Cosmic Pursuits
Basic astronomy and night sky information
Sky This Month
The Night Sky This Month – March 2018
Messier 51, the Whirlpool Galaxy, and its companion NGC 5195. Credit: Terry Hancock at GrandMesaObservatory.com.
All five bright planets, Mercury, Venus, Mars, Jupiter, and Saturn, make an appearance in the night sky this month. The two inferior planets (Mercury and Venus) are visible close together in the western sky after sunset. The others are all visible after midnight, each of them rising a little earlier each night as they approach opposition later this spring and summer. Jupiter, in particular, is a dazzling sight as it grows bright and large enough to invite careful inspection with a telescope well after midnight. Even Uranus makes a cameo as it comes within just 4 degrees of Venus at the end of March.
The prominent constellations Orion, Taurus, and Canis Major all move westward as March progresses. Deep sky observers welcome the beginning of galaxy season as the Earth's nightward side aims out of the plane of the Milky into the depths of intergalactic space. Here's what to see in the night sky this month…
The northern winter constellations move towards the southwest in early March.
2 March. Full Moon, 0:51UT.
3 March. The two inner planets, Mercury and Venus, are just a finger-width apart, low over the western horizon after sunset, for the next couple of days. The two planets are plenty bright, but they are still difficult to see in the bright twilight sky. Bring a pair of binoculars to try to spot these two worlds. In a telescope, both appear nearly fully lit at the beginning of March. Venus appears about twice the size of Mercury. Mercury moves higher, away from Venus, until mid-month. Then it moves back towards the horizon. Venus also moves higher, though more languorously, during the month, and it remains conspicuous and bright at magnitude -3.9.
5-15 March. As the Moon stays out of the way, look for the white, pyramidal glow of the zodiacal light towards the west well after sunset. Dark sky is essential.
7 March. Look for the waning gibbous Moon and the bright planet Jupiter rising in the east together just before midnight.
9 March. Jupiter begins its retrograde motion. It now moves westward along the ecliptic each night until July 11 when it starts moving eastward again. The planet gets a little fatter and brighter during the month, and by the end of March it's about 43" across and it shines at magnitude -2.4.
9 March. Last Quarter Moon, 11:20UT.
15 March. Mercury reaches greatest eastern elongation, a scant 18 degrees from the Sun.
17 March. New Moon, 13:12UT.
18 March. Look for a slender crescent Moon along with the planets Venus and Mercury in the western sky after sunset.
The Moon, Venus, Mercury, and much fainter Uranus in the western sky after sunset on March 19, 2018.
20 March. The season changes at 16:15 UT as spring begins in the northern hemisphere and autumn begins in the southern hemisphere.
22 March. Much of the world will see the Moon, now a waxing crescent, graze the bright star Aldebaran in the constellation Taurus. Observers in western and northern Canada and northern Europe will see the star pass behind the Moon. Timing for the occultation is at this link:
https://www.lunar-occultations.com/iota/bstar/0322zc692.htm
24 March. First Quarter Moon, 15:35UT.
28 March. Now here's a planet pairing you don't see too often: Venus and Uranus. The two planets are just 4 degrees apart today and visible in the western sky after sunset. Venus, of course, is an easy sight. But to see 6th-magnitude Uranus in the bright twilight sky, you will need at least a pair of binoculars, and more likely a telescope.
Looking to the south in late March, the planets Jupiter, Mars, and Saturn mingle with the stars of Libra and Sagittarius.
29 March. Mars finds itself above the Teapot of Sagittarius in the early morning hours at the end of the month. Today, the Red Planet is about 2 degrees west of Saturn in this southern region of the ecliptic. The planets make their closest approach for the year on April 2. As March ends, both planets shine with the same brightness, about magnitude +0.3, but their colors are remarkably different. Mars is clearly red-orange, or ochre, while Saturn is pale straw. Both planets will continue to brighten and grow larger on their way to opposition later this year.
31 March. Full Moon, 12:37UT.
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