March opens with a spectacular pairing of the two brightest planets at dusk, Venus and Jupiter.
They appear closest to each other, just a half-degree apart—about the apparent width of the moon’s disk—on Wednesday, March 1. They’re still 11-12° above the western horizon at nightfall, as twilight ends, nearly an hour and a half after sunset. If mountains don’t block your view, you’ll catch the brilliant pair in a dark sky—a truly impressive sight! Their background stars of Pisces, the Fishes, are no brighter than third magnitude, compared to Venus at magnitude -4, and Jupiter at -2, so the planets will really stand out!
Celebrate spring 2023 on your early evening strolls. Enjoy observing the changing positions of the moon and four evening planets against the background of the zodiac constellations.
The gibbous moon, about three-quarters full on March 1, is in the constellation Gemini, 90 degrees east of the planet pair that evening. Note the “Twin” stars Pollux and Castor, 4.5° apart, about 10-11° east of the moon on March 1. Mars, of magnitude +0.4 in Taurus, is about 22-23° west of the moon, or one-quarter of the way from the moon back toward the Venus-Jupiter pair. Taurus includes some beautiful star fields for binoculars: Aldebaran and the Hyades cluster, making a V-shaped pattern representing the head of the Bull; and the compact Pleiades, or Seven Sisters star cluster. Just 4.5° from Mars on March 1—same as the separation between Pollux and Castor—is the 1.7-magnitude star Elnath, marking the tip of the Bull’s northern horn.
Watch nightly for changes of the moon and planets. The moon, in a more distant part of its orbit in early March, is moving at a somewhat leisurely pace of 12° per day, compared to its average rate of 13.2°. But that’s still much faster than the planets! Venus in March is shifting its position against the background stars by 1.2° per day; Jupiter by 0.2°; and Mars by 0.4-0.5° daily.
On the evening of Thursday, March 2, the moon will pass within 2° south of Pollux, while the Venus-Jupiter pair will be separated by 1°. On each successive evening, Jupiter appears lower, with Venus a little higher.
By Friday evening, March 3, Venus and Jupiter are 2° apart, and the moon is in Cancer, the Crab, 13-16° below the bright Twin stars of Gemini. Look for the star Regulus, heart of Leo, the Lion, in the eastern sky, 24° below the moon. Do you notice any change in the separation between Mars and the star marking the tip of the horn of Taurus? They’re now within 4° apart, a little closer than the Pollux-Castor pair.
On Saturday, March 4, at dusk, the bright planets are nearly 3° apart, and the moon has moved closer to Regulus. On March 5, Venus-Jupiter are nearly 4° apart, and the moon, now 98 percent full, passes just 4° to the north of Regulus.
On March 6, you can still catch the moon rising a little north of east shortly before sunset—but this is the last day you can do so. As the sky darkens, look for Regulus within 13° to the upper right of the moon. Venus and Jupiter are nearly 5° apart in the west. The moon is full overnight, reaching opposition to the sun at 4:40 a.m. on Tuesday, March 7.
On March 7 at dusk, Venus and Jupiter are nearly 6° apart. The moon, technically past full, rises in twilight, not long after sunset. You can start following the waning moon in the morning sky.
On March 8 at dusk, Venus-Jupiter are nearly 7° apart, and the gap between them continues to widen by nearly an additional degree daily. On this and the next two evenings, Mars and Elnath appear just 3.1° apart, their least separation.
While you’re out watching the evening planets, be sure to check out the collection of bright seasonal stars. Beginning in the southern sky with blue-white Sirius, at magnitude -1.4 the brightest—but not as bright as Venus or Jupiter—go in clockwise order around the large oval, sometimes called the Winter Ellipse: Sirius, Procyon, Pollux and Castor, Capella, Aldebaran, Rigel (Orion’s foot) and back to Sirius. Betelgeuse (Orion’s shoulder) and Mars are inside the oval. Orion’s three-star belt, midway between Rigel and Betelgeuse, points toward Sirius in one direction, and toward Aldebaran and the Pleiades in the other. Note the triangle of three reddish objects—Mars, Betelgeuse and Aldebaran.
