This Week's Sky at a Glance, January 22 – 30

By: Alan MacRobert January 22, 2021 0

FRIDAY, JANUARY 22

■ Right after dark, face east and look very high. The bright star there is Capella, the Goat Star. To the right of it, by a couple of finger-widths at arm's length, is a small, narrow triangle of 3rd and 4th magnitude stars known as "the Kids." Though they're not exactly eye-grabbing, they form a never-forgotten asterism with Capella.

■ Look lower left of the waxing gibbous Moon for Aldebaran, as shown below. Closer to the Moon's upper left, can you see the Pleiades through the moonlight?

The waxing gibbous Moon stalks across Taurus from the 22nd through the 24th, stepping through the gap between Aldebaran and the Pleiades. (The Moon in these scenes is always drawn three times its actual apparent size.)

SATURDAY, JANUARY 23

■ Aldebaran shines below the waxing gibbous Moon this evening (by 4°), as shown above. Spot the Pleiades farther to the Moon's upper right. Far beneath them all is Orion.

SUNDAY, JANUARY 24

■ The waxing gibbous Moon now shines at the horntips of Taurus: look for Beta Tauri to the Moon's upper left and fainter Zeta Tauri to the Moon's lower left. Farther right of the Moon is orange Aldebaran.

MONDAY, JANUARY 25

■ Orion is now high in the southeast right after dark, and he stands highest due south around 9 p.m. Orion is the brightest of the 88 constellations, but his main pattern is surprisingly small compared to some of his dimmer neighbors. The biggest of these is Eridanus the River to his west, enormous but hard to trace. Dimmer Fornax the Furnace, to Eridanus's lower right, is almost as big as Orion! Even the main pattern of Lepus, the Hare cowering under Orion's feet, isn't much smaller than he is.

TUESDAY, JANUARY 26

■ The waxing gibbous Moon shines in the middle of Gemini, with Castor and Pollux to its left. Farther to the Moon's lower right is Procyon. Even farther to the Moon's right, Orion strides up the sky.

WEDNESDAY, JANUARY 27

■ The Moon shines under Pollux and Castor this evening.

The brighter star to the Moon's lower right is Procyon, the Little Dog Star in Canis Minor. Farther to Procyon's lower right is Sirius, the Big Dog Star, in Canis Major.

THURSDAY, JANUARY 28

■ Full Moon (exactly so at 2:16 p.m. EST). It shines this evening in dim Cancer, below Castor and Pollux and almost equally far above late-rising Regulus (for North America).

■ Zero-magnitude Capella high overhead, and equally bright Rigel in Orion's leading foot, have almost the same right ascension. This means they cross your sky’s meridian at almost exactly the same time: around 8 or 9 p.m. now, depending on how far east or west you live in your time zone. (Capella goes exactly through your zenith if you're at latitude 46° north: Portland, Oregon; Portland, Maine; Montreal; central France.)

So, whenever Capella passes its very highest, Rigel always marks true south over your landscape, and vice versa.

FRIDAY, JANUARY 29

■ The Moon, a day past full, rises in late twilight. Once it's well up look for Regulus 4° or 5° to its lower right, and Algieba, slightly fainter, a similar distance to the Moon's left or lower left.

SATURDAY, JANUARY 30

■ Once it's fully dark, spot the equilateral Winter Triangle in the southeast. Sirius is its brightest and lowest star. Betelgeuse stands above Sirius by about two fists at arm's length. To the left of their midpoint is Procyon.

This Week's Planet Roundup

Mercury is having an excellent apparition in evening twilight. Mercury is often called "elusive," but this week it's easy. Look for it low in the west-southwest about 40 or 50 minutes after sunset. In addition to being nearly as high as it ever gets in twilight (for skywatchers at mid-northern latitudes), Mercury is also brighter than usual, about magnitude –0.5 all week.

Venus (magnitude –3.9) is finally disappearing into the glow of sunrise. Early in the week, you might try looking for it just above the southeast horizon about 25 minutes before sunup.

Mars (about magnitude +0.3, in Aries) shines pale yellow-orange high in the south in late twilight. It's still very high in the southwest as late as 8 p.m. It sets in the west around 1 a.m.

Mars continues to fade and shrink into the distance. It's about 8 arcseconds wide in a telescope now and is as gibbous as it gets, 89% sunlit from Earth's point of view.

Jupiter and Saturn are out of sight behind the glare of the Sun.

Uranus (magnitude 5.7, in Aries) is just a few degrees below Mars in early evening. In binoculars Uranus is a little pinpoint "star." But with an apparent diameter of 3.6 arcseconds, it's a tiny, fuzzy ball at high power in even a smallish telescope with sharp optics — during spells of good seeing. Finder chart (without Mars).

Neptune (magnitude 7.9, in Aquarius) is sinking away low in the west-southwest after dark.

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 minus 5 hours. (Universal Time is also known as UT, UTC, GMT, or Z time. For more see Time and the Amateur Astronomer.)

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 magazine of 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.

Pocket Sky Atlas cover, Jumbo edition — The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6, and hundreds of telescopic galaxies, star clusters, and nebulae among them. Shown here is the Jumbo Edition, which is in hard covers and enlarged for easier reading outdoors at night. Sample charts. More about the current editions.

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) or Uranometria 2000.0 (stars to magnitude 9.75). And be sure to read how to use sky charts with a telescope.

You'll also want a good deep-sky guidebook, such as Sky Atlas 2000.0 Companion by Strong and Sinnott, or the bigger (and illustrated) 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."

Audio sky tour. Out under the evening sky with your
earbuds in place, listen to Kelly Beatty's monthly
podcast tour of the heavens above. It's free.

"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

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