Department of Public Affairs

University of Toronto

Toronto, Ontario


Professor Raymond Carlberg, Department of Astronomy

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U of T Public Affairs

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By Janet Wong

Gaze into the vastness of the universe this evening and in all likelihood
those galaxies look just as they did five billion years ago, and they
didn’t get to their locations by random chance, says U of T astronomy
professor Raymond Carlberg.

In the earliest moments after the big bang, waves were created in the
universe, Carlberg explains. When a wave became large enough, it eventually
collapsed under its own gravity to create what is called a dark halo. The
gravitational force of the dark halo sucked in and compressed the gas
particles around it, and it is in this environment that galaxies are bred,
running contrary to the notion that galaxies — and their resulting stars
and planets — form randomly in the universe.

By measuring clusters of galaxies from the present time back to when the
universe was about five billion years younger, Carlberg and his team of
researchers found that these clusters experienced little, if any, change.
Once the drama of the initial burst of star formation is over, galaxies
settle into peaceful and essentially stable clusters. This runs counter to
some prevailing theories that suggest galaxy clusters are prone to rapid

“We now know that the clustering of galaxies did not happen at random and
changed little over the past five billion years. Cosmologists now need to
use new telescopes to go into even earlier times to see the dark halos just
as they are collapsing and beginning to draw together the gas that creates
a young galaxy.”

Carlberg’s findings will be published in The Astrophysical Journal.

[Janet Wong is a news services officer with the Department of Public Affairs.]