A galaxy cluster is like a cosmic blender. It stirs up the galaxies and the space between them. Nothing is left undisturbed.

A perfect example is the Virgo Cluster. It consists of more than 1500 individual galaxies, centered about 55 million light-years away. Most of them are fairly small and faint. But a few are monsters – many times the size and mass of our home galaxy, the Milky Way.

The cluster’s galaxies are packed fairly close together. So the gravity of each galaxy pulls at its neighbors. That distorts the shape of some of the neighbors, making them lopsided. It also causes big clouds of gas to collapse and give birth to new stars. And it pulls many stars out of the galaxies, into the space between them. In fact, up to one-tenth of the stars in the cluster may be roaming through intergalactic space.

The cluster’s brightest galaxy is Messier 49. It was the first to be discovered, in 1771. It’s a giant elliptical, so it looks like a fat, fuzzy rugby ball. It’s much bigger than the Milky Way, and many times its mass. And a supermassive black hole inhabits its heart.

The biggest and heaviest member of the cluster is Messier 87, and we’ll talk about it tomorrow.

The Virgo Cluster is centered along the border between Virgo and Leo. That spot is low in the east at nightfall and climbs high across the sky later on. Many of the galaxies are easy targets for small telescopes.

Script by Damond Benningfield