A Tour of Arp 299

Narrator (April Hobart, CXC): What would happen if you took two galaxies and mixed them together over millions of years? A new study using data from NASA's X-ray Observatory and other telescopes reveals the cosmic culinary outcome.

Arp 299 is a system located about 140 million light years from Earth. It contains two galaxies that are merging, creating a partially blended mix of stars from each galaxy in the process.

However, this stellar mix is not the only ingredient. Data from Chandra reveal 25 bright X-ray sources sprinkled throughout the Arp 299 concoction. Fourteen of these sources are such strong emitters of X-rays that astronomers categorize them as "ultra-luminous X-ray sources," or ULXs.

These ULXs are found embedded in regions where stars are currently forming at a rapid rate. Most likely, the ULXs are binary systems where a neutron star or black hole is pulling matter away from a companion star that is much more massive than the Sun. These double star systems are called high-mass X-ray binaries.

Such a loaded buffet of high-mass X-ray binaries is rare, but Arp 299 is one of the most powerful star-forming galaxies in the nearby Universe. This is due at least in part to the merger of the two galaxies, which has triggered waves of star formation. The formation of high-mass X-ray binaries is a natural consequence of the blossoming star birth in Arp 299 as some of the young massive stars, which often form in pairs, evolve into these systems.

While Arp 299 is intriguing itself, this system also has similarities to more distant galaxies. This gives astronomers a chance to sample a local version of faraway cosmic creations, providing hints to the ingredients and recipe that created them.