Stellar Snowball

The closest star to the Earth, aside from the Sun, is Proxima Centauri, a small red dwarf star that is part of the Alpha Centauri system, roughly 4 light years away.  If you don’t know light years, the distance is a staggering 37,800,000,000,000 Km.  Beyond that our stellar neighbourhood fills in as you move 20 light years in any direction, and by 100 light years, there are dozens of stars around us.  This gives a stellar density of about 0.14 stars per cubic parsec (a parsec is about 3.26 light years), pretty normal in terms of the number of stars in a given space.   And even with those incredible distances between stars, we still have a bright and beautiful night sky to see each night. But the extremes of stellar density are truly amazing.

Image Credit & Copyright: Roberto Colombari

In the center of a globular star cluster, there can be as many as 1000 stars per cubic parsec, where stars can be as close to each other as Neptune is to the Earth.  This doesn’t sound that cluttered, but it would make for a very bright night sky

In a globular cluster, most of the stars are ancient, much older than our Sun, giving them a redder appearance, with little gas or dust in the mix. With such an extreme stellar density, stars often collide and merge to form massive blue stars called blue stragglers, due to their slow movement through the cluster.  Most galaxies have globular clusters, and even the Milky Way has about 150 of them. Though they have strange orbits that take them high above the galactic plane in a spherical distribution.

Studying globular clusters gives insight into the formation of galaxies, as they are thought to be remnants of ancient protogalaxies that formed the Milky Way.  If you’re out observing, you can see the closest ones in the sky with only a pair of binoculars.  They look like fuzzy snowballs in the sky, until to take a picture of one, revealing the fuzzy ball to be a buzzing hive of stars.

Charles Messier catalogued quite a few of them while he was looking for comets, though I wonder if he understood their true nature.

Leave a Reply

Your email address will not be published. Required fields are marked *