Galactic hit-and-run collision spawns firestorm of starbirth in its wake

Galaxy NGC 4485, located some 25 million light years from Earth in the constellation Canes Venatici, apparently avoided a direct hit during an encounter with a larger galaxy millions of years ago, a glancing blow that triggered a firestorm of chaotic starbirth on one side and leaving the other side relatively intact. Even so, the seemingly intact region shows signs of a previous spiral structure, an indication the galaxy was evolving normally in the past. The offending galaxy in the apparent hit and run is NGC 4490, out of view in this image. The two galaxies are now separated by about 24,000 light years.

NGC 4485. Image: NASA and ESA; Acknowledgment: T. Roberts (Durham University, UK), D. Calzetti (University of Massachusetts) and the LEGUS Team, R. Tully (University of Hawaii), and R. Chandar (University of Toledo)

For context, here is a wide view of the two galaxies:

In this ground-based view, NGC 4485 is the smaller galaxy of the central pair. The larger galaxy is NGC 4490. Image: NASA, ESA, Digitized Sky Survey 2 (Acknowledgement: Davide De Martin)

And here is a view of NGC 4490 from the Hubble Space Telescope:

The Hubble Space Telescope captured this view of NGC 4490’s central region. Image: ESA/Hubble & NASA