Mars near the Pleiades (Chris Vaughan, Starry Night Education)

This Week’s Sky: March 1 to 7, 2021

As the Moon wanes into the week, catch Mars passing the Pleiades on Wednesday and Mercury joining Jupiter pre-dawn on Friday.

Monday, March 1 – Zodiacal light (after dusk)

Zodiacal light (Chris Vaughan, Starry Night Education)

If you live in a location where the sky is free of light pollution, you might be able to spot the zodiacal light, which will appear during the two weeks that precede the new Moon on Saturday, March 13. After the evening twilight has disappeared, you’ll have about half an hour to check the western sky for a broad wedge of faint light extending upwards from the horizon and centred on the Ecliptic (i.e. below Mars). That glow is the zodiacal light — sunlight scattered from countless small particles of material that populate the plane of our Solar System. Don’t confuse it with the brighter Milky Way, which extends upwards from the northwestern evening horizon at this time of year.

Read “How do I see the zodiacal light?” by Elizabeth Howell

Wednesday, March 3 – Mars near the Pleiades (evening)

Mars near the Pleiades (Chris Vaughan, Starry Night Education)

In the western sky on the evenings surrounding Wednesday, March 3, the eastward orbital motion (brown line) of the reddish planet Mars will carry it past the blue-white stars of the Pleiades star cluster, also known as Messier 45, the Seven Sisters, the Hole in the Sky and Subaru. The planet and the cluster will be only a few finger widths apart for several nights, with Mars positioned to the lower left (or to the celestial south) of the Pleiades. They’ll be close enough to easily fit Mars and the Pleiades within the field of view of your binoculars (red circle).

Thursday, March 4 – Minor planet Vesta at opposition (all night)

Minor planet Vesta at opposition (Chris Vaughan, Starry Night Education)

On Thursday, March 4, the Earth’s orbital motion will carry us between the minor planet (4) Vesta and the Sun. Because it will be opposite the Sun in the sky, Vesta will be visible all night long, and shine at its brightest for the year (magnitude 5.8). It will be well within reach of binoculars (red circle) and small telescopes. Look for the asteroid in Leo, approximately one finger’s width to the left (or 1 degree to the celestial northeast) of the bright star Chertan. Vesta will travel close to Chertan for more than a week (red path with labeled dates:time).

Friday, March 5 – Mercury joins Jupiter (pre-dawn)

Mercury joins Jupiter (Chris Vaughan, Starry Night Education)

On the mornings surrounding Friday, March 5, the speedy planet Mercury will move close to much brighter Jupiter. Look for the duo sitting low over the east-southeastern horizon after they rise together at about 5:15 a.m. local time. At closest approach on Friday morning, Mercury will be located about 20 arc-minutes to the upper left (or celestial north) of Jupiter, allowing both planets to appear together in the eyepiece of a backyard telescope (red circle). The optimal viewing time for observers at mid-northern latitudes will be 5:45 to 6 a.m., before the sky brightens fully. Observers at more southerly locations will see the planets in a darker sky. If your skies aren’t clear on Friday, look for Mercury to Jupiter’s upper right on Thursday, and to Jupiter’s lower left on Saturday.

Friday, March 5 – Third quarter Moon (at 8:30 p.m. EST)

Third quarter Moon (Chris Vaughan, Starry Night Education)

When the Moon reaches its third quarter phase at 8:30 p.m. EST on Friday, March 5 (or 1:30 GMT on Saturday, March 6), it will rise in the middle of the night, and then remain visible in the southern sky all morning. At this phase, the Moon is half-illuminated, on its western side, towards the pre-dawn Sun. Third quarter moons are positioned ahead of the Earth in our trip around the Sun. About 3.5 hours later, Earth will occupy that same location in space. The ensuing week of moonless evening skies will be ideal for observing deep sky targets.

Read “Running the Messier marathon,” by Chris Vaughan

Saturday, March 6 – Mercury at greatest western elongation (pre-dawn)

Mercury at greatest western elongation (Chris Vaughan, Starry Night Education)

On Saturday, March 6, Mercury will reach its widest angle of 27 degrees west of the Sun, and peak visibility for the current morning apparition. Look for the swiftly-moving planet shining very low in the east-southeastern sky, near brighter Jupiter, between about 5:45 and 6 a.m. in your local time zone. Through a telescope, Mercury will exhibit a 57-per-cent-illuminated, waxing gibbous phase. Unfortunately, Mercury’s position below the shallowly-dipping morning Ecliptic will make this a poor apparition for mid-Northern latitude observers, but the best showing of 2021 for those located near the Equator and farther south.

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 to tour the universe together.