Galaxy Evolution After the Big Bang: Unraveling the Metamorphosis