This Week's Sky at a Glance, March 8 – 17

FRIDAY, MARCH 8

■ Bright Sirius stands due south on the meridian just as twilight fades into night. Sirius is the bottom star of the equilateral Winter Triangle. The triangle's other two stars are orange Betelgeuse to Sirius's upper right (Orion's shoulder) and Procyon to Sirius's upper left. This is the time of year when the Winter Triangle teeters in balance on Sirius in early evening.

SATURDAY, MARCH 9

■ Sirius is the overwhelmingly brightest star of Canis Major. In a very dark sky the Big Dog's realistic stick figure is fairly plain to see — the dog is in profile, prancing to the right on his hind legs, with Sirius as his shiny dog tag.

But for most of us only his five brightest stars show through the light pollution. These form the unmistakable Meat Cleaver. Sirius and Murzim (to its right) are the wide top end of the Cleaver, with Sirius sparkling on its top back corner. Down to Sirius's lower left is the Cleaver's other end including its short handle, formed by the triangle of Adhara, Wezen, and Aludra. The Cleaver chops toward lower right.

■ Algol shines at its minimum brightness, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 10:07 p.m. Eastern Standard Time (7:07 p.m. PST). Algol takes several additional hours to fade and to rebrighten. Comparison-star chart, with north up. Remember, celestial north is always the direction toward Polaris as you look across the sky.

■ Daylight saving time begins at 2 a.m. Sunday morning for most of North America. Clocks spring ahead an hour.

SUNDAY, MARCH 10

■ On the traditional divide between the winter and spring sky is the dim constellation Cancer. It's between Gemini to its west and Leo to its east.

Cancer holds something unique in its middle: the Beehive Star Cluster, M44. The Beehive shows dimly to the naked eye if you have little or no light pollution. Where to look? It's a bit less than halfway from Pollux in Gemini to Regulus in Leo. With binoculars it's easy even under worse conditions. Look for a scattered clump of faint little stars. They're magnitudes 6½ on down.

■ New Moon (exact at 5:00 a.m. on this date Eastern Daylight Time; 9:00 UT).

MONDAY, MARCH 11

■ Pollux and Castor in Gemini pass nearly overhead soon after nightfall this week if you live in the world's mid-northern latitudes. They go smack overhead if you're near latitude 30° north: Austin, Houston and the US Gulf Coast, northernmost Africa, Tibet, Shanghai.

The "twin" heads of the Gemini figures are fraternal twins at best. Pollux is visibly brighter than Castor and pale orange. And as for their physical nature, they're not even the same species.

Pollux is a single orange giant. Castor is a binary pair of two much smaller, hotter, white main-sequence stars, a fine double in amateur telescopes. A scale model: If Pollux were a basketball, Castor A and B would be a tennis ball and a baseball about a half mile apart from each other.

Moreover, Castor A and B are each closely orbited by an unseen red dwarf — a dim marble in our scale model just a foot or so from the tennis ball and the baseball.

And a very distant tight pair of red dwarfs, Castor C, is visible in amateur scopes as a single, 10th-magnitude speck 70 arcseconds south-southeast of the main pair. In our scale model, they would be a pair of marbles about 3 inches apart at least 10 miles from Castor A and B.

Space is big.

TUESDAY, MARCH 12

■ By nightfall, the Big Dipper is high in the northeast and beginning to tip left. Look left of its center, by about three fists at arm's length, for Polaris in the dim Little Dipper.

Other than Polaris, all you may see of the Little Dipper through light pollution are the two stars forming the outer edge of its bowl: Kochab (similar to Polaris in brightness) and below it, fainter Pherkad. Find these two "Guardians of the Pole" to Polaris's lower right by about a fist and a half at arm's length.

Now is the time of year when the two Guardians line up exactly vertically around the end of twilight.

■ Algol should be at minimum light for a couple hours this evening centered on 7:56 p.m. EDT.

