This Week’s Sky at a Glance, February 7 – 16 – Sky & Telescope

FRIDAY, FEBRUARY 7

■ Orion is now high in the southeast right after dark. Left of it is Gemini, headed up by Castor and Pollux at far left. The stick-figure Twins are still lying on their sides.

Well below their legs shines bright Procyon. Standing 4° above Procyon is 3rd-magnitude Gomeisa, Beta Canis Minoris, the only other easy naked-eye star of Canis Minor. The Little Dog is seen in profile, but only his back and the top of his head. Procyon marks his rump, Beta CMi is the back of his neck, and two fainter stars just above that are the top of his head and his nose. Those last two are only 4th and 5th magnitude, respectively. Binoculars help through light pollution.

SATURDAY, FEBRUARY 8

■ The bright gibbous Moon shines over Mars, Pollux, and Castor at nightfall, as shown below. As evening grows late this scene rotates clockwise, so that by 10 or 11 p.m. Mars shines straight left of the Moon.

■ Have you ever closely compared the colors of Betelgeuse and Aldebaran? Can you detect any difference in their colors at all? I can’t, really. Yet Aldebaran, spectral type K5 III, is often called an “orange” giant, while Betelgeuse, spectral type M1-M2 Ia, is usually called a “red” supergiant. Their temperatures are indeed a bit different: 3,900 Kelvin and 3,600 Kelvin, respectively.

And compare them both with Mars. To me, Mars looks slightly more yellowish orange and the two stars a slightly more reddish orange.

A complication: Betelgeuse is brighter than Aldebaran, and Mars is even brighter. To the human eye the colors of bright objects appear, falsely, to be desaturated: looking paler (whiter) than they really are. Think overexposure. You can get a slightly better read on the colors of bright points by defocusing them, to spread their light over a larger area of your retina.

■ Jupiter’s innermost large moon, Io, crosses the planet’s bright face from 8:33 to 10:44 p.m. EST tonight, distantly followed by its tiny black shadow (more readily detectable) from 9:46 to 11:58 p.m. EST. Io and its shadow move from celestial east to west with respect to Jupiter. Callisto shines in the foreground nearby.

SUNDAY, FEBRUARY 9

■ Tonight the bright Moon shines amid Mars, Pollux, and Castor. The scene above shows them the way they’re oriented at nightfall.

■ With a telescope, watch a little east of Jupiter’s limb for Europa to emerge from eclipse out of Jupiter’s shadow at 6:36 p.m. EST, if the sky is dark enough by then at your longitude. The farther east you live the better.

Then at 9:16 p.m. EST, observers anywhere in North America can watch for Io also to emerge from eclipse.

MONDAY, FEBRUARY 10

■ After dinnertime Sirius the Dog Star blazes in the southeast, the brightest star of Canis Major. Look below Orion.

In a dark sky where lots of stars are visible, the constellation’s points can be connected to form a convincing dog seen in profile. He’s currently standing on his hind legs, facing right. Sirius shines on his chest like a bright dogtag, to the right or lower right of his faint triangular head.

But through the light pollution where most of us live, only his five brightest stars are easily visible. These form the Meat Cleaver. Sirius is the cleaver’s top back corner, and its blade faces right. Its short handle is down below pointing lower left.

TUESDAY, FEBRUARY 11

■ Full Moon this evening and tomorrow evening. It’s exactly full at 8:53 a.m. February 12th EST, about halfway between the two evenings for the longitudes of the Americas.

This evening the Moon rises in the east-northeast about a half hour before sunset. Watch it emerge into view through the fading daylight.

Once the sky is fully dark, look for 1st-magnitude Regulus coming up about a fist at arm’s length below the Moon.

WEDNESDAY, FRBRUARY 12

■ Tonight the still-full Moon rises a little after sunset rather than a little before. Once the sky is dark, spot Regulus less than 2° to the Moon’s right. To reduce the Moon’s glare, cover it with two of your fingertips held out: one for each eye. Close one eye and position the fingertip you see, then do the same for the other.

THURSDAY, FEBRUARY 13

■ By 9 p.m. or so, the Big Dipper stands on its handle in the northeast. In the northwest, Cassiopeia also stands on end (its brighter end) at about the same height. Between them is Polaris.

FRIDAY, FEBRUARY 14

■ Orion stands at his highest in the south by about 8 p.m., looking smaller than you probably remember him appearing early in the winter when he was low. You’re seeing the “Moon illusion” effect. Constellations, not just the Moon, look bigger when they’re low.

