Sir Patrick Moore (1923-2012)

Sir Patrick Moore

Sir Patrick Moore




BBC News: Sir Patrick Moore: Chris Lintott’s tribute
Discovery News: Astronomer Patrick Moore Dies at 89

The Discovery Channel Telescope Is ONLINE!





Congratulations to everyone at Lowell Observatory on a job well done!

BIG PICS: The DCT First Light Gallery.


When Venus Transited the Sun








Today’s horoscope says: Expect some angry emails.



Alas, no.











The White House Astronomy Night: Change, Delivered

In agreement with Phil Plait, this video made me smile too. A lot.

President Obama (now a Nobel Peace Prize recipient) hosted an astronomical party on the White House lawn on October 7th for an audience of 150 middle school students from the Washington area and some guests of honour (including Charlie Bolden, NASA Administrator and Buzz Aldrin, Apollo legend). It looked like a really exciting event for all the school kids involved.

This was my favourite bit:

So, there are a lot of mysteries left, and there are a lot of problems for you students to solve, and I want to be a president who makes sure you have the teachers and the tools that you need to solve them. That’s why we’re working to reinvigorate math and science in your schools and attract new and qualified science teachers in your classrooms, some with lifetimes of experience […] That’s how we’ll move American students to the top of the pack in math and in science over the next decade to guarantee that America will lead the world in discovery in this new century.” –President Barack Obama, Oct. 3rd.

Was there ever an astronomy party on the White House lawn during the previous administration?

Venus is Lonely. Very, Very Lonely


Venus is a hellish world. Although the planet is nearly the same size of Earth, that’s where the similarities end. Having said that, it does have an atmosphere, but it’s not the kind of atmosphere you would ever want to spend time breathing in. Composed of a dense carbon dioxide/nitrogen mix where clouds are made from sulphuric acid, you can forget about Venus as a tropical holiday destination. Even if you found a way to ‘breathe’ on Venus, you’d need to prepare yourself for the scorching 470°C surface temperatures and bone crushing pressures 100 times the pressure we are used to on Earth.

Doesn’t sound like a very nice place does it? Certainly an interesting world, providing us with invaluable science (after all, the reason for the extreme temperatures on Venus is due to a run-away greenhouse effect, it could help us understand the growing problems we are facing with our comparatively mild global warming woes), but an unlikely candidate for human colonization (unless we lived in the clouds).

Venus might not be a popular world for mankind to live on, but it doesn’t seem to be a popular world for natural satellites to orbit around either. It doesn’t have any moons, and astronomers are a little confused as to why this is the case. The only other planet without moons is the innermost terrestrial planet, Mercury. Every other planet in the Solar System has at least one natural satellite.

For hundreds of years, astronomers have been on the lookout for anything orbiting Venus but they’ve had little luck. However, some of the earliest observations of Venus appeared to indicate the presence satellites (in 1645, F. Fontana mentioned the possibility of a satellite discovery, followed by further observations in the late 1600’s and 1700’s). Since 1768, there have been no further reports of any satellite sightings. 1956 was the last published survey for Venusian satellites, using photographic plates, and that survey (published by Gerard Kuiper in 1961) drew up blanks for any satellites measuring over 2.5 km wide.

The lack of Venusian moons is puzzling, as a Venus-moon interacting mechanism has often been invoked as the reason why Venus has a retrograde spin (i.e. viewed from the ‘top’ of the Solar System plane, Venus has a clockwise rotation, whereas the rest of the planets, apart from Uranus — that spins on its side, bizarrely — have an anti-clockwise, or prograde, spin). Perhaps Venus once had a moon, but it has since been lost due to gravitational interactions with other Solar System bodies, or due to tidal instabilities, the innermost terrestrial planets collided with their large satellites a long time ago.

This is where Scott Sheppard from the Carnegie Institution of Washington and Chadwick Trujillo from the Gemini Observatory (Hawaii) step in. In a recent publication titled, “A Survey for Satellites of Venus,” Sheppard and Trujillo pick up where Kuiper left off, and carry out a systematic survey searching for any natural satellites around Venus. Only this time, by using the cutting-edge 6.5 meter telescope and IMACS wide-field CCD imager at Las Campanas observatory in Chile, they looked for objects only a few hundred meters in diameter.

The researchers scanned the interior of the Venusian ‘Hill Sphere’ to see if any undiscovered tiny moons were lurking. The Hill sphere is the volume of space surrounding a planetary body where natural satellites can orbit without being destabilized by the gravitational effects of the Sun. If there are any unforeseen moons, they should be found in stable orbits within the Hill sphere.

Sheppard and Trujillo have drawn blanks. Although a few errant asteroids were detected, no natural satellites down to a diameter of 600 meters were discovered. They surveyed 90% of the Venusian Hill sphere, and 99% of the inner Hill sphere (0.7rH) — the volume of space predicted to contain the stable orbits of natural satellites.

This new survey improves the non-detection of satellites down to a factor of 50 on previous studies, thereby proving Venus either, a) never possessed any satellites over 1km in diameter, or b) the orbits of past large satellites have become unstable and crashed into Venus or flung into space.

Either way, Venus remains alone, with only the ESA Venus Express for company

Source: A Survey for Satellites of Venus, Sheppard & Trujillo, 2009. arXiv:0906.2781v1 [astro-ph.EP]

Hubble and Atlantis Transit the Sun (Photo)

The Hubble Space Telescope and Shuttle Atlantis pass in front of the blank Sun. Can't see their silhouettes? Click on the image for the large version and look in the bottom-left-hand corner. That's no sunspot pair... (©Thierry Legault)


Thierry Legault is one highly skilled astrophotographer. The transit of the Hubble Space Telescope and Space Shuttle Atlantis took only 0.8 seconds to clear the disk of the Sun, so Legault rapidly took four pictures per second, starting his series of pictures two seconds before the pair were predicted to pass in front of the Sun.

STS-125 Atlantis and Hubble Solar Transit. The image was captured from Florida at 12:17pm EST on May 13th as the Shuttle approached the orbiting telescope at 600km from Earth (©Thierry Legault)


In the image above, the 35 meter-long Atlantis is easily identifiable, but the tiny speck of the 13 meter-long Hubble isn’t so easy to define, but the result is superb. According to Legault’s website, this is the only picture of the STS-125 and the observatory, orbiting at an altitude of 600 km.

Back in July 2008, Astroengine reported on the transit of the International Space Station across the disk of the Sun. Fortunately, in both cases, the Sun’s face was blank, and no sunspots are prominent enough to ruin the view.


Sources: NASA on Flickr, Astrosurf