Sky at a Glance | December 31st, 2010

Dawn view
The waning Moon passes Venus, Antares, and low Mercury in the dawn. (These scenes are drawn for the middle of North America. European observers: move each Moon symbol a quarter of the way toward the one for the previous date. For clarity, the Moon is shown three times actual size.)

Friday, December 31

  • The eclipsing variable star Algol in Perseus is at its minimum light, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 6:47 p.m. EST. It takes several more hours to rebrighten.

  • After the noise and revelry at the turning of midnight, step outside into the silent, cold dark. If the sky is clear, Sirius will be shining at its highest due south. To its upper right, Orion is just beginning to tilt westward. To Sirius's upper left shines Procyon. And (if you're near latitude 39° north) Capella and the Castor-Pollux pair straddle the zenith. You're seeing a preview of how the stars will be arranged at nightfall toward winter's end.

  • At dawn on the morning of January 1st (are you really going to be up then?) look far below Venus in the southeast for the thin crescent Moon. Antares and Mercury are also in the scene, as shown here.

    Saturday, January 1

  • Sirius, the Dog Star, sparkles low in the east-southeast after dinnertime. Procyon, the Little Dog Star, shines in the east about two fist-widths at arm's length to Sirius's left. If you live around latitude 30° (Tijuana, New Orleans, Jacksonville), the two canine stars will be at the same height above your horizon soon after they rise. If you're north of that latitude, Procyon will be higher. If you're south of there, Sirius will be the higher one.

  • At dawn Sunday morning, look for very thin waning crescent Moon lower right of Mercury low in the southeast, as shown above. Binoculars will become necessary as dawn brightens.

    Sunday, January 2

  • Uranus (magnitude 5.9) is within ½° of Jupiter this evening through Wednesday evening. It's just above or upper right of Jupiter as seen with binoculars from mid-northern latitudes. Don't confuse it with the 5.5-magnitude star 20 Piscium to Jupiter's lower right. Can you see a hint of aquamarine-green color in Uranus?

    Bright Orion , faint rabbit
    Lepus, the Hare, eternally crouches below Orion's feet.

    Monday, January 3

  • South of the feet of bright Orion, the Hunter, crouches dim Lepus, the Hare, quarry that Orion seems to be completely overlooking. Unlike many constellations, Lepus looks just like what it's supposed to represent. The Hare has a bunched-up body, long ears below Rigel, and a pointy nose aimed west. Under moderate to serious light pollution only his two neck stars are visible, but you can find the rest with binoculars. Just remember that Lepus is quite a bit larger than a binocular's field of view.

  • The Quadrantid meteor shower may be visible tonight, depending on your location. Best chances are early Tuesday morning from Europe through Central Asia; also possible Monday evening for eastern North America. For more info see the January Sky & Telescope, page 40.

  • Earth passes through perihelion, its closest to the Sun for the year (just 3.4% closer than at aphelion in July).

    Tuesday, January 4

  • Bright Vega is getting low now in the northwest after dark. Above it shines Deneb, the head of the Northern Cross — which has turned nearly upright as it heads down to plant itself in the northwestern horizon (as seen from mid-northern latitudes).

  • New Moon (exact at 4:03 a.m. EST). The new Moon partially eclipses the Sun for a large region of Africa, Eastern Europe, and Southwest Asia; see maps and other info. You can watch a webcast of the partial eclipse here, here, or here.

    Wednesday, January 5

  • By 8 p.m. the Winter Triangle is well up in the east-southeast. It consists of Betelgeuse in Orion's leftmost corner, bright Sirius far below, and Procyon to the left of these two. It's altogether nicer than the more famous Summer Triangle — brighter, more colorful, and equilateral!

    Scorpius has begun its slow trek from dawn backward through the night to become an evening constellation of summer. (The blue 10° scale as about the width of your fist held at arm's length.)

    Thursday, January 6

  • The two inner planets, Venus and Mercury, continue shining in the southeast at dawn almost unchanged since the beginning of the week, as shown at right for tomorrow morning. But notice that Antares and the rest of the starry background have slid a little higher toward Venus: the season marches on.

    Friday, January 7

  • This week is the coldest of the year on average. But look low in the east-northeast after 9 or 9:30 p.m. and there you'll see Regulus and the Sickle of Leo already on the rise — a distant foreshadowing of the coming of spring.

