Steve’s Virtual Planet

M6 - The Cosmic Distance Scale

What do you get when you put a bunch of bright young stars together in a prominent place? No, it’s not a Hollywood casting party, it’s an open cluster! In fact, you could end up with as many as a thousand stars in one bunch. It’s “Bigger than the Oscars”!!! But we’re talking about open clusters here, not film stars.

There are quite a few open clusters in our galaxy, the Milky Way, over a thousand actually. They are usually relatively close to Earth in the so called galactic plane and thus a little easier to study. They are key elements in our understanding of stellar evolution and astronomers can use them to get a better grasp of the size of our galaxy and the universe in general.

This way of measuring how big things really are out there is known as the Cosmic Distance Scale. In order to make such measurements, we need a reference, a cosmic yard stick. And that’s where Open Clusters come in. One such cluster is The Butterfly Cluster, also known as Messier 6 (M6 is the catalog number). It’s in the constellation Scorpius.

The web site Astronomy Picture of the Day (APOD) recently had a page on M6 and the topic of how it’s used to measure this scale. Check out the link for the Great Shapley-Curtis debate over the “Scale of the Universe”. It’s guaranteed to make you feel .. well .. small!

Enjoy the party .. and .. Clear skies!