This Week's Sky at a Glance, February 14 – 23

FRIDAY, FEBRUARY 14

■ Jupiter remains high overheard this week, toward the south in early evening as shown below. It makes a right triangle with Aldebaran and the Pleiades.

■ 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, lurks Lepus the Hare. Like Canis Major, this is a constellation with a connect-the-dots pattern 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 the planet'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.

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

SATURDAY, FEBRUARY 15

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

■ A subtler deep-sky catch is in the vicinity. Kemble's Cascade, much fainter, awaits your binoculars very high in the north-northwest. This is a dim but rather famous asterism, a straight star chain 2¼° long named in 1980 for its noticer Fr. Lucian Kemble of Canada. But it's located in dim, big, 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. They're 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, as seen in the photo above. These, combined with the mag-4.9 star near the middle of the Cascade, make a good finding aid.

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 cluster's center? It's a wide telescopic double. Its components are near-twins: magnitudes 7.0 and 7.1, 17 arcseconds apart.

SUNDAY, FEBRUARY 16

■ The waning gibbous Moon rises around 10 p.m. tonight, with Spica following it up just 2° or 3° below it (for North America). The Moon will draw closer to Spica through the night, to pass only about 1° under it around dawn on the 17th. As indicated below.

MONDAY, FEBRUARY 17

■ 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 18

■ 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.

WEDNESDAY, FEBRUARY 19

■ Certain deep-sky objects hold secret surprises within or near them. During evening now in this dark of the Moon, get out your telescope and sky atlas for a go at Bob King's eight Hidden Gems in Common Deep-Sky Objects now in view.

■ Algol should be at its minimum light, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 8:52 p.m. EST. It takes several hours to rebrighten. Comparison-star chart, with north up. (Celestial north is always the direction in the sky toward Polaris. Outside at night, turn the chart around to match.)

THURSDAY, FEBRUARY 20

■ This is a fine week to look for the zodiacal light if you live in the mid-northern latitudes, now that the early-evening sky is moonless and the ecliptic tilts high upward from the western horizon at nightfall. From a clear dark site with clean air, look west at the end of twilight for a dim but huge, tall pyramid of pearly light. It's tilted to the left, aligned along the constellations of the zodiac.

What you're seeing is sunlit interplanetary dust, originating from old asteroid collisions and long-evaporated comets, orbiting the Sun near the ecliptic plane.

■ Last-quarter Moon (exactly so at 12:33 p.m. today). The Moon will rise around 2 a.m. tonight, with orange Antares just a degree or two above it. By the beginning of Friday's dawn they'll be hanging beautifully in the south, a little farther apart.

FRIDAY, FEBRUARY 21

■ After dinnertime at this time of year, five carnivore constellations are rising upright in a row from the northeast to south. They're all presented in profile with their noses pointed up and their feet (if any) to the right. These are Ursa Major the Big Bear in the northeast (with the Big Dipper as its brightest part), Leo the Lion in the east, Hydra the Sea Serpent in the southeast, Canis Minor the Little Dog higher in the south-southeast, and bright Canis Major the Big Dog in the south.

SATURDAY, FEBRUARY 22

■ Sirius blazes high in the south on the meridian by about 8 or 9 p.m. now. Using binoculars or a scope at low power, examine the spot 4° south of Sirius (directly below it when on the meridian). Four degrees is somewhat less than the width of a typical binocular's or finderscope's field of view. Can you see a dim little patch of speckly gray haze there? That's the open star cluster M41, about 2,300 light-years away. Its total magnitude adds up to 5.0.

Sirius, by comparison, is only 8.6 light-years away — and being so near to us, it shines some 400 times brighter than that entire cluster.

SUNDAY, FEBRUARY 23

■ Have you ever seen Canopus, the second-brightest star after Sirius? It lies almost due south of Sirius, by 36°. That's far enough south that it never appears above your horizon unless you're below latitude 37° N (southern Virginia, southern Missouri, central California). And near there, you'll need a very flat south horizon. Canopus crosses the south point on the horizon just 21 minutes before Sirius does.

So, when to look? Canopus is due south when Beta Canis Majoris — Murzim the Announcer, the 2nd-magnitude star about three finger-widths to the right of Sirius — is at its highest due south over your landscape. That's about 8 p.m. now, depending on how far east or west you are in your time zone. Drop straight down from Murzim then.

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This Week's Planet Roundup

Mercury is hidden deep in the sunset.

Venus (magnitude –4.8, in Pisces) shines as the bright "Evening Star" in the west during and after twilight, not quite as high as earlier in the winter. It sets about two hours after dark.

In a telescope this week Venus is a striking crescent about 25% sunlit. Venus is enlarging week by week as it swings toward us — it's now about 41 arcseconds from pole to pole, about the same apparent diameter as Jupiter. And it's waning in phase as it draws closer to our line of sight to the Sun. It'll be about 55 arcseconds in diameter by mid-March when it plunges down into the sunset as a very thin crescent.

Mars (about magnitude –0.6, in Gemini) comes into view in twilight as a steady orange spark high in the east. Now a month past opposition, it continues to fade. As darkness deepens, watch for fainter Pollux and Castor (magnitudes 1.1 and 1.6) to emerge lower left and left of it, respectively. The triangle the three make is now almost isosceles, with Mars as its long point.

The triangle becomes exactly isosceles (as best as the eye can judge) for several days around February 21st. It stays unchanged for that long because, coincidentally, Mars comes to the stationary point of its retrograde loop right around then: on February 24th.

For telescope users, Mars is nice and high all evening. It has shrunk a bit to 12 arcseconds in diameter and is becoming slightly gibbous. A map of Mars's major surface features is in the January Sky & Telescope, page 48, and in Bob King's Mars Extravaganza online. 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, 36° 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 forms an almost exact right triangle with them this week and next.

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

In a telescope, Jupiter is about 42 arcseconds wide. For timetables of the doings of Jupiter's Galilean moons, and the meridian transits of its Great Red Spot, see the February Sky & Telescope, page 51.

Saturn, magnitude +1.1, is about two fists down below Venus in late twilight, lower every day.

Uranus, magnitude 5.7 at the Taurus-Aries border, is still high toward the southwest right after dark, 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.

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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 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.

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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 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.

For the attitude every new amateur astronomer needs, read Jennifer Willis's Modest Expectations Give Rise to Delight.

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 (with 201,000+ stars to magnitude 9.5, and 14,000 deep-sky objects selected to be detectable by eye in large amateur telescopes), and Uranometria 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.

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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.

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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

"Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence."
            — John Adams, 1770

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