This Week's Sky at a Glance
Some night sky sights for January 17 25
Supernova in M82! On Tuesday January 21st astronomers first noticed an 11th-magnitude supernova in the galaxy M82 in Ursa Major. It's in the evening sky in reach of amateur telescopes, and it may not be done brightening yet. See our article, Bright Supernova in M82.
Friday, January 17
Saturday, January 18
Sunday, January 19
Monday, January 20
Wednesday, January 22
Thursday, January 23
Friday, January 24
Saturday, January 25
Want to become a better astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.
This is an outdoor nature hobby. For an easy-to-use constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential guide to astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).
Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The standards are the little Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger and deeper Sky Atlas 2000.0 (stars to magnitude 8.5); and once you know your way around, the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.
You'll also want a good deep-sky guidebook, such as Sue French's Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, the bigger Night Sky Observer's Guide by Kepple and Sanner, or the beloved if dated Burnham's Celestial Handbook.
Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically (able to point with better than 0.2° repeatability, which means fairly heavy and expensive). As Terence Dickinson and Alan Dyer say in their invaluable Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."
This Week's Planet Roundup
Mercury (magnitude –0.9) is emerging into twilight view after sunset. Look for it above the west-southwest horizon about 30 to 45 minutes after sunset. It's becoming higher in darker twilight every day.
Venus (about magnitude –4.4) is now plain to see low in early dawn; look east-southeast. It too is becoming higher every day.
In a telescope Venus is a very thin, large crescent following its inferior conjunction on January 11th.
Mars (magnitude +0.5, in Virgo) rises around 11 or midnight. Spica, not quite as bright at magnitude +1.0, rises about 6° below it. They're highest in the south before the first light of dawn, with Spica now to Mars's lower left.
In a telescope Mars is still pretty small, 8 arcseconds wide. It'll be nearly twice this diameter (15.1″) when closest in mid-April.
Jupiter (magnitude –2.7, in Gemini) dominates the eastern sky in the evening and crosses nearly overhead (for mid-northern observers) around 11 p.m.
Saturn (magnitude +0.6, in Libra) rises around 2 a.m. and is well up in the southeast as dawn begins to brighten. By then it's far lower left of Mars and Spica, and even farther below brighter Arcturus.
Uranus (magnitude 5.9, in Pisces) is still well up in the southwest right after dark. Finder chart.
Neptune (magnitude 8.0, in Aquarius) is low in the west-southwest at nightfall.
All descriptions that relate to your horizon including the words up, down, right, and left are written for the world's mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America.
Eastern Standard Time (EST) is Universal Time (UT, UTC, or GMT) minus 5 hours.
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