working at the observation base of the institute at the Crimean Astrophysical Observatory (CrAO) in Nauchnyy settlement on the Crimean peninsula. In 1998 she was promoted to senior scientific worker at CrAO. The Minor Planet Center (MPC) credits her with the discovery of 267 numbered minor planets, which she made at CrAO between 1966 and 1992. Several of these discoveries she made in collaboration with her husband and with Tamara Smirnova.
Honors.
The asteroid 2325 Chernykh, discovered in 1979 by Czech astronomer Antonín Mrkos, was named in her and her husband's honour. The official naming citation was published by the MPC on 1 June 1981 ().
List of discovered minor planets.
Two of her notable discoveries are 2127 Tanya – named after Russian child diarist Tanya Savicheva, and 2212 Hephaistos, a near-Earth object of the Apollo group of asteroids.


Baker Observatory

The William G. and Retha Stone Baker Observatory is an astronomical observatory owned and operated by Missouri State University. It is located in Marshfield, Missouri.
About the observatory.
The William G and Retha Stone Baker Observatory is located ten miles northwest of Marshfield in Webster County (off Route 38 on Old Hillcrest Road). The Observatory houses a 14-inch (0.36 meter) Schmidt-Cassegrain and a 16-inch (0.4 meter) Cassegrain . The 16-inch Cassegrain Reflecting Telescope (with CCD attached camera) is on loan to MSU from Cerro Tololo Inter-American Observatory in Chile. This telescope was one of the first telescopes to be used at Kitt Peak National Observatory. In comparison to observations performed by eye, the CCD camera makes this telescope as powerful as a 100-inch (2.5 meter) telescope. Missouri State recently purchased an additional 16 inch Schmidt-Cassegrain reflector which is currently being set up to allow for remote operation from campus.
The Observatory is used on clear evenings for laboratory work by students in beginning and intermediate Astronomy courses, and by advanced undergraduate students and faculty conducting Astronomical research. The Observatory houses many smaller telescopes for students to use in addition to the two large instruments.
The public may visit the Observatory and view the night sky through telescopes, either at open houses or during the Ozarks Amateur Astronomers Club meetings. Open houses are conducted by the Department of Physics and Astronomy twice each year, in April or May, and in September or October. Admission is free.


William Sadler Franks

William Sadler Franks (26 April 1851 in Newark, Nottinghamshire – 19 June 1935 in East Grinstead) was a British astronomer.
He published a catalogue of the colours of 3890 stars.
Franks was employed between 1892 and 1904 by the wealthy amateur astronomer Isaac Roberts as an assistant to support the photographic observations of star clusters and nebulae at Roberts's private observatory at Crowborough in Sussex.
In 1910 he was hired by F. J. Hanbury (of the Allan and Hanbury firm) to work as an observer at Hanbury's private Brockhurst Observatory at East Grinstead in Sussex. He continued his studies of the colours of stars there, and also made micrometer measurements of double stars. In 1923 he won the Jackson-Gwilt Medal of the Royal Astronomical Society.
One of the other observers who used the Brockhurst Observatory with Franks was a teenage Patrick Moore (fourteen years old at Franks's death).


Risa Wechsler

Risa H. Wechsler is an American physicist and Professor of Physics at Stanford University and of Particle Physics and Astrophysics at SLAC National Accelerator Laboratory. She is the director of the Kavli Institute for Particle Astrophysics and Cosmology. She is an Elected Fellow of the American Physical Society since 2017 and a Fellow of the American Association for the Advancement of Science since 2020.
A cited expert in cosmology, large-scale structure, and galaxy formation, her interests are astrophysics and dark matter and energy. She was the Co-Spokesperson of the Dark Energy Spectroscopic Instrument Collaboration until mid-2018 and has played a leading role in the Dark Energy Survey.
She has appeared on the BBC show Horizon: The Mystery of Dark Energy, the Science Channel's Space's Deepest Secrets: Secret History of the Big Bang and on the PBS show Science Bytes: Dark Matters.
In 2019, she collaborated on an exhibit with the artist Oxossi Ayofemi at the Contemporary Jewish Museum in San Francisco.
Education.
She earned her S.B. in Physics from Massachusetts Institute of Technology in 1996 and her Ph.D from University of California, Santa Cruz in 2001. She was a NASA Hubble Fellow at the University of Chicago from 2003-2006.
Publications.
A list of Wechsler's publications can be found here.


February 2009 lunar eclipse

A penumbral lunar eclipse took place on February 9, 2009, the first of four lunar eclipses in 2009, and being the deepest of three penumbral eclipses. It also happened on the Lantern Festival, the first since February 20, 1989. The tables below contain detailed predictions and additional information on the Penumbral Lunar Eclipse of 9 February 2009.
Eclipse Season.
This is the second eclipse this season.
First eclipse this season: 26 January 2009 Annular Solar Eclipse
Visibility.
The eclipse was not visible in the East coast of the United States, South America and southernmost Mexico, Western Africa and western Europe. Best visibility was expected over most of Asia, the Western US, Mexico and throughout the Pacific region.
Relation to other eclipses.
Half-Saros cycle.
A lunar eclipse will be preceded and followed by solar eclipses by 9 years and 5.5 days (a half saros). This lunar eclipse is related to two partial solar eclipses of Solar Saros 150.


List of lunar meteorites

This is a list of lunar meteorites. That is, meteorites that have been identified as having originated from Earth's Moon.
Notes.
Where multiple meteorites are listed (e.g. NWA 4472/4485), they are believed to be pieces of the same original body. The mass shown is the total.
Source: University of Washington in St Louis, Department of Earth and Planetary Science.


Bing Zhang

Bing Zhang is a Chinese astrophysicist and professor at the University of Nevada, Las Vegas. He is best known for his research in gamma-ray bursts, fast radio bursts, and other high-energy astrophysical phenomena. He is the author of the book "The Physics of Gamma-Ray Bursts".
Life.
Bing Zhang was born in 1968 in Shanxi, China. He received his B.S. (1991), M.S. (1994), and Ph.D. (1997) from Peking University. After postdoctoral fellowships at NASA Goddard Space Flight Center and Pennsylvania State University, he joined the University of Nevada, Las Vegas in 2004 where he is holding a tenured faculty position.
Career.
Zhang is a theoretical astrophysicist closely working with observers. According to the Astrophysics Data System, he has published more than 700 entries, including more than 450 refereed papers as of 2021. He is known for his theoretical work on several subjects in the field of gamma-ray bursts (GRBs): e.g., a canonical afterglow lightcurve and interpretation, a prompt emission model invoking internal collision-induced magnetic reconnection, a magnetar central engine, a quasi-universal structured jet,
a physical classification scheme, among others. His work has been found useful in interpreting the rapidly growing body of GRB data, and several of his predictions have been verified by observations. Together with Peter Mészáros and Pawan Kumar, Zhang wrote two influential review articles in the GRB field. He also wrote a comprehensive, 579 pages book on the physics of GRBs, which serves as an advanced textbook for graduate students and as a reference for researchers in the field of GRBs.
Zhang has participated in a number of observational campaigns in collaboration with observers. Some major discoveries to which Zhang made significant contributions include: discovery of the first short GRB afterglow, discovery of X-ray flares following GRBs, discovery of the first jetted tidal disruption event, discovery of an X-ray transient marking the birth of a magnetar, and making a connection between fast radio bursts and a Galactic magnetar.
Zhang is an advocate of using Breakthrough Starshot techniques to study "relativistic astronomy". He also suggested that Communicative Extraterrestrial intelligence (CETI) may use fast radio burst-like signals to communicate, and that one can use all-sky radio monitors to place quantitative constraints on the signal emission rate of CETI.
Positions.
Zhang is an elected Fellow of the American Physical Society (2014). He holds the position of Distinguished Professor in the Department of Physics and Astronomy, as well as serving as Associate Dean for Research of the College of Sciences at the University of Nevada, Las Vegas.
Personal life.
Zhang is married to Chaohui Huang with two children, Rachel C. Zhang and Raymond M. Zhang.


