Globular clusters are dense systems of very ancient stars, gravitationally bound into a single structure about 100-200 light-years across.
The word globulus, from which these clusters take their name, is Latin for small sphere.
Globular clusters are among the oldest known objects in the Universe and are relics of the first epochs of galaxy formation.
They contain hundreds of thousands or perhaps a million stars. The large mass in the rich stellar center of a cluster pulls the stars inward to form a ball of stars.
It is thought that every galaxy has a population of globular clusters. Some, like our own Milky Way Galaxy, have a few hundred, while elliptical galaxies can have several thousand.
“A densely packed, roughly spherical collection of stars, Palomar 6 lies close to the center of the Milky Way, where interstellar gas and dust absorb starlight and make observations more challenging,” Hubble astronomers said.
“This absorption by interstellar material affects some wavelengths of light more than others, changing the colors of astronomical objects and causing them to appear redder than they actually are.”
“We call this process ‘reddening,’ and it makes determining the properties of globular clusters close to the Galactic center particularly difficult.”
Otherwise known as ESO 520-21, Palomar 6 lies in the constellation of Ophiuchus.“Ophiuchus was one of the 48 constellations which appeared in the writings of the second-century Egyptian astronomer Ptolemy, all of which are among the 88 constellations officially recognized by the International Astronomical Union today,” the astronomers said.
“Not all the constellations proposed by astronomers throughout history have survived, however — forgotten or obsolete constellations include Felis (the Cat), Rangifer (the Reindeer), and even Officina Typographica (the Printer’s Workshop).”