Trumpler 16 is an open star cluster within the Carina Nebula (NGC 3372 or the Eta Carinae Nebula), located about 7,500 light-years away from Earth in the southern constellation of Carina (the Keel). It is slowly moving toward us at roughly 25 kilometers per hour.

This young cluster contains over 560 stars, including a significant population of very young stars, and three of the biggest and most impressive stars from our galaxy: Eta Carinae (not visible in this image), WR 25 and Tr16-244. Although intermediate-mass stars have been forming continuously over the last 10 million years, the high-mass stars formed within the last 3 million years.

What seems to be a single bright star might actually turn out to be several stars close together. Eta Carinae, with a mass of 100 to 150 times the mass of our Sun, probably coexists in a binary state with another massive supergiant; WR 25, the brightest object in the above image, consists of at least two separate stars of which the brightest star appears to be about 50 times the mass of our Sun. Additionally, Tr16 -244 (the third brightest, just to the upper left of WR 25) consists of at least three individual stars. The second brightest in this image, to the left of WR 25, is a low-mass star located much closer to Earth than the Carina Nebula.