William Atkins
Saturday, 04 April 2009 19:57
Science -
Space
Page 2 of 3
These galaxies (and clusters of galaxies) play a constant game of tug of war (tug o’ war) with each other, with each one trying to strong-arm the other with their gravitational field (the rope that binds them together).
So, the astronomers can measure this tugging of the galaxies and then calculate their movements based on this gravitational exchange. By doing this, they can map these visible and invisible galaxies (at least invisible to us).
In fact, Dr. Jones states,
"Light can be obscured, but you can't hide gravity.” [AAO]
However, some of these movements (tuggings) can not be explained by just the normal matter in the Universe. Scientists contend that dark matter is also involved with these motions.
Dr. Jones states further, "
They can have individual velocities of several hundred kilometres per second. There is not enough visible matter to explain such velocities. The key to dark matter is in these local motions." [Sydney Morning Herald article “
Galaxy quest illuminates dark corners of the universe.”]
This survey will help to explain how much of this gravitational motion is from ordinary matter and how much is from dark matter.
According to the AAO article,
“The survey was carried out with the 1.2-m UK Schmidt Telescope, which is operated by Siding Spring Observatory in New South Wales, Australia.”
And,
“Broader and shallower than previous comparable surveys—it covered twice as much sky as the Sloan Digital Sky Survey—it has recorded the positions of more than 110 000 galaxies over more than 80% of the Southern sky, out to about two thousand million light-years from Earth [a redshift of 0.15].”
Page three concludes with more information, and the map produced by this team of astronomers.
