As the Moon wanes from the evening night, thoughts here at Astroguyz turn towards the wonders of the deep sky.
M13 in Hercules. (Credit: Digitized Sky Survey).
One of the finest sights in the northern hemisphere is the globular cluster M13 in the constellation Hercules. This globular cluster lies on the edge of the four star asterism known as the Keystone, (see link for a map!) and generally makes anyone’s short list of favorite deep sky objects. During the month of August, M13 transits near the zenith shortly after sunset for mid-northern latitudes. Even a small 60mm refractor will reveal a small, nebulous fuzzy patch a degree below Eta Herculis; a larger aperture will easily disclose an explosion of stars. Globulars like M13 are thought to contain several hundred thousand stars, and lies about 25,000 light years distant. In 1974, the Arecibo radio telescope beamed a short message towards M13, the idea being that a large profusion of stars meant a high chance that an intelligent civilization may be listening. However, clusters such as M13 are now known to harbor first generation stars that are very metal poor, and hence not very good candidates for complex organisms.
This weeks’ astro-word of the week is Globular cluster. Or do you say Globe-ular? These are very tightly bound, spherical organizations of stars. They are also some of the oldest structures known; at 10+ billion years of age, some Globulars nearly predate the universe itself! Our galaxy alone has 158 globular clusters thus far indentified, mostly located in the galactic halo; a larger galaxy may posses as many as 500 or more.