The globular star cluster M13 in Hercules is about 25,000 to 30,000 light years from Earth. The Sun's motion in space, the rotation of the Milky Way galaxy, and the revolution of the cluster around the center of our galaxy brings the cluster 150 miles closer every second. Nevertheless, even at that rate it will take many, many years before we have to start putting on extra suntan lotion when we go outside. The cluster is home to more than 100,000 stars.
Some astronomers estimate the total number of stars in the cluster at one million.
It is approximately 150 to 160 light years in diameter. This colossal assemblage of stars is over 12 billion years old. Images of the cluster give the impression that stars in the center of the cluster are crowded together virtually in contact. This is an illusion caused by the innumerable star images that, at this vast distance, seem to merge together. According to Burnham's Celestial Handbook , in a scale model of the star cluster where the stars are the size of a grain of sand, even in the closely packed center of the cluster the grains of sand would be separated from each other by the greater part of a mile.