by David Kindy/Smithsonianmag.com
About 80,000 light-years from Earth in the Milky Way’s inner halo, a sparse collection of stars called Palomar 5 has long baffled astronomers. Its total mass is somewhat smaller than expected, and the star cluster is trailed by very thin streams of stars stretching some 22,800 light-years behind it.
Now, in a new study published July 5 in the journal Nature Astronomy, researchers suggest more than 100 black holes may be tucked within Palomar 5, which could explain its ability to spit out trails of stars.
A team of researchers led by astrophysicist Mark Gieles of the University of Barcelona in Spain, set out to model the evolution of star clusters to find out how Palomar 5 formed. They used computer simulations to calculate how stars in a cluster interact gravitationally as they orbit the center of the Milky Way, reports John Timmer of Ars Technica.
The most important factor in Palomar 5’s formation turned out to be the presence of black holes. At first, scientists expected to find around 30 black holes in Palomar 5. They were surprised to learn that the cluster holds as many as 124 black holes.