Norma – The Amazing Sky

The southern Milky Way is populated by the sky’s best clusters of stars.

Here are three of the southern sky’s best star clusters, in portraits I took earlier this month from Australia.

At top, my main image takes in a great contrasting pair of star clusters. Both lie in the constellation of Puppis, once part of the ship Argo Navis.

At left is the stunningly rich NGC 2477, so packed with stars it almost ranks as a globular cluster, not one of the sparser open clusters. At least that’s the impression it gives in the eyepiece. But instead of containing hundreds of thousands of stars, as do globulars, NGC 2477 “only” has 300 stellar members. They are just very tightly packed in one of the richest open star clusters in the sky. If it had been farther north NGC 2477 would certainly rate as one of the top 100 sky sights, and carry some memorable name after a fanciful resemblance to who knows what! Instead, it carries but a catalog number.

Next to it, at right, is NGC 2451, more typical of open clusters. It has a central bright star, this one naked eye, surrounded by 40 or so lesser stars of contrasting colour and brightness. The two clusters make a great side-by-side comparison in any low-power telescope.

Much farther along the southern Milky Way is this rich open cluster (above), NGC 6067, in Norma, itself embedded in one of the richest star clouds of the southern Milky Way, the Norma Star Cloud. Here you are gazing for 6800 light years toward the cluster which shines suspended against the background of the even more distant inner arms of our spiral galaxy.

So NGC 6067 looks a little like an island of blue stars amid the dust-reddened background of more distant stars in the Milky Way — an island in a sea of stars.

This image looks toward the inner spiral arm of our Milky Way called the Norma Arm, where stars bunch together to form the rich Norma Starcloud, a prominent patch in the southern Milky Way. What you see here is all stars, lots and lots of stars.

Seemingly embedded in the sea of stars is an island of brighter stars called the Norma star cluster, or more prosaically NGC 6067. It’s about 6800 light years away, much closer to us than the more distant stars behind it. It is literally floating in front of the background sea of stars.

As with the previous image, this is a wide field shot, taken with the 135mm telephoto, to frame the field much as it would appear in binoculars. This shot is a stack of six 2-minute unguided exposures at ISO 1250 with the Canon 7D riding on the little Kenko tracking platform. It’s one of a couple of dozen fields I shot the first night of shooting on Chile in May.