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RSAA News of the Month: March 2003

Stromlo Plays Key Role in Measuring Age of Universe

 

Despite the destruction of telescopes on Mount Stromlo in the Canberra bushfires only three weeks ago, ANU astronomers have played a crucial role in the first ever accurate measurement of the age of our universe.

An American team of astronomers, combining new satellite data with an Australian 3-dimensional galaxy map, has announced that the universe started in a fiery explosion, thirteen thousand, seven hundred million years ago.

RSAA's Dr Matthew Colless, leader of the team that made the galaxy map, remarks: "It is amazing that we should even think of trying to measure the size, shape and age of the whole universe. It is wonderful that Australian astronomers have been able to make a pivotal contribution to solving this fundamental question".

Although the telescopes at Mt Stromlo were destroyed, the Research School of Astronomy and Astrophysics (RSAA) also has an observatory at Siding Spring Mountain, near Coonabarabran, NSW. One of the telescopes at Siding Spring is the Anglo-Australian Telescope (AAT), which was used to make a map of the positions of galaxies in a region of the nearby universe. By combining the data from this map with just-released data from NASA's Wilkinson Microwave Anisotropy Probe (WMAP), the American team were able to measure not only the age of our universe, but also its shape and composition, all with unparalleled precision.

The Australian data was obtained by the 2dF Galaxy Redshift Survey (2dFGRS) team, a combination of astronomers from RSAA, Anglo-Australian Observatory, and Australian and overseas universities. The data is presented in the first diagram. This shows the slice of the universe surveyed by the 2dF Galaxy Redshift Survey. Every dot is a galaxy, with the Milky Way at the centre; distance from the centre is redshift and angle around the circumference is angle on the sky. There are 221,283 galaxies in this slice, which shows the highly-structured nature of the galaxy distribution. By analysing this structure the 2dFGRS team were able to obtain a precise new measure of the density of the universe.

The second diagram is the American team's map of the cosmic microwave background, obtained with the WMAP satellite. The fluctuations, which show as colour changes, are a few ten-thousandths of a degree Kelvin. The fluctuations are the cooling remnant of the fireball of the Big Bang, and show the structure of the universejust 379,000 years after the Big Bang. Similar structures of "streamers and clumps" appear in both diagrams. The new measurement of the age of the universe, and of other fundamental quantities, is based on comparing the structures seen by WMAP at this early time with the structures observed by the 2dFGRS team in the map of galaxies at the current time.

As well as measuring the age of the universe, the results show that the Big Bang and Inflation theory of the creation of the Universe is right on target. They also show that the Hubble Constant, the measure of how fast the Universe is expanding, is very close to 71 kilometers per second per megaparsec.

"We make extensive use of the 2dFGRS data," says David Spergel, one of the leaders of the NASA effort. "Without it, the NASA data alone would not have been enough to solve many of these mysteries."

Mt Stromlo Director Prof Penny Sackett, said: "For months now, astronomers around the world have been waiting with baited breath for the release of these results. It is truly an historic event, not only for astronomy but for all of humanity. We are overjoyed to have made such a large contribution."

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