Sky at a Glance | December 10th, 2010

During the 2004 Geminid meteor shower, Alan Dyer caught a bright fireball cutting across Sirius (near the bottom of the track). Orion is to the upper right. He used a tripod-mounted digital camera with a wide-field 16-mm lens for a 1-minute exposure at f/2.8 and ISO 800. Expect to shoot a lot of frames before you get this lucky! Click image for larger view.
Alan Dyer

Friday, December 10

  • Keep an eye out for early Geminid meteors! If you see a shooting star, trace its path backward far across the sky. If this line passes near Castor in Gemini, a Geminid is almost certainly what you've seen. Article.

  • Jupiter shines far upper left of the Moon after dusk. A similar distance to the Moon's right is Altair. Look lower left of the Moon for Fomalhaut, sometimes called "the Autumn Star."

    Saturday, December 11

  • The nearly first-quarter Moon this evening forms a roughly equilateral triangle with bright Jupiter to its upper left and Fomalhaut to its lower left.

  • Jupiter's Great Red Spot crosses the planet's central meridian around 9:27 p.m. EST.

    Sunday, December 12

  • High in the south at dusk, Jupiter shines left of the Moon. Above them stands the Great Square of Pegasus. As evening grows late, the whole tableau shifts lower to the southwest and tilts to the right.

    View in bright twilight!
    Use binoculars or a wide-field scope to search for these two planets 20 or 30 minutes after sunset. Their visibility in bright twilight is exaggerated here.

    Monday, December 13

  • A twilight challenge! Mercury and Mars appear closest, 1° apart, very low in the southwest after sunset. You'll need optical aid; the illustration here exaggerates their visibility in the still-bright sky 20 or 30 minutes after sunset.

  • The Geminid meteor shower should peak late tonight. Best viewing will be after midnight, but some meteors will can be seen in mid- and late evening the despite moonlight and the low altitude of the shower's radiant (near Castor). Already, early this morning, observers were counting 40 Geminids per hour according to the International Meteor Organization (IMO). See our article. And see the IMO's graph of the shower's behavior, based on careful standardized-method amateur counts being reported worldwide.

  • First-quarter Moon (exact at 8:59 a.m. EST). Jupiter is below it at dusk, and lower left of it later in the evening.

  • Jupiter's Great Red Spot crosses Jupiter's central meridian around 8:06 p.m. Pacific Standard Time.

    Tuesday, December 14

    Don't give up on the Geminid meteors even though we're past the 13th! The shower continues at reduced rates for at least a couple days.

  • The beginning of winter is just a week away, but Vega, the "Summer Star," still shines as the brightest star in the west-southwest in early evening after dark. The brightest star above Vega is Deneb in Cygnus. Vega is 25 light-years from Earth. Deneb, a white supergiant, is about 1,600 light-years distant.

    Wednesday, December 15

  • By about 9:30 p.m. local time this week (depending on where you live), the dim Little Dipper hangs straight down from the North Star as if from a nail on the north wall of the sky — and the brighter Big Dipper is rearing upward on its handle low in the north-northeast.

    Thursday, December 16

  • Jupiter's Great Red Spot crosses Jupiter's central meridian around 8:36 p.m. Eastern Standard Time.

    Friday, December 17

  • This evening, look lower left of the Moon (by a little more than a fist-width at arm's length) for the delicate Pleiades star cluster. Below the Pleiades by a roughly similar distance is orange Aldebaran. Far off to their left shines brighter Capella.

    The Moon takes three nights to pass from one end of the constellation Taurus to the other. (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 its actual apparent size.)

    Saturday, December 18

  • This evening the Pleiades are only about 2° left or upper left of the gibbous Moon as seen from North America, as shown at right. Use binoculars to penetrate the bright moonlight.

  • Have you made your plans for North America's total eclipse of the Moon day after tomorrow, the night of December 20–21? The Moon will be high in the late-night or early-morning sky. See the December Sky & Telescope, page 61, or our article online: A Sky-High Lunar Eclipse.



    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).

    Sky Atlas 2000.0 (the color Deluxe Edition is shown here) plots 81,312 stars to magnitude 8.5. That includes most of the stars that you can see in a good finderscope, and typically one or two stars that will fall within a 50× telescope's field of view wherever you point. About 2,700 deep-sky objects to hunt are plotted among the stars.
    Alan MacRobert

    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

    Jupiter on Dec. 15, 2010
    Jupiter's Great Red Spot and surroundings on December 15th. The central-meridian longitude (System II) was 163°. South is up. Note the thin streamer of dark material all the way across the disk just above the bright Equatorial Zone. It's from the South Equatorial Belt Outbreak on the other side of the planet, now more than a month old.

    Mercury is fading rapidly and dropping of sight into the sunset.

    Venus (magnitude –4.8) blazes in the southeast before and during dawn. It's now at its greatest height as the "Morning Star." In fact Venus rises some two hours before the first glimmer of dawn (for skywatchers at mid-northern latitudes), a weird UFO of a thing in the east-southeast.

    Look for fainter Spica well to Venus's upper right, and for Saturn above Spica. Even farther to Venus's upper left is Arcturus.

    Mars (magnitude +1.3) is deep in bright evening twilight near Mercury. They appear closest, 1° apart, on Monday the 13th as shown near the top of this page. Try sweeping for them with binoculars or a wide-field telescope soon after sunset. Good luck.

    Jupiter (magnitude –2.5, at the Pisces-Aquarius border) shines in the south to southwest during evening, the brightest starlike point in the sky.

    Jupiter Dec. 13, 2010
    Jupiter's other side. By December 13th, the dark markings issuing from the South Equatorial Belt Outbreak formed a very obvious, turbulent diagonal line most of the way around the planet. It's now detectable visually in almost any telescope capable of showing belts on Jupiter. Note also the activity in the North Equatorial Belt and the great blue festoons in the bright Equatorial Zone. Christopher Go took this image at 11:15 UT, when the central-meridian longitude (System II) was 267°. South is up.
    In a telescope it has shrunk to 41 arcseconds wide. Jupiter's missing South Equatorial Belt continues re-forming, as dark markings spread east and west around the planet from the storm spot that broke out in the SEB's latitude a month ago. That original outbreak site transits Jupiter's central meridian about 3 hours and 40 minutes after the Great Red Spot.

    As for the Great Red Spot, it's 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 (magnitude +0.8, in Virgo) rises around 1 or 2 a.m. and is well up the southeast before and during dawn, far upper right of brilliant Venus. Don't confuse it with Spica below it.

    In a telescope, see if you can detect the new white storm known as the North Electrostatic Disturbance, seen with dramatic clarity in the image below. Visually the spot will be much harder to see. The best time to observe Saturn with a telescope is during early dawn, when it's as high as possible. Saturn's rings have widened to 10° from edge-on.

    Saturn on Dec. 13. 2010
    Saturn's new white spot leaps out from this stacked-video image made by Christopher Go with his 11-inch scope. "I was even able to see it distinctly visually!" he writes. He took the image at 20:39 UT December 13th. The spot was at System III longitude 261° and is moving toward higher longitudes. South is up.

    Uranus (magnitude 5.8) is 2° east of Jupiter.

    Neptune (magnitude 7.9, in Capricornus) is still up in the southwest right after dark. It shares the same telescopic field with 5th-magnuitude 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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