2.1 APOD

This photograph shows I Zwicky 18, until recently thought to be the youngest known galaxy in space. Some of the stars in it are only about 500 million years old, while the Sun in our solar system is about 4.5 billion years old. The Hubble Space Telescope recently took pictures that revealed that I Zwicky 18 was much older than it appeared. The pictures show that there are older stars mixed in with the bright young stars. Astronomers now believe that I Zwicky 18 is 10 billion years old. Relative to other galaxies its age, I Zwicky 18 forms new stars very frequently, explaining why it was thought to be so young. Another galaxy is visible to the right of I Zwicky 18. Astronomers think that the changes in gravitational pull between the two galaxies may be the reason for the quick star production in I Zwicky 18.