Planets of the Month: January 2023

by Erich Karkoschka

Venus is becoming a more obvious evening “star” since it sets past dusk by mid-month.
Saturn is higher in the southwest at dusk, but then gets passed by Venus on the 22nd at less than 0.4 degrees separation, the closest planet pair this year. The brightness difference of four magnitudes makes Saturn look unusually faint.
Jupiter follows higher with a transit (highest in the sky) just before sunset. On the 28th, Ganymede’s shadow is visible from sunset to 8:30 pm.
Uranus and Neptune are in the vicinity of Jupiter. Neptune is 8 degrees to the west of Jupiter, which is the current minimum. Uranus is 45 degrees to the east of Jupiter, but will get close to it this summer.
The month after a great occultation of Mars by the moon, we get another one with the same planet and very conveniently high in the evening sky. Mars will be occulted on the 30th from 9:44 to 10:51 pm, with the disappearance occurring at the dark limb so that the event is easy to watch naked eye. Disappearance and reappearance occurs gradually over some 15 seconds each time due to the 11 arc-second diameter of Mars. The reappearance is interesting to watch in a telescope.
Comet ZTF will get circumpolar at the end of the month and move at 6 degrees per day. Its brightness may peak at magnitude 5 at the last day of the month.