Miriam Burland

Miriam Seymour Burland (1902 – April 1, 1996) was a Canadian astronomer. She was the first woman on staff at the Dominion Observatory, when she joined the Astrophysics Division in 1927.
Early life.
Miriam Seymour Burland was born in Montreal, the daughter of Benjamin Burland and Bertha Belasco Burland. Her mother was active in the social life of Saint-Lambert, as founder of the town's Tuesday Musical Club and the Christmas Tree League. Miriam Burland attended Longueuil High School in Montreal, and studied mathematics and physics at McGill University, where she was also an avid ice hockey player. She trained as an astronomer at McGill, under Vibert Douglas.
Career.
Burland joined the Astrophysics Division at the Dominion Observatory in 1927, and was the first woman on staff at the Observatory. In the 1930s she served in leadership positions at the Ottawa Centre of the Royal Astronomical Society of Canada (RASC), including a term as president. She worked on photoelectric photometry of Cepheid variables, and later studied meteors. She was on three teams of scientists observing major solar eclipses in Canada, in 1932, 1954, and 1962.
From the mid-1950s, still the only woman astrophysicist on staff, she served as the observatory's education and information liaison, compiling reports, arranging public tours, and answering inquiries. She and Peter Millman coordinated a meteor observation program in Canada for the International Geophysical Year (1957-1958). In 1960, she was among the observatory's representatives at the opening of the Dominion Radio Astrophysical Observatory in British Columbia. In the 1960s, she served on the National Committee for Canada in the International Astronomical Union. She was a regular contributor to the "Journal of the Royal Astronomical Society of Canada". She was received the RASC's Service Award in 1963. "I know there are five PhDs who became scientists because of visits to the Observatory and my interest in their careers," she noted on the occasion of her retirement from the Dominion Observatory in 1967.
Publications.
Publications by Burland included "Combined Radar, Photographic and Visual Observations of the Perseid Meteor Shower of 1947" ("Nature" 1948, with Peter Millman and D. W. R. McKinley), and "Wave Lengths, Equivalent Widths, and Line Profiles in the Spectrum of the Star H. D. 190073" ("Canadian Journal of Research" 1949, with C. S. Beals).
Personal life.
Miriam Seymour Burland was active in the Zonta Club in Ottawa, and served as its president in 1941. She died in 1996, aged 93 years, in Ottawa.


Meade LX90

The Meade LX90 is a Schmidt-Cassegrain design of telescope made by Meade Instruments for the mid-priced (2000 USD circa 2008) commercial telescope market. It uses a similar optical system to the bigger and more expensive Meade LX200—although it lacks some useful functions like primary mirror locking. The LX90 telescopes were equipped with Autostar soon after its 1999 introduction by Meade instruments. Optical apertures included in the product line included 8 (20 cm), 10 (25 cm) and 12 (30 cm) inches on a double tine fork mount and Autostar system.


Anne Archibald

Anne M. Archibald is a Canadian astronomer known for her observations of pulsars and as one of the developers of SciPy, a scientific programming library for the Python programming language.
She is a senior lecturer in astronomy at Newcastle University in the UK.
Education and career.
Archibald did her undergraduate studies in mathematics at the University of Waterloo, including internships involving computer graphics and the image analysis of radar data. After doing a master's degree in pure mathematics at McGill University, she became a doctoral student of astrophysicist Victoria Kaspi at McGill, and won both the Cecilia Payne-Gaposchkin Doctoral Dissertation Award in Astrophysics of the American Physical Society and the J.S. Plaskett Medal of the Canadian Astronomical Society for her 2013 doctoral dissertation, "The End of Accretion: The X-ray Binary/Millisecond Pulsar Transition Object PSR J1023+0038".
After postdoctoral research at ASTRON and then at the Anton Pannekoek Institute for Astronomy, both in the Netherlands and supported by a Veni fellowship of the Netherlands Organisation for Scientific Research, she became a senior lecturer at Newcastle University in 2019.


Bruce Elmegreen

Bruce Gordon Elmegreen (born 24 February 1950) is an American astronomer.
Life.
Elmegreen was born in Milwaukee, and received his bachelor's degree in 1971 from the University of Wisconsin–Madison and his PhD in 1975 from Princeton University in astrophysics under Lyman Spitzer. From 1975 to 1978 he was a Junior Fellow at Harvard University. From 1978 to 1984 he was an assistant professor at Columbia University. Beginning in 1984 he has been employed at IBM doing research at the Thomas J. Watson Research Center.
His research deals with interstellar gas with a focus on star formation in gaseous nebulae and large-scale structure of spiral galaxies. Using computer model simulations, he proved the existence of standing waves in spiral galaxies.
Since 1976 he has been married to the astronomer Debra Meloy Elmegreen (born 1952), who is a professor at Vassar College. In 2013, they authored a paper together, "The Onset of Spiral Structure in the Universe", published in the "Astrophysical Journal".
Honors and awards.
In 2001 Elmegreen received the Dannie Heineman Prize for Astrophysics. In 2020 he was elected a Legacy Fellow of the American Astronomical Society


July 2083 lunar eclipse

A total lunar eclipse will take place on July 29, 2083. The Moon will be plunged into darkness for 1 hour and 30 minutes, in a deep total eclipse which will see the Moon 48% of its diameter inside the Earth's umbral shadow. The visual effect of this depends on the state of the Earth's atmosphere, but the Moon may be stained a deep red colour. The partial eclipse will last for 3 hours and 33 minutes in total.
The moon will pass through the center of the Earth's shadow. This is the last central lunar eclipse of Saros cycle 130.
Related lunar eclipses.
Half-Saros cycle.
A lunar eclipse will be preceded and followed by solar eclipses by 9 years and 5.5 days (a half saros). This lunar eclipse is related to two annular solar eclipses of Solar Saros 137.


Radiative levitation

Radiative levitation is the name given to a phenomenon that causes the spectroscopically-derived abundance of heavy elements in the photospheres of hot stars to be very much higher than solar abundance or than the expected bulk abundance; for example, the spectrum of the star Feige 86 has gold and platinum abundances three to ten thousand times higher than solar norms.
The mechanism is that heavier elements have large photon absorption cross-sections when partially ionized (see opacity), so efficiently absorb photons from the radiation coming from the core of the star, and some of the energy of the photons gets converted to outward momentum, effectively 'kicking' the heavy atom towards the photosphere. The effect is strong enough that very hot white dwarfs are significantly less bright in the EUV and X-ray bands than would be expected from a black-body model.
The countervailing process is gravitational settling, where, in very high gravitational fields, the effects of diffusion even in a hot atmosphere are cancelled out to the point that the heavier elements will sink unobservably to the bottom and lighter elements settle on the top.


KATRIN

KATRIN is a German acronym (Karlsruhe Tritium Neutrino Experiment) for an undertaking to measure the mass of the electron antineutrino with sub-eV precision by examining the spectrum of electrons emitted from the beta decay of tritium. The experiment is a recognized CERN experiment (RE14). The core of the apparatus is a 200-ton spectrometer. In 2015, the commissioning measurements on this spectrometer were completed, successfully verifying its basic vacuum, transmission and background properties. The experiment began running tests in October 2016. The inauguration took place 11 June 2018, with the first tritium measurements by the experiment (the so-called First Tritium or FT 2-week engineering run in mid-2018). The projected experiment duration at the time was 5 years. The first science measurements (so-called first campaign) took place 10 April 2019.
Construction and assembly.
The spectrometer was built by MAN DWE GmbH in Deggendorf. Although only 350 km from Karlsruhe, the tank's size made land transport impossible. Instead, it was shipped by water, down the Danube to the Black Sea, through the Mediterranean Sea and Atlantic Ocean to Rotterdam, then up the Rhine to Karlsruhe. This 8600 km long detour limited land travel to only the final 7 km from the Leopoldshafen docks to the laboratory.
The construction proceeded well with several of the major components on-site by 2010. The main spectrometer test program was scheduled for 2013 and the complete system integration for 2014. The experiment is located at the former Forschungszentrum Karlsruhe, now Campus Nord of the Karlsruhe Institute of Technology.
Experiment.
The beta decay of tritium is one of the least energetic beta decays. The electron and the neutrino which are emitted share only 18.6 keV of energy between them. KATRIN is designed to produce a very accurate spectrum of the numbers of electrons emitted with energies very close to this total energy (only a few eV away), which correspond to very low energy neutrinos. If the neutrino is a massless particle, there is no lower bound to the energy the neutrino can carry, so the electron energy spectrum should extend all the way to the 18.6 keV limit. On the other hand, if the neutrino has mass, then it must always carry away at least the amount of energy equivalent to its mass by "E" = "mc"2, and the electron spectrum should drop off short of the total energy limit and have a different shape.
In most beta decay events, the electron and the neutrino carry away roughly equal amounts of energy. The events of interest to KATRIN, in which the electron takes almost all the energy and the neutrino almost none, are very rare, occurring roughly once in a trillion decays. In order to filter out the common events so the detector is not overwhelmed, the electrons must pass through an electric potential that stops all electrons below a certain threshold, which is set a few eV below the total energy limit. Only electrons that have enough energy to pass through the potential are counted.
First results from the first measurement campaign (10 April - 13 May 2019) were published 13 September 2019. They put the upper bound of electron neutrino mass to 1.1 eV.
As of September 2019, the experiment hopes to achieve 3 measuring campaigns, each comprising 65 days of active measurement, in a year. The experiment reckons it needs 1000 days of measurement to reach target sensitivity of 0.2 eV (upper limit for neutrino mass). Thus the final results are expected in 5–6 years.
Importance.
The precise mass of the neutrino is important not only for particle physics, but also for cosmology. The observation of neutrino oscillation is strong evidence in favor of massive neutrinos, but gives only a weak lower bound.
Along with the possible observation of neutrinoless double beta decay, KATRIN is one of the neutrino experiments most likely to yield significant results in the near future.


