2021, January 13: Evening Planets

January 13, 2021:  Mercury and Jupiter can be found in the west-southwest during bright evening twilight.  Mars is higher in the sky when the sky is darker.  It is nearing the planet Uranus.

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 7:16 a.m. CST; Sunset, 4:43 p.m. CST.  Check local sources for sunrise and sunset times for your location.

Mercury and Jupiter appear low in the west-southwest as night falls.  To the unaided eye, the planets appear as overly bright stars.

Thirty minutes after sunset, Jupiter is less than 5° in altitude.  Find a clear horizon to see them.  Mercury is over 3° to the upper left of brighter Jupiter.  This observation is difficult to make.  Use a binocular to initially spot these planets. Catch Jupiter before it leaves the evening sky.

As the sky darkens further, Mars is high in the south-southeast in a dim star field in Aries.  The planet passes the star Gamma Arietis (γ Ari on the chart).  The gap is wide, 6.0°, but γ Ari, Beta Arietis, and Hamal are the three brightest stars in the constellation.  The trio is far from the ecliptic, where the planets appear in the sky.

Mars is approaching dim Uranus.  The distant planet is at the limit of human eyesight, but not considered one of the “naked-eye planets.”  Use a binocular to find an aquamarine “star” 3.7° to the lower left of Mars.  The star 19 Arietis (19 Ari) is shown on the chart for scale.

A telescope needs about 100x magnification to see the planet’s spherical shape,

Mars passes the distant world in a week, although the moon is in the vicinity on that evening.

Read about Mars during January.

Detailed Note: Thirty minutes after sunset, Jupiter is over 4° in altitude above the west-southwest horizon, 3.3° to the lower right of Mercury. One hour after sunset, Mars (m = 0.1) is 6.0° to the lower left of γ Ari.  Look for the planet and the star over 60° up in the south-southeast. Uranus is 3.7° to the lower left of Mars.

Read more about the planets during January.