First galaxies arrived early, and overweight
Infrared is the new black, dahling
Galaxies might have started to form far earlier than scientists had previously thought, according to new results from teams working on the Spitzer and Hubble space telescopes.
Speaking at the Royal Astronomical Society's annual conference in Birmingham this week, Andrew Bunker, from the university of Exeter, explained that he and his team had new evidence that could give theorists a bit of a scare. Using data from three of the most important telescopes we have - Hubble, Hawaii's optical Keck telescope and Spitzer, an infrared space telescope - the team has shown that galaxies nearly 13 billion light-years away are far older than anyone had expected.
Theoretical predictions for the history of star formation are highly uncertain. There is a general consensus that the universe was pretty dark for most of the first billion years, and that the first stars "switched on" after several hundred million years.
The galaxies spotted by Bunker and his research team were blazing with light when the universe was less than a billion years old, and were already several hundred million years old themselves. The team also found some that were almost as big as galaxies we see today, another odd finding since galaxies grow by colliding with and absorbing other galaxies.
Michelle Doherty from the Institute of Astronomy in Cambridge commented: "It could be that these were some of the first galaxies to be born".
Hard data from this era is thin on the ground. Stars and galaxies that old are a long way away from us: 13bn light years, give or take a couple of aeons. This means that their visible light has been absorbed by gas and dust clouds on its journey from the edges of the universe to our little globe.
Infrared radiation is not absorbed, however, so this is where scientists look. And over the last five years researchers in Australia have built a new instrument, dubbed "DAZLE" that will help them in their search.
The Dark Age Redshift Lyman Explorer (DAZLE) has been designed to search for infrared objects that emit no optical radiation whatsoever. It has been optimised to search for faint emission lines in the spectra of very distant galaxies. These frequencies are very hard to spot because the earth's atmosphere glows at very similar frequencies. DAZLE is equipped with special filters to block out this interference, so giving astronomers a clear view into the past.
Dr. Richard McMahon from the Institute of Astronomy, University of Cambridge explained that the instrument will be used to search for objects with a red-shift of up to 8.8. To put that into context, the galaxies found by the team at Exeter have a redshift of six.
"Previous attempts to look back this far in time have so far been unsuccessful, so this could be a groundbreaking observation," he said.
This era in the history of our universe is very interesting because it is around this point that the universe heated up for the second time. After the big bang, the temperature dropped to almost absolute zero, McMahon said.
"However, since humans exist we know that the Universe must have been heated up again. We shall use DAZLE to try to determine exactly when the Universe was heated up for the second time, during the birth of the first stars." ®
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