What Do You Think?

[troach]

hum ... seems several things in astronomy that so many want to claim as absolute fact might be getting ready to change or at least modified.

It is important to always remember as we learn more what was taught and sometimes preached as fact will probably in time change to something very different as time progresses.

Simple case and point consider how the the structure of an atom has been taught (as fact) and changed over the years.


http://www.sciencealert.com.au/features/20112103-21969.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+sciencealert-latestfeatures+%28ScienceAlert-Latest+Features%29


Big Bang survivors send astronomy back to the drawing board
Monday, 21 March 2011
By Julian Cribb
pederk_-_star_explosion.jpg
Cosmological theory proposes that the
universe was formed by the "big bang".
Image: pederk/iStockphoto

Early in its life the universe underwent an epoch of explosive star formation, its infant galaxies sparkling with vitality as stars clumped and supernovae crackled amid swirling penumbras of gas and dust. After a few billion years things settled into a more stable state – the cosmos we largely see today.

Now a team of astronomers from Swinburne University of Technology has opened a startling new window into the early story of the universe, with the discovery of a unique set of galaxies close in space and time to our own Milky Way – yet resembling in every way the turbulent, rumbustious galaxies, bursting with fresh energy, of that bygone era more than 10 billion years ago. It’s a finding that promises to take astronomy a broad leap closer to one of its grails: understanding the processes that give rise to star formation and galactic development.

Their discovery was remarkable enough to earn them one of science’s most coveted laurels – a cover story in the international scientific journal Nature – rare at any time, but doubly so for the fact that it was lead author and doctoral student Andy Green’s first published scientific paper.

Behind any important scientific discovery nowadays is an ocean of hard slog, frustration and voluminous data crunching and, just occasionally, the odd, blissful eureka moment. It was no different for Andy and the team led by Professor Karl Glazebrook at the Swinburne Centre for Astrophysics and Supercomputing.

They began by asking themselves a very difficult question: how did the vigorous star-forming galaxies of 10 billion or more years ago really work – what was driving the phenomenal burst of vitality at this critical juncture in the life of the cosmos?

Quest leads to eureka moment

Between them and the answer stood the enormous lapse of time and space since the universe was young. The fact that these youthful galaxies were no more than indistinct blobs of light on the far horizon of space-time scarcely detected by the most powerful of telescopes and sensitive of instruments.

Their solution was to switch the focus of the search to a far more recent set of galaxies, barely one-tenth the age of these primal furnaces of star formation, to see if they could spot signs of similar vigorous internal activity and perhaps connect the evolutionary dots between the universe of then and that of now.

“Nobody had thought to look at local galaxies in quite this way before,” Professor Glazebrook explains. “We were studying galaxies with a red shift of 0.1 – in other words only about 1.3 billion years in look-back time. Less than a tenth the age of the universe.”

This involved a quest to search through the million or so galaxies assembled by the Sloan Digital Sky Survey, which spans about a quarter of the night sky visible from Earth in the general proximity of our Milky Way. Being much closer and more contemporary, the astronomers expected to see galaxies much like ours – mature, stable, structured, predictable. But to give themselves the best chance they picked out, for closer scrutiny, a ratbag handful of galaxies that seemed far more agitated than their stately peers.

Between the team and the answer also lay the bane of optical astronomers: the weather. Ten nights of their precious observing time on the Anglo-Australian Telescope (AAT) and the Australian National University’s 2.3-metre telescope at Siding Spring, NSW, were lost to cloud and drizzle, Andy recalls. “But it gave us time to think in more detail about what we were really hoping to find.”

When the skies finally cleared and the telescope was at last able to harvest the meagre photons from galaxies a billion or so light years distant, the results were startling.

The team was using one of astronomy’s most potent instruments, an integrated field spectrograph, which essentially gathers the full spectrum of light emitted by the object in every one of its pixels. In optical astronomy, colour equals information: in particular the red- or blue-shift of hydrogen ions reveals whether they are moving away from or towards the observer, and this in turn signals how turbulent are conditions in their vicinity.

