“It's like dropping a stone into a pond, only in this case, the pond is the galaxy, and the wave is the compression of gas. Each wave represents a burst of star formation, with the youngest stars found in the outer ring.”
“The dramatic plunge has left the Cartwheel galaxy with a crisp, bright ring around a zone of relative calm. Usually a galaxy is brighter toward the center, but the ultraviolet view indicates the collision actually smoothed out the interior of the galaxy, concentrating older stars and dust into the inner regions. It's like the calm after the storm of star formation.”
