See what's up in the night sky for March 2021, including stargazing events and the moon's phases, in this Space.com gallery courtesy of Starry Night Software.
Monday, March 1 - Zodiacal Light (after dusk)
If you live in a location where the sky is free of light pollution, you might be able to spot the Zodiacal Light, which will appear during the two weeks that precede the new moon on Saturday, March 13. After the evening twilight has disappeared, you'll have about half an hour to check the western sky for a broad wedge of faint light extending upwards from the horizon and centered on the ecliptic (i.e., below Mars). That glow is the zodiacal light - sunlight scattered from countless small particles of material that populate the plane of our solar system. Don't confuse it with the brighter Milky Way, which extends upwards from the northwestern evening horizon at this time of year.
Wednesday, March 3 - Mars near the Pleiades (evening)
In the western sky on the evenings surrounding Wednesday, March 3, the eastward orbital motion (brown line) of the reddish planet Mars will carry it past the blue-white stars of the Pleiades star cluster, also known as Messier 45, the Seven Sisters, the Hole in the Sky, and Subaru. The planet and the cluster will be only a few finger widths apart for several nights, with Mars positioned to the lower left (or to the celestial south) of the Pleiades. They'll be close enough to easily fit Mars and the Pleiades within the field of view of your binoculars (red circle).
Thursday, March 4 - Minor planet Vesta at opposition (all night)
On Thursday, March 4, the Earth's orbital motion will carry us between the minor planet (4) Vesta and the sun. Because it will be opposite the sun in the sky, Vesta will be visible all night long, and shine at its brightest for the year (magnitude 5.8) - well within reach of binoculars (red circle) and small telescopes. Look for the asteroid in Leo, approximately one finger's width to the left (or 1 degree to the celestial northeast) of the bright star Chertan. Vesta will travel close to Chertan for a number of nights (red path with labeled dates:time).
Friday, March 5 - Mercury joins Jupiter (pre-dawn)
When the moon reaches its third quarter phase at 9:37 GMT (or 2:37 a.m. EST) on Wednesday, January 6, it will rise at about midnight, and then remain visible in the southern sky all morning. At third, or last, quarter the moon is illuminated on its western side, towards the pre-dawn Sun. Third quarter moons are positioned ahead of the Earth in our trip around the Sun. About 3½ hours later, Earth will occupy that same location in space. The week of dark, moonless evening skies that follow this phase will be ideal for observing deep sky targets.
Friday, March 5 - Third quarter moon (at 8:30 p.m. EST)
When the moon reaches its third quarter phase at 8:30 p.m. EST on Friday, March 5 (or 1:30 GMT on Saturday, March 6), it will rise in the middle of the night, and then remain visible in the southern sky all morning. At this phase the moon is half-illuminated, on its western side - towards the pre-dawn sun. Third quarter moons are positioned ahead of the Earth in our trip around the Sun. About 3½ hours later, Earth will occupy that same location in space. The ensuing week of moonless evening skies will be ideal for observing deep sky targets.
Saturday, March 6 - Mercury at greatest western elongation (pre-dawn)
On Saturday, March 6, Mercury will reach its widest angle of 27° west of the sun, and peak visibility for the current morning apparition. Look for the swiftly-moving planet shining very low in the east-southeastern sky, near brighter Jupiter, between about 5:45 and 6 a.m. in your local time zone. In a telescope (inset) Mercury will exhibit a 57%-illuminated, waxing gibbous phase. Mercury's position below the shallowly-dipping morning ecliptic (green line) will make this a poor apparition for mid-Northern latitude observers, but the best showing of 2021 for those located near the Equator, and farther south.
Tuesday, March 9 — Old moon meets Saturn (pre-dawn)
In the southeastern pre-dawn sky on Tuesday, March 9, the old crescent moon will begin a trip past the bright planets gathered there. When the moon rises it will be positioned less than a fist's diameter to the right (or 8 degrees to the celestial southwest) of magnitude 0.7 Saturn. By the time the sky begins to brighten at about 6 a.m., much brighter Jupiter, and then fainter Mercury, will have risen — forming a line to the lower left (east) of Saturn, and making a lovely photo opportunity when composed with some interesting landscape.
