M 33 - The "Triangulum" Spiral Galaxy (a.k.a. NGC 598)

NASA's Galaxy Evolution Explorer Mission celebrates its sixth anniversary studying galaxies beyond our Milky Way through its sensitive UltraViolet telescope, the only such far-UltraViolet detector in space.
The mission studies the shape, brightness, size and distance of distant galaxies across 10 BY of cosmic history, giving scientists a wealth of data to help us better understand the origins of the universe. One such object is pictured here, the galaxy NGC 598, more commonly known as M 33.
The image shows a map of the recent star formation history of M 33. The bright blue and white areas are where star formation has been extremely active over the past few million years. The patches of yellow and gold are regions where star formation was more active 100 MY ago.
In addition, the UltraViolet image shows the most massive young stars in M 33. These stars burn their large supply of Hydrogen fuel quickly, burning hot and bright while emitting most of their energy at UV wavelengths. Compared with low-mass stars like our Sun, which live for billions of years, these massive stars never reach old age, having a lifespan as short as a few million years.

The California Institute of Technology, in Pasadena, Calif., leads the Galaxy Evolution Explorer Mission and is responsible for science operations and data analysis. NASA's Jet Propulsion Laboratory, also in Pasadena, manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. South Korea and France are the mission's international partners.