This month, take your choice: If you concentrate your viewing primarily during the evening hours you can admire Venus which attains its greatest angular distance from the sun and its highest altitude in its 8-year cycle of recurring evening apparitions. The blazing planet finishes the month just a couple of degrees shy of the Pleiades Star Cluster. On the other hand, if you confine your skywatching to the predawn hours, there are three bright planets (Mars, Jupiter and Saurn) that will engage in a planet pas du trois; the opening act of a show that will be staged by these performers, lasting to nearly the end of this year. Jupiter and Saturn come to conjunction once in 20 years (on average) and will spend much of 2020 slowly approaching each other, finally engaging in an amazing conjunction – the closest between the two in nearly four centuries – several days before Christmas.
Mars, meanwhile continues to approach Earth, brightening at a rather slow pace. But that increase in brightness will accelerate dramatically during spring and summer and by early fall the red planet will have shifted into our evening sky. Then millions will gaze at it, a fiery light high in our eastern sky less than 39 million miles away; a nearby world in space. NASA has recently suggested that perhaps by the year 2035, when Mars and Earth are exceptionally close again, people will be gazing at Earth from the surface of Mars. See: https://www.space.com/nasa-aims-for-2035-mars-landings-iac.html
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.
Planet Viewing Guide
Mercury—having passed inferior conjunction on February 26th, becomes a morning object in March. Binoculars are essential to find it during this unfavorable apparition for mid-northern observers. From March 10th through the 31st, Mercury rises in the east-southeast about an hour before the sun and brightens from magnitude +1.0 to +0.1. On the morning of the 23rd, Mercury pulls out to its greatest western elongation (maximum angular separation) of 27.8 degrees from the sun – about the maximum ever possible. This makes for a superb apparition for observers in the Southern Hemisphere. But at mid-northern latitudes, the +0.3 magnitude planet climbs just 5 degrees high in a bright twilight sky about 30 minutes before sunup and will likely require binoculars to glimpse.
Venus—in late March reaches the summit of a magnificent climb into the evening sky. The circumstances of its apparitions repeat themselves almost exactly every eight years, so this is the highest Venus has gotten in the evening since 2012; it won't do so again until 2028. Around sunset you should already be able to find it, gleaming like a speck of silver, roughly halfway up in the western sky. On the evening of March 24th, Venus attains its greatest angular separation from the sun, when it sets a full four hours after the sun for mid-northern observers. In a telescope, Venus typically appears exactly half illuminated a few days before a greatest evening elongation. Look for yourself and try to ascertain on which night the terminator (the line dividing light and dark on Venus) looks the straightest. On the 28th, although they are widely separated by nearly 8 degrees, Venus and a lovely crescent moon make for an eye-catching sight in the evening sky, the moon appearing to the far left of Venus. Notice also the Pleiades star cluster about 5 degrees above Venus. The brilliant planet is well below the Pleiades as March begins. But it is heading almost directly toward the cluster and is only a couple of degrees below it by month's end.
Earth—on March 19th, at 11:50 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. This is the earliest that the vernal equinox has occurred in 124 years.
Mars—rises about three hours ahead of the sun, and brightens from magnitude +1.1 to +0.8 during March. Meanwhile, the red planet moves 22 degrees eastward, from Sagittarius into Capricornus by the 31st. On the 18th, the late crescent moon will move into the planetary group. About two hours before sunrise, it will be below Mars, with the planet standing off its upper cusp, and Jupiter above and to the left. Slowly, the moon will move past Mars and toward Jupiter, but the rising sun will brighten the sky and cause Jupiter to disappear before the moon can pass it. Then, two mornings later, Mars skims just to the lower right of Jupiter and on the final day of the month, passes a similar distance from Saturn. The main reason for all this being that Mars moves rapidly eastward, while Jupiter and especially Saturn's motion are more sluggish.
Jupiter—like Mars, also rises a few hours before the sun but is best seen, especially in telescopes, as dawn is starting to break. At that hour the king-sized world shines fairly low in the southeast with the Teapot of Sagittarius to its right. On the morning of March 4th, about 90 minutes before sunrise, Mars, Jupiter and Saturn will be strung out diagonally in that order from upper right to lower left, low in the southeast sky, Jupiter equally spaced by 8 degrees from Mars and Saturn. During the balance of the month, the arrangement of these three worlds will noticeably change. On the 20th, for example, Mars and Jupiter are in conjunction; Mars passes 0.7 degrees to the lower right of the much brighter Jupiter. Finally, on the morning of March 26th, the three planets are equally spaced again but much closer together, Jupiter and Mars and Mars and Saturn each separated by only 3½ degrees; going from right to left: Jupiter, Mars and Saturn.
Saturn—quietly shifting from Sagittarius into Capricornus on the 21st, certainly deserves close examination as soon as it emerges from the glow of sunrise this month. Saturn rises about a half hour before the first light of dawn in early March, and nearly an hour and a half before at month's end. But its southern declination will keep it frustratingly low for northern observers. The best views will be after dawn begins, and the farther south you are the better. On the 31st, Mars finishes the month passing 0.9 degrees to the lower right of Saturn. They'll make for an eye-catching pair, partly because of their color contrast (Mars orange-yellow, Saturn yellow-white) and also because they are of nearly the same brightness: Mars is magnitude +0.8 while Saturn is +0.7.
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 in New York's lower Hudson Valley. Follow us on Twitter @Spacedotcom and on Facebook.