Since mid-February the evening sky has been adorned by two bright planets. That will come to an end after the first week of March when a rapidly fading Mercury falls into the sunset fires, leaving Mars — which itself is also dimming, albeit at a much slower pace — as the lone evening planet. Late in the month it will be passing below the Pleiades star cluster. About 2 to 3 hours after Mars disappears below the west-northwest horizon, Jupiter emerges into view low in the southeast. A couple of hours later, Saturn appears and then around the time that the dawn is breaking the night comes dazzling Venus. Finally, by month’s end Mercury too becomes a morning object, though it is very low to the east-southeast horizon and will be quite difficult to pick out against the brightening twilight sky.
In our schedule, remember that when measuring the angular separation between two celestial objects, your clenched fist held at arm’s length measures roughly 10-degrees. Here, we present a schedule below which provides some of the best planet viewing times as well directing you as to where to look to see them.
A Reminder: Daylight Saving Time returns on March 11th, the second Sunday in March. Except in the states of Arizona and Hawaii, and the Canadian province of Saskatchewan, clocks are to be moved forward one hour at 2:00 a.m. The mnemonic is: "Spring forward, Fall back."
Mercury will be visible in the western evening sky twilight for the first third of March while it descends sunward, completing its best appearance for 2019 for the Northern Hemisphere. The best viewing time will be around 7 p.m. local time. During this period the planet's apparent disk size will increase and its illuminated phase will decrease to a slim crescent. On March 7, look for the very young crescent moon sitting eight degrees to the left of Mercury. Following inferior conjunction on March 15, Mercury will enter the eastern pre-dawn sky — exhibiting a waxing crescent and becoming readily visible only towards month-end due to the very shallow morning ecliptic.
Mercury — starts this month as a +0.1-magnitude object that sets nearly due west 1½ hours after the sun. Moving rapidly toward inferior conjunction on March 14th, Mercury quickly drops lower into the sunset glow and during the first week of March fades by 0.3 magnitude per day. Mercury is still very hard to see low in the dawn by month's end.
Venus will spend March low in the eastern pre-dawn sky, slowly swinging eastward towards the sun. Over the course of the month, Venus' disk will shrink slightly in apparent diameter while its illuminated phase will grow from 72 percent to 81 percent. Between 5 a.m. local time and dawn on March 2, the slim crescent moon will be positioned 4.5 degrees to the right of Venus, making a lovely photo opportunity when composed with a foreground landscape.
Venus — is the bright "Morning Star" low in the east-southeast during dawn. It’s brilliant, as always, but it doesn't peek above the east-southeast horizon until around the start of morning twilight. In March its lead on the rising sun decreases slightly from 2 to 1¾ hours, and its magnitude dims slightly, from -4.1 to -4.0. It starts the month in Sagittarius, but on March 2nd it crosses over into the boundaries of Capricornus, then moves into Aquarius on the 25th. Also on the 2nd and you’ll find it glowing prominently about 5 degrees to the left of the crescent moon.
Earth – undergoes a change of season on March 20th. At 5:58 p.m. EDT the sun appears to cross the celestial equator moving north. Spring begins in the Northern Hemisphere and autumn begins in the Southern Hemisphere.
Mars will spend March in the western evening sky. It will be among the stars of Aries until March 23, when it will cross into Taurus. Mars' steady eastward motion has been counteracting the westward migration of the background stars. But by the end of the month, the arrival of later sunsets will require skywatchers to observe Mars while it is lower in the sky. During March, Mars will shrink slightly in apparent disk diameter and its brightness will decrease from magnitude 1.19 to 1.45. On March 11, the waxing crescent moon will be positioned a generous palm's width (7 degrees) to the left of Mars. On March 30, Mars will pass within three finger widths of the bright open star cluster known as the Pleiades (Messier 45), a sight best seen before 10 p.m. local time.
Mars — moves 18 degrees eastward during March, from Aries into Taurus. Late in the month the red planet will pass near the Pleiades. Spring comes to Mars's northern hemisphere this month only 3 days after it does to the same hemisphere of Earth. But Mars now appears so tiny in telescopes that most observers will see no details on the orange dot. On the evening of March 11th, Mars, which has faded to magnitude +1.3, appears as an orange-yellow star well to the right of a waxing crescent moon.
During March, very bright Jupiter (average magnitude -2.15) will rise in the hours after midnight and then move into the southern sky by dawn. Throughout the month, the planet will grow slightly brighter and larger in telescopes as Earth slowly draws closer to it in preparation for opposition in June. Jupiter will remain in southeastern Ophiuchus all month while slowly moving eastward. Several double shadow transit events will occur on Jupiter in March, including a very good one on March 25. On March 27, the waning gibbous moon will be positioned less than four degrees to the left of Jupiter. The duo will rise after 2:15 a.m. local time and remain observable until mid-morning, allowing Jupiter to be found in daylight using the moon as a reference.
Jupiter — reaches western quadrature (90 degrees west of the sun) on March 13th. This is when Jupiter's shadow is cast farthest west, facilitating observations of the planet's eclipses of its four bright satellites. The king of the planets, now at magnitude -2.1, comes up around 2:30 a.m. local daylight time. As morning twilight begins a few hours later, Jupiter stands more than a dozen degrees to the left of the ruddy 1st-magnitude star Antares. In the predawn southeast sky of March 27th, you will find Jupiter sitting a few degrees to the right of the moon.
Saturn will be observable in the southeastern pre-dawn sky during March, appearing as a yellowish, visual magnitude 0.6 object located to the left of the Teapot asterism of Sagittarius. Over the course of the month Saturn will rise earlier while it climbs away from the Sun. On March 1, the waning crescent moon will land three degrees to the upper right of yellowish Saturn. Later that same day, observers in most of Micronesia, northern Polynesia (except Hawaii), Central America, and Southern North America can see the moon occult Saturn in daylight. The moon will revisit Saturn on March 29, when the waning crescent moon will be positioned two degrees to the lower left of the ringed planet. Hours earlier, observers in the eastern edge of Brazil, southern Africa, Madagascar, the southern tip of India, and Sri Lanka can see the moon occult Saturn.
Saturn — a ringed bauble through a telescope, rises in the small hours of the morning and is fairly well-placed for observing just before dawn. Twice during this month, Saturn will have a rendezvous with the moon. Early on the morning of March 1st, after 4:30 a.m. local standard time, look low near the southeast horizon and you’ll see Saturn about 4 degrees to the lower left of a slender crescent moon. Then on the morning of March 29th, the moon and Saturn have a second March meeting with the ringed world, shining at magnitude +0.5, floating to the upper left of the moon.
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications, and he is also an on-camera meteorologist for Verizon FiOS1 News in New York's Lower Hudson Valley.