Australasian Science: Australia's authority on science since 1938

Galactic Dinosaurs Aren’t Extinct

By David Reneke

Astronomers have found that compact massive galaxies that roamed the early universe have been hiding in plain sight.

The full text of this article can be purchased from Informit.

One of the biggest mysteries in galaxy evolution is the fate of the compact massive galaxies that roamed the early universe. Astronomers at Swinburne University of Technology believe they have discovered the answer.

“When our universe was young, there were lots of compact, elliptical-shaped galaxies containing trillions of stars,” Prof Alister Graham said. “Due to the time taken for light to cross the vastness of space, we see these distant galaxies as they were in our young universe. However, in the present-day universe, very few such spheroidal stellar systems have been observed.”

The most popular theory had been that, over time, galaxy mergers might have led to their destruction and transformation into larger elliptical galaxies. However, there have not been enough galactic collisions to account for the reduction in the number of these compact spheroids.

The Swinburne astronomers have eliminated the need for this problematic theory because they have now located the missing galaxies. “They were hiding in plain sight,” said co-author

Dr Bililign Dullo. “The spheroids are cloaked by discs of stars that were likely built from the accumulation of hydrogen gas and smaller galaxies over the intervening eons.” Furthermore, the number of such hidden systems roughly matches the number of compact massive galaxies in the early universe.

“Unlike...

The full text of this article can be purchased from Informit.