Astronomers are watching galaxies pop out bundles of newborn stars 12 billion light years away, thanks to a huge, sensitive new telescope in the Chilean Andes.
The Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope, built by an international collaboration that included Canada's National Research Council, was officially inaugurated just this week.
But it has already allowed scientists to observe in unprecedented detail galaxies in the very distant universe — 12 billion years back in time — when our universe, now estimated to be 13.7 billion years old, was less than 2 billion years old. (The light has taken 12 billion years to reach Earth, and therefore shows us what was happening at the source 12 billion years ago). The data collected by ALMA, an array of dozens of gigantic satellite dishes, also made it possible to calculate just how far away those galaxies are.
The observations, some of which were published this week in Nature and others that will be described in two upcoming articles in the Astrophysical Journal, show that just one billion years after the Big Bang, the universe was already home to many distant, star-forming galaxies called starburst galaxies.
"It just tells us earlier in the history of the universe, there might have been very large scale galaxy formation and star formation that might have happened earlier than we thought," said Yashar Hezaveh, an astrophysicist at McGill University in Montreal, who led one of the new studies and co-authored the others.
"So perhaps it's going to help us understand some of the processes that could cause the formation of these galaxies."
And at least one of those galaxies could be seen to contain lots of water, suggesting that it may have already harboured a massive black hole at that ancient time.
Hezaveh said one of the big questions that astrophysicists would like to answer is why those galaxies were forming stars so rapidly — at a rate of 4,000 per year. In comparison, our own Milky Way galaxy produces just one star a year.
Because the ancient starburst galaxies are so far away, they appear extremely faint.
Bigger, brighter and warped
But some of them are still detectable because of an effect called gravitational lensing. The effect occurs when the gravity of a galaxy between the Earth and the distant galaxy bends the light of the distant galaxy, making it appear bigger and brighter – up to 20 or 30 times bigger and brighter.
A massive galaxy (in blue) bends the light of a more distant galaxy, forming a ring-like image of the background galaxy which is observed by ALMA, in this artist's impression. (Y. Hezaveh/McGill University) "Basically, it helps us see things in the background galaxy that we wouldn't be able to see otherwise," said Hezaveh in an interview.
Unfortunately, gravitational lensing often splits the image into multiple versions, as a prism does. And it distorts the picture, the way funhouse mirrors at an amusement park can warp your reflection, Hezaveh said.
His role in the study was to correct for that distortion.
"If you know something about how the mirror is, how it has stretched you and squeezed you, then you can correct for the image and really say what that person really looks like," he said.
Seeing in the dark
Even with gravitational lensing, the galaxies observed by ALMA are very hard to detect. That's not only because they're very far away, but also because they emit no visible light or heat — the only "light" they give off is in the form of radio waves.
"We detect what's actually going on in those dark areas," said Alison Peck, the telescope's deputy project scientist. "These are regions that it's never been possible to observe before."
René Plume, an astrophysicist at the University of Calgary, said previous images of galaxies forming in the early universe "have just been fuzzy blobs in space."
With ALMA, he added, "we're going to really be able to start to see some of the detail of this formation process that's going on."
Additional detail is also what Hezaveh is looking forward to. The data from the study released this week was gathered a year ago, when only 16 of ALMA's massive dish antennas had been installed. The last seven of the telescope's full array of 66 antennas are currently being tested, according to the European Southern Observatory, one of the partners in the $1.4 billion project.
Hezaveh said that with 16 antennas, he and his collaborators were only able to see how the distant galaxies look on average, but they will be able to do much more detailed science in the future when all 66 antennas are up and running.
With files from Vik AdhopiaAnda sedang membaca artikel tentang
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