Moon, Jupiter, Mars Strut Their Stuff Tonight

The half moon glides by brilliant Jupiter the next two nights. Map created with Stellarium

Cast a glance upward at the moon tonight. That big, bright object just a few degrees to its south is the planet Jupiter. The two will be sky buddies the next couple evenings.

Through binoculars the 6-day-old moon will reveal a variety of crisp-edged craters along the terminator, the boundary between lunar day and night.  Most prominent tonight is a remarkable chain of impact craters – Theophilus, Cyrillus and Catharina.

Theophilus is named after an ancient Greek geographer and measures 68 miles across. It fairly fresh as lunar craters go, with a sharp-edged rim and a couple of distinctive central mountain peaks. Theophilus overlaps the much older Cyrillus, which is 61 miles across and named for a 4th century theologian.

One of the best known features on the moon is the Theophilus crater chain. Watch for it tonight in a small telescope. Photo: Bob King

Scientists determine relative crater age by looking at which craters overlap others (the ones on top are younger) and noting how worn or broken their rims are. Cyrillus’s rim is worn down and much less crisp than Theophilus to the north. The final crater is the chain, Catherina, named for St. Catherine, a Greek theologian and philosopher, is 62 miles across and even more beaten down than Cyrillus.

Jupiter, its moon Io and Io's shadow tonight at 6:30 p.m. CST. South is up as viewed in most telescope. Credit: Meridian

You should be able to spot the trio in binoculars, but the best view will be through a telescope. And it doesn’t have to be a big one. Even a cheap department store scope will do the job. While you’re at it, point it at Jupiter. The two most prominent stripes – the North and South Equatorial Belts – are easy to see across the planet’s midsection. This evening the shadow of Jupiter’s moon Io will hover over the South Equatorial Belt from 5 to 7 p.m. CST. Look for a tiny, inky-black dot. Io itself will shine brightly nearby due west of the planet.

Finally, Mars rises around 8:45 p.m. and is high enough by 11 p.m. to have cleared the atmospheric muck for a sharp view. With a 4-inch or larger telescope magnifying around 150x, not only is the north polar cap a snowy white oval, but the planet’s most obvious dark marking, Syrtis Major, is front and center. This vaguely triangular patch is an enormous extinct shield volcano. Another easy feature to look for is the fat, dark rim along the polar cap called Utopia. The second of the two Viking landers touched down there in September 1976.

Even small telescopes can pick out some of Mars' more obvious features this week. Credit: Damian Peach

Because a day on Mars is 37 minutes longer than Earth’s, all Martian surface features gradually drift to the east as the nights go by. Tonight Syrtis Major and Utopia face us square on around 11:30 CST, tomorrow they’ll do so around midnight and on the 31st around 12:30 a.m. They’re also easily seen up to a couple hours before and after those times.

In the coming weeks, I’ll have more tips on how to observe the Red Planet as we approach opposition in March.

If it’s clear the next few nights, don’t miss this opportunity to spot several of Mars best landmarks.

2 Responses

  1. Debra

    Excellent and very informative article Bob it has given me some great ideas to look out for in the sky over the next few days.

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