This Week’s Sky at a Glance, November 30– December 8

Friday, November 30

• Two faint fuzzies naked-eye: The Andromeda Galaxy (M31) and the Perseus Double Cluster are two of the most famous deep-sky objects. They're both cataloged as 4th magnitude, and in a fairly good sky you can see each with the unaided eye. They're only 22° apart, very high toward the east early these evenings — to the right of Cassiopeia and closer below Cassiopeia, respectively.

But they look rather different, the more so the darker your sky. See for yourself. Find them with the all-sky constellation map in the center of the December Sky & Telescope. If your sky is too bright, try binoculars.

Saturday, December 1

• Vega still shines brightly in the west-northwest after dark. The brightest star above it is Deneb, the head of the big Northern Cross, which is made of the brightest stars of Cygnus. At nightfall the shaft of the cross extends lower left from Deneb (by about two fists at arm's length). By about 11 or midnight, it plants itself more or less upright on the northwest horizon.

Sunday, December 2

• Algol should be at its minimum brightness, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 9:53 p.m. EST. Algol takes several additional hours to fade and to rebrighten.

• Look southeast just as dawn begins tomorrow (about 90 minutes before your local sunrise), and there will be Venus just a few degrees below the waning crescent Moon. Look to their right for Spica, much fainter, before dawn grows too bright.

Monday, December 3

• As dawn begins tomorrow morning the 4th, the crescent Moon, Venus, and Spica form a gently curving arc low in the east, in that order upper right from the Moon.

High to their upper left is Arcturus.

Tuesday, December 4

• At this time of year the Big Dipper lies down lowest soon after dark, due north. It's entirely below the north horizon if you're as far south as Miami. But by midnight, the Dipper is standing straight up on its handle in fine view in the northeast.

• Meanwhile, high above, the bowl of the Little Dipper is descending in the evening, lower left of Polaris. By 10 or 11 p.m. it hangs straight down from Polaris.

Wednesday, December 5

• The W of Cassiopeia now stands on end after dark, very high in the northeast. The bottom star of the W is Epsilon (ε) Cassiopeiae. That's your starting point for hunting down the little-known star cluster Collinder 463, sparse and loose but visible in binoculars. It's 8° to Epsilon's north, surrounded by a nice quadrilateral of 4th- and 5th-magnitude stars about 3° wide. Use Chart 1 of the Pocket Sky Atlas.

• Algol should be at minimum brightness for a couple hours centered on 6:42 p.m. EST.

Thursday, December 6

• Neptune very close to Mars. This evening, as seen from North America, Neptune appears only 1/3° from Mars — which is 1400 times brighter! Look for Neptune with your scope to Mars's east-northeast, then use high power to check that it's non-stellar. See Mars and Neptune Have a Close Shave.

Friday, December 7

• Now Neptune appears about 1/4° to Mars's southwest.

• Comet Wirtanen may or may not come within binocular, or even small-telescope, range as it passes unusually close by Earth for the next couple weeks. Start trying now while the evening sky is still moonless and dark! See Comet 46P/Wirtanen Approaches Earth, but as Joe Rao warns there, keep your expectations low.

• Earliest sunset of the year (if you're near latitude 40° north). By the time of the solstice and longest night on December 21st, the Sun actually sets 3 minutes later than now. And the latest sunrise doesn't come until January 4th. These slight discrepancies arise from the tilt of Earth's axis and the ellipticity of Earth's orbit.

• New Moon (exact at 2:20 a.m. on this date EST).

Saturday, December 8

• Orion is coming into good view low in the east after dinnertime now. And that means Gemini is also coming up to its left (for the world's mid-northern latitudes). The head stars of the Gemini twins, Castor and Pollux, are at the left end of the Gemini constellation — one over the other, with Castor on top.

High above Orion is Aldebaran, at one tip of the V-shaped asterism made of the brightest stars of the Hyades cluster. And high above Aldebaran and the Hyades are the Pleiades, smaller but brighter. The Pleiades are about as big as your fingertip at arm's length. Pleiades are about 440 light-years distant; the Hyades are 150.

Far to their left shines bright Capella.

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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.

Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas (in either the original or Jumbo Edition), which shows stars to magnitude 7.6.

Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many. The next up, once you know your way around, are the even larger Interstellarum atlas (stars to magnitude 9.5) and 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, or the bigger Night Sky Observer's Guide by Kepple and Sanner.

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 (meaning heavy and expensive). And 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."

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This Week's Planet Roundup

Mercury brightens and emerges into good dawn view toward the end of this week. By Thursday Dec. 6 it's magnitude +0.5 and brightening fast. Look for it just above the southeast horizon, 25° to the lower left of Venus. Binoculars may help.

Venus (magnitude –4.8, in Virgo) rises as an eerie "UFO" above the east-southeast horizon a good two hours before the first light of dawn. As dawn arrives, Venus is the brilliant "Morning Star" dominating the southeast. Look for Spica, much fainter, to its right.

In a telescope Venus is a shrinking and thickening crescent, waxing from 25% to 30% sunlit this week. For the sharpest telescopic views, follow it up higher all the way past sunrise and into the blue sky of day.

Mars (magnitude 0.0, in Aquarius) still shines highest in the south at nightfall and sets by midnight. In a telescope it's gibbous and quite small: 9 arcseconds from pole to pole. For a Mars map that displays which side is facing Earth at your time and date, use our Mars Profiler.

Jupiter is hidden behind the glare of the Sun.

Saturn (magnitude +0.6, in Sagittarius) is sinking away very low in the southwest in twilight. You'll find it nearly 40° below Altair and about 60° lower right of Mars.

Uranus, near the Aries-Pisces border, is pretty easy to see in binoculars at magnitude 5.7 — with a good finder chart, if you know the constellations well enough to see where to start with the chart.

Neptune, magnitude 7.9 in Aquarius, is very near Mars this week! See December 6 and 7 above. Finder chart (without Mars).

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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 or GMT) minus 5 hours.

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"The dangers of not thinking clearly are much greater now than ever before. It's not that there's something new in our way of thinking, it's that credulous and confused thinking can be much more lethal in ways it was never before."
— Carl Sagan, 1996

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"Objective reality exists. Facts are often determinable. Vaccines save lives. Carbon dioxide warms the globe. Bacteria evolve to thwart antibiotics, because evolution. Science and reason are not a liberal conspiracy. They are how we determine facts. Civilization's survival depends on our ability, and willingness, to do this."
— Alan MacRobert, your Sky at a Glance editor

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"Facts are stubborn things."
— John Adams, 1770

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