Mars was at opposition on 8 December 2022 and remains bright, prominent and beautiful to observe through a telescope in January 2023.

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However, things are changing and not for the better. Mars is currently in Taurus, shining at mag. –1.2 on 1 January, a bright orange beacon to the west of the Pleiades open star cluster.

Through the eyepiece it shows a 14-arcsecond disc and detail should be easily discernible through a 150mm or larger instrument at high powers.

Changes in the relative apparent size of Mars as it moves away this month. Credit: Pete Lawrence
Changes in the relative apparent size of Mars during January 2023. Credit: Pete Lawrence

It has a close encounter with a 91%-lit waxing Moon on the evening of 3 January, both objects appearing just 1.6° apart (centre-to-centre) at 19:15 UT.

After its closest approach to Earth on 1 December, Mars is now moving away, evidenced by a drop in brightness to mag. –0.7 on 15 January, showing an apparent size of 12 arcseconds.

By 31 January, Mars shines at mag. –0.3 and appears 10 arcseconds across through the eyepiece.

See Mars change direction in the night sky

A composite image showing the apparent reversal of Mars's movement in the night sky. Credit: Pete Lawrence
A composite image showing the apparent reversal of Mars's movement in the night sky. Credit: Pete Lawrence

The bright orange dot of Mars is easy to see and its colour is obvious to the naked eye.

It appears to move west against the distinctive stars of Taurus for the first week of January but this motion then becomes slow and hard to detect.

On 12 January the geometry of both Earth and Mars's orbits make it look as if the Red Planet reverses direction.

After this ‘stationary point’ Mars begins to head east among the stars once again.

Chart showing Mars's apparent motion in the sky, January 2023
Around 12 January 2023, Mars appears to stop then change direction to begin travelling east. Credit: Pete Lawrence

A westerly direction is referred to as retrograde; easterly prograde.

This opposition of Mars has presented the planet to us sideways-on, with both polar regions visible.

We should now see the large north polar hood (NPH) which shrouds the northern cap, start to break up, finally revealing the cap itself.

How to see the planets in January 2023

planets january 2023

Mars

  • Best time to see: 1 January, 21:54 UT
  • Altitude: 62°
  • Location: Taurus
  • Direction: South
  • Features: Albedo markings, polar caps, weather
  • Recommended equipment: 75mm or larger

Mercury

  • Best time to see: 31 January, 40 minutes before sunrise
  • Altitude: 3.4° (very low)
  • Location: Sagittarius
  • Direction: Southeast

Starts the month not far from bright Venus in the evening sky, but at mag. +1.6 on 1 January and dimming thereafter, Mercury is difficult to spot in the evening twilight. Inferior conjunction is on 7 January, with Mercury a morning object thereafter.

On 19 January it will be at mag. +0.5 with a slender 9%-lit waning crescent Moon 16° to the right as seen from the UK. Greatest western elongation on 30 January sees the planet 25° west of the Sun. It shines at mag. 0.0, rising 1.5 hours before sunrise on this date, visible low above the southeast horizon.

Venus

  • Best time to see: 31 January, 40 minutes after sunset
  • Altitude: 12°
  • Location: Aquarius
  • Direction: Southwest

A brilliant mag. –3.8, evening planet. On 1 January it is 5.6° from mag. +1.6 Mercury, setting 80 minutes after the Sun. Venus is close to Saturn on 22 January, the two worlds just 26 arcminutes apart at sunset. Saturn will be harder to see at mag. +0.8.

On the following evening, the pair now appear separated by just under 1°, with a beautiful 5%-lit waxing crescent Moon 5° to the southeast. By the end of the month, Venus sets 135 minutes after sunset.

Jupiter

  • Best time to see: 1 January, 17:30 UT
  • Altitude: 36°
  • Location: Pisces
  • Direction: South

Jupiter is best at the start of January, thereafter losing altitude as darkness falls. A waxing crescent Moon sits nearby on evenings of 25 and 26 January, mag. –2.1 Jupiter forming a striking sight with the Moon’s crescent.

Saturn

  • Best time to see: 1 January, 17:30 UT
  • Altitude: 15°
  • Location: Capricornus
  • Direction: Southwest

Evening planet not well-placed. At mag. +0.8, Saturn is joined by mag. –3.8 Venus on 21 and 22 January. By 31 January, the observational window for Saturn draws to a close.

Uranus

Best time to see: 1 January, 20:18 UT

Altitude: 53°

Location: Aries

Direction: South

Well-placed evening planet on the naked-eye threshold from a dark site. On 1 January at 22:30 UT, Uranus experiences a shallow occultation by the Moon’s southern edge, an event heavily influenced by location (for more info read our guide to the occultation of Uranus). Uranus is visible under dark sky conditions at its highest point, due south, most of the month.

Neptune

Best time to see: 1 January, 20:18 UT

Altitude: 31°

Location: Aquarius

Direction: South-southwest

Mag +7.9 Neptune is 8° west of mag –2.1 Jupiter on 1 January, this separation increasing to 12° by the month's end. A 20%-lit waxing crescent Moon sits between Jupiter and Neptune on the evening of 25 January, slightly south of the imaginary line between both planets.

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This guide originally appeared in the January 2023 issue of BBC Sky at Night Magazine.

Authors

Pete Lawrence, astronomer and BBC The Sky at Night presenter.
Pete LawrenceAstronomer and presenter

Pete Lawrence is an experienced astronomer and astrophotographer, and a presenter on BBC's The Sky at Night.