When two galaxies are in the process of merging, the gravitational interaction can trigger waves of star formation.
This is the case for NGC 4490, a spiral galaxy that has collided with a smaller galaxy to the upper right but not seen in this image. Scientists think that these two galaxies have already had their closest approach and are now separating from one another.
Some of the point-like sources of X-rays represent stellar-mass black holes and neutron stars within the galaxy. In this image of NGC 4490, X-rays from Chandra (purple) have been combined with an optical image from Hubble (red, green, and blue).
Image credit: NASA/CXC/SAO Larger image
