2021, January 15: Crescent Moon, Evening Planets

January 15, 2021:  The crescent moon, Mercury, and Jupiter group in the southwestern sky after sunset.  Mars is higher in the southeast near Beta Arietis.  The Red Planet is nearing a conjunction with Uranus.

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 7:16 a.m. CST; Sunset, 4:45 p.m. CST.  Check local sources for sunrise and sunset times for your location.

This evening, thirty minutes after sunset, the thin waxing moon is about 20° up in the southwest. 

Use the lunar crescent as a guide to locate Mercury, nearly 20° to the moon’s lower right. The planet is less than 10° in altitude.  If you have a clear look at the horizon, bright Jupiter is to Mercury’s lower right.

As the sky darkens further, Mars is high in the south-southeast.  The planet is dimming every few nights as Earth moves away from the Red Planet.

The Red Planet is parading eastward in Aries.  This evening the planet passes 7.3° to the lower left of Beta Arietis (β Ari on the chart), one of the three brightest stars in the constellation.  The trio is far from the ecliptic and any planet-star conjunctions are very wide.

This evening Mars is approaching the dimmer planet Uranus, that is at the limit of human eyesight and covered by the terrestrial illumination of bright city lights.  Use a binocular to see Uranus 2.8° to the lower left of Mars.

For scale the star 19 Arietis (19 Ari) is 2.2° to the upper left of Mars.  Use a binocular to gauge the separation from 19 Ari to Mars, then look nearly the same distance to the lower left of Mars to see the aquamarine star that is planet Uranus.  A telescope with magnifications around 100x should show the spherical nature of the distant world. Tonight, The planet’s distance from us is over 19 times the earth-sun distance.

Read about Mars during January.

Detailed Note: Thirty minutes after sunset. the moon (2.8d, 9%) is about 20° up in the southwest.  The crescent is about 18° to the upper left of bright Mercury.  The speedy planet is 5.8° to the upper left of Jupiter. In a darker sky and over 60° up in the south-southeast, the Red Planet passes 7.3° to the lower left of Beta Arietis (β Ari, m = 2.6).  The Red Planet is 2.2° to the lower right of 19 Arietis (19 Ari, m = 5.7) and 2.8° to the upper right of Uranus.

Read more about the planets during January.