Crux – the southern cross

August 13, 2017

Astronomy

Crux, the southern cross, started showing up on some constellation maps in the early 1600’s. It became accepted more or less officially in 1679 when Augustin Royer insisted on tearing Crux away from Centaurus, of which it was a part since ancient times. It’s just as well because Crux is one of the most easily recognizable and memorable groups of stars in the whole sky.

Down under, where folks eat something disgusting called Vegemite, and where they call lobsters “shrimps,” the stars of Crux never set. That’s why lots of southern nations identify strongly with these stars, in the same way that many in the north identify with the Big Dipper. The popularity of Crux is in spite of its diminutive size, the smallest of all 88 constellations.

In the more ancient of ancient times, Crux was visible for part of the year from Greece and much of Europe. But the wobbling of the Earth carried it a bit farther south so that by 400 AD it was no longer visible from European nations. Some people actually say Christ is the reason for this. Whatever. Some people probably blame Obama.

Acrux is the brightest star of the group and in fact it is the 12th brightest star in the whole sky (not counting the sun). That puts it in some elite company, one of the top 12, that’s kind of a cool-kids club.

The Coalsack Nebula is in Crux. It’s a huge batch of dust blocking part of our view of the Milky Way next to the lower left part of the cross. It’s about 35 light years across the filthy thing. That’s a helluva dust bunny. The cloud is 600 light years away from us.

There is a gorgeous open star cluster to be had in Crux, if you are ever star hopping from the southern latitudes. In the 19th century Sir John Herschel called it “A casket of variously coloured precious stones.” So now it’s called the Jewel Box. It’s worthy of the title. The three bright stars in the middle of the cluster are known as “The Traffic Lights.” Stop and take a look but if you hear a bunch of honking and yelling, drive on. This light isn’t going to turn green any time soon.

Carpe Noctem

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