A Tour of IC 10

Narrator (April Jubett, CXC): Long before Starburst® became a popular brand of candy, starbursts were known to astronomers. In 1887, American astronomer Lewis Swift discovered a glowing cloud, or nebula, that turned out to be a small galaxy about 2.2 million light years from Earth. Today, it is known as the "starburst" galaxy IC 10, referring to the intense star formation activity occurring there.

More than a hundred years after Swift's discovery, astronomers are studying IC 10 with the most powerful telescopes of the 21st century. New observations with NASA's Chandra X-ray Observatory reveal many pairs of stars that may one day become sources of perhaps the most exciting cosmic phenomenon observed in recent years: gravitational waves.

By analyzing Chandra observations of IC 10 spanning a decade, astronomers found over a dozen black holes and neutron stars feeding off gas from young, massive stellar companions. Such double star systems are known as "X-ray binaries" because they emit large amounts of X-ray light. As a massive star orbits around its compact companion, either a black hole or neutron star, material can be pulled away from the giant star to form a disk of material around the compact object. Frictional forces heat the infalling material to millions of degrees, producing a bright X-ray source.

When the massive companion star runs out fuel, it will undergo a catastrophic collapse that will produce a supernova explosion, and leave behind a black hole or neutron star. The end result is two compact objects: either a pair of black holes, a pair of neutron stars, or a black hole and neutron star. If the separation between the compact objects becomes small enough as time passes, they will produce gravitational waves. Over time, the size of their orbit will shrink until they merge. LIGO has found three examples of black hole pairs merging in this way in the past two years.

Astronomers will continue to study IC 10 and other similar galaxies to better understand more about X-ray binaries and their connection to the exciting and evolving field of gravitational wave astronomy.