The year 2020 will evolve into the "Year of the Planets," with Venus soaring high into the western sky by late winter and early spring.
Mars will spend much of this year slowly approaching the Earth, finally arriving at opposition in early October and glowing like a fiery beacon high in our early fall skies. Jupiter and Saturn will approach each other during winter and early spring, closing to within 5 degrees of each other in May, before separating for the rest of the spring and the summer, before they again approach each other in September, ultimately squeezing together in December for their closest conjunction in nearly four centuries.
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More: The Night Sky This Month: January 2020 Guide
As for this month, Venus dazzles us in the southwest sky at sunset. Mercury begins appearing far below and to Venus's right during the final week of the month. Also during the finally week of January, Jupiter will emerge into view low in the southeast just prior to sunrise. Mars also can be seen in the southeast, rising about three hours before sunrise and hovering near its "rival," the ruddy star, Antares around the 18th. Saturn is the only planet "out of the loop" so to speak, arriving at conjunction with the sun near mid-month, and unobservable for all of January.
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 – is at superior conjunction on Jan. 10th. By the 24th this planet sets ¾ hour after the sun and at magnitude -1.1 should be easily located low in the west-southwest sky. By month's end it will be setting a full hour after the sun. On the 25th, about a half hour after sunset, use binoculars to scan low above the west-southwest horizon for the exceedingly thin arc that is a waxing crescent moon, only one day past new. And a couple of degrees to its immediate right will be Mercury.
Venus – the "goddess of love," doesn't set until about 2½ hours after the sun at the start of January, improving to 3 hours at month's end. During January it brightens a trace, from magnitude -4.0 to -4.1. In a telescope Venus is a dazzling but small gibbous disk, waning from 83% to 75% lit. On the evening of Jan. 28th, more than one-third up from the west-southwest horizon will be the two brightest objects in our night sky: a lovely crescent moon and situated well to its right, dazzling Venus.
Earth – will be closest to the sun for the year at 2:48 a.m. EST; a distance of 91,398,199 miles (147,091,143 km). We are 3.28 percent closer to the sun than we will be when the Earth is at aphelion next July 4th.
Mars – continues to dawdle in the predawn morning sky. On Jan. 18th, Mars will be passing less than 5 degrees to the upper left of its "rival," the 1st magnitude ruddy star Antares, with the star appearing nearly twice as bright as the red planet. Two mornings later, on the 20th, a rather striking isosceles triangle is formed using a lovely waning crescent moon, Mars and Antares. Mars is at the vertex angle, with the Mars/moon and Mars/Antares sides measuring 5 degrees in length. Antares and the moon form the base and are separated by 8 degrees. Mars is 189 million miles from Earth and still looks tiny in telescopes. But 2020 will be a great year for Mars, with the planet's disk looming nearly five times wider by early October and appearing 40 times brighter than it does now.
Jupiter – will be unobservable for the first three weeks of the New Year, but Jan. 22nd provides us with our first opportunity to this giant planet, finally emerging back into view, low in the morning twilight sky. About 40 minutes before sunrise look very low toward the southeast horizon for an exceedingly thin waning crescent moon; binoculars will certainly help. Once sighted, sweep about 8 degrees to its lower left and you should find Jupiter, evident through the bright twilight sky by virtue of its great brightness (magnitude -1.9).
Saturn – arrives at conjunction behind the sun on Jan. 13th and hence is invisible for this entire month.
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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.
