Peeking out
constellations along the ecliptic.
Try viewing the bright planet in twilight to minimize the intense glare. The apparent diameter of Jupiter spans 36" on March 1 and drops to 34" by March 31. Telescopes reveal the four Galilean moons as well as a rich display of atmospheric features crossing the disk. Most apparent is the pair of dark equatorial belts straddling the equator. The Great Red Spot comes into view every other day or so as it rounds the planet once every 10 hours.
Io, Europa, Ganymede, and Callisto orbit Jupiter with periods ranging from nearly 1.8 to 17 days. As the Jupiter observing season comes to an end, the number of transits and occultations diminishes. Even so, there’s a couple you can catch.
Watch on March 8 as
Europa is visible early in the evening, then disappears behind Jupiter’s limb just after 9:30 p.m. CST. On March 14, lucky observers from the eastern two-thirds of the country experience Ganymede reappearing from behind Jupiter at 10:09 p.m. EDT (note the change to DST), just as Io is approaching the same limb to begin a transit. Io begins transiting around 10:40 p.m. EDT.
On March 17, Europa is transiting as darkness falls in the Midwest. The moon is followed at length by its shadow, which appears shortly before 10:35 p.m. EDT.
Wrap up the month with a fine transit of Io and its shadow on March 30. It’s underway by nightfall across the Midwest. Io leaves the disk at 10:22 p.m. CDT, with Jupiter very low in the western sky. The shadow departs 48 minutes later, visible from the Pacific time zone and some parts of the Mountain time zone.
If you’re wondering why Callisto isn’t undergoing any events, it’s because the tilt of the satellites’ orbital plane relative to our line of sight is sufficient that Callisto misses Jupiter. You can see this on March 18, when the large moon skirts above the northern edge of the planet.
March opens with Uranus 8° northeast of Jupiter; the planets close in to 3.5° on the 31st. Uranus shines at magnitude 5.8 and is most easily spotted in binoculars. At the end of March Uranus stands 2° south of Delta (δ) Arietis, a 4th-magnitude star also known as Botein, located 9.5° southwest of the Pleiades (M45).
A fine crescent Moon joins Uranus and Jupiter March 13, the same night 243 years ago that William Herschel discovered Uranus from his backyard in Bath, England. Uranus lies about 6° due east of the Moon. This distant planet, once thought to be at the outer edge of the solar system, now lies 20.1 astronomical units
(1.87 billion miles) from Earth and through a telescope shows off a tiny, bluish-green, 3"-wide disk. (One astronomical unit, or AU, is the average Earth-Sun distance.)
On March 30 and 31, Comet 12P/Pons-Brooks stands within 1° of Hamal, the brightest star in Aries. The comet could be an easy binocular object. Last seen in 1954, it underwent outbursts that were also observed in 2023, so there’s a chance it could even exceed binocular visibility for short periods. In the second week of March the comet lies in Andromeda, passing 9° south of M31 on the 12th.
After crossing northern Pisces, Pons-Brooks lies 3° due south of M33, the Triangulum Galaxy, on March 23.
The morning sky hosts Venus, Mars, and Saturn, although the viewing window is limited.
On March 1 you’ll find Venus and Mars less than 4° apart and very low in the eastern sky less than an hour before sunrise. Venus rises about an hour before the Sun and shines at magnitude –3.9, an easy object to spot. Mars, on the other hand, glows at magnitude 1.3 and will require binoculars to find in the rapidly growing twilight. Each morning Venus pulls farther away from Mars; the pair is joined by the waning crescent Moon on March 7 and 8. Look on the 7th for the slender crescent 18° west of Venus — Mars lies just above a point midway on a line between them. The crescent Moon is more difficult to spot on the 8th, almost 6° south of Venus. The Moon stands only 1° high 30 minutes before sunrise and competes with the bright twilight.
Venus passes 0.3° north of Saturn on March 21, the latter of which recently came out of solar conjunction. It’s a difficult pairing to see: Venus stands 1° high 30 minutes before sunrise, and Saturn glows at magnitude 1 some 40" to its east. Binoculars will aid in spotting Saturn, while Venus is easy to follow as the sky brightens.
On the last day of March, Venus, Saturn, and Mars are lined up along the ecliptic, spanning 17.5°. Mars rises around 5:30 a.m. local daylight time, followed 20 minutes later by Saturn. Mars is now magnitude 1.1 and Saturn is still magnitude 1. Look for the pair about 45 minutes before sunrise, low in the east. Venus rises 15 minutes later; as twilight swallows Mars and Saturn’s glow, Venus remains bright enough to be seen.
Neptune reaches conjunction with the Sun on the 17th and is not visible this month.