Our Milky Way Galaxy is surrounded by about 150 globular clusters, formed about 11.5 billion years ago, 2.3 billion years after the Big Bang and shortly before the rate of cosmic star formation reached its peak, 10 billion years ago –a period known as “cosmic high noon.” The largest numbers of globular clusters, over ten to twenty thousand, are found around giant galaxies at the centers of galaxy clusters that contain hundreds to thousands of galaxies bound together by gravity, infused by hot gas (up to ten times hotter than the center of the Sun) that far outweighs all the stars in the galaxies comprising the galaxy cluster combined.
In January of 2016 we reported that “A globular cluster might be the first place in which intelligent life is identified in our galaxy,” according to Rosanne DiStefano of the Harvard-Smithsonian Center for Astrophysics (CfA). Globular star clusters are extraordinary in almost every way. They’re densely packed, holding a million stars in a ball only about 100 light-years across on average. They’re old, dating back almost to the birth of the Milky Way. And according to new research, they also could be extraordinarily good places to look for space-faring civilizations.
Future Laser Interferometer Gravitational-Wave Observatory (LIGO) alerts may likely come from a globular cluster, with the closest cluster residing about 7,000 light years from Earth. When a gravitational wave transit the Milky Way, it stretches and squashes space-time, making pulsars and the Earth jiggle.
Astronomers using the NASA/ESA Hubble Space Telescope to study some of the oldest and faintest stars in the globular cluster NGC 6752 (above) have made an unexpected finding. They discovered a dwarf galaxy in our cosmic backyard, only 30 million light-years away while studying white dwarf stars within NGC 6752. The aim of their observations was to use these stars to measure the age of the globular cluster, but in the process they made a surprising discovery.