Thursday, July 15, 2010

Fire and Ice

In my last post, I invited you to face west and gaze upon a gem of an asterism called the Diamond of Virgo. This time, let’s look for the fire in the ice.

Star maps created with Your Sky

First, look about midway between the stars Denebola (denn-EBB-oh-luh) in Leo the Lion and Cor Caroli (core CARE-oh-lye) in Canes Venatici the Hunting Dogs. From a dark site, you should be able to spot a naked-eye sparkly cloud. This is the Coma Star Cluster, an open cluster in the constellation Coma Berenices (KOH-mah bare-uh-NIGH-seez) aka Berenice’s Hair. An open cluster is a collection of stars that formed around the same time in the same cloud of gas and dust. About 40 stars burn brightly in this cluster. You can read more about the Coma Star Cluster and Berenice’s Hair by following this link.

Second, if you have access to a telescope (four-inch diameter or larger would be best), you can delve into the burning heart of the Diamond. Locate Vindemiatrix (vin-duh-mee-AY-tricks), a star positioned nearly equidistant from the Diamond stars Denebola and Arcturus. If you draw an imaginary line between Denebola and Arcturus, Vindemiatrix will lie slightly to the left of that line, in the direction of Spica. Vindemiatrix, which like Spica is in the constellation Virgo the Maiden, is about the same brightness as Cor Caroli.

Now point your telescope midway between Denebola and Vindemiatrix. If you’re under a good black sky and you’ve dark adapted (avoided all white light) for at least 20 minutes, you should see some little glowing smudges. Unlike the Coma Star Cluster, which lies in the Milky Way, these objects lie beyond the Milky Way. These are galaxies in the famous Virgo Cluster of Galaxies; some are brighter and easier to spot than others. Give yourself plenty of time at the eyepiece to allow the faint light from these distant galaxies to accumulate on your retinas.

A galaxy is an immense gravitationally-bound system of stars. Approximately 2,000 galaxies, gravitationally bound to one another, make up the massive Virgo Cluster. The combined gravity from that enormous collection of galaxies even exerts an influence on other galaxy groups around it, including one very important to us: the group containing our home galaxy, the Milky Way. Someday, in the very distant future, our Milky Way may find itself pulled into the Virgo Cluster to become one of its member galaxies.

Imagine the hundreds of billions of burning Suns that make up one galaxy. Now multiply that image by 2,000. That’s a whole lot of firepower.