15 June 2013


The Stars of Hercules
The early summer skies feature a fascinating constellation that climbs high into the night sky and provides several interesting features to see with the naked eye, binoculars or a telescope. Hercules is the Roman mythological hero that is adapted from the Greek hero Heracles. In the night sky, he is kneeling in the sky with a club overhead, engaged in battle with other mythological enemies throughout the heavens. Similar to Orion the Hunter, Hercules has a distinctive shape; in stark contrast to Orion, Hercules has no bright stars - no first magnitude stars, and only one that is barely second magnitude, and hence Hercules takes some effort to find. But it's worth the effort.

Hercules is visible due east after sunset in June, and is directly overhead by midnight. The middle four stars form a distinctive shape, well known to astronomers as the Keystone. This trapezoidal shape is the center of the figure of Hercules, and it contains a beautiful deep space object known as Messier 13, the Great Globular Cluster in Hercules. It is a spectacular sight to behold in binoculars or a telescope; M13 is a rich cluster that shimmers from the 300,000 stars located in it.

The stars of Hercules are not particularly bright, but they are quite interesting. One of the brightest stars is called Rasalgethi, and it is a a binary star system with a red giant star and a companion that orbit each other every 3,600 years. The brightest star is called Kornephoros, a yellow giant star 148 light years from Earth.

Exploring the heavens is more fun when you know what to look for. Spend a few minutes on Hercules with a telescope or binoculars, and you'll see plenty of interesting objects, even from within a big city.

Image courtesy of SkySafari.

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