Now we know, thanks to a cool image from NASA's Chandra X-ray Observatory. The image of "Arp 299," which was released Monday, is a composite of visible light and X-ray light.

In the image, X-rays are represented with pink and blue colors, while visible light is red, green, and blue.

Arp 299 is located about 140 million light years from Earth and contains two galaxies that have been merging for millions of years, creating a blended mix of stars from each galaxy in the process.

It's also one of the most powerful star-forming galaxies in the nearby universe, NASA said. This is due in part to the merger of the two galaxies, which has triggered waves of star formation.