If you happen to be in a very dark place, with little light pollution, look toward the western sky as twilight ends on clear evenings during March 10-22; that would be about 1.5 hours after sunset. Look for a huge, faint pyramid of light, with its nearly vertical axis along the ecliptic or centerline of the zodiac—roughly a line from Venus toward Mars—broader and brighter near its base and near its axis, and tapering off higher in the sky. You might want to block Venus with your hand or with a tree. It’s the Zodiacal Light, from sunlight reflecting off dust particles in the inner solar system.
We’ll come back to the evening sky when the moon returns on March 22. Keep track of Jupiter until then, because it will come in handy to locate the thin returning lunar crescent, and a few days later, the innermost planet, Mercury, emerging from the far side of the sun.
After the switch to daylight saving time on Sunday, March 12, you won’t have to get up so early to see a dark predawn sky. Use the morning twilight chart below about an hour before sunrise to find these six bright stars: the Summer Triangle of Vega, Altair, and Deneb well up in the east; reddish Antares, heart of the Scorpion, in the south; and golden Arcturus, high in the southwest, with blue-white Spica, spike of grain in the hand of Virgo, below. Watch the waning moon pass above Spica on March 10, and hopscotch from west of Antares to east of it on March 13-14. By March 18, Saturn emerges very low in the east-southeast, 17-18° to the lower left of a 14 percent crescent moon. On Sunday, March 19, the old, 7 percent crescent moon appears 2° to the lower right of 0.9-magnitude Saturn.
On Monday, March 20, as the sun passes from south to north of the equator at 2:24 p.m., spring begins in Earth’s northern hemisphere.
By March 22, three weeks have elapsed since the close pairing of Venus and Jupiter on March 1. Look in the west about 30-40 minutes after sunset for the thin, 3 percent crescent moon, within 18° to the lower right of Venus. Jupiter will be 2-3° to the lower right of the moon. Tonight’s crescent moon marks the beginning of the month of Ramadan for followers of Islam: One month of daily fasting from sunrise to sunset begins on Thursday. Continue to track departing Jupiter, because in a few days, it will help you locate emerging Mercury.
Follow the moon daily at dusk, and watch for these events: On March 23, the moon is 5° below Venus; it’s 7° above Venus on March 24. On March 25, the moon is within 2° south of Pleiades. On March 26, the moon is 9° north of Aldebaran and 17-18° west of Mars; Mars has crossed from Taurus into Gemini.
On March 27, Mercury (magnitude -1.4) passes 1.3° north (to the right) of Jupiter. Look for the pair 25° to the lower right of Venus. Mars is within 6° to the upper left of the moon, now a fat crescent, 41 percent full. On March 28, Mars is within 7° to the lower right of the first quarter moon, which is half full and 90 degrees, or one quarter-circle east of the sun. Jupiter, now 2° to the lower left of Mercury, appears lower each evening and will soon disappear into the sun’s glare. Mercury appears a little higher each night, until April 11, when it reaches its best position in the evening sky for this year.
On March 29, the moon is 3-5° from the Twin stars, Pollux and Castor. Can you still spot Jupiter, 3.5° to the lower right of Mercury? At nightfall, using binoculars, try for sixth-magnitude Uranus, 1.5° to the upper left of Venus. On March 30, the moon, 69 percent full, is 9-13° east of the Twins. Using binoculars at nightfall, try for Uranus within 1.3° to the lower left of Venus.
Illustrations of many of the events described here, including nightly views following the March 1 conjunction of Venus-Jupiter, appear on the March 2023 Sky Calendar. Subscription info and a sample issue are available at www.abramsplanetarium.org/skycalendar.
Robert Victor originated the Abrams Planetarium monthly Sky Calendar in October 1968 and still produces issues occasionally. He enjoys being outdoors sharing the wonders of the night sky. Robert Miller, who provided the twilight charts, did graduate work in planetarium science and later astronomy and computer science at Michigan State University, and remains active in research and public outreach in astronomy.