Comet Humason

Comet Humason, formally designated C/1961 R1 (a.k.a. 1962 VIII and 1961e), was a non-periodic comet discovered by Milton L. Humason on September 1, 1961. Its perihelion was well beyond the orbit of Mars, at 2.133 AU. The outbound orbital period is about 2516 years. The diameter of its comet nucleus is estimated at around 30−41 km.
It was a "giant" comet, much more active than a normal comet for its distance to the Sun, with an absolute magnitude of 1.5−3.5, it could have been up to a hundred times brighter than an average new comet. It had an unusually disrupted or "turbulent" appearance. It was also unusual in that the spectrum of its tail showed a strong predominance of the ion CO+, a result previously seen unambiguously only in Comet Morehouse (C/1908 R1).


Misalignment mechanism

The misalignment mechanism is a hypothesized effect in the Peccei–Quinn theory proposed solution to the strong-CP problem in quantum mechanics. The effect occurs when a particle's field has an initial value that is not at or near a potential minimum. This causes the particle's field to oscillate around the nearest minimum, eventually dissipating energy by decaying into other particles until the minimum is attained.
In the case of hypothesized axions created in the early universe, the initial values are random because of the masslessness of axions in the high temperature plasma. Near the critical temperature of quantum chromodynamics, axions possess a temperature-dependent mass that enters a damped oscillation until the potential minimum is reached.


Williams Observatory

Craven E. Williams Observatory is an astronomical observatory owned and operated by Gardner-Webb University. Built in 1990 and named for the ninth president of the university, it is located in Boiling Springs, North Carolina (USA). Among its instruments, the observatory features a Schmidt-Cassegrain telescope. The observatory is home to the Cleveland County Astronomical Society, and also holds monthly open houses for the community. Dr. Don Olive, an astronomer, oft-alleged nuclear physicist, and professor of science at the university maintains and opens the observatory to the campus and community on occasion.


Joint Astronomy Centre

The Joint Astronomy Centre (JAC) was a management organisation based in Hilo, Hawaii, which from c.1980-2015 operated two large telescopes at Mauna Kea Observatory on behalf of an international consortium from the United Kingdom, Canada and the Netherlands, and provided support for other telescopes and public outreach activities. The JAC also maintained the Starlink Project between 2006 and 2015. Following withdrawal of funding by the partner nations, on March 1, 2015 the Joint Astronomy Centre closed and the facility was handed over to the East Asian Observatory which now runs the James Clerk Maxwell Telescope.
The major telescopes formerly operated by the JAC were:


Samar Safi-Harb

Samar Safi-Harb is a professor in the Department of Physics and Astronomy at the University of Manitoba and a Canada Research Chair in Supernova Remnant Astrophysics. She is currently the Vice President of the Canadian Astronomical Society.
Background and education.
Samar Safi-Harb grew up in Lebanon during the Lebanese civil war. Despite loving physics in high school, Safi-Harb thought she would become a medical doctor and started a pre-medical physics undergraduate degree at the American University of Beirut. After her undergraduate degree, she chose to follow her passion in physics and pursued graduate studies in physics at the University of Wisconsin-Madison, receiving her MSc in 1993 and her PhD in 1997.
Following her graduate studies, Safi-Harb completed a fellowship at NASA's Goddard Space Flight Center where she worked in the high energy astrophysics lab. In 2000, she left NASA to start the University of Manitoba's graduate astrophysics program.
Research.
Safi-Harb's research focuses on high energy studies of the remnants leftover by supernovae, including neutron stars and their nebulae. In 2021, Safi-Harb and her former graduate student Harsha Blumer published their results from their observations of the magnetar Swift J1818.0−1607, first detected by the NASA’s Neil Gehrels Swift Observatory in 2020, using the Chandra X-Ray Observatory.


Solar eclipse of February 6, 2027

An annular solar eclipse will occur on February 6, 2027. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide.
Images.
Animated path


