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Articles by J. Alex Knoll

Help plot the stars and shine a light on light pollution


This nebula is alive with stars


Now Playing In the Sky Near You


A recent solar flare could present Northern Lights to Southerners

A powerful solar flare on January 7 launched a barrage of plasm our way, which has the chance of producing auroras at much lower latitudes than usual. Scientists expect the activity to begin before dawn Thursday, January 9, which is too late to help given this issue’s release that day. But solar astronomers don’t rule out more blasts to come, as this solar flare, technically called a coronal mass ejection, was caused by an eruption from a massive and very active sunspot, AR1944, which is facing earth head-on. The sunspot, “as wide as seven earths,” NASA reported, is “one of the largest sunspots seen in the last 10 years.”
    Called aurora borealis when seen north of the equator and corona borealis to the south, these displays are the result of powerful bursts of radiation from the sun. Earth’s atmosphere blocks that harmful radiation, or these would be lethal events, but as the charged particles collide with earth’s own magnetically charged atmosphere, they produce a vivid and eerie light show. While these aurora are harmless to life, they can wreak havoc on our satellites, disrupting GPS, cellular reception and radio and television transmissions. The flare has already forced private space company Orbital Sciences to delay the launch of an unmanned cargo craft to the International Space Station.
    Any chance to see the so-called Northern Lights as far south as the Chesapeake is well worth keeping an eye on the sky over the next few nights.
    The moon is also busy this week. It visits over the weekend, to the left of the moon Friday night, look for the Pleiades star cluster. At first glance the Pleiades appear as a fuzzy patch of light in the constellation Taurus. But closer examination on a clear night reveals six stars shaped like a miniature dipper.
    Saturday the Pleiades are above the moon, while below the moon is Aldebaran, the red eye of the bull, and the Hyades star cluster.
    On Tuesday, the near-full moon is five degrees south of Jupiter. Tuesday, January 7, marked the anniversary of Galileo Galilei’s 1610 discovery of Jupiter’s largest three moons,  Io, Europa and Ganymede (he discovered Callisto a few days later). Today, a good pair of binoculars will reveal more of mighty Jove’s orbiting satellite’s than the great astronomer’s first telescope.
    Wednesday the 15th marks January’s full Wolf Moon, which also reaches apogee, its farthest point in orbit from earth, making this full moon the smallest of the year.
    Venus reaches inferior conjunction, Saturday, passing between the earth and sun, leaving our morning skies only to reappear as the Evening Star thereafter. Unlike the transit of Venus in 2012, this time Venus will pass five degrees north of the sun — still far too close to watch without a solar filter. Viewed with telescope or binoculars and the proper eye protection, our sister planet appears as a wide but razor-thin crescent.

Our closest approach to the sun does make for the shortest season

Twilight Thursday and Friday evening reveals the new crescent moon low in the southwest with Venus blazing a few degrees away tight against the horizon. Venus sinks lower in the early evening sky over the next week, finally disappearing between the sun and earth on January 11. Then, after a few days absence, it reappears in pre-dawn skies, where it will blaze as the Morning Star until autumn.
    Moonless skies provide a dark backdrop for this year’s Quadrantid meteor shower, which is at its best in the wee hours before dawn Friday and Saturday. Best viewing will be from a dark location after midnight. Meteors will radiate from the constellation Boötes, but can appear anywhere in the sky. The Quadrantids can produce from 50 to 100 meteors an hour, but timing — or more aptly, luck — is essential, as this shower peaks within just a few hours, and then it’s over.
    You shouldn’t have any trouble spotting Jupiter, which reaches opposition Sunday, when it will shine in our night skies from sunset until sunrise, far brighter than any star. At opposition, the gaseous giant is its closest to earth and farthest from the sun, with earth right between the two.
    Mars rises around midnight and is high in the south as daybreak approaches. Far below the red planet is Saturn, actually a little brighter but harder to see so tight against the horizon.
    Saturday, earth reaches its closest point to the sun for the year — called perihelion. At that point the sun is roughly 3 million miles closer to the sun than it is at aphelion in July. While 3 million miles may seem like a lot, the distance has little correlation with the change of seasons, which are a result of earth’s 231⁄2-degree tilted axis. It does, however, affect the length of the seasons, since when the earth is nearest the sun it is also traveling its fastest — more than three percent faster than at aphelion. As a result, the seasons come and go quicker this time of year, with the time between December’s solstice and March’s equinox almost five days shorter than from June’s solstice until September’s equinox. As a result, winter is the shortest season for those of us in the Northern Hemisphere.
    Saturday, two weeks after solstice, is the latest sunrise of the year. Sunrise comes a few seconds earlier than the day before, and while the change will be subtle at first, by the end of the month the sun will rise more than 10 minutes earlier than it does now.

The interloper visits Spica and Mercury

Mercury is putting on its best pre-dawn show of 2013, more than doubling in brightness this week, from +1 magnitude to –0.5 (each order of magnitude is exponential, so an increase from +1 to 0 is a doubling). Monday marks the innermost planet’s greatest elongation — its farthest point away from the sun as seen from earth and its highest point above the horizon. Mercury rises a little before 6am and climbs nearly 15 degrees above the southeast horizon before the sun rises more than an hour later. Ten degrees above Mercury is blue-white Spica, but even this first-magnitude star pales compared to Mercury this week.
    First discovered last September, Comet ISON is heading into the inner solar system for the first time, coming within 700,000 miles of the sun November 27. If the comet survives that close encounter, it could live up to the comet of the century billing. If not, the next two weeks are your best chance to spot this long-distance traveler.
    With binoculars or a small telescope, look for ISON one degree to the west of Spica Sunday before dawn and less than one-half degree to the east of the star the next morning. By next Thursday and Friday, ISON will be within 10 degrees of Mercury — well within your binoculars’ field of view. Perhaps by then it will be bright enough to see with the unaided eye.
    Sunday marks the full moon, the Beaver Moon and the Frost Moon according to lore. The full moon floats just six degrees below the miniature dipper-shape of the Pleiades star cluster, while Monday night it is even closer to Aldebaran, the red eye of Taurus the bull.
    The full moon’s glow washes out all but the brightest meteors in this year’s Leonid shower, which peaks between the 16th and 18th. Still, the Leonids are active through the month, so patience or luck will likely reward you with a few of these shooting stars.

July brings the first of three Super Moons

     As twilight settles to darkness, look to the southwest for ruddy Mars beside the ice-blue of Spica until they set around midnight. Mars is the brighter of the two. They will be their closest Sunday, with less than 1.5 degrees separating them. After that, Mars keeps on trucking, setting course for a conjunction with Saturn on August 4.

Will the Boötids show or no?

Friday’s new moon provides a dark backdrop for the annual Boötid meteor shower, which peaks after sunset that night and before dawn Saturday. Most years the Boötids are a modest shower, topping out at a dozen meteors an hour. But every now and then, it storms.

It’s a matter of angles

June’s full Honey, Mead or Rose Moon falls around midnight Thursday.

A tribute to one man’s time in Korea
