NASA’s Hubble Provides First Census of Galaxies Near Cosmic Dawn
WASHINGTON — Using NASA’s Hubble Space Telescope, astronomers announced Dec. 12 they have seen further back in time than ever before and 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 are from an ambitious Hubble survey of an intensively studied patch of sky known as the Ultra Deep Field (UDF). In the 2012 campaign, called UDF12, a team of astronomers led by Richard Ellis of the California Institute of
Technology in Pasadena used Hubble’s Wide Field Camera 3 (WFC 3) to peer deeper into space in near-infrared light than any previous Hubble observation.
The observations were made during six weeks in August and September, and the first scientific results now are appearing in a series of scientific papers. The UDF12 team is releasing these unique data to the public after preparing them
for other research groups to use.
The results show a smooth decline in the number of galaxies looking back in time to about 450 million years after the theorized big bang. The observations support the idea 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.
Looking deeper into the universe also means peering further back in time. The universe is estimated to be 13.7 billion years old. The newly discovered galaxies are seen as they looked 350 to 600 million years after the big bang. Their light is just arriving at Earth now. Astronomers study the distant universe in near-infrared light because the expansion of space stretches ultraviolet and visible light from galaxies into infrared wavelengths, a phenomenon called “redshift.” The more distant a galaxy, the higher its redshift.