Far side of the Moon

 The far side of the Moon is the lunar hemisphere that always faces away from Earth, as opposed to the opposite near side. Compared to the near side, the far side's terrain is rugged, with a multitude of impact craters and relatively few flat and dark lunar maria ("seas"). It has one of the largest craters in the Solar System, the South Pole–Aitken basin. The hemisphere is sometimes called the "dark side of the Moon", where "dark" means "unknown" instead of "lacking sunlight" both sides of the Moon experience two weeks of sunlight while the opposite side experiences two weeks of night.
About 18 percent of the far side is occasionally visible from Earth due to libration. The remaining 82 percent remained unobserved until 1959, when it was photographed by the Soviet Luna 3 space probe. The Soviet Academy of Sciences published the first atlas of the far side in 1960. The Apollo 8 astronauts were the first humans to see the far side in person when they orbited the Moon in 1968. All manned and unmanned soft landings had taken place on the near side of the Moon, until 3 January 2019 when the Chang'e 4 spacecraft made the first landing on the far side.
Astronomers have suggested installing a large radio telescope on the far side, where the Moon would shield it from possible radio interference from Earth.
Definition.
Tidal forces from Earth have slowed the Moon's rotation to the point where the same side is always facing the Earth—a phenomenon called tidal locking. The other face, most of which is never visible from the Earth, is therefore called the "far side of the Moon". Over time, some parts of the far side can be seen due to libration. In total, 59 percent of the Moon's surface is visible from Earth at one time or another. Useful observation of the parts of the far side of the Moon occasionally visible from Earth is difficult because of the low viewing angle from Earth (they cannot be observed "full on").
The phrase "dark side of the Moon" does not refer to "dark" as in the absence of light, but rather "dark" as in unknown: until humans were able to send spacecraft around the Moon, this area had never been seen. While many misconstrue this to think that the "dark side" receives little to no sunlight, in reality, both the near and far sides receive (on average) almost equal amounts of light directly from the Sun. However, the near side also receives sunlight reflected from the Earth, known as earthshine. Earthshine does not reach the area of the far side that cannot be seen from Earth. At night under a "full Earth" the near side of the Moon receives on the order of 10 lux of illumination (about what a city sidewalk under streetlights gets; this is 34 times more light than is received on Earth under a full Moon) whereas the dark side of the Moon during the lunar night receives only about 0.001 lux of starlight. Only during a full Moon (as viewed from Earth) is the whole far side of the Moon dark. The word "dark" has expanded to refer also to the fact that communication with spacecraft can be blocked while the spacecraft is on the far side of the Moon, during Apollo space missions for example.
Differences.
The two hemispheres of the Moon have distinctly different appearances, with the near side covered in multiple, large "maria" (Latin for 'seas,' since the earliest astronomers incorrectly thought that these plains were seas of lunar water).
The far side has a battered, densely cratered appearance with few maria. Only 1% of the surface of the far side is covered by maria, compared to 31.2% on the near side. One commonly accepted explanation for this difference is related to a higher concentration of heat-producing elements on the near-side hemisphere, as has been demonstrated by geochemical maps obtained from the Lunar Prospector gamma-ray spectrometer. While other factors, such as surface elevation and crustal thickness, could also affect where basalts erupt, these do not explain why the far side South Pole–Aitken basin (which contains the lowest elevations of the Moon and possesses a thin crust) was not as volcanically active as Oceanus Procellarum on the near side.
It has also been proposed that the differences between the two hemispheres may have been caused by a collision with a smaller companion moon that also originated from the Theia collision. In this model, the impact led to an accretionary pile rather than a crater, contributing a hemispheric layer of extent and thickness that may be consistent with the dimensions of the far side highlands. However, the chemical composition of the far side is inconsistent with this model.
The far side has more visible craters. This was thought to be a result of the effects of lunar lava flows, which cover and obscure craters, rather than a shielding effect from the Earth. NASA calculates that the Earth obscures only about 4 square degrees out of 41,000 square degrees of the sky as seen from the Moon. "This makes the Earth negligible as a shield for the Moon [and] it is likely that each side of the Moon has received equal numbers of impacts, but the resurfacing by lava results in fewer craters visible on the near side than the far side, even though both sides have received the same number of impacts."
Newer research suggests that heat from Earth at the time when the Moon was formed is the reason the near side has fewer impact craters. The lunar crust consists primarily of plagioclases formed when aluminium and calcium condensed and combined with silicates in the mantle. The cooler, far side experienced condensation of these elements sooner and so formed a thicker crust; meteoroid impacts on the near side would sometimes penetrate the thinner crust here and release basaltic lava that created the maria, but would rarely do so on the far side.
Exploration.
Early exploration.
Until the late 1950s, little was known about the far side of the Moon. Librations of the Moon periodically allowed limited glimpses of features near the lunar limb on the far side, but only up to 59% of the total surface of the moon. These features, however, were seen from a low angle, hindering useful observation (It proved difficult to distinguish a crater from a mountain range). The remaining 82% of the surface on the far side remained unknown, and its properties were subject to much speculation.
An example of a far side feature that can be seen through libration is the Mare Orientale, which is a prominent impact basin spanning almost , yet this was not even named as a feature until 1906, by Julius Franz in "Der Mond". The true nature of the basin was discovered in the 1960s when rectified images were projected onto a globe. The basin was photographed in fine detail by Lunar Orbiter 4 in 1967.
Before space exploration began, astronomers did not expect that the far side would be different from the side visible to Earth. On October 7, 1959, the Soviet probe Luna 3 took the first photographs of the lunar far side, eighteen of them resolvable, covering one-third of the surface invisible from the Earth. The images were analysed, and the first atlas of the far side of the Moon was published by the USSR Academy of Sciences on November 6, 1960. It included a catalog of 500 distinguished features of the landscape. A year later, the first globe (1: scale) containing lunar features invisible from the Earth was released in the USSR, based on images from Luna 3. On July 20, 1965, another Soviet probe, Zond 3, transmitted 25 pictures of very good quality of the lunar far side, with much better resolution than those from Luna 3. In particular, they revealed chains of craters, hundreds of kilometers in length, but, unexpectedly, no mare plains like those visible from Earth with the naked eye. In 1967, the second part of the "Atlas of the Far Side of the Moon" was published in Moscow, based on data from Zond 3, with the catalog now including 4,000 newly discovered features of the lunar far side landscape. In the same year, the first "Complete Map of the Moon" (1: scale) and updated complete globe (1: scale), featuring 95 percent of the lunar surface, were released in the Soviet Union.
As many prominent landscape features of the far side were discovered by Soviet space probes, Soviet scientists selected names for them. This caused some controversy, and the International Astronomical Union, leaving many of those names intact, later assumed the role of naming lunar features on this hemisphere.
Further survey mission.
On April 26, 1962, NASA's Ranger 4 space probe became the first spacecraft to impact the far side of the Moon, although it failed to return any scientific data before impact.
The first truly comprehensive and detailed mapping survey of the far side was undertaken by the American unmanned Lunar Orbiter program launched by NASA from 1966 to 1967. Most of the coverage of the far side was provided by the final probe in the series, Lunar Orbiter 5.
The far side was first seen directly by human eyes during the Apollo 8 mission in 1968. Astronaut William Anders described the view:
It has been seen by all crew members of the Apollo 8 and Apollo 10 through Apollo 17 missions since that time, and photographed by multiple lunar probes. Spacecraft passing behind the Moon were out of direct radio communication with the Earth, and had to wait until the orbit allowed transmission. During the Apollo missions, the main engine of the Service Module was fired when the vessel was behind the Moon, producing some tense moments in Mission Control before the craft reappeared.
Geologist-astronaut Harrison Schmitt, who became the last to step onto the Moon, had aggressively lobbied for his landing site to be on the far side of the Moon, targeting the lava-filled crater Tsiolkovskiy. Schmitt's ambitious proposal included a special communications satellite based on the existing TIROS satellites to be launched into a Farquhar–Lissajous halo orbit around the L2 point so as to maintain line-of-sight contact with the astronauts during their powered descent and lunar surface operations. NASA administrators rejected these plans on the grounds of added risk and lack of funding.
The idea of utilizing Earth–Moon for communications satellite covering the Moon's far side has been realized, as China National Space Administration launched Queqiao relay satellite in 2018. It has since been used for communications between the Chang'e 4 lander and Yutu 2 rover that have successfully landed in early 2019 on the lunar far side and ground stations on the Earth. And L2 is proposed to be "an ideal location" for a propellant depot as part of the proposed depot-based space transportation architecture.
Chandrayaan-2, India's second lunar probe in 2019, captured images from far side terrain, Jackson (crater) and poles of the Moon.
Soft landing.
The China National Space Administration's "Chang'e 4" made the first ever soft landing on the lunar far side on 3 January 2019. The craft included a lander equipped with a low-frequency radio spectrograph and geological research tools.
Potential.
Because the far side of the Moon is shielded from radio transmissions from the Earth, it is considered a good location for placing radio telescopes for use by astronomers. Small, bowl-shaped craters provide a natural formation for a stationary telescope similar to Arecibo in Puerto Rico. For much larger-scale telescopes, the crater Daedalus is situated near the center of the far side, and the rim would help to block stray communications from orbiting satellites. Another potential candidate for a radio telescope is the Saha crater.
Before deploying radio telescopes to the far side, several problems must be overcome. The fine lunar dust can contaminate equipment, vehicles, and space suits. The conducting materials used for the radio dishes must also be carefully shielded against the effects of solar flares. Finally, the area around the telescopes must be protected against contamination by other radio sources.
The Lagrange point of the Earth–Moon system is located about above the far side, which has also been proposed as a location for a future radio telescope which would perform a Lissajous orbit about the Lagrangian point.
One of the NASA missions to the Moon under study would send a sample-return lander to the South Pole–Aitken basin, the location of a major impact event that created a formation nearly across. The force of this impact has created a deep penetration into the lunar surface, and a sample returned from this site could be analyzed for information concerning the interior of the Moon.
Because the near side is partly shielded from the solar wind by the Earth, the far side maria are expected to have the highest concentration of helium-3 on the surface of the Moon. This isotope is relatively rare on the Earth, but has good potential for use as a fuel in fusion reactors. Proponents of lunar settlement have cited the presence of this material as a reason for developing a Moon base.


