This Week's Sky at a Glance
Some daily events in the changing sky for January 4 – 12.
Two comets float high in this week's evening sky, which remains dark and moonless (or nearly so). Comet Holmes is still in Perseus, very dim but big — more than 1° across. Look for it just northwest of Algol all week. Bring binoculars, and give your eyes plenty of time of dark-adapt. Here's a chart.
Comet 8P/Tuttle, shown at far right, is very different: much tinier than Holmes, greener, and about magnitude 6.0. Using binoculars, watch it race southward from Pisces into Cetus this week. See the article and chart in the January Sky & Telescope, page 73, or the brief version online.
S&T's Tony Flanders writes: "I drove last night [Jan. 3] to my club’s observing site in Westford, near the edge of the Boston suburbs. It’s not a very dark location. Nonetheless, Comet Holmes was quite easy to locate naked-eye, appearing only a little more diffuse than the nearby Double Cluster. Through both my 10x30 and 15x70 binoculars, it was a vague ellipse about 60′ by 45′, slightly brighter toward the major axis, but otherwise featureless.
"I picked up Comet Tuttle easily with my 10x30 binoculars, and the comet appeared quite bold through my 15x70s. It was a nearly circular blob getting continuously brighter toward the center. I managed to see it intermittently without any optical aid, but only because I knew exactly where to look."
Moonlight will return to brighten the evening sky for nearly two weeks starting around January 12th.
Friday, January 4
Saturday, January 5
Sunday, January 6
Monday, January 7
Tuesday, January 8
Wednesday, January 9
Thursday, January 10
Friday, January 11
Saturday, January 12
Want to become a better amateur astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope. For an easy-to-use constellation guide covering the whole evening sky, use the big monthly foldout map in each issue of Sky & Telescope, the essential magazine of 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 maps; the standard is Sky Atlas 2000.0) and good deep-sky guidebooks (such as Sky Atlas 2000.0 Companion by Strong and Sinnott, the even more detailed Night Sky Observer's Guide by Kepple and Sanner, or the enchanting though increasingly dated Burnham's Celestial Handbook). Read how to use them effectively.
More beginners' tips: "How to Start Right in Astronomy".
This Week's Planet Roundup
Mercury (magnitude –1) is very low in the glow of sunset. Late this week, look for it just above the west-southwest horizon about 30 minutes after sundown. It's on its way up into better view next week and the week after.
Venus (magnitude –3.9, in southern Ophiuchus) is the bright "Morning Star" low in the southeast before and during dawn. To its lower right, look for much dimmer Antares sparkling orange-red.
Mars is a couple weeks past opposition, shining bright yellow-orange (magnitude –1.3) in the east after dark. It's in the northeastern corner of Taurus. Mars is at its highest toward the south around 10 or 11 p.m. — passing near the zenith for observers at mid-northern latitudes.
Mars diminishes in apparent size this week, from 15.2 to 14.4 arcseconds in diameter. It's falling behind us as Earth moves ahead of it in our faster orbit around the Sun. It's also becoming noticeably gibbous again. For all about observing Mars with a telescope, see the guide and Martian surface-feature map in the November Sky & Telescope, page 66. A short version is online.
Jupiter is still buried deep in the glow of dawn. But it's bright enough (magnitude –1.8) that you may spot it if you look just above the southeast horizon, far lower left of brighter Venus, 20 or 30 minutes before sunrise. Bring binoculars. (To find your local sunrise time, make sure you've put your location into our online almanac, and make sure the Daylight Saving Time box is unchecked.)
On what date can you first catch Jupiter? Once you've found it, watch it get higher and easier each morning in January as it closes in on Venus. On January 5th they're still 27° apart, but the gap between them is narrowing by about 1° per day. These two brightest of planets are heading toward a close conjunction (0.6° apart) on the morning of February 1st.
Saturn (magnitude +0.5, in Leo) rises in the east around 9 p.m. and is highest in the south in the early-morning hours. Fainter Regulus (magnitude +1.4) is 8° west of Saturn: to its upper right after they rise, and to its lower right when they fade out in the glow of dawn in the west-southwest. Only a little dimmer than Regulus is Gamma Leonis (magnitude +2.1), 8° to Regulus's north. The three make an eye-catching triangle.
Uranus (magnitude 5.9, in Aquarius) is still observable in the southwest right after dark. Use the finder chart in last July's Sky & Telescope, page 60, or online.
Neptune (magnitude 8.0, in Capricornus) is getting low in the sunset.
All descriptions that relate to your horizon or zenith — including the words up, down, right, and left — are written for the world's midnorthern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America. Eastern Standard Time (EST) equals Universal Time (UT, UTC, or GMT) minus 5 hours.
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