Summer Star Clusters Dazzle This Week

Last week, I spoke about Scorpius the Scorpion, with its reddish heart star, Antares, dominating the southern sky around 11 p.m.  Far off to the right of Antares is Saturn in the SW.   

Follow the body of the Scorpion as it curves to the left to form the tail and stinger. To Scorpius’ left lies Sagittarius the Archer. 

If you witness a centaur, resplendent with bow and arrow drawn to kill Scorpius, may I suggest therapy; however, if you see a really cool teapot complete with handle, lid, and spout, you’ll be visualizing something which is considerably easier to see.  A map is available at the URL below.  

One of my favorite open clusters of the heavens, M7, is located between the tail of the Scorpion and the spout of the teapot.  If dark enough skies prevail, it is an easy naked eye target, especially if viewed with averted vision. The problem is its closeness to the horizon, only 15 degrees at its highest point (40 degrees N. latitude). View at 11 p.m. 

Often M7 goes unnoticed behind trees and buildings, or blends with pockets of horizon hugging light pollution and haze.  Binoculars will reveal this gem with its stars splattered over a region nearly six times the area of the full moon.  Its size is certainly a function of its closeness to the Earth, only 1,000 light years distant.  M7’s age has been estimated to be about 220 million years.  

You cannot view M7 without taking in the beauty of its slightly fainter neighbor, M6, above and to the right.  At a distance of 1,500 light years, M6 is a more concentrated grouping of stars than M7.  It is also about half of M7’s age.  

Open clusters are sites where star generation has occurred. They differ from the older, larger globular clusters which formed in galaxies during the rough and tumble early days of the universe.  Some astronomers believe that globulars were actually the first galaxies to form, and then were cannibalized into the larger galactic structures that we see today.

© Gary A. Becker—www.astronomy.org

Moravian College Astronomy