Cebrenia quadrangle

The Cebrenia quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is located in the northeastern portion of Mars’ eastern hemisphere and covers 120° to 180° east longitude (180° to 240° west longitude) and 30° to 65° north latitude. The quadrangle uses a Lambert conformal conic projection at a nominal scale of 1:5,000,000 (1:5M). The Cebrenia quadrangle is also referred to as MC-7 (Mars Chart-7). It includes part of Utopia Planitia and Arcadia Planitia.
The southern and northern borders of the Cebrenia quadrangle are approximately and wide, respectively. The north to south distance is about (slightly less than the length of Greenland). The quadrangle covers an approximate area of 4.9 million square km, or a little over 3% of Mars’ surface area.
Origin of name.
Cebrenia is a telescopic albedo feature centered on 50° N and 150° E on Mars. The feature is named after Cebrenia, a country near ancient Troy. The name was approved by the International Astronomical Union (IAU) in 1958.
Physiography and geology.
The quadrangle's prominent features are the large craters Mie and Stokes, a volcano, Hecates Tholus, and a group of mountains, Phlegra Montes. This area is a flat, smooth plain for the most part, so the relatively large craters Mie and Stokes really stand out. The Galaxias Region has an area of chaos, where the ground seems to have collapsed.
Viking II (part of Viking program) landed near Mie on September 3, 1976. Its landing coordinates were 48° N and 226° W.
Results from Viking II mission.
What it would look like walking around the landing site.
The sky would be a light pink. The dirt would also appear pink. The surface would be uneven; the soil would be formed into troughs. Large rocks would be spread about. Most of the rocks are similar in size. Many of the rocks would have small holes or bubbles on their surfaces caused by gas escaping after the rocks came to the surface. Some boulders would show erosion due to the wind. Many rocks would appear to be perched, as if wind removed much of the soil at their bases. In the winter snow or frost would cover most of the ground. There would be many small sand dunes that are still active. The wind speed would typically be 7 meters per second (16 miles per hour). There would be a hard crust on the top of the soil similar to a deposit, called caliche which is common in the U.S. Southwest. Such crusts are formed by solutions of minerals moving up through soil and evaporating at the surface. Scientists, in a September, 2009 article in the journal Science, have asserted that if Viking II only dug four (4) inches deeper, it would have reached a layer of almost pure ice.
Analysis of soil.
The soil resembled those produced from the weathering of basaltic lavas. The tested soil contained abundant silicon and iron, along with significant amounts of magnesium, aluminum, sulfur, calcium, and titanium. Trace elements, strontium and yttrium, were detected. The amount of potassium was 5 times lower than the average for the Earth's crust. Some chemicals in the soil contained sulfur and chlorine that were like typical compounds remaining after the evaporation of sea water. Sulfur was more concentrated in the crust on top of the soil then in the bulk soil beneath. The sulfur may be present as sulfates of sodium, magnesium, calcium, or iron. A sulfide of iron is also possible. The Spirit Rover and the Opportunity Rover both found sulfates on Mars. The Opportunity Rover (landed in 2004 with advanced instruments) found magnesium sulfate and calcium sulfate at Meridiani Planum. Using results from the chemical measurements, mineral models suggest that the soil could be a mixture of about 90% iron-rich clay, about 10% magnesium sulfate (kieserite?), about 5% carbonate (calcite), and about 5% iron oxides (hematite, magnetite, goethite?). These minerals are typical weathering products of mafic igneous rocks. Studies with magnets aboard the landers indicated that the soil is between 3 and 7 percent magnetic materials by weight. The magnetic chemicals could be magnetite and maghemite. These could come from the weathering of basalt rock. Experiments carried out by the Mars Spirit Rover (landed in 2004) indicated that magnetite could explain the magnetic nature of the dust and soil on Mars. Magnetite was found in the soil and that the most magnetic part of the soil was dark. Magnetite is very dark.
Search for life.
Viking did three experiments to look for life. The results were surprising and interesting. Most scientists now believe that the data were due to inorganic chemical reactions of the soil, although a few scientists still believe the results were due to living reactions. No organic chemicals were found in the soil. However, dry areas of Antarctica do not have detectable organic compounds either, but they have organisms living in the rocks. Mars has almost no ozone layer, like the Earth, so UV light sterilizes the surface and produces highly reactive chemicals such as peroxides that would oxidize any organic chemicals. The Phoenix Lander discovered the chemical perchlorate in the Martian Soil. Perchlorate is a strong oxidant so it may have destroyed any organic matter on the surface. If it is widespread on Mars, carbon-based life would be difficult at the soil surface.
Research, published in the Journal of Geophysical Research in September 2010, proposed that organic compounds were actually present in the soil analyzed by both Viking 1 and 2. NASA's Phoenix lander in 2008 detected perchlorate which can break down organic compounds. The study's authors found that perchlorate will destroy organics when heated and will produce chloromethane and dichloromethane, the identical chlorine compounds discovered by both Viking landers when they performed the same tests on Mars. Because perchlorate would have broken down any Martian organics, the question of whether or not Viking found life is still wide open.
Ice exposed in new craters.
Impressive research, reported in the journal Science in September 2009, has showed that some new craters on Mars show exposed, pure, water ice. After a time, the ice disappears, evaporating into the atmosphere. The ice is only a few feet deep. The ice was confirmed with the Compact Imaging Spectrometer (CRISM)] on board the Mars Reconnaissance Orbiter (MRO). The ice was found in a total of 5 locations. Three of the locations are in the Cebrenia quadrangle. These locations are , and .
This discovery proves that future colonists on Mars will be able to obtain water from a wide variety of locations. The ice can be dug up, melted, then taken apart to provide fresh oxygen and hydrogen for rocket fuel. Hydrogen is the powerful fuel used by the space shuttle main engines
Other craters.
Impact craters generally have a rim with ejecta around them, in contrast volcanic craters usually do not have a rim or ejecta deposits. Sometimes craters will display layers. Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed onto the surface. Hence, craters can show us what lies deep under the surface.
Hecates Tholus.
Recent research leads scientists to believe that Hecates Tholus erupted explosively about 350 million years ago, which is a not that long ago for Mars. The eruptions created depressions on the flanks of the volcano. And just five million years ago, glacial deposits formed inside these depressions. Some valleys on Hecates show a parallel drainage pattern.
Volcano-ice interactions.
Large amounts of water ice are believed to be present under the surface of Mars. Some channels lie near volcanic areas. When hot subsurface molten rock comes close to this ice, large amounts of liquid water and mud may be formed. Hrad Vallis in the Cebrenia quadrangle is close to Elysium Mons, a large volcano, which may have supplied water to create the channel. Hrad Vallis is pictured below.
Galaxias region.
The ground in Galaxias seems to have collapsed. Such land forms on Mars are called "Chaos terrain." Galaxias Chaos is different from many other chaotic regions. It does not have associated outflow channels, and it does not display a great elevation difference between it and the surrounding land area, as most of the other chaos regions. Research by Pedersen and Head, published in 2010, suggests that Galaxias Chaos is the site of a volcanic flow that buried an ice-rich layer, called the Vastitas Borealis Formation (VBF). It is generally believed that the VBF is a residue from water-rich materials deposited by large floods. The VBF may have been of varied thickness and may have contained varied amounts of ice. In the thin atmosphere of Mars, this layer would have slowly disappeared by sublimation (changing from a solid directly to a gas). Since some areas would have sublimated more than others, the upper lava cap would not be supported evenly and would crack. Cracks/troughs may have begun from sublimation and shrinkage along the edges of the lava cap. Stress from the undermining of the cap edge would have made cracks in the cap. Places with cracks would undergo more sublimation, then the cracks would widen and form the blocky terrain characteristic of regions of chaos. The sublimation process may have been aided by heat (geothermal flux) from magma movements. There are volcanoes, namely Elysium Montes and Hecates Tholus, nearby which most likely are surrounded by dikes, which would have heated the ground. Also, a warmer period in the past would have increased the amount of water sublimating from the ground.
Evidence of Glaciers.
Glaciers, loosely defined as patches of currently or recently flowing ice, are thought to be present across large but restricted areas of the modern Martian surface, and are inferred to have been more widely distributed at times in the past. Lobate convex features on the surface known as viscous flow features and lobate debris aprons, which show the characteristics of non-Newtonian flow, are now almost unanimously regarded as true glaciers. However, a variety of other features on the surface have also been interpreted as directly linked to flowing ice, such as fretted terrain, lineated valley fill, concentric crater fill, and arcuate ridges. A variety of surface textures seen in imagery of the midlatitudes and polar regions are also thought to be linked to sublimation of glacial ice. ,
The pictures below show features that are probably associated with glaciers.
Channels.
There is enormous evidence that water once flowed in river valleys on Mars. Images of curved channels have been seen in images from Mars spacecraft dating back to the early seventies with the Mariner 9 orbiter. Indeed, a study published in June 2017, calculated that the volume of water needed to carve all the channels on Mars was even larger than the proposed ocean that the planet may have had. Water was probably recycled many times from the ocean to rainfall around Mars.
Pedestal craters.
A pedestal crater is a crater with its ejecta sitting above the surrounding terrain and thereby forming a raised platform (like a pedestal). They form when an impact crater ejects material which forms an erosion-resistant layer, thus causing the immediate area to erode more slowly than the rest of the region. Some pedestals have been accurately measured to be hundreds of meters above the surrounding area. This means that hundreds of meters of material were eroded away. The result is that both the crater and its ejecta blanket stand above the surroundings. Pedestal craters were first observed during the Mariner missions.


