Seven Primitive Galaxies at the Dawn of Time |
Using NASA’s Hubble Space Telescope, astronomers have uncovered a previously unseen population of seven primitive galaxies that formed more than 13 billion years ago, when the universe was less than 3 percent of its present age. The deepest images to date from Hubble yield the first statistically robust sample of galaxies that tells how abundant they were close to the era when galaxies first formed.
The results show a smooth decline in the number of galaxies with increasing look-back time to about 450 million years after the big bang. The observations support the idea that galaxies assembled continuously over time and also may have provided enough radiation to reheat, or reionize, the universe a few hundred million years after the big bang.
These pioneering observations blaze a trail for future exploration of this epoch by NASA’s next-generation spacecraft, the James Webb Space Telescope. Looking deeper into the universe also means peering farther back in time. The universe is now 13.7 billion years old. The newly discovered galaxies are seen as they looked 350 million to 600 million years after the big bang. Their light is just arriving at Earth now.
The greater depth of the new Hubble images, together with a carefully designed survey strategy, allows this work to go further than previous studies, thereby providing the first reliable census of this epoch, say the researchers. Notably, one of the galaxies may be a distance record breaker, observed 380 million years after the birth of our universe in the big bang, corresponding to a redshift of 11.9.
The results are from an ambitious Hubble survey of an intensively studied patch of sky known as the Ultra Deep Field (UDF). In the new 2012 campaign, called UDF 2012, a team of astronomers led by Richard Ellis of the California Institute of Technology in Pasadena, Calif., used Hubble’s Wide Field Camera 3 (WFC3) to peer deeper into space in near infrared light than any previous Hubble observation. The observations were made over a period of six weeks during August and September, and the first scientific results are now appearing in a series of scientific papers. The UDF 2012 team is publicly releasing these unique data, after preparing them for other research groups to use. continue reading