WEDNESDAY, MARCH 13

■ The highlight of the early evening sky tonight is the crescent Moon and Jupiter keeping close company in the west, as shown below. They're only 3° apart.

THURSDAY, MARCH 14

■ Now the thicker crescent pairs up with the delicate Pleiades cluster high over Jupiter, as shown above. The Moon and Pleiades are only a couple degrees apart at nightfall, depending on where you are. For much of North America, the Moon draws closer to the cluster before moonset.

FRIDAY, MARCH 15

■ The Big Dipper glitters softly high in the northeast these evenings, standing on its handle. You probably know that the two stars forming the front of the Dipper's bowl (currently on top) are the Pointers; they point to Polaris, currently to their left or lower left.

And, you may know that if you follow the curve of the Dipper's handle out and around by a little more than a Dipper length, you'll arc to Arcturus, now rising in the east.

But did you know that if you follow the Pointers backward the opposite way, you'll land in Leo?

Draw a line diagonally across the Dipper's bowl from where the handle is attached, continue far on, and you'll go to Gemini.

And look at the two stars forming the open top of the Dipper's bowl. Follow this line past the bowl's lip far across the sky, and you cruise to Capella.

SATURDAY, MARCH 16

■ First-quarter Moon (exact at 12:11 a.m. tonight Eastern Daylight Time). Just below the Moon is 2nd-magnitude Beta Tauri, El Nath. Much farther below are Aldebaran, and then lower, the Pleiades. Bright Jupiter shines beneath the Pleiades.

Looking wider, the Moon is nearly midway between Capella two fists at arm's length to its upper right and Betelgeuse two fists to its lower left.

SUNDAY, MARCH 17

■ The Moon, a day past first quarter, is approaching Castor and Pollux high overhead, as shown below.

■ Look for Arcturus, the Spring Star, very low in the east-northeast after nightfall and higher in the east later in the evening. By modern measurements Arcturus is visual magnitude –0.05, making it the fourth-brightest nighttime star. It's bested only by Sirius, Canopus, and Alpha Centauri (counting the combined light of Alpha Cen A and B; they appear single to the unaided eye).

But for northerners who can never see Canopus or Alpha Cen, Arcturus is bested by Sirius alone, which now glitters in the south-southwest after dark. However, Vega and Capella are very close on its heels, brightness-wise.

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This Week's Planet Roundup

Mercury is beginning to emerge very low in the afterglow of sunset. About 35 to 45 minutes after sunset, look for it a little above your horizon due west. It's very far below Jupiter and a bit right. The later in the week the better your chances. At least Mercury is brighter than usual, about magnitude –1.0.

Venus, magnitude –3.8, peeks up very low in bright dawn. Look for it just above your east-southeast horizon about 30 or 20 minutes before sunrise. For Venus, the earlier in the week the better.

Mars, magnitude +1.3, is also deep in the sunrise, upper right of Venus but only a hundredth as bright! The separation between them widens from 8° to 11° this week.

Jupiter, magnitude –2.2 in Aries, is the bright white "star" fairly high in the west in twilight, and lower later. In a telescope Jupiter has shrunk to only 35 arcseconds wide. It's nearly as distant and small as it gets.

Saturn is out of sight behind the glare of the Sun.

Uranus, magnitude 5.7 in Aries, is 5° above Jupiter. Right after dark, use the finder charts for it in last November's Sky & Telescope, pages 48-49.

Neptune is hidden in conjunction with the Sun.

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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. Eastern Daylight Time (EDT) is Usal 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.

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), which shows all 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) or Uranometria 2000.0 (stars to mag 9.75). 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.

Can computerized telescopes replace charts? Not for beginners I don't think, especially not 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 the sky. 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."

If you do get a computerized scope, make sure the drives can be disengaged so you can swing it around and point it readily by hand if you want, rather than only slowly by the electric motors.

However, finding faint telescopic objects the old-fashioned way with charts isn't simple either. Learn the 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."
            — John Adams, 1770

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