Alfred Weld

Alfred Weld S. J. (1823 Leagram, Lancashire – 1890 South Africa) was an English Jesuit priest, professor of Science and Director of Stonyhurst Observatory. While working at the observatory, he welcomed in 1848 the Italian refugee Jesuit, Angelo Secchi, who went on to be a pioneer in Astronomy. Weld was ordained in 1854. After briefly managing St Marys Hall in Lancashire, he became Novice Master at Manresa House, Roehampton. During this period, in 1862, he was the founding editor of the Jesuits' in-house magazine, "Letters and Notices" (still circulating in the new Millennium) and ensured the "The Month" (a Catholic review) was edited by the Society. It was his desire to foster a community of writers. The anonymous author of his obituary in "Letters and Notices", wrote: “It is no exaggeration then to say that the literary work of the Province, so promising, so prolific, and so fruitful of good which has marked the last thirty years, is in great measure due to the initiatif and large-minded encouragement of Father Weld.” It was during Weld's time at the helm that the poet Gerard Manley Hopkins was welcomed into the Society.
Weld was rapidly elected Provincial of the English Province in 1864.
In 1871 he became Rector of St Beuno's Theological College in Wales. Two years later in 1873 he became English Assistant to the Jesuit General, Peter Jan Beckx. He spent the last three years of his life with the Zambesi Mission, having first directed operations from Rome and then going out himself to replace Henri Depelchin SJ to rescue the failed settlement, carry on missionary work and manage St Aidan's College in Grahamstown, (now Makhanda, Eastern Cape).
Alfred Weld was born into an old English recusant family, son of Mary Searle and George, eighth son of Thomas Weld (of Lulworth) and Mary Stanley-Massey-Stanley. His paternal grandfather was the benefactor and founder of the Jesuit Stonyhurst College. Cardinal Weld was his uncle.
Publications.
His publications include:


Galactic ridge

The galactic ridge is a region of the inner galaxy that is coincident with the galactic plane of the Milky Way. It can be seen from Earth as a band of stars which is interrupted by 'dust lanes'. In these 'dust lanes' the dust in the gaseous galactic disk (or plane) blocks the visible light of the background stars. Due to this, many of the most interesting features of the Milky Way can only be viewed in X-rays. Along with the point X-ray sources which populate the Milky Way, an apparently diffuse X-ray emission concentrated in the galactic plane is also observed. This is known as the galactic ridge X-ray emission (GRXE). These emissions were originally discovered by Diana Worrall and collaborators in 1982, and since then the origins of these emissions have puzzled astrophysicists around the globe.
It was initially believed, due to the difficulty of resolving the GRXE into point sources, that the x-ray emissions were truly diffuse in nature and that their origin might be a Galactic plasma rather than distant stellar sources. It was thought to be caused by low energy cosmic rays interacting with cold gas in the region, which heated up the gas and caused it to emit X-rays. However it was discovered that the temperature of a gas producing such an emission would have to be around tens of millions of degrees. This temperature is far too high for a gas to be bound gravitationally to the galaxy. Therefore, it was proposed that the GRXE might be caused by many extremely remote and outlying stars. In 2009, after decades of attempting to resolve the GRXE, Mikhail Revnivtsev, his partner Sazonov and their colleges managed to resolve approximately 80% of the emissions over the course of 12 days using the Chandra X-ray observatory. During this time period a total of 473 sources of x-ray emission were detected in an area that is significantly smaller than the size of a Full Moon. This is one of the highest densities of x-ray sources ever seen in our Galaxy.
Due to this amazing discovery it is now thought that about 80% of the emission comes from discrete sources such as white dwarfs and stars with active coronae.
However, recent work by researchers at the Max Planck Institute for Astrophysics suggests that the GRXE may indeed consist of an additional, diffuse component after all. This diffuse component could arise not from the thermal emission of a very hot plasma but from the reprocessing by the interstellar gas of the X-ray radiation produced by luminous X-ray binary sources located in the Galaxy. X-ray binaries are the most luminous sources of X-rays in galaxies such as the Milky Way. These binary systems emit X-ray radiation when material or substance from a so-called donor star falls into the strong gravitational field of a compact object, such as a neutron star or a black hole. This X-ray radiation illuminates the atoms and molecules in the Galactic interstellar gas, which then scatter the incoming photons in different directions and at different energies. The resulting emission appears truly diffuse to the viewer.
The Galactic Ridge has a width of 5° latitude (b) and ±40° longitude (l) in the Galactic coordinate system.
The first instrument that was able to measure diffuse X-ray emission was the HEAO A2 (High Energy Astrophysical Observatory). However it was created to study the large-scale structure of the galaxy and the universe, and to yield high-quality spatial and spectral data in the X-ray region. Still, the HEAO A2 produced valuable information on discrete X-ray sources such as binary star systems, hot white dwarfs, cataclysmic variables and supernova remnants. The HEAO A2 also allowed for the study of extragalactic objects, for example radio galaxies, Seyfert galaxies, and quasars. Elihu Boldt was the principal investigator of the HEAO A2 instrument, however he worked alongside G. Gamire on the project. The HEAO A2 was launched into space in 1977, where its job was to scan the sky for approximately 17 months. It (the HEAO A2) produced the first low-background, all-sky maps in the 2-60 keV band, and for its time the HEAO A2 produced the best spectra ever obtained over 2-60 keV energy range.


Soil color

Soil color does not affect the behavior and use of soil; however, it can indicate the composition of the soil and give clues to the conditions that the soil is subjected to. Soil can exhibit a wide range of colour; grey, black, white, reds, browns, yellows and greens. Varying horizontal bands of colour in the soil often identify a specific soil horizon. The development and distribution of color in soil results from chemical and biological weathering, especially redox reactions. As the primary minerals in soil parent material weather, the elements combine into new and colorful compounds. Soil conditions produce uniform or gradual color changes, while reducing environments result in disrupted color flow with complex, mottled patterns and points of color concentration.
Causes.
Soil color is produced by the minerals present and by the organic matter content. Yellow or red soil indicates the presence of oxidized ferric iron oxides. Dark brown or black color in soil indicates that the soil has a high organic matter content. Wet soil will appear darker than dry soil. However, the presence of water also affects soil color by affecting the oxidation rate. Soil that has a high water content will have less air in the soil, specifically less oxygen. In well drained (and therefore oxygen rich) soils, red and brown colors caused by oxidation are more common, as opposed to in wet (low oxygen) soils where the soil usually appears grey or greenish by the presence of reduced (ferrous) iron oxide. The presence of other minerals can also affect soil color. manganese oxide causes a black color, glauconite makes the soil green, and calcite can make soil in arid regions appear white.
Organic matter tends to make the soil color darker. Humus, the final stage of organic matter breakdown, is black. Throughout the stages of organic matter breakdown, the colour imparted to the soil varies from browns to black. Sodium content influences the depth of colour of organic matter and therefore the soil. Sodium causes the organic matter (humus) to disperse more readily and spread over the soil particles, making the soil look darker (blacker). Soils which accumulate charcoal exhibit a black color.
Classification.
Often described by using general terms, such as dark brown, yellowish brown, etc., soil colors are also described more technically by using Munsell soil color charts, which separate color into components of hue (relation to red, yellow and blue), value (lightness or darkness) and chroma (paleness or strength).


Water on Mercury


Thomas Maclear

Sir Thomas Maclear (17 March 1794 – 14 July 1879) was an Irish-born South African astronomer who became Her Majesty's astronomer at the Cape of Good Hope.
Life.
He was born in Newtownstewart, County Tyrone, Ireland, the eldest son of Rev James Maclear and Mary Magrath. In 1808 he was sent to England to be educated in the medical profession. After passing his examinations, in 1815 he was accepted into the "Royal College of Surgeons" of England. He then worked as house-surgeon in the Bedford Infirmary.
In 1823 he went into partnership with his uncle at Biggleswade, Bedfordshire. Two years later in 1825 he was married to Mary Pearse, the daughter of Theed Pearse, Clerk of the Peace for the county of Bedford.
Maclear had a keen interest in amateur astronomy, and would begin a long association with the Royal Astronomical Society, to which he would be named a Fellow. In 1833, when the post became vacant, he was named as Her Majesty's Astronomer at the Cape of Good Hope, and arrived there aboard the "Tam O'Shanter" with his wife and five daughters, to take up his new duties in 1834. He worked with John Herschel until 1838, performing a survey of the southern sky, and continued to perform important astronomical observations over several more decades. The Maclears and Herschels formed a close friendship, the wives drawn together by the unusual occupations of their husbands and the raising of their large families. Mary Maclear, like Margaret Herschel, was a noted beauty and intelligent, though suffering from extreme deafness.
Between 1841 and 1848, Maclear would be occupied in performing a geodetic survey for the purpose of recalculating the figure of the Earth (its dimensions and shape) via an arc measurement. He caused a beacon to be erected on top of Table Mountain which was used as a triangulation station for the checking of de Lacaille's arc measurement.
He became close friends with David Livingstone, and they shared a common interest in the exploration of Africa. He performed many other useful scientific activities, including collecting meteorological, magnetic and tide data.
In 1861 his wife died.
Two years later he was granted a pension, but did not retire from the observatory until 1870. He lived thereafter at Grey Villa, Mowbray.
By 1876, he had lost his sight, and he died three years later in Cape Town, South Africa. He is buried next to his wife in the grounds of the Royal Observatory.


