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Globular Clusters: Giant Spherical Collections Of Stars


Our Milky Way galaxy contains at least 200 billion stars and is thought to be at least 100,000 lightyears in diameter.  For amateur astronomers, globular clusters are one of the most favorite objects to observe.  These are giant spherical collections of stars that orbit just outside our Milky Way galaxy.  

Globular Clusters contain tens of thousands to hundreds of thousands of stars all bound by their mutual gravity.  There are about 150 globulars in our Milky Way galaxy.  These stars are some of the oldest stars in the universe.  

Globular clusters are high-density objects where the average distance between stars is about 1 lightyear.  As you get to the central regions of globulars, the distance between the stars is even closer.  During summer, using binoculars or small telescopes, we can observe dozens of globular.  The most famous for northern hemisphere observers is Messier 13, located in the constellation Hercules.  

Even in a small telescope, an observer can enjoy hundreds of stars.  On the evening of July 25 to 27, the giant planet Jupiter will pass above the globular cluster known as MGC 6235, located in the southern sky in the constellation Ophiuchus.  Even though the globular can’t be seen with your naked eye, Jupiter is easy to see, as it’s the brightest object in that part of the sky.  

With a small telescope, you should see both objects in the field of view.  As you observe these 2 objects, light takes 38 minutes to reach our telescope from Jupiter, while light from the more distant globular, 6235, takes 38,000 lightyears.  Knowing this gives you a good idea of how far away these globular clusters are compared to planets in our solar system.