Some daily events in the changing sky for January 4 – 12.

M33 and Comet Tuttle, Dec. 30, 2007

On the evening of December 30th, Mike Broussard of Maurice, Louisiana, caught Comet Tuttle passing very close by M33, the Pinwheel galaxy in Triangulum. This is, in part, a composite image. He used a Televue 85-mm refractor to take 81 60-second exposures, and merged the result with his previous images of M33 taken with the Televue 85-mm and with an 8-inch Schmidt-Newtonian telescope. Details.

The colors are accurate; a comet's characteristic green tint comes from fluorescence by the cometary gases C2 and CN. M33 is mostly bluish because it's dominated by star-forming regions rich in very luminous young, hot, blue-white stars. The red glows in the spiral arms are hydrogen-dominated emission nebulae. The brown patches are light-absorbing interstellar dust: star-smoke. Click image for larger view.

See also Jim McGaha's extraordinary wide-field image of both comets, M33, and M31.

Mike Broussard

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


  • When you check on Comet Holmes with your telescope, what else near it in Perseus can you find? There's more for your scope in the comet's vicinity than you probably think. See Sue French's "Deep-Sky Wonders" article and chart in the January Sky & Telescope, page 80.



  • Tomorrow morning in early dawn, the crescent Moon poses near Antares below Venus, as shown at below.


Looking southeast an hour before sunrise

The waning crescent Moon passes Venus and Antares at 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.

Sky & Telescope diagram

Saturday, January 5


  • Latest sunrise of the year (at 40° north latitude). The earliest sunset of the year comes in early December, and the longest night of the year is midway between.


Sunday, January 6


  • In the eastern sky this week, brilliant Mars continues to shine near the center of a huge, lopsided rectangle of bright stars. These are: Capella far to Mars's upper left, orange Aldebaran far to Mars's upper right, orange Betelgeuse (in Orion's shoulder) far to Mars's lower right, and the Castor-and-Pollux pair even farther to Mars's lower left. The eye-catching star much closer above Mars is Beta Tauri (El Nath), magnitude 1.6.



  • Also about Mars: tonight the planet appears at its farthest-north declination, just short of +27°. This is the farthest north it will be on the celestial sphere until 2040, when it will peak about ¼° farther north.


Monday, January 7


  • R Leonis, one of the brightest long-period variable stars in the sky, should be just starting down from its maximum light (about magnitude 5.8) this week. For a chart see the June 2005 Sky & Telescope, page 71.


Tuesday, January 8


  • New Moon (exact at 6:37 a.m. EST).


Wednesday, January 9


  • The thin crescent Moon is close to Mercury very low in the afterglow of sunset — a lovely but challenging sight. Bring binoculars. See the illustration below.
    Looking southwest in bright twilight

    Back in the evening sky, the waxing crescent Moon points the way to Mercury starting January 9th. (The blue 10° scale is about the size of your fist held at arm's length.)

    Sky & Telescope diagram



  • The bright eclipsing variable star Algol (Beta Persei), right near Comet Holmes, should be in one of its periodic dimmings, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 1:42 a.m. Thursday morning EST; 10:42 p.m. Wednesday evening PST. Algol takes several additional hours to fade and to rebrighten. For all times of Algol's minima this month, good worldwide, see the January Sky & Telescope, page 78.


Thursday, January 10


  • Spot the waxing crescent Moon in the southwest soon after sunset. If it were a bow, it would be shooting an arrow right at Mercury far to its lower right, as shown at right.


Friday, January 11


  • The bow of the thickening crescent Moon continues to shoot its invisible arrow at Mercury after sunset, though from farther away than it did yesterday.


Saturday, January 12


  • Algol should be at minimum light for a couple hours centered on 9:31 p.m. EST.


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 on evening of Dec. 31, 2007

Mars on New Year's Eve. Sean Walker took this image at 10:59 p.m. EST, when the central-meridian longitude was 202°. North is up; the big dark band across the southern hemisphere is Mare Cimmerium (left) and Mare Sirenum (lower right). Upward from Cimmerium stick distinctive little Gomer Sinus with its companion protrusion just to its left (celestial east; following). Note the evening clouds along the right-hand (celestial west; preceding) limb.

Click the image for an animation of the entire rotating planet (2MB animated gif). Walker created the animation in WinJupos freeware using 14 of his images taken between October 5th and December 31st, 2007. WinJupos can map your photos onto a Mercator projection, combine them to cover the complete planet if you have enough of them, then remap the Mercator projection onto a rotating globe. (The little moons zipping across were artificially added by the program.)

S&T: Sean Walker

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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