The first few galaxies studied yielded two results in particular – one showing pockets with high rates of star formation and the other strong turbulence in the gas and dust around them. Taken together they revealed a seething furnace in which stars were being born at impetuous rates.

To the astonishment of the team nearly a third of their hand-picked sample objects turned out in both respects to resemble the giant firecracker galaxies of the early universe. “It was a eureka moment for us – really quite exciting,” Andy confesses.

“We compared the data from the first galaxy with that of others, and we saw the same trend in about 20 out of the 65 we were studying. It was then we realised we’d found something really unusual, a new class of galaxies. It was one of those times when you go ‘A-ha!’

“We had simply no idea that these highly turbulent star-forming galaxies still existed in the more recent universe,” he explains. “Until then we had considered them to be a feature of this much earlier and more energetic phase following the Big Bang.

Yet here they were – rare, but nevertheless active.” Although it is hard as yet to make a precise estimate, such galaxies probably comprise less than one per cent of all those in our own galactic neighbourhood, puzzling survivors from a cosmic era long gone.

Galactic ‘fossils’ key to evolutionary insights

Just as palaeontologists study ‘living fossils’ such as the coelacanth and lungfish to trace the evolutionary pathways from early fishes through to land animals, the Swinburne team now plans to use these highly turbulent galaxies to observe the processes that drive star formation and galactic evolution and to gain insight into the processes that established the early universe, Professor Glazebrook says.

Being so much closer at hand, they are easier to resolve with today’s most powerful instruments. In time they will provide fodder for next-generation devices such as the Giant Magellan Telescope and the Thirty Meter Telescope, both due for completion in the 2020s.

One of the most important questions that the Swinburne team is seeking to answer is how turbulence and star formation are linked. Are the gigantic swirls of gas and dust a precondition for many stars to form or a consequence of their forming – or both? The two are certainly related, but which drives the other? How is the process regulated? And if the swirling gas provides the primary material, where does it come from?

“Discovering these odd galaxies has raised more questions than it answers,” Andy admits. “Another is why they are still behaving this way, 10 billion years after the universe’s peak period of star formation. Are they simply late bloomers and something has held them back? Or have they been triggered by recent events, such as a collision between two or more galaxies?”

The work of finding out has already begun, using the world’s most powerful telescope, the 10-metre Keck II atop Mauna Kea in Hawaii, where Swinburne astronomers enjoy the rare privilege of regular observing time. Here, says Professor Glazebrook, the team will enjoy resolutions 10 times or more greater than on the Australian instruments. Each incremental advance in observational power will unlock more detail of how stars are born, and so the journey to enlightenment will continue.

The team’s report, High star formation rates as the origin of turbulence in early and modern disk galaxies, was unusual enough to catch the eye of the editors of Nature, but what set the seal on their report was some remarkable artwork by theoretician Rob Crane, who uses the Swinburne supercomputer to model galactic evolution.

“I asked Rob what images he had that might illustrate the kind of conditions we were studying – and he found a really good one,” Andy recounts.

The editor was impressed – and the almost unheard-of event of a graduate student making the cover of Nature with their first paper came to pass, albeit backed by an international team of eight distinguished astronomers.

“It was a great moment for Andy and for Swinburne,” Karl Glazebrook reflects. But you can just tell his focus is on the great moments still to come, as the team penetrates further into the mystery of how suns are born.

MORE INFORMATION

High star formation rates as the origin of turbulence in early and modern disk galaxies by Andrew W. Green, Karl Glazebrook, Peter J. McGregor, Roberto G. Abraham, Gregory B. Poole, Ivana Damjanov, Patrick J. McCarthy, Matthew Colless, and Robert G. Sharp, was published in Nature Vol 467, October 2010.

View an animation of star formation here (http://astronomy.swin.edu.au/). The same link takes you to details of Swinburne’s upcoming free astronomy public lectures.