Under Orion’s feet, and to the right of Sirius now, hides Lepus the Hare. Like Canis Major, this is a constellation with a connect-the-dots that really looks like what it’s supposed to be. It’s a crouching bunny, with his nose pointing lower right, his faint ears extending up toward Rigel (Orion’s brighter foot), and his body bunched to the left. His brightest two stars, 3rd-magnitude Alpha and Beta Leporis, form the back and front of his neck.

■ With a telescope this evening, watch Jupiter’s moon Ganymede slowly fade from sight around 7:25 p.m. EST as it enters eclipse by Jupiter’s shadow. Ganymede will be the one about a Jupiter diameter to Jupiter’s celestial east-northeast.

Then watch Ganymede slowly reappear out of Jupiter’s shadow around 9:56 p.m. EST, farther to Jupiter’s east.

Jupiter’s shrunken Great Red Spot should cross the planet’s central meridian about a half hour later, around 10:27 p.m. EST.

SATURDAY, FEBRUARY 15

■ Right after night is completely dark this week, the W of Cassiopeia shines high in the northwest, standing almost on end. Near the zenith is Capella.

The brightest star about midway between Cassiopeia and Capella (and a little off to the side) is Alpha Persei, magnitude 1.8. It lies on the lower-right edge of the Alpha Persei Cluster: a large, elongated, very loose swarm of fainter stars about the size of your thumbtip at arm’s length. At least a dozen are 6th magnitude or brighter, bright enough to show very well in binoculars. Look fairly soon after dark before the Moon rises.

Alpha Per, a white supergiant, is a true member of the group and is its brightest light. It and the rest are about 580 light-years away. For more see Steve O’Meara’s “The Hidden Wonders of Perseus” in the February Sky & Telescope, page 45.

■ Another deep-sky catch in the vicinity: Kemble’s Cascade, much fainter, awaits your binoculars very high in the north-northwest these evenings. This is a dim but rather famous asterism, a straight star chain 2¼° long named in 1980 for its noticer Fr. Lucian Kemble in Canada. But it’s located in dim, sprawling, shapeless Camelopardalis the Giraffe, which I find to be one of the most difficult constellations to navigate.

Here’s a shortcut. Draw a line from Algol through Alpha Persei. Extend the line farther on by exactly 1½ times that length. You’re now very close to the east end of the chain: a pair of stars magnitudes 6.8 and 6.2 a third of a degree apart (at the top of the image below).

The Cascade currently hangs down from the southernmost of those two (the fainter of them) in early evening. Most of its 15 or so other members are 7th to 9th magnitude, so you’ll need a fairly dark sky. Averted vision helps, as always for faint sights.

Below (west of) its bottom end is a gentle arc of three brighter stars, mags 4.8 to 5.8.

Bonus for telescopes: That 6.2-mag star 1/3° to the right of the Cascade’s top is the brightest star of the sparse, very small open cluster NGC 1502, less than 0.1° wide. Its next-brightest dozen stars are all 9th and 10th magnitude.

And that 6.2-mag star near the center of NGC 1502 is a wide telescopic double. Its components are near-twins: mags 7.0 and 7.1, 17 arcseconds apart.

SUNDAY, FEBRUARY 16

■ A fast-creeping red dwarf. Have you ever seen a red dwarf star? These are the most common stars in space, but they’re so intrinsically dim that not one of them is among the 6,000 pinpoints visible to the naked eye on even the darkest nights. One of the nearest and brightest red dwarfs lies just 3° west of Procyon, nicely placed these winter evenings. It’s Luyten’s Star, also known as GJ 273, and at visual magnitude 9.9 it’s in range of small telescopes. Use the finder charts with Bob King’s article Catch Luyten’s Star.

This humble object is very close to us as stars go, only 12.3 light-years away, so it is also a high proper motion star; it creeps across its celestial backdrop by 3.7 arcseconds per year. This means that a careful visual telescope user might detect its motion in as little as about 3 years, writes King, “depending on its proximity to field stars and the making and breaking of distinctive alignments with other stars.” He suggests, “Make an initial observation, note the position in a sketch, map or photo, and then return a couple years later. Hey, no hurry.”

To locate and identify Luyten’s Star with King’s charts you’ll need to be good at telescopic star-hopping. This is an essential skill for any amateur astronomer to develop so you don’t get lost in space. See How to Use a Star Chart with a Telescope, and expect a certain amount of frustration at first. Everyone goes through this. Don’t give up.

