Hubble finds a new contender for galaxy distance record
By Paul Ridden
February 1, 2011
Pushing the NASA/ESA Hubble Space Telescope to the very limit of its technical ability, an international collaboration of astronomers believe they have discovered the oldest and furthest ancient galaxy ever seen. Light from the new object is thought to have taken some 13.2 billion years to reach the telescope, with the age of the Universe itself said to be 13.7 billion years. It's also said to be older than the current record holder, which set the bar by forming 600 million years after the Big Bang.
The discovery has been given the catchy name of UDFj-39546284 and is most likely a compact galaxy of blue stars from around 480 million years after the Big Bang. It's on the small size – over a hundred such mini-galaxies would be needed to make up the Milky Way. It's also too faint to be confirmed spectroscopically using current equipment, but it does suggest that galaxy growth increased by a factor of ten from the time of the previous record holder to that of the latest discovery.
"We're seeing huge changes in the rate of star birth that tell us that if we go a little further back in time we're going to see even more dramatic changes," said Garth Illingworth of the University of California, Santa Cruz.
As old as the Universe itself
Astronomers are not sure exactly when the very first stars appeared, but each step further away from Earth takes them deeper into the formative years of the Universe. "We're moving into a regime where there are big changes afoot" continued Illingworth. "Another couple of hundred million years back towards the Big Bang, and that will be the time when the first galaxies really are starting to build up."
Rychard Bouwens of Leiden University in the Netherlands added that "these observations provide us with our best insights yet into the likely nature of the earlier generation of primeval objects that we are yet to find."
The Hubble Ultra Deep Field-Infrared (HUDF-IR) data was taken in the late summers of 2009 and 2010, and was followed by a year of detailed analysis before the object was identified. Astronomers measure how much light from a distant object has been stretched by the expansion of space, a value called the redshift or z. In general terms, the greater the value of z for a galaxy, the further away and older it is from our view point – the Milky Way.
Prior to Hubble, astronomers could hope to see as far as redshift 1. This was initially increased to z4, and then to z6 by the Advanced Camera for Surveys in 2004. The first infrared camera to be installed allowed glimpses even further back into the mists of space and time, but z8 was only achieved after the installation of the Wide Field Camera 3.
The astronomers say that there is evidence to suggest that the faint dot of starlight in the latest Hubble images is a compact galaxy of hot stars that first started to form over 100-200 million years earlier, from gas trapped in a pocket of dark matter.
Big hopes for future galaxy gazing
Unfortunately, the team will have to wait for official confirmation. Actual redshift values can only be determined by spectroscopic analysis and the new candidate is too faint for study at the moment. Such things will be in the hands of Hubble's successor, the James Webb Space Telescope, which is expected to explore deeper into infrared wavelengths and reveal the more distant proto-galaxies when it launches in 2014.
It's hoped that the new equipment will allow researchers to gaze back to around 275 million years after the Big Bang, and quite possibly even further. It's estimated that the very first stars were formed between z30 and z15.
The international team which made the discovery is made up of members from Leiden University, Carnegie Observatories, ETH Zurich, University of Colorado, Yale University, the Space Telescope Science Institute, and University of California, Santa Cruz. The discovery was reported in the January 27 edition of the British science journal Nature.