Dwarf Galaxies –“The Cosmic Equivalent of Viewing Ancient Greece Live, Today”




Dwarf galaxies are the equivalent of historical villages. They still have most of their ‘old buildings’ intact, so we know what they were like when they were first built." according to David Nicholls. who led new research conducted at Australian National University. "On the other hand, in huge cities like Beijing, nearly all the old buildings have been ripped up and you can’t tell what they were like originally – just like larger galaxies."

Nicholls, from the Research School of Astronomy and Astrophysics, part of the ANU College of Physical and Mathematical Sciences, used the ANU 2.3 metre telescope at the Siding Spring Observatory to study distant dwarf galaxies. The galaxies are regarded as ideal ‘laboratories’ for finding out how the Universe has evolved since the Big Bang.

“At the beginning of the Universe, the only elements around were hydrogen and helium. Big stars formed from these elements and, as they evolved, burned the hydrogen and helium into an ‘ash’ of heavier elements. This ash included nitrogen, carbon and oxygen, which are essential for life,” Nicholls said.

“When these big stars ran out of fuel, they blew up in the form of supernovae and mixed the heavier elements back into the hydrogen clouds. New stars grew from the enriched gas. But in Dwarf galaxies, this process has happened very slowly,” he said.

“By studying dwarf galaxies, we can see what the Universe was like long ago. To do this, we measure the light from the various elements mixed into the hydrogen clouds in the dwarf galaxies, which tells us how enriched they are and how they have evolved since the Universe began.” It's the comsic archeological equivalent of viewing ancient Greece live, today.

But when he started to analyze his measurements, Nicholls discovered that the data didn’t fit the conventional theories. He set out to solve the mystery, and made an unexpected discovery.

“I found that the energies of the electrons in the gas clouds were not distributed the way people had always thought they should be. I used similar measurements of electron energies made by space probes in our Solar System as the basis for a new theory about how gases behave in distant galaxies. To my surprise, it explained my data and also solved other problems that had remained unexplained for over 40 years.”

Nicholls said his research will allow more accurate measurements of the elements in distant galaxies and help to explain the evolution of the Universe.

The research is published in The Astrophysical Journal and is available online.

The Radio/Optical Image at top of page is of dwarf galaxy UGC 5288. The bright white center object is visible-light; purple is giant hydrogen-gas disk. Using the National Science Foundation's Very Large Array (VLA) radio telescope, astronomers found that this small galaxy 16 million light-years from Earth is surrounded by a huge disk of hydrogen gas that has not been involved in the galaxy's star-formation processes and may be primordial material left over from the galaxy's formation.  

The Daily Galaxy via Australian National University

Image credit: Van Zee, NOAO, NRAO/AUI/NSF


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