I Zwicky 18

I Zwicky 18, was once thought to be the youngest galaxy ever detected at between 500 million and one billion years old, and about 59 million light years away. A dwarf irregular galaxy, it is typical of the types of galaxy that formed in the early days of the Universe.  It is producing many new stars in the areas that show as intensely blue/white in the picture.  The outer tendrils are gas that has been heated by the radiation produced by star formation.  Recent Hubble images of I Zwicky 18 show a population of old faint stars intermixed  with the  bright stars.  Therefore it appears that the galaxy is about the same age as its neighbors, including our Milky Way, at about 10 billion years old.  The recent formation of many new stars is probably the result of gravitational disruption caused by I Zwicky 18's smaller companion galaxy, not seen in this image.

Credit: NASA