Galaxy's age puzzles scientists
Wednesday, 17 Oct 2007 17:35
The galaxy I Zwicky 18
Science In Focus
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New evidence has found that what was once thought to be one of the youngest galaxies in the universe is actually much older.
Observations made by the space telescope Hubble have also shown that the galaxy is further away than previously thought.
Images of I Zwicky 18 taken 40 years ago suggested that it was a relatively young galaxy of the nearby universe.
At that time scientists proposed that the galaxy had erupted with star formation billions of years after other galaxies including the Milky Way.
But Hubble has found faint old red stars within the galaxy, suggesting that its star formation started at least one billion years ago and possibly as much as ten billion years ago.
"Although the galaxy is not as youthful as was once believed, it is certainly developmentally challenged and unique in the nearby Universe," said astronomer Alessandra Aloisi from the European Space Agency/Space Telescope Science Institute, who led the new study.
The new Hubble data also places I Zwicky 18 at 59 million light years away, almost ten million light years more distant than previously believed.
The findings are published in the Astrophysical Journal Letters.