Venus, January 2023. (Chris Vaughan and Starry Night Education) | SkyNews
Venus, January 2023. (Chris Vaughan and Starry Night Education)

Planets at a Glance: January 2023

Weather permitting, January should provide skywatchers with a good to decent opportunity to view the planets this month.

What planetary events are coming up in the night sky? Read about Venus, Mercury, Mars, Jupiter, Saturn, Uranus and Neptune and what’s going on in our Solar System in Planets at a Glance.

Mercury 

Mercury, January 2023. (Chris Vaughan and Starry Night Education) | SkyNews
Mercury, January 2023. (Chris Vaughan and Starry Night Education)

For the first several days of January, Mercury will be visible with increasing difficulty just above the west-southwestern sky as it departs from much brighter Venus and drops sunward. In a telescope it will display a waning crescent phase. Mercury will pass the Sun at inferior conjunction on January 7 and become observable in the eastern predawn sky after mid-month. 

On January 18, Mercury will end a westerly retrograde loop. The following morning, the old crescent Moon will shine 14.5 degrees to its southwest. On January 30, Mercury will achieve greatest western elongation, 25 degrees from the Sun, and maximum visibility. 

With Mercury positioned close to the tilted morning ecliptic, the appearance of the planet will be relatively good for both Northern and Southern Hemisphere observers. 

The optimal viewing times at mid-northern latitudes will start around 6:15 a.m. local time. Viewed in a telescope that day, the planet will exhibit a waxing, slightly gibbous phase, with the medium-bright star Omicron Sagittarii shining close by. Only turn your optics towards Mercury if the Sun is completely below the horizon. 

Venus

Venus, January 2023. (Chris Vaughan and Starry Night Education) | SkyNews
Venus, January 2023. (Chris Vaughan and Starry Night Education)

Venus will remain a feature of the southwestern evening sky during January. Its steadily widening elongation from the Sun, and the steeper tilt of the ecliptic, will lift the brilliant, magnitude -3.8 planet higher into the sky after sunset. 

Venus will speed eastward through the stars of Capricornus from January 2-23, passing close to some of the Sea-Goat’s brighter stars from January 13-21. Venus will pass Saturn in an extremely close conjunction on the evenings surrounding January 22, when they will be separated by only 20 arcminutes. On January 28, it will cross into Aquarius. 

Viewed in a telescope this month, Venus will exhibit a nearly fully-illuminated disk that will grow from 10.4 to 11.1 arcseconds over the month. The very young crescent Moon will shine below (southwest) and to the upper left (east) of Venus-Saturn on January 22 and 23 respectively, making a lovely photo opportunity. 

Mars

Mars, January 2023. (Chris Vaughan and Starry Night Education) | SkyNews
Mars, January 2023. (Chris Vaughan and Starry Night Education)

Mars will spend January in central Taurus, positioned about eight degrees north of its bright reddish star Aldebaran. A month after its opposition, Mars remains an all-night target, although its apparent brightness will halve from magnitude -1.19 to -0.26 over the month. 

On January 12, Mars’ westerly retrograde motion towards the Pleiades cluster will slow to a stop. After that date, Mars will resume its regular eastward prograde motion at an accelerating pace. Telescope views of Mars during January will display its pale ruddy disk with darker surface features. Its size will shrink dramatically from 14.5 to 10.7 arcseconds, and it will wane in illuminated phase from 97 per cent to 92 per cent — all due to Earth’s increasing distance from the planet. 

The waxing gibbous Moon will shine two degrees east of Mars on January 3, and return to sit a similar distance to its west on January 30. 

Jupiter

Jupiter, January 2023. (Chris Vaughan and Starry Night Education) | SkyNews
Jupiter, January 2023. (Chris Vaughan and Starry Night Education)

Jupiter will be observable during early evenings in January. However, by the end of the month its bright white point of light will be descending the western sky at dusk, shortening the telescope-viewing window. 

The magnitude -2.3 planet will decrease slightly in apparent brightness as it slides steadily eastward through western Pisces. Its distance to the east of much fainter Neptune will increase from 8.5 to 12.6 degrees. The asteroids Juno and Vesta will chase Jupiter along a parallel track running six degrees to Jupiter’s south. Juno, the more easterly of the pair, will overtake Jupiter around mid-month. 

