An international team of astronomers led by scientists at the University of California, Riverside, has found an unusual monster galaxy that existed about 12 billion years ago, when the universe was only 1.8 billion years old.

Dubbed XMM-2599, the galaxy formed stars at a high rate and then died. Why it suddenly stopped forming stars is unclear.

“Even before the universe was 2 billion years old, XMM-2599 had already formed a mass of more than 300 billion suns, making it an ultramassive galaxy,” said Benjamin Forrest, a postdoctoral researcher in the UC Riverside Department of Physics and Astronomy and the study’s lead author. “More remarkably, we show that XMM-2599 formed most of its stars in a huge frenzy when the universe was less than 1 billion years old, and then became inactive by the time the universe was only 1.8 billion years old.”

The team used spectroscopic observations from the W. M. Keck Observatory’s powerful Multi-Object Spectrograph for Infrared Exploration, or MOSFIRE, to make detailed measurements of XMM-2599 and precisely quantify its distance.