Our celestial neighbourhood in March

PICK OF THE MONTH: Venus

Best time to see: 1 March, 40 minutes before sunrise
Altitude: 10˚ (low)
Location: Sagittarius Direction: Southeast Features: Phase, faint shaded markings.
Recommended equipment: 75mm, or larger

Venus is a morning object at present, rising a couple of hours before the Sun at the month’s start and 80 minutes before the Sun at the end. The planet reaches dichotomy this month, passing from crescent through to gibbous phase. Dichotomy is the term used to indicate when a planet (or the Moon) reaches the 50 per cent phase. This month, dichotomy should occur on 21 March, but due to what’s known as the ‘phase anomaly’, through the eyepiece of a telescope Venus will appear half-lit a few days later than this theoretical prediction. The phase anomaly is believed to be caused by how the planet’s thick atmosphere scatters sunlight. Take a look through a telescope and make an estimate of the phase in the run up towards and beyond the 21st.

Venus drops in brightness over March, but only by a fifth of a magnitude. On the 1st this most brilliant of planets appears to shine at mag. –4.4. On the 31st, at mag. –4.2, Venus will still look intense against the morning’s dawn twilight. It appears best at the month’s start with a darker sky.

Mars and Saturn appear close to Venus. Saturn will be too close to the Sun to see properly at the month’s start, but it will be visible with Venus and Mars at the month’s end. On the 25th, Venus sits 4.6˚ from mag. +1.1 gain much altitude above the southeast horizon as sunrise approaches. An 18%-lit Mars, and 4.1˚ from +0.9 Saturn, but the squat triangle formed by the three fails to waning crescent Moon lies below the trio on the morning of the 28th.

Mercury

Mercury is a morning planet, not well placed at the start of March. On the 1st it shines at mag. –0.1, lies 2˚ southwest of mag. +0.9 Saturn and rises 30 minutes before the Sun. That offset deteriorates over the following days, and as a consequence, from the UK at least, Mercury is unlikely to be seen with the naked eye over the rest of the month.

Mars

Best time to see: 31 March, 50 minutes before sunrise
Altitude: 3˚ (very low)
Location: Capricornus
Direction: Southeast

Mars is visible in the morning sky as a mag. +1.3 object rising 90 minutes before the Sun on the 1st, when it appears 5˚ below mag. –4.4 Venus. Over the next few mornings, Mars and Venus appear to converge, both planets appearing separated by just 4˚ on the 12th. A lovely, albeit rather low, triangular grouping of Mars, Venus and Saturn can be seen low above the southeast horizon 40 minutes prior to sunrise on the 24th. By the 31st, Mars will have brightened to mag. +1.1 and rises 80 minutes before the Sun. The Mars, Saturn and Venus triangle will be contained to an area less than 6˚ across on 31 March.

Through an eyepiece Mars is a bit disappointing, appearing to have an apparent diameter of 5 arcseconds at the month’s end. However, this will change during the year as Mars approaches opposition in early December 2022.

Jupiter

Jupiter reaches solar conjunction on 5 March and despite drawing away from the Sun’s position rapidly, is unlikely to be seen this month. On 31 March, mag. –1.9 Jupiter rises just 20 minutes before the Sun.

Saturn

Best time to see: 31 March, 50 minutes before sunrise
Altitude: 3˚ (very low)
Location: Capricornus
Direction: East-southeast

Saturn is a morning planet, slowly crawling away from the Sun during the month. Its placement in the sky isn’t very optimal at present, the planet not gaining much altitude despite rising at a reasonable time before the Sun. If you have a flat southeast horizon, look out for mag. +0.9 Saturn, mag. +1.1 Mars and mag. -4.2 Venus together between 22–31 March. A thin, 18%-lit waning crescent Moon sits below the trio on the morning of the 28th.

Uranus

Best time to see: 1 March, 19:50 UT
Altitude: 33˚
Location: Aries
Direction: West-southwest

Mag. +7.9 Uranus may be seen 30˚ above the west-southwest horizon as true darkness arrives on the 1st. A 17%-lit waxing crescent Moon sits 6.5˚ to the southwest of Uranus on the evening of the 6th, and as a 25%-lit waxing crescent, 6˚ to the planet’s east on the 7th. By mid-March, Uranus appears a fraction over 20˚ up above the western horizon as true darkness descends, but by the month’s end it falls to just 8˚. As a result, March marks the end of the current observational window for this distant world.

Neptune

Neptune is in conjunction with the Sun on 13 March; consequently, the planet is not visible this month.

More ONLINE

Print out observing forms for recording planetary events

The planets in March

The phase and relative sizes of the planets this month. Each planet is shown with south at the top, to show its orientation through a telescope

Jupiter’s moons: March

Using a small scope you can spot Jupiter’s biggest moons. Their positions change dramatically during the month, as shown on the diagram. The line by each date represents 00:00 UT.