Wednesday, March 10 - Crescent moon near Saturn and Jupiter (pre-dawn)
The moon's visit with the bright morning planets will continue on Wednesday, March 10, when the slim crescent moon will shift east to sit below and between bright, magnitude -2.0 Jupiter and fainter Saturn. Because the moon will be riding 5 degrees south of the ecliptic, it will rise after Mercury joins the planet party. The scene will make another terrific photo opportunity, especially for observers viewing from more southerly latitudes — where the sun will be farther below the horizon and the moon will be higher.
Thursday, March 11- Old moon below Mercury (pre-dawn)
Observers viewing from southern latitudes will be able to see the old crescent moon complete its passage of the pre-dawn bright planets on Thursday, March 11. After the moon rises over the east-southeastern horizon, it will shine a palm's width below (or 6 degrees to the celestial southeast) of magnitude 0.0 Mercury — with much brighter Jupiter and slightly fainter Saturn forming a row to Mercury's upper right (west).
Saturday, March 13 - New moon (at 10:21 GMT)
At 5:21 a.m. EST, or 10:21 GMT, on Saturday, March 13, the moon will officially reach its new moon phase. While new, the moon is traveling between Earth and the sun. Since sunlight can only reach the far side of the moon, and the moon is in the same region of the sky as the sun, the moon becomes completely hidden from view for about a day. After the new moon phase Earth's celestial night-light will return to shine in the western evening sky.
Sunday, March 14 - Daylight Saving Time begins (at 2 a.m.)
For jurisdictions that employ Daylight Saving Time (DST), clocks should be set forward by one hour at 2 a.m. local time on Sunday, March 14. For stargazers, the time change, plus the fact that sunset occurs 1 minute later each day near the March equinox, will mean that dark-sky observing cannot commence until much later in the evening — possibly after the bedtime of junior astronomers. The difference from local time to Greenwich Mean Time (GMT), or the astronomers' Universal Time (UT), will be reduced by one hour when DST is in effect. Daylight Saving Time will end on November 7, 2021.
Tuesday, March 16 - Crescent moon near Uranus (evening)
In the western sky on Tuesday evening, March 16, the young crescent moon will be positioned several finger widths to the lower left (or 3.5 degrees to the celestial southwest) of the planet Uranus — allowing both objects to share the field of view of binoculars (red circle). Normally, visits by the moon make seeing magnitude 5.8 Uranus more difficult — but the 12%-illuminated crescent moon won't be excessively bright. Alternatively, note the brighter stars near the moon that night, such as Menkar in Cetus (to the moon's upper left) and Hamal and Sheratan in Aries (to the moon's upper right) and then use them to locate slow-moving Uranus on a subsequent moonless night.
Friday, March 19 - Moon and Mars (evening)
In the southwestern sky after dusk on Friday, March 19, look for the reddish, medium-bright dot of Mars shining several finger widths to the lower right (or 3 degrees to the celestial northwest) of the waxing crescent moon. The two objects will appear together in the field of view of your binoculars (red circle). The duo will set together in the west after about 1 a.m. local time.
Saturday, March 20 - Equinox (at 9:37 GMT)
On Saturday, March 20 at 9:37 GMT (or 5:37 a.m. EDT) the sun will cross the celestial equator traveling north, marking the vernal equinox in the northern hemisphere and the beginning of northern spring. Days and nights will be of equal length on that day, and the sun will rise due east and set due west.
Saturday, March 20 - View the "Lunar X" (at 22:30 GMT)
Several times a year, for a few hours near its first quarter phase, a feature on the moon called the Lunar X becomes visible in strong binoculars and backyard telescopes. When the rims of the craters Purbach, la Caille, and Blanchinus are illuminated from a particular angle of sunlight, they form a small, but very obvious X-shape. The Lunar X is located near the terminator, about one third of the way up from the southern pole of the Moon (at 2° East, 24° South). The 'X' is predicted to peak in intensity at about 6:30 p.m. EDT on Saturday, March 20. That will be in waning daylight for observers in the eastern Americas - but you can observe the moon in a telescope during daytime, if you take care to avoid the sun. The 'X' will persist until about 8 p.m. EDT. This event should be visible anywhere on Earth where the moon is shining, especially in a dark sky, between 21:00 and 23:59 GMT.