    Saturday, January 8

  • Venus is at greatest elongation, 47° west of the Sun in the morning sky. This is nearly when Venus appears half-lit, or at dichotomy, in a telescope. In the coming weeks and months Venus will grow thickly gibbous while shrinking in apparent diameter; it's pulling far ahead of Earth in its faster orbit and is beginning to swing around to the far side of the Sun.



    Sky at a Glance is now an iPhone app! Put S&T SkyWeek on your iPhone, iPad, or iPod Touch and get the above listings anytime, anywhere — with interactive sky maps! Tap a button to see the scene described, customized for your location worldwide. From there you can scroll the view all around the sky, zoom in or out, change to any time or date, and turn on animation. Go to Apple's iTunes store from your device and buy S&T SkyWeek — just 99 cents!


    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 map in the center of each issue of Sky & Telescope, the essential magazine of astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

    Pocket Sky Atlas
    The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but that's less than one star in an entire telescopic field of view, on average. By comparison, Sky Atlas 2000.0 plots 81,312 stars to magnitude 8.5, typically one or two stars per telescopic field. Both atlases include many hundreds of deep-sky targets — galaxies, star clusters, and nebulae — to hunt among the stars.
    Sky & Telescope

    Once you get a telescope, to put it to good use you must have a detailed, large-scale sky atlas (set of charts). The standards are the
    Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger Sky Atlas 2000.0 (stars to magnitude 8.5); and the even larger and deeper Uranometria 2000.0 (stars to magnitude 9.75). And read how to use your charts effectively.

    You'll also want a good deep-sky guidebook, such as Sky Atlas 2000.0 Companion by Strong and Sinnott, or the more detailed and descriptive Night Sky Observer's Guide by Kepple and Sanner, or the classic if dated Burnham's Celestial Handbook.

    Can a computerized telescope take their place? I don't think so — not for beginners, anyway, and especially not on mounts that are less than top-quality mechanically. As Terence Dickinson and Alan Dyer say in their 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 is having an excellent morning apparition for skywatchers in the Northern Hemisphere. Look for it shining at magnitude 0 low in the east-southeast about an hour before your local sunrise time. It's very far to the lower left of bright Venus. Look also for fainter Antares, more directly below Venus; see the sky scene at the top of this page.

    Venus (magnitude –4.6) blazes as the "Morning Star" in the southeast before and during dawn. In fact Venus rises some two hours before the first glimmer of dawn (for mid-northern latitudes) — a weird UFO of a thing in the east-southeast. In a telescope, once it gets higher, Venus appears almost exactly half-lit: at dichotomy.

    Look for Saturn and Spica very far to Venus's upper right in the south, and Arcturus even higher above Venus.

    Mars is lost in the glow of sunset.

    Jupiter (magnitude –2.3, at the Pisces-Aquarius border) shines in the south during twilight and southwest later in the evening, still the brightest starlike point in the evening sky. But it now sets by about 11 p.m. In a telescope Jupiter has shrunk to only 38 arcseconds wide as Earth rounds to the far side of the Sun from it. But keep watch anyway on Jupiter's South Equatorial Belt re-forming, as dark markings spread east and west all around the globe from the storm spot that broke out in the SEB's latitude in November.

    Jupiter's Great Red Spot is near System II longitude 157°. Assuming it stays there, here's a list to print out of all the Great Red Spot's predicted transit times for the rest of this observing season.

    Saturn with white storm, Jan. 2, 2010
    ," he writes. South is up." credits="Donald C. Parker" width="" height="" align="right"]
    Saturn (magnitude +0.8, in Virgo) rises around midnight or 1 a.m. but is best seen in a telescope high in the south-southeast to south before and during dawn (far upper right of brilliant Venus). Don't confuse Saturn with Spica below or lower left of it.

    In a telescope, Saturn's new white spot has grown and spread far around the planet! See our article Saturn's New Bright Storm. Here are the predicted transit times of the storm's original outbreak site across the center of Saturn's disk.

    Saturn's rings, meanwhile, have widened to 10° from edge-on, the widest they've appeared since 2007. And see how many of Saturn's satellites you can identify in your scope using our Saturn's Moons tracker.

    Uranus (magnitude 5.9) is within 0.7° of Jupiter this week! They're in conjunction, 0.5° apart, on January 3rd and 4th, with Uranus north of Jupiter.

    Neptune (magnitude 7.9, at the Capricornus-Aquarius border) is still up in the southwest right after dark, near Mu Capricorni. See our finder charts for Uranus and Neptune online or (with article) in the September Sky & Telescope, page 56.


    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) equals Universal Time (also known as UT, UTC, or GMT) minus 5 hours.


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