Michael Ovenden

Prof Michael William Ovenden FRSE FRAS (1926 – 1987) was a 20th-century British astronomer who was President of the Astronomical Society of Glasgow and Professor of Astronomy at University of British Columbia.
Life.
He was born on 21 May 1926 in the Muswell Hill district of north London. His first degree was from Queen Mary College, London in 1947. He then went to Cambridge University where he received an MA.
In 1953 he began lecturing in Astronomy at Glasgow University being promoted to Senior Lecturer in 1964.
In 1964 he was elected a Fellow of the Royal Society of Edinburgh. His proposers were Peter Alan Sweet, Hermann Bruck, Hugh Butler, and Peter Fellgett.
In 1966 he emigrated to Canada to take the role as Professor of Astronomy at the University of British Columbia.
He retired in 1985 due to ill-health and died of a heart attack on 15 March 1987 in Vancouver in Canada.


115P/Maury

115P/Maury, is a periodic Jupiter-family comet, discovered on August 16, 1985, from the Palomar Observatory by Alain Maury. When the comet was first announced on 1985 September 6, the confirmation came quickly from other observers located at the Palomar Observatory. To the initial announcement of the comet, several confirmations were announced in multiple different reports were compiled by S. Singer-Brewster, D. Schneeberger, and M. Gallup that found the 15th-magnitude trail of the comet on a plate exposed with the 0.46-m Schmidt telescope. These came from the staff at Palomar Observatory, who used the 1.5-m reflector and a CCD to detect the comet. The comet was continued to be followed and detected, leading to Scientist giving the comet a 8.6 to 8.8 orbital period.


Virgo in Chinese astronomy

The modern constellation Virgo lies across one of the quadrants symbolized by the Azure Dragon of the East (東方青龍, "Dōng Fāng Qīng Lóng"), and Three Enclosures (三垣, "Sān Yuán"), that divide the sky in traditional Chinese uranography.
The name of the western constellation in modern Chinese is 室女座 ("shì nǚ zuò"), which means "the virgin constellation".
Stars.
The map of Chinese constellation in constellation Virgo area consists of :


Habitable Exoplanets Catalog


Emily Rice

Emily Rice is an astronomy professor at the City University of New York. In addition to her scientific contributions to the study of the atmospheric properties of low mass astronomical bodies, she has become well known for her astronomy-related public outreach projects. She is the co-founder of an astro-centric fashion blog titled the STARtorialist, a host for the public outreach series Astronomy on Tap, a parody video creator, and a current research associate for the American Museum of Natural History in New York City. She has also served as a public presenter at the Hayden Planetarium in New York.
Education.
Rice attended the University of Pittsburgh where she was awarded two B.A. degrees, one in Physics & Astronomy, and the other in German. Following her graduation from the University of Pittsburgh, she then moved to Los Angeles where she completed her M.S. and her Ph.D. at the University of California, Los Angeles. Her master's thesis centered around the characterization of stars within the a young star cluster in the constellation of Aquila. The results of her thesis, which relied upon high-resolution spectra obtained by Lisa Prato, were published in the Astrophysical Journal in 2006 and in the upcoming Handbook of Star Forming Regions. For her Ph.D., Rice investigated the physical properties of brown dwarf atmospheres and current model deficiencies via near-infrared spectra. Once her Ph.D. was completed, she served as a postdoctoral fellow for Rebecca Oppenheimer at the American Museum of Natural History in the Exoplanet Group.
Career.
Rice is a current faculty member in the Department of Physics & Astronomy at the College of Staten Island, which is part of the City University of New York. In addition to her role as an Associate Professor, she is also a founding member of the Brown Dwarfs in New York City (BDNYC) research group. Her work primarily focuses on near-infrared spectra to characterize the properties of the lowest mass objects in our galaxy, namely: brown dwarfs, very low-mass stars, and giant exoplanets, as well as investigating stellar and planetary system formation mechanisms. Her work has resulted in over 30 co-authored publications. Rice also co-designed and authored a collection of introductory astronomy labs for use in entry-level astronomy courses entitled Astronomy Labs: A Concept Oriented Approach.
She is also well known for her continued involvement with the American Museum of Natural History as a research associate and occasional planetarium presenter at the Hayden Planetarium.
In 2015, she was awarded the Henry Wasser Award for Outstanding Scholarship from CUNY Academy for the Humanities and Sciences.
Public outreach.
Though she has made tremendous contributions to her field of research, Rice stands out for her successful public outreach activities. She is the co-founder, with Summer Ash of an astronomy-centered fashion blog called the STARtorialist, which boasts the tagline: "Where science meets fashion and scientists get fabulous".
She also dons the moniker DJ Carly Sagan, in honor of the legendary science popularizer Carl Sagan, to organize and host engaging, free-to-the-public science gatherings and presentations at bars in New York City as part of the Astronomy on Tap series.


