Astronomers using NASA’s Hubble Space Telescope, have spotted 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.
This new image of the Hubble Ultra Deep Field (HUDF) 2012 campaign reveals a previously unseen population of seven faraway galaxies, which are observed as they appeared in a period 350 million to 600 million years after the big bang. The galaxy census is the most robust sample of galaxies ever found at these early epochs. The galaxies were seen in near-infrared light using Hubble’s Wide Field Camera 3. The colored squares in the main image outline the locations of the galaxies. Enlarged views of each galaxy are shown in the black-and-white images. The red lines mark each galaxy’s location. The “redshift” of each galaxy is indicated below each box, denoted by the symbol “z.” Redshift measures how much a galaxy’s ultraviolet and visible light has been stretched to infrared wavelengths by the universe’s expansion. The larger the redshift, the more distant the galaxy, and therefore the farther astronomers are seeing back in time. One of the seven galaxies may be a distance breaker, observed at a redshift of 11.9. The galaxy is seen as it appeared 380 million years after the big bang, when the universe was less than 3 percent of its present age. Credit: NASA, ESA, R. Ellis (Caltech), and the UDF 2012 Team
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 public is invited to participate in a “First Census of Galaxies Near Cosmic Dawn” webinar, in which key astronomers of the Hubble Ultra Deep Field 2012 team will discuss how they obtained their result and what it tells us about galaxy formation in the very early universe.
Participants will be able to send in questions for the panel of experts to discuss.
The webinar will be broadcast at 1:00 pm EST on Friday, December 14, 2012.