Planets! Plus the Full Worm Moon, Zodiacal Light, Comet Tuttle, and an Asteroid!

Star Walk
4 min readMar 13, 2017

A Binocular Comet

Comet 41P/Tuttle-Giacobini-Kresak can be spotted in binoculars or a small telescope this week. The bright moon early in this week will make it harder to see. As darkness falls around 7:30 pm local time, it is halfway up the eastern sky. By midnight, it is nearly straight overhead. Tonight (Sunday), the comet is in the feet of Ursa Major (Big Bear), about 15° (1.5 clenched fist widths) to the upper right of Merak, the bottom star of the Big Dipper. It’s moving towards Merak at a rate of about 1.25° (a thumb’s width) per day. I’ll post a diagram here. Expect the comet to appear as a faint greenish blob (quite different from a star). If it develops a tail, it will point roughly away from the Big Dipper. Keep an eye on it — this comet has a reputation for sudden outbursts that dramatically brighten it.

The Moon and Planets

Full Moon in Solar Walk 2 app.

Tonight (Sunday), the Full Worm Moon, Crow Moon, Sap Moon or Lenten Moon, all traditional nick-names after the early stirrings of spring and religious lunar observances, will rise in the east at sundown. For the rest of the week, the moon shifts east, rises later, and wanes towards last quarter. Starting in late evening on Tuesday, Jupiter and the waning gibbous moon will rise together in the eastern sky about 9:40 pm local time. With the moon less than 4 degrees to the lower left of the planet, they’ll fit within a binocular field of view and make a nice photo opportunity. As they slowly draw apart, the pair will cross the night sky together and be visible low in the southwestern sky before sunrise.

Mercury has started its best evening apparition of the year for mid-northern latitude observers, becoming visible low in the west about 8 pm by next weekend. During the month, it approaches Earth — causing its disk to increase in diameter, while dropping in brightness, and waning from a nearly full disk to half illuminated. On March 18 and 19, look for descending Venus about 9 degrees to the north (right) of Mercury.

Mercury’s trajectory in Star Walk 2 app.

This is our last week to enjoy extremely bright white Venus in the western evening sky. It is rapidly dropping into the sunset, setting after 9 pm local time. A telescope will reveal that it is showing a thin crescent phase, and its disk is slowly growing larger as it moves towards Earth on its way towards inferior conjunction with the Sun next week. Much dimmer, reddish Mars is still halfway up the western sky after sunset, and is setting about 10:45 pm local time this week.

Bright, white Jupiter is just a few finger widths to the upper left of Virgo’s (the Maiden) brightest star Spica. They both rise in the east about 9:30 pm local time this week. Jupiter reaches its highest point, over the southern horizon, at 3:15 am. And by dawn, it is above the western horizon. Visible in a good backyard telescope, Jupiter’s moon Europa casts its black round shadow on the planet on Mar 15 from 11 pm to 1 am EDT. Io’s shadow crosses the planet on Mar 18 from 1:20 am to 3:30 am EDT. The Great Red Spot is visible on Jupiter for about three hours centred on Mar 14 at both 3:15 am and 11:05 pm EDT (as it rises), as well as Mar 17 at 12:45 pm EDT and Mar 19 at 10:10 pm EDT.

Yellowish Saturn rises in the southeast about 3 am local time, and can be spotted until before 7 am, when it’s two fist diameters above the southern horizon. During this summer’s Saturn season, the bright reddish star Antares in Scorpius (the Scorpion) is less than 20° to the right (southwest) of the planet.

Spot an Asteroid

At visual magnitude 7.1, asteroid (4) Vesta is observable in binoculars or a small telescope throughout March. It is moving within the constellation of Gemini (the Twins), ranging between 2.5 and 4 degrees (three or four finger widths) to the right of the bright star Pollux. Ceres is also available, near Mars.

Asteroid Vesta in Star Walk 2 app.

Zodiacal Light

During moonless periods in February and March annually, the steep evening ecliptic favors the appearance of the zodiacal light in the western sky for about half an hour after evening twilight ends. This is reflected sunlight from interplanetary particles of matter concentrated in the plane of the solar system. Once it’s dark, between now and the new moon on March 27, look south of west (near Mars) for a broad wedge of faint light rising from the horizon. It will be centered on the ecliptic.

Astronomy news for the week (from March 12th) by Chris Vaughan.



Star Walk

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