Stellar structure

Stellar structure models describe the internal structure of a star in detail and make predictions about the luminosity, the color and the future evolution of the star. Different classes and ages of stars have different internal structures, reflecting their elemental makeup and energy transport mechanisms.
Energy transport.
Different layers of the stars transport heat up and outwards in different ways, primarily convection and radiative transfer, but thermal conduction is important in white dwarfs.
Convection is the dominant mode of energy transport when the temperature gradient is steep enough so that a given parcel of gas within the star will continue to rise if it rises slightly via an adiabatic process. In this case, the rising parcel is buoyant and continues to rise if it is warmer than the surrounding gas; if the rising parcel is cooler than the surrounding gas, it will fall back to its original height. In regions with a low temperature gradient and a low enough opacity to allow energy transport via radiation, radiation is the dominant mode of energy transport.
The internal structure of a main sequence star depends upon the mass of the star.
In stars with masses of 0.3–1.5 solar masses (), including the Sun, hydrogen-to-helium fusion occurs primarily via proton–proton chains, which do not establish a steep temperature gradient. Thus, radiation dominates in the inner portion of solar mass stars. The outer portion of solar mass stars is cool enough that hydrogen is neutral and thus opaque to ultraviolet photons, so convection dominates. Therefore, solar mass stars have radiative cores with convective envelopes in the outer portion of the star.
In massive stars (greater than about 1.5 ), the core temperature is above about 1.8×107 K, so hydrogen-to-helium fusion occurs primarily via the CNO cycle. In the CNO cycle, the energy generation rate scales as the temperature to the 15th power, whereas the rate scales as the temperature to the 4th power in the proton-proton chains. Due to the strong temperature sensitivity of the CNO cycle, the temperature gradient in the inner portion of the star is steep enough to make the core convective. In the outer portion of the star, the temperature gradient is shallower but the temperature is high enough that the hydrogen is nearly fully ionized, so the star remains transparent to ultraviolet radiation. Thus, massive stars have a radiative envelope.
The lowest mass main sequence stars have no radiation zone; the dominant energy transport mechanism throughout the star is convection.
Equations of stellar structure.
The simplest commonly used model of stellar structure is the spherically symmetric quasi-static model, which assumes that a star is in a steady state and that it is spherically symmetric. It contains four basic first-order differential equations: two represent how matter and pressure vary with radius; two represent how temperature and luminosity vary with radius.
In forming the stellar structure equations (exploiting the assumed spherical symmetry), one considers the matter density formula_1, temperature formula_2, total pressure (matter plus radiation) formula_3, luminosity formula_4, and energy generation rate per unit mass formula_5 in a spherical shell of a thickness formula_6 at a distance formula_7 from the center of the star. The star is assumed to be in local thermodynamic equilibrium (LTE) so the temperature is identical for matter and photons. Although LTE does not strictly hold because the temperature a given shell "sees" below itself is always hotter than the temperature above, this approximation is normally excellent because the photon mean free path, formula_8, is much smaller than the length over which the temperature varies considerably, i. e. formula_9.
First is a statement of "hydrostatic equilibrium:" the outward force due to the pressure gradient within the star is exactly balanced by the inward force due to gravity. This is sometimes referred to as stellar equilibrium.
where formula_11 is the cumulative mass inside the shell at formula_7 and "G" is the gravitational constant. The cumulative mass increases with radius according to the "mass continuity equation:"
Integrating the mass continuity equation from the star center (formula_14) to the radius of the star (formula_15) yields the total mass of the star.
Considering the energy leaving the spherical shell yields the "energy equation:"
where formula_17 is the luminosity produced in the form of neutrinos (which usually escape the star without interacting with ordinary matter) per unit mass. Outside the core of the star, where nuclear reactions occur, no energy is generated, so the luminosity is constant.
The energy transport equation takes differing forms depending upon the mode of energy transport. For conductive energy transport (appropriate for a white dwarf), the energy equation is
where "k" is the thermal conductivity.
In the case of radiative energy transport, appropriate for the inner portion of a solar mass main sequence star and the outer envelope of a massive main sequence star,
where formula_20 is the opacity of the matter, formula_21 is the Stefan–Boltzmann constant, and the Boltzmann constant is set to one.
The case of convective energy transport does not have a known rigorous mathematical formulation, and involves turbulence in the gas. Convective energy transport is usually modeled using mixing length theory. This treats the gas in the star as containing discrete elements which roughly retain the temperature, density, and pressure of their surroundings but move through the star as far as a characteristic length, called the "mixing length". For a monatomic ideal gas, when the convection is adiabatic, meaning that the convective gas bubbles don't exchange heat with their surroundings, mixing length theory yields
where formula_23 is the adiabatic index, the ratio of specific heats in the gas. (For a fully ionized ideal gas, formula_24.) When the convection is not adiabatic, the true temperature gradient is not given by this equation. For example, in the Sun the convection at the base of the convection zone, near the core, is adiabatic but that near the surface is not. The mixing length theory contains two free parameters which must be set to make the model fit observations, so it is a phenomenological theory rather than a rigorous mathematical formulation.
Also required are the equations of state, relating the pressure, opacity and energy generation rate to other local variables appropriate for the material, such as temperature, density, chemical composition, etc. Relevant equations of state for pressure may have to include the perfect gas law, radiation pressure, pressure due to degenerate electrons, etc. Opacity cannot be expressed exactly by a single formula. It is calculated for various compositions at specific densities and temperatures and presented in tabular form. Stellar structure "codes" (meaning computer programs calculating the model's variables) either interpolate in a density-temperature grid to obtain the opacity needed, or use a fitting function based on the tabulated values. A similar situation occurs for accurate calculations of the pressure equation of state. Finally, the nuclear energy generation rate is computed from nuclear physics experiments, using "reaction networks" to compute reaction rates for each individual reaction step and equilibrium abundances for each isotope in the gas.
Combined with a set of boundary conditions, a solution of these equations completely describes the behavior of the star. Typical boundary conditions set the values of the observable parameters appropriately at the surface (formula_15) and center (formula_14) of the star: formula_27, meaning the pressure at the surface of the star is zero; formula_28, there is no mass inside the center of the star, as required if the mass density remains ; formula_29, the total mass of the star is the star's mass; and formula_30, the temperature at the surface is the effective temperature of the star.
Although nowadays stellar evolution models describe the main features of color–magnitude diagrams, important improvements have to be made in order to remove uncertainties which are linked to the limited knowledge of transport phenomena. The most difficult challenge remains the numerical treatment of turbulence. Some research teams are developing simplified modelling of turbulence in 3D calculations.
Rapid evolution.
The above simplified model is not adequate without modification in situations when the composition changes are sufficiently rapid. The equation of hydrostatic equilibrium may need to be modified by adding a radial acceleration term if the radius of the star is changing very quickly, for example if the star is radially pulsating. Also, if the nuclear burning is not stable, or the star's core is rapidly collapsing, an entropy term must be added to the energy equation.


Bluestonehenge

Bluestonehenge or Bluehenge (also known as West Amesbury Henge) is a prehistoric henge and stone circle monument that was discovered by the Stonehenge Riverside Project about south-east of Stonehenge in Wiltshire, England. All that remains of the site is the ditch of the henge and a series of stone settings, none of which is visible above ground.
Excavations.
The site was excavated in August 2008 and again in August 2009; it is considered to be an important find by archaeologists.
Full details of the discovery were published in the 2010 January / February edition of "British Archaeology".
Mike Parker Pearson and his team of researchers played a key role in the discovery of this new henge site along the River Avon that links to Stonehenge. This new site was uncovered through excavation during the Stonehenge Riverside Project; it was given the name “Bluestonehenge” or “Bluehenge” because traces of bluestones were found during the excavation.
The term “henge” is often incorrectly thought to mean a circular structure of stones. In fact, henge in archaeology refers to an enclosed structure made of compressed earth, containing a ditch on the inside of the bank, giving the perception of keeping something inside the enclosure, rather than keeping out others. Stonehenge may be improperly named, according to the original archeological definition, as its ditch is located on the outside of the bank.
Initial findings.
The monument has been tentatively dated to between about 3000 and 2400 BC. Radiocarbon dating of antler tools found at the site has provided only an approximate date of 2469 to 2286 BC for the dismantling of the stones. Tests on an antler pick found at the bottom of a stonehole have so far failed, due to inadequate collagen in the sample.
Excavation revealed several stone settings that are thought to have been erected some time between 3400-2500 BC, due to two flint chisel arrowheads being found that are in a style commonly used during that period. It is estimated that there may have been as many as 27 stones in a circle in diameter. Charcoal was found in some holes, suggesting that burning may have taken place there. One suggestion is that the henge was a site for cremations. Within the stone circle there were imprints of the bases from the original stones, which have been compared to the bluestones located in Stonehenge and have been found to have matching dimensions.
The name "Bluestonehenge" is derived from the discovery of small stone chips in some of the stone settings. These bluestones are also found in Stonehenge and consist of a wide range of rock types originally from Pembrokeshire, west Wales, some away. Archaeologist Mike Parker Pearson suspects that any bluestones in the circle may have been removed around 2500 BC and incorporated into Stonehenge, which underwent major rebuilding work at about that time.
The stone circle settings were surrounded by a henge, comprising an ditch and outer bank which appears to date from approximately 2400 BC. Unlike Stonehenge, this monument does not appear to have any significant solar or lunar orientations.
Context.
The henge is located beside the River Avon in West Amesbury. Immediately beside it is the Avenue, a linear ditch and bank route that leads to Stonehenge. Mike Parker Pearson has suggested that the site may have been used for ceremonial purposes – possibly as a stopping place along a routeway between Durrington Walls and Stonehenge.
It is thought that it was a ceremonial route from an area of life at Durrington Walls, through Bluestonehenge and along the "Stonehenge Avenue", to arrive at the site of an individual's final resting place in Stonehenge. This theory can be supported by the numerous cremation burials (over 200) that have been uncovered during excavation work around Stonehenge. Analysis of these remains also leads researchers to believe it was a ceremony for the wealthier in the region, or of royal lineage, or even for those who helped initiate construction of Stonehenge. This select group of individuals was believed to be male adults who were 25–40 years old and who seemed quite healthy.
Mike Parker Pearson’s past experience working with a colleague from Madagascar also helped to shape his theory. He believes that the choice of stone material for Stonehenge is significant. Past civilizations often reserved stone for construction of their ancestors’ tombs, while the perishable material, such as the wood used for the Durrington Walls timber circles, was reserved for the living. Parker Pearson believes that Durrington Walls may have been a "land of the living" while Stonehenge (which was Britain's largest known cemetery at the time) was a "domain of the dead".


Selenean summit

Selenean summit refers to the "highest" point on the Moon, notionally similar to Mount Everest on the Earth.
At some 10,786 m (35,387 ft) above the lunar mean, it is nearly twenty percent 'taller' than Earth's relative highest point, Everest. The summit is located along the north-eastern rim of Engel'gardt crater. Although methods of measurement differ somewhat (e.g., the Moon lacks a sea level), since its discovery in 2010 by the LRO teams, nowhere else has surpassed this region's height measurements on the lunar surface. Approximate coordinates for the summit are .
The summit is located on the far side of the Moon relative to Earth.