Sunday, March 21- First quarter moon near Messier 35 (at 14:40 GMT)
When the moon completes the first quarter of its orbit around Earth at 10:40 a.m. EDT (or 14:40 GMT) on Sunday, March 21, the relative positions of the Earth, sun, and moon will cause us to see it half-illuminated - on its eastern side. At first quarter, the moon always rises around noon and sets around midnight, so it is also visible in the afternoon daytime sky. The evenings surrounding first quarter are the best for seeing the lunar terrain when it is dramatically lit by low-angled sunlight. By the time the sky fully darkens in the Americas, the moon's eastward orbital motion (green line) will have carried it about four finger widths to the upper left (or 4 degrees east) of the prominent open star cluster in Gemini known as Messier 35 or the Shoe-Buckle Cluster. That cluster's stars, which are visible in binoculars (red circle), are located to the right of Tejat and Propus, the medium-bright stars that mark Castor's toes.
Monday, March 22 - Mars and Aldebaran (evening)
In the western sky on the nights surrounding March 20, Mars' eastern motion along the ecliptic will carry it past a "twin", the bright, reddish star Aldebaran in Taurus. Mars will outshine the star only slightly, and their colors will be very similar. During the period of closest approach, around March 18-22, the pair will be separated by 7 degrees, with Mars on the upper right (northerly) side of the star. Mars' better-known twin is the star Antares, the "rival of Mars", in Scorpius.
Wednesday, March 24 - Sinus Iridum's Golden Handle (all night)
On Wednesday night, March 24, the pole-to-pole terminator that divides the lit and dark hemispheres of the waxing gibbous moon will fall to the left (or lunar west) of Sinus Iridum, the Bay of Rainbows. The circular, 155 mile (249 km) diameter feature is a large impact crater that was partly flooded by the same basalts that filled the much larger Mare Imbrium to its right (lunar east). The "Golden Handle" is produced because slanted sunlight is brightening the eastern (right-hand) side of the prominent, curved Montes Jura mountain range (the old crater rim) that surrounds the bay on the top and left (north and west). The rim extends into Mare Imbrium as a pair of protruding promontories named Heraclides and Laplace at the bottom and top, respectively. You can see the feature with sharp eyes - and easily in binoculars and backyard telescopes. Sinus Iridum is almost craterless, but hosts a set of northeast-oriented dorsae or "wrinkle ridges" that are revealed under magnification at this phase.
Friday, March 26 - Comparing the twins (evening)
While the moon is bright and the planets are absent, skywatchers can still enjoy viewing bright stars. The twin stars of Gemini, Castor and Pollux, shine high in the western sky after dusk. A closer look with your unaided eyes will reveal that the twins are quite dissimilar. The left-hand (easterly) star Pollux is nearly twice as bright as sibling Castor to its right (west). Pollux' K0 spectral class gives it a warmer color than white, A1-class Castor. In a backyard telescope Castor is revealed to be a delightful multiple star system, with several fainter companions distributed around a bright, close-together pair.
Sunday, March 28 - Full Worm Moon (at 18:48 GMT)
The March full moon, known as the Worm Moon, Crow Moon, Sap Moon or Lenten Moon, always shines in or near the stars of Leo. Full moons always rise in the east as the sun sets, and set in the west at sunrise. When fully illuminated, the moon's geology is enhanced, especially the contrast between the ancient cratered highlands and the younger smoother maria. This full moon is occurring 1.5 days before perigee, the point in the moon's orbit when it is closest to Earth, making this the first of four consecutive supermoons in 2021.
Tuesday, March 30 - Zodiacal Light Again (after dusk)
At the end of March we receive another opportunity to view the Zodiacal Light - if you live in a location where the sky is free of light pollution. After the evening twilight has disappeared, you'll have about half an hour to check the western sky for a broad wedge of faint light extending upwards from the horizon and centered on the ecliptic (i.e., below Mars). The viewing period will end with the new moon on April 11.