Astro Bob blog: Face-time with the ScorpionIf you're not afraid of getting stung, swing your binoculars toward Scorpius tonight
By: Bob King, Duluth News Tribune
Face time with the scorpion
Mushrooms in a frothy cream sauce? No, these are dunes near Mars' North Pole sculpted by the wind. Credit: NASA/JPL/Univ. of Arizona
This is just such a compelling compelling image I thought you'd enjoy seeing it. The photo was taken on May 30 by the Mars Reconnaissance Orbiter of a series of sand dunes near the North Pole of Mars. It's summer there so most of the ice has disappeared. In Mars' thin air, ice passes directly from a solid to a vapor when the temperature climbs. There are still tiny remnants of ice that look like blue-white spots here and there. Can you spot any?
All three of our featured deep sky objects in Scorpius are visible in a typical pair of 8x40 or 7x50 binoculars. If your skies are really dark, you can even see M6 and M7 faintly with naked eye alone. This map shows the sky about 11 p.m. looking south. Created with Stellarium
Yesterday we introduced the constellation Scorpius, which is well placed for observation during early summer. If you have a pair of binoculars or a telescope, you're in luck, because the scorpion offers several tantalizing star clusters. To find them, start you evening viewing session at twilight's end and allow your eyes 10-15 minutes to adapt to the dark. Antares is easy to pick out since it's the only bright, red star low in the southern sky. Point your binoculars at Antares and look a little over a degree (two full moons) to its right. See that dim, fuzzy patch? That's a whopping big globular cluster called M4 (below), one of the closest to the sun at a distance of only 7,200 light years.
In my 8x40 binoculars I can see a sizeable soft glow with a slightly brighter center. Globular clusters pack hundreds of thousands of stars into spheres dozens to hundreds of light years across. They remind me of chandeliers aglow in the great auditorium of the Milky Way. Some are so compact, they're nearly impossible to resolve into individual stars in amateur telescopes, while others are loose and gangly. M4 is one of the looser ones. Many individual stars, including a fascinating bar-shaped concentration running down its center, can be seen in even a small 4.5" scope.
The other two deep sky wonders on our list , M6 and M7, are star clusters but a different variety called open clusters. They're loose and open (hence the name) compared to the globulars and formed in the more recent past from dust and gas clouds in our galaxy's spiral arms. Many open clusters resolve into individual stars with the slightest optical aid; some like the Seven Sisters Cluster and the Hyades don't even need that.
M7 is so big and loose. Wide-field binoculars show it to better advantage than most telescopes. Credit: John Chumack
To see M6 and M7 best, plan on staying up just a bit later. They're further east and need another half hour to hour before rising high enough to clear the horizon haze. If your view to the south-southeast is unimpeded, I think you'll be surprised how large, rich and bright M7 is. You can't miss it in binoculars -- the cluster's located one binocular field of view to the upper left of the Stinger star in the tail. Once you've found M7, you're only one additional binocular field from M6, better known as the Butterfly Cluster. This group is smaller and more compressed than its neighbor M7. Any small telescope reveals a butterfly's wings outlined in stars.
The Butterfly Cluster or M6 isn't far from M7 and resembles a butterfly in outline when viewed in a small, low power telescope. Credit: Ole Nielsen
M6 is only about half a degree across compared to M7's degree and a half. Its smaller size can be attributed to its greater distance: 1600 light years versus 800. These two clusters hint of the richness of the Milky Way which broadens into a torrential river of light in southern Scorpius. From a dark sky site, especially if you live in the southern U.S., the sight is unforgettable. Don't pass up the chance, no matter where you live, to take a drive to the country this week and next, to see these sights yourself.
The Milky Way crosses through eastern and southern Scorpius in this photo taken from the southern hemisphere where the constellation passes directly overhead this time of year. The white glow is the unresolved glow of countless billions of stars. The dark spidery shapes in the foreground are gigantic clouds of interstellar dust and gas called dark nebulas. New star clusters like M6 and M7 are born within these clouds. Credit: ESO/S.Guisard
(Photo of M4 cluster by Hunter Wilson)