This Week’s Planet Roundup

Mercury is out of sight deep in the sunset.

Venus (magnitude –4.8, in Pisces) shines brightly as the “Evening Star” in the west-southwest during twilight, then lower in the west as evening grows late. It sets about two hours after dark.

In a telescope this week, Venus is a crescent about 31% sunlit. Venus is enlarging week by week as it swings toward us — it’s now about 36 arcseconds from pole to pole — while waning in phase as it draws closer to our line of sight to the Sun. It’ll be about 55 arcseconds in diameter near winter’s end when it becomes a very thin crescent plunging down into the sunset.

Mars comes into view in twilight as a steady orange spark high in the east. As darkness deepens, watch for Castor and Pollux to emerge left and lower left of it. Watch the changing shape of the triangle they make.

Mars, three weeks past opposition, is fading and shrinking. It’s now about magnitude –0.3 and 12½ arcseconds in diameter. It passes just south of the zenith around 10 or 11 p.m.

For telescope users, a map of Mars’s major surface features is in the January Sky & Telescope, page 48. See also Bob King’s Mars Extravaganza online with a surface-feature map. To find which side of Mars (i.e. which part of the map) will be facing you at the date and time you’ll observe, use our Mars Profiler tool.

Jupiter, two months past opposition, shines bright white (magnitude –2.4) in Taurus, 38° west along the ecliptic from Mars. It dominates the high south after dusk near Aldebaran and the Pleiades. Examine the triangle Jupiter makes with those two landmarks. It will be an exact right triangle on February 23rd and 24th.

Later in the evening Jupiter moves lower in the southwest. It sets in the west-northwest around 2 or 3 a.m.

In a telescope, Jupiter is about 42 arcseconds wide.

Saturn, magnitude +1.1, is increasingly difficult to pick up way below Venus as twilight fades into night. It’s the steady little spark 15° under Venus on Friday February 7th, and 19° under Venus by the 14th. Binoculars help.

Uranus, magnitude 5.7 at the Taurus-Aries border, is very high toward the southwest in early evening, 18° west of Jupiter along the ecliptic. You’ll need a good finder chart to tell it from the similar-looking surrounding stars. See last November’s Sky & Telescope, page 49.

Neptune, magnitude 7.9, is lost in the sunset afterglow between Venus and Saturn.

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 and graphics that also depend on longitude (mainly Moon positions) are for North America.

Eastern Standard Time (EST) is Universal Time minus 5 hours. UT is also known as UTC, GMT, or Z time.

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 a more detailed 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 much more detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas, in either the original or Jumbo Edition. Both show all 30,000 stars to magnitude 7.6, and 1,500 deep-sky targets — star clusters, nebulae, and galaxies — to search out among them.

Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many, as well as many more deep-sky objects. It’s currently out of print, but maybe you can find one used.

The next up, once you know your way around well, are the even larger Interstellarum atlas (201,000+ stars to magnitude 9.5, and 14,000 deep-sky objects selected to be detectable by eye in large amateur telescopes), andUranometria 2000.0 (332,000 stars to mag 9.75, and 10,300 deep-sky objects). And read How to Use a Star Chart with a Telescope. It applies just as much to charts on your phone or tablet as to charts on paper.

You’ll also want a good deep-sky guidebook. A beloved old classic is the three-volume Burnham’s Celestial Handbook. An impressive more modern one is the big Night Sky Observer’s Guide set (2+ volumes) by Kepple and Sanner. The pinnacle for total astro-geeks is the new Annals of the Deep Sky series, currently at 11 volumes as it works its way forward through the constellations alphabetically. So far it’s up to H.

Can computerized telescopes replace charts? Not for beginners I don’t think, and not for scopes on mounts and tripods that are less than top-quality mechanically. Unless, that is, you prefer spending your time getting finicky technology to work rather than learning how to explore the sky. 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 and a curious mind.” Without these, “the sky never becomes a friendly place.”

If you do get a computerized scope, make sure that its drives can be disengaged so you can swing it around and point it readily by hand when you want to, rather than only slowly by the electric motors (which eat batteries).

However, finding faint telescopic objects the old-fashioned way with charts isn’t simple either. Do learn the essential tricks at How to Use a Star Chart with a Telescope.

Audio sky tour. Out under the evening sky with your
earbuds in place, listen to Kelly Beatty’s monthly
podcast tour of the naked-eye 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