Our new year begins with Jupiter and Saturn still relatively close to each other after their "Great Conjunction" 10 days earlier.
Jupiter is readily seen shining brightly through the glow of evening twilight, while Saturn glows with only 1/10th of Jupiter's radiance and may be harder to see. Binoculars will certainly be beneficial in sighting it.
Mercury — about 2½ times dimmer than Jupiter, but four times brighter than Saturn — forms a tight triangle with them on Jan. 10, but stands only about 8 degrees above the west-southwest horizon a half hour after sunset. Make sure there are no tall obstructions (buildings or trees) in that direction if you hope to make a sighting. Yellow-orange Mars, still glowing bright at zero magnitude, will be in the vicinity of the moon on the evenings of Jan. 20 and 21.
Finally, the lone morning planet is Venus, dazzling as usual though now quite low in the twilight southeastern sky, which will lie near to a razor-thin crescent moon just prior to sunup on January 11.
In our schedule below, 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.
Mercury should make its first evening appearance of 2021 on the evening of Jan. 10, visible low in the afterglow of sunset, forming a triangle with Jupiter and Saturn. Look low near the west-southwest horizon about a half hour after sunset (see "Jupiter and Saturn" below). Two weeks later, on Jan. 24, Mercury is at greatest elongation, shining 18.6 degrees east of the sun.
From Jan. 21 to 28, you should see Mercury fairly easily if you look west-southwest from a spot with an unobstructed horizon, again about 30 minutes after sunset. At that time Mercury is at least 10 degrees above the horizon for observers around latitude 40 degrees north. If you keep watching as the sky grows darker, you may see that Mercury is flanked by the stars Fomalhaut far to its left and Altair even farther to its right, but at magnitude -0.5, the speedy planet is far brighter than either star.
Venus is coming to the end of what has been a spectacular morning apparition. Observers at mid-northern latitudes will see Venus around 10 degrees above the southeast horizon a half hour before sunrise on New Year's Day but only a couple of degrees above the horizon at the corresponding time on Jan. 31.
On the morning of Jan. 11, Venus shines 4 degrees to the left of a very thin crescent moon forming a spectacular pair very low in the southeast dawn twilight, 60 to 30 minutes before sunrise.
Earth will arrive at perihelion, its closest point to the sun in its orbit — a distance of 91,399,454 miles (147,093,163 km), on Jan. 2 at 8:51 a.m. EST
Mars, at the beginning of 2021, shines at magnitude -0.2 and crosses the meridian shortly after the end of evening twilight. During the first month of the year, the Red Planet shifts eastward through the constellation Aries, but loses nearly half of its brilliance, fading to magnitude +0.4 as its distance from us increases from 84.4 million to 110.9 million miles (135.8 million to 178.4 million km).
As darkness falls on the evening of Jan. 20, take note of yellow-orange Mars glowing 7½ degrees to the upper left of the first quarter moon. The next night, you'll see Mars a similar distance from the moon, but to its upper right.
Jupiter and Saturn
Jupiter and Saturn, the "Dynamic Planet Duo" of the summer and fall of 2020, will spend the second week of January in the vicinity of the smallest and closest planet to the sun — Mercury — and together will form a small, neat triangle low in the west-southwest sky at dusk on Jan. 10. Binoculars are strongly suggested as they will help pick up the planets against the bright twilight sky. Jupiter will be at the top of the triangle and is the brightest of the trio at magnitude -1.9, with Mercury (-0.9) and Saturn (+0.6) forming the base angles. The sides of the triangle each measure roughly 2 degrees.
This might be the last evening view of Jupiter and Saturn; while Mercury gets higher in the coming days, Jupiter and Saturn will be sinking into the sunset fires. Saturn will disappear first, followed by Jupiter by mid-month. Saturn is in conjunction with the sun on the Jan. 20 and Jupiter on Jan. 29 as both enter the morning sky.
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.