In a backyard telescope, Jupiter will exhibit dark equatorial bands across a disk that diminishes in size from 39.2 to 36.1 arcseconds. The Great Red Spot will appear every second or third night, and Jupiter’s four large Galilean satellites will eclipse and occult one another, and cast round, black shadows on the planet on January 2, 5, 12, and 25. 

On the evening of January 6, observers with telescopes in southern and eastern Asia and south to western Australia can watch the shadows of Ganymede and Io slide across that planet’s disk together for 102 minutes. The waxing crescent Moon will shine several degrees to the southwest of Jupiter on January 25. 

Saturn

Saturn, January 2023. (Chris Vaughan and Starry Night Education) | SkyNews
Saturn, January 2023. (Chris Vaughan and Starry Night Education)

Saturn will shine above the southwestern horizon after sunset during January. At the beginning of the month, its yellow-tinted magnitude 0.8 dot will form a small triangle to the right (northwest) of the medium-bright stars Deneb Algedi and Nashira, which form the tail of Capricornus, the Sea-Goat. 

Viewed in a telescope early in the month, Saturn will show an apparent disk diameter of 15.5 arcseconds. Its rings will subtend more than double that span. Saturn’s motion sunward will reduce its elongation from 42 to 14 degrees over the course of month, causing the planet to end January shining in twilight just above the horizon near Venus. Venus will pass Saturn in an extremely close conjunction on the evenings surrounding January 22, when they will be separated by only 20 arcminutes. Then Saturn will drop lower. 

The very young crescent Moon will shine below (southwest) and to the upper left (east) of Venus-Saturn on January 22 and 23 respectively, making a lovely photo opportunity. 

Uranus

Uranus, January 2023. (Chris Vaughan and Starry Night Education) | SkyNews
Uranus, January 2023. (Chris Vaughan and Starry Night Education)

The blue-green, magnitude 5.7 planet Uranus will be observable nearly all night long this month. The planet’s 3.7 arcseconds-wide disk will be most easily resolved in telescopes during early evenings, when it will be highest in the sky. The planet’s westerly retrograde motion through southern Aries will slow until it becomes stationary on January 22-23. After that, Uranus will slowly begin to move east again. 

On the evening of January 1 in the Americas, the waxing gibbous Moon will shine just to the east of Uranus. For observers in the Canadian Maritimes and eastward across Greenland, Iceland, most of northern Europe, and most of northern and western Russia, the Moon will have occulted Uranus starting around 21:00 GMT. 

The half-illuminated Moon will return to the west of Uranus on January 28. Observers in Alaska, far northern Canada, Svalbard, and Greenland can see the Moon occult Uranus starting around 04:30 GMT on January 29. On nights when the Moon is not as close, Uranus can be found using binoculars. To spot it, look a generous fist’s width to the lower left (or 12.5 degrees southeast of) Aries’ brightest star Hamal and only a palm’s width north of the star Mu Ceti. 

Neptune

Neptune, January 2023. (Chris Vaughan and Starry Night Education) | SkyNews
Neptune, January 2023. (Chris Vaughan and Starry Night Education)

In January, the distant, blue planet Neptune will be observable during early evenings as a magnitude 7.9 speck creeping slowly eastward in northeastern Aquarius, near that constellation’s border with Pisces. To aid your search, Neptune will be located between far brighter Jupiter and the medium-bright star Phi Aquarii, which will shine 5.6 degrees to Neptune’s west-southwest. Over the month, Jupiter’s position to the northeast of Neptune will increase from from 8.5 to 12.6 degrees. In a telescope, Neptune’s tiny apparent disk size will span 2.2 arcseconds. 

Chris Vaughan is a science writer, geophysicist, astronomer, planetary scientist and an “outreach RASCal.” He writes Astronomy Skylights, and you can follow him on Twitter at @astrogeoguy. He can also bring his Digital Starlab portable inflatable planetarium to your school or other daytime or evening event. Contact him through AstroGeo.ca to tour the Universe together.

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