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This Week's Sky at a Glance, March 7 – 16

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FRIDAY, MARCH 7

■ The Moon, just past first quarter, shines upper right of the Mars-Castor-Pollux triangle as the stars come out, as shown for this date below. As evening progresses, the whole arrangement quickly rotates clockwise as it moves westward across the sky, if you keep turning to face it directly. Such rapid apparent rotation always happens for star patterns passing near the zenith. So by as early as 8 p.m., the Moon will be directly right of Mars when you stand facing them.

Moon with Mars near Castor and Pollux, March 8, 2025

SATURDAY, MARCH 8

■ The Moon horns in on the Mars-Castor-Pollux triangle this evening, as indicated above. Watch the Moon also change its separation with respect to background objects as the hours pass. The Moon travels eastward along its orbit by almost one Moon diameter per hour.

■ Daylight-saving time, observed in most of North America, begins at 2:00 a.m. Sunday morning March 9. Clocks "spring ahead" an hour. Daylight time for North America runs from the second Sunday in March to the first Sunday in November. Daylight time is not used in Hawaii, Saskatchewan, Puerto Rico, or in most of Arizona.

SUNDAY, MARCH 9

■ It's not spring for a couple more weeks, but the Spring Star Arcturus seems eager to get rolling. It now rises above the east-northeast horizon around 9 p.m. daylight-saving time, depending on your location.

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 the Dipper's 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 11 p.m. Arcturus quite dominates the eastern sky.

MONDAY, MARCH 10

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

Those "twin" heads of the Gemini figures are fraternal twins at best. Pollux is visibly brighter than Castor, and it's pale orange-yellow compared to Castor's white (though it's less strongly yellow-orange than Mars). And as for their physical nature, the two stars are 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 the size of a basketball, Castor A and B would be a white cue ball and a white golf ball 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, each just a foot or so from their bright primaries.

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 away from Castor A and B.

Even inside a sextuple star system, space is much bigger than you think.

Moon passing Regulus and Leo, March 11-13, 2025

TUESDAY, MARCH 11

■ The Moon shines near Regulus tonight. Watch the gap between them shrink from 3° or 4° at nightfall (for North America, as shown above) to only 1° or so by the time they set in the west-northwest in early dawn.

■ Algol should be at its minimum brightness, magnitude 3.4 instead of its usual 2.1, for about two hours centered on 11:37 p.m. EDT (8:37 p.m. PDT). Algol takes several additional hours to fade and to rebrighten. Comparison-star chart, with north up. (Celestial north is always the direction in the sky toward Polaris. Outside at night, turn charts around to match.)

WEDNESDAY, MARCH 12

■ Bright Sirius now stands due south on the meridian just as twilight fades away 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 balances on Sirius shortly after dark.

THURSDAY, MARCH 13

■ Total eclipse of the full Moon tonight for the Americas, westernmost Europe, and westernmost Africa.

For North Americans it happens late in the night. Partial eclipse begins at 1:09 a.m. Friday morning EDT, total eclipse begins at 2:26 a.m. EDT, mid-eclipse is at 2:59 a.m. EDT, total eclipse ends at 3:32 a.m. EDT, and partial eclipse ends at 4:48 a.m. EDT. For much more about this eclipse see the March Sky & Telescope, page 48.

The Moon will be near the apogee of its orbit, making it a minimoon: appearing just a bit smaller than the average full Moon.

The Moon's celestial-eastern edge was just emerging from Earth's shadow on the night of November 18-19, 2021.

FRIDAY, MARCH 14

■ The very slightly gibbous Moon, less than a day past full, rises in twilight. As it climbs higher after dark, keep watch below it (by about two fists at arm's length) for springtime Spica to show up. Spica rises about 1½ to 2 hours after the Moon does, depending on your location.

Moon passing Spica, March 15-16, 2025

■ Algol should be at its minimum brightness, magnitude 3.4 instead of its usual 2.1, for about two hours centered on 8:26 p.m. EDT Friday evening.

SATURDAY, MARCH 15

■ Now the waning Moon rises around the end of twilight, with Spica less than a fist beneath it as shown above.

Right of Spica by a fist and a half, look for the four-star pattern of Corvus, the springtime Crow, as illustrated above.

About twice as far left of Spica and the Moon sparkles bright Arcturus.

SUNDAY, MARCH 16

■ And now the Moon, waning further, rises about an hour after full dark, following Spica up this time rather than preceding it. To plan for some deep-sky observing, be set up and ready to go as soon as twilight ends in order to catch the window of darkness before the lunar sky-floodlight turns on.

■ For instance, on the traditional divide between the winter and spring sky lies the dim constellation Cancer. It's now very high toward the south-southeast in early evening, 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? The Beehive is a bit less than halfway from Pollux in Gemini to Regulus in Leo. With binoculars it's easy, even under worse sky conditions. Look for a scattered clump of faint little stars, magnitudes 6½ on down.

Use a telescope to hunt out the much smaller, fainter open cluster M67 some 9° below the Beehive. Find M67 1.8° due west of 4th-magnitude Alpha Cancri.

This Week's Planet Roundup

Mercury remains well placed in the evening twilight all week, but it's fading fast. About 40 or 50 minutes after sunset look for it low in the west, lower left or left of bright Venus. Mercury is 7° to the lower left of Venus on March 7th. They're 5½° apart at their wide conjunction on March 11th and 12th.

Mercury dwindles from magnitude –0.1 on March 7th to +1.6 on March 14th. By that date, binoculars will help as you look for it 6° to Venus's left.

Venus (magnitude –4.5, in Pisces) is the bright "Evening Star" in the west in twilight. It's dropping lower day by day, setting a half hour after twilight's end on March 7th, but when the last of twilight is still in progress on the 14th.

Venus now shows its most dramatic phase: a remarkably thin crescent in a telescope or good binoculars. It narrows from a mere 8% sunlit on March 7th to just 4% on March 14th. Get your telescope on it as early in twilight as you possibly can, before is sinks too deep into the bad low-altitude seeing. Better yet, locate it telescopically in the blue-sky daylight of late afternoon.

If you have unusually sharp or well-corrected vision, can you detect Venus's crescent shape with your naked eyes as twilight fades? See the March 3rd entry here last week.

Venus is on its way to passing a wide 8.4° north of the Sun at inferior conjunction on March 22nd.

Mars (about magnitude 0.0, in central Gemini) comes into view in twilight as a steady orange spark very high toward the south. It continues to fade as it shrinks into the distance.

As darkness deepens, watch for fainter Pollux and Castor (magnitudes 1.1 and 1.6) to emerge upper left of it. The triangle the three of them make is changing faster now, as Mars appears to accelerate away from the end of its retrograde loop. The triangle becomes an exact right triangle on March 15th.

For telescope users, Mars has shrunk to 10 arcseconds in diameter and is plainly gibbous (93% sunlit). A map of Mars's 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.

Mars on Feb. 15, 2025. Image by Christopher Go

Jupiter shines bright white (magnitude –2.2) in Taurus, 36° west along the ecliptic from Mars. Jupiter dominates the high southwest after dusk near Aldebaran and the Pleiades. The triangle it makes with them is becoming isosceles, with the Pleiades forming the triangle's long point.

Later in the evening Jupiter moves lower toward the west. It sets in the west-northwest around 2 a.m. daylight-saving time.

In a telescope Jupiter is about 38 arcseconds wide, smallish for Jupiter, as Earth far outpaces it in our faster motion around the Sun. For timetables of the doings of its Galilean moons and the meridian transits of its Great Red Spot, see the March Sky & Telescope, page 50.

Jupiter with Great Red Spot, Jan. 25, 2025

Saturn is hidden in conjunction with the Sun.

Uranus, magnitude 5.8 on the Taurus-Aries border, is still fairly high in 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 long gone 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. Eastern Daylight Time (EDT) is UT minus 4 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.

Pocket Sky Atlas cover, Jumbo edition

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