APOD 2.1

I Zwicky 18, galaxy on the left which spans over 3,000 light-years, was thought to be one of the youngest galaxies that we know because its bright stars only seem to be 500 million years old. Astronomers were very intrigued by this galaxy because it resembles other early forming galaxies. The galaxy is only 59 million light-years away, relatively close, but is surrounded by other galaxies that are much older. Recent images by Hubble Space Telescope, reveal a population of old, bright stars intermixed with the bright stars within the I Zwicky 18 galaxy. So now, I Zwicky 18 is thought to be about 10 billion years old like its neighboring galaxies, but seemed to have an episode of new star formation. The possible reason for this new star development may be related to the changing gravtitational influence of I Zwicky 18's smaller companion galaxy, visible on the upper right. This is really interesting, especially because for so long, astronomers thought this galaxy was so young, but is actually relatively old. It is also interesting that it experienced this burst of new star formation, which makes the galaxy appear to be much younger than it really is.