This Week’s Sky at a Glance, February 21 – March 2 – Sky & Telescope

The T Cor Bor watch picks up again. Last summer and fall, many watched closely for the recurrent nova T Coronae Borealis to blow up again for the first time in almost 80 years.

It didn’t. Nor has it in the months since. But now it’s showing new spectroscopic signs of big things getting ready to occur. . . maybe.

Corona Borealis currently rises in the northeast around 10 pm and passes nearly overhead before dawn. Use the finder charts (with comparison-star magnitudes) in Bob King’s T Coronae Borealis article, and check on the latest brightness observations by AAVSO members. Let’s hope for better luck this year.

The nova normally sputters along at 10th magnitude but erupted to magnitude 2 or 3 in just a few hours at its last outburst in 1946, to match Alpha Coronae Borealis or nearly so.

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 telescope starting at low power, examine the spot 4° south of Sirius: directly below it when near 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. (Murzim is the star forming the top edge of the Meat Cleaver’s blade.) That happens about 8 p.m. now, depending on how far east or west you are in your time zone. Drop straight down from Murzim then.

MONDAY, FEBRUARY 24

■ It’s not spring for four more weeks, but the Spring Star Arcturus seems eager to climb into view. It rises above the east-northeast horizon around 8 or 9 now, depending on both your latitude and longitude.

To see where to watch for Arcturus-rise, find the Big Dipper as soon as the stars come out; it’s high in the northeast. Follow the curve of its handle down and around to the lower right by a little more than a Dipper-length. That’s the spot on the horizon to watch.

By 10 or 11 p.m. Arcturus dominates the eastern sky.

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

TUESDAY, FEBRUARY 25

■ Want to try for Sirius B, the famous white dwarf? Sirius A and B are still 11 arcseconds apart, very near their widest apparent separation in their 50-year orbit. They will remain so for the next couple years before they noticeably start closing up again.

You’ll want at least a 10-inch scope and a night of really excellent seeing. Keep checking night after night; the seeing makes all the difference for Sirius B. Use extreme high power, when Sirius is standing at its very highest like it is now. See the Sirius-B-hunting tips in Bob King’s article Sirius B – a New Pup in My Life.

The “Pup” is northeast of the Dog Star and 10 magnitudes fainter: one ten-thousandth as bright. As Bob recommends, put a homemade occulting bar across your eyepiece’s field stop: a tiny strip of aluminum foil held to the field stop with a bit of tape, with one edge crossing the center of the field. Use a pencil point to nudge the edge of the foil into sharp focus as you look through the eyepiece, holding it up to a bright background indoors.

In the telescope, rotate the eyepiece so you can hide blinding Sirius A just behind the strip’s northeastern edge. If a diffraction spike gets in the way, rotate the telescope’s tube if you can.

WEDNESDAY, FEBRUARY 26

■ Certain deep-sky objects hold secret surprises within or near them. During evening 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 that are now in view.

THURSDAY, FEBRUARY 27

■ It’s almost March now. So quite soon after dark, the bowl of the Big Dipper rises as high in the northeast as Cassiopeia has descended to in the northwest. Midway between them, as always, is Polaris.

■ New Moon (exactly so at 7:45 p.m. EST).

FRIDAY, FEBRUARY 28

■ While twilight is fading 20 or 30 minutes after sunset, look 16° below Venus (about a fist and a half at arm’s length) for Mercury and, even lower, a very thin crescent Moon, as shown below. Saturn so dim and low is probably out of reach even with binoculars.

SATURDAY, MARCH 1

■ Now the crescent Moon, thicker and higher, hangs lower left of Venus as shown above (for North America). They’re 6° or 7° apart.

■ Look east after dark this week for the constellation Leo climbing nicely up in the almost-spring sky. Its brightest star is Regulus. The Sickle of Leo, about a fist and a half long, extends upper left from there. It’s shaped like a backward question mark.

Leo’s rear quarters and tail are a fist or so to the Sickle’s lower left.

SUNDAY, MARCH 2

■ February was Orion’s month to stand at his highest in the south in early evening. Now March pushes him westward and spotlights his dog, Canis Major sporting Sirius on his chest, center stage on the meridian.

Sirius is not only the brightest star in our sky after the Sun, it’s also the closest naked-eye star after the Sun, at 8.6 light-years, for those of us living at mid-northern latitudes.

Alpha Centauri is the actual closest star at 4.3 light-years, but you have to be farther south to see it. And in the northern sky three dim red-dwarf stars are closer than Sirius, but these require binoculars or a telescope.

This Week’s Planet Roundup

Mercury begins emerging into view very low in the sunset this week. Around February 24th, start looking for it just above the horizon due west about 30 minutes after sundown.

Mercury is now bright at about magnitude –1.2, but binoculars will still help when it’s low in bright twilight. It will get a little higher each evening. It’s heading into a fine showing next week.

Venus (still magnitude –4.8, in Pisces) shines as the bright “Evening Star” in the west during and after twilight. But it’s getting lower now day by day, and at an increasing pace. It sets hardly more than an hour after dark.

In a telescope this week, Venus displays a striking crescent about 20% sunlit and 46 arcseconds from pole to pole. Venus is enlarging as it swings toward us while 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 will plunge down into the sunset as a very thin crescent.

Mars (about magnitude –0.4, in Gemini) comes into view in twilight as a steady orange spark very high in the southeast. It continues to fade week by week as it shrinks into the distance. As darkness deepens, watch for fainter Pollux and Castor (magnitudes 1.1 and 1.6) to emerge left of it.

The triangle that the three make is exactly isosceles on February 21st and remains practically so all week. The triangle stays unchanged for so long because Mars is very near the stationary point of its retrograde loop, exactly so on February 24th.

For telescope users Mars is ideally placed very high through the evening. It has shrunk to 11½ arcseconds in diameter and is obviously a bit gibbous (94% sunlit). 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 shines bright white (magnitude –2.4) in Taurus, 35° west along the ecliptic from Mars. It dominates the high southwest after dusk near Aldebaran and the Pleiades. Jupiter still makes a right triangle with them.

Later in the evening they move lower toward the west. Jupiter sets in the west-northwest around 1 or 2 a.m.

In a telescope Jupiter is about 40 arcseconds wide. For timetables of the doings of its Galilean moons and the meridian transits of its Great Red Spot, see the February Sky & Telescope, page 51.

Saturn is lost deep in the sunset.

Uranus, magnitude 5.7 at the Taurus-Aries border, is still high toward the southwest right after dark, about 20° 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 is lost in the sunset.

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.

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.

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; 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