a tight and dense gathering of stars that takes its name from the fact that it looks like a globe or ball
A rich cluster containing tens of thousands to over a million stars. Globular clusters populating the outer galactic halo contain low metalicity population II stars, some among the oldest known stars in the universe. M13 in Hercules is a spectacular sight in a 10-inch telescope.
A spherical cluster of many thousands of stars. Globular clusters usually have a size of 50 to 150 light years and are found scattered in a spherical halo surrounding galaxies.
A star cluster containing 50,000 to 1 million stars in a sphere about 75 light years in diameter; generally old metal poor and found in the spherical component of the galaxy.