Saturn-Mar2021
Saturn, March 2021 (Chris Vaughan, Starry Night Education)

March 2021: Planets at a glance

This month, the old crescent Moon passes south of the pre-dawn planets from March 9-11, and Mars moseys between the Hyades and Pleiades.

Listen to the story

For those of you who like to listen to your stories, click below to hear Susan Trishel Monsøn reading Chris Vaughan’s summary of the planets movements this month.

Mercury

Mercury, March 2021 (Chris Vaughan, Starry Night Education)

The steeply dipping morning ecliptic will keep Mercury just above the eastern horizon during the pre-dawn throughout March, but it will only be observable by mid-northern latitude observers until about mid-month, with the best viewing time landing at 6 a.m. local time. (Meanwhile, the Southern Hemisphere will see the best Mercury apparition for 2021!)

The speedy planet will begin March positioned slightly above and between Jupiter and Saturn, pass within 20 arc-minutes to the north of much brighter Jupiter on March 5, and then reach peak visibility at greatest western elongation, 27 degrees from the Sun, on March 6. Viewed in a telescope during the month, Mercury will sport a disk that decreases in apparent diameter from 7.8 to 5.4 arc-seconds, and a phase that waxes from 48-per-cent to 85-per-cent illuminated. The slim crescent of the old Moon will pass well to the south of Mercury on March 10-11.

Venus

Venus, March 2021 (Chris Vaughan, Starry Night Education)

Venus will be too close to the Sun to see during March. The planet will pass the Sun at superior conjunction on March 26, and then Venus will enter the western evening sky for a lengthy stay.

Mars

Mars, March 2021 (Chris Vaughan, Starry Night Education)

Mars’ eastward orbital motion along the Ecliptic during March will keep it from sliding sunward with the rest of the stars, allowing us to view the planet from dusk until about midnight. In northern Taurus all month long, Mars will pass between the Hyades and Pleiades star clusters on the nights surrounding March 7-8. On those evenings Mars will appear with the Pleiades in binoculars. The bright, waxing crescent Moon will hop past Mars on March 18-19. A few nights later, Mars will pass only seven degrees north of a “twin,” Taurus’ bright, reddish star Aldebaran. Long past its prominence of October 2020, Mars continues to steadily fade in brightness and apparent size as Earth pulls away from it. It will shine at magnitude 0.9 on March 1 and fade to magnitude 1.3 on March 31. Over the same interval, its apparent disk size will decrease from 6.3 to 5.2 arc-seconds.

Jupiter

Jupter, March 2021 (Chris Vaughan, Starry Night Education)

Magnitude -2.0 Jupiter will shine in the east-southeastern pre-dawn sky during March – but the shallow morning ecliptic will keep the planet relatively low, even once it emerges from the morning twilight towards the end of the month. Jupiter and Saturn will both be traveling eastward within the boundaries of Capricornus in March – with fainter Saturn sitting 8-12 degrees to Jupiter’s (upper right) west. Fast-moving Mercury will pass 20 arc-minutes to the north of much brighter Jupiter on March 5. The old crescent Moon’s passage south of the pre-dawn planets from March 9-11 will make several lovely photo opportunities (especially for observers living at tropical latitudes where the Moon and planets will shine in a darker sky). Viewed in a telescope during March, Jupiter will exhibit a growing disk that spans about 34 arc-seconds.

Saturn

Saturn, March 2021 (Chris Vaughan, Starry Night Education)

During March, Saturn will shine in a darkened, east-southeastern pre-dawn sky, among the stars of western Capricornus, but the shallow morning Ecliptic will keep the ringed planet from climbing very high before sunrise. Magnitude-0.7 Saturn will rise at about 5:40 a.m. local time on March 1 and at 4:45 a.m. at month-end. Much brighter Jupiter will be positioned about 10 degrees to Saturn’s lower left (east), and speedy Mercury will move just above and between the gas giants during the first week of the month. The old crescent Moon’s passage south of the pre-dawn planets from March 9-11 will make several lovely photo opportunities (especially for observers living at tropical latitudes where the Moon and planets will shine in a darker sky). When viewed through a telescope, Saturn’s mean apparent disk size of 15.6 arc-seconds will increase slightly during March.

Uranus

During March, magnitude-5.8 Uranus will be slowly traveling eastward through the stars of southwestern Aries. It will be descending the western sky after dusk, making the blue-green planet an early evening target only. Telescope views of Uranus will show its tiny 3.5 arc-seconds-wide disk. On March 16, the waxing crescent Moon will shine 3.5 degrees to the southwest of Uranus. Note Uranus’ position about midway between the medium-bright stars Menkar (Alpha Ceti) and Sheratan (Beta Arietis) and search for it with binoculars, or even your unaided eyes, on a subsequent moonless night.

Neptune

Distant blue Neptune will be too close to the Sun for observing during March. After it passes the Sun at solar conjunction on March 10-11, it will eventually re-appear in the eastern pre-dawn sky.

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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