Henize 2-10

This galaxy looks at first to be a normal small elliptical, but on closer examination it contains a mature starburst, about 10 million years old, that was probably started when Henize 2-10 swallowed an even smaller galaxy. The picture, taken at Tel Aviv University's Wise Observatory, shows the faintest parts of the Halpha emission (the bright center is whited out); note the shells and streamers of ionized gas and the little clump of emission outside the main part of the galaxy on the right. That clump is a small star cluster that formed at the end of the tidal tail that remained after the little galaxy was swallowed.