This image, taken with the #Wide Field Planetary Camera 2 on board the #NASA/#ESA Hubble #Space Telescope, shows the globular #cluster Terzan 1. Lying around 20,000 light-years from us in the #constellation of #Scorpius (The Scorpion), it is one of about 150 globular clusters belonging to our #galaxy, the Milky Way.
Typical globular clusters are collections of around a hundred thousand stars, held together by their mutual #gravitational attraction in a #spherical shape a few hundred light-years across. It is thought that every galaxy has a population of globular clusters. Some, like the #Milky Way, have a few hundred, while #giant elliptical galaxies can have several thousand.
They contain some of the oldest stars in a galaxy, hence the reddish #colors of the stars in this image ‚” the bright blue ones are foreground #stars, not part of the cluster. The ages of the stars in the globular cluster tell us that they were formed during the early stages of #galaxy formation! Studying them can also help us to understand how galaxies formed.
Terzan 1, like many globular clusters, is a #source of X-rays. It is likely that these X-rays come from binary star #systems that contain a dense #neutron star and a normal star. The neutron star drags #material from the companion star, causing a burst of X-ray emission. The system then enters a quiescent #phase in which the neutron star cools, giving off X-ray #emission with different characteristics, before enough material from the companion builds up to trigger another outburst. by stephenhawking1982