Found roughly 50 million light-years from Earth in the constellation of Ursa Major, this is NGC 3310: a spiral galaxy with a turbulent past. Around 100 million years back, it violently clashed with one of its neighbors, inciting a chain reaction that culminated in a burst of star formation activity taking place within its borders.
This burst was triggered by something called density waves, which propagate when a change in gravity compresses the galaxy’s gas supply, causing sections to collapse. This Hubble-composite showcases generations of stars that came before and after the merger, revealing that the young outnumber the old (some are so young, in fact, that astronomers now think the aftereffects of a merger linger longer than we previously suspected).
There are several hundred star clusters in NGC 3310, visible in the Heritage image as the bright blue diffuse objects that trace the galaxy’s spiral arms. Each of these star clusters represents the formation of up to about a million stars, a process that takes less than 100,000 years. In addition, hundreds of individual young, luminous stars can be seen throughout the galaxy.
Once formed, the star clusters become redder with age as the most massive and bluest stars exhaust their fuel and burn out. Measurements in this image of the wide range of cluster colors show that they have ages ranging from about one million up to more than one hundred million years.
All in all, NGC 3310 spans approximately 50,000 light-years across, which makes it only half the size of the Milky Way (though by some estimates, it may be much smaller than that, perhaps just 22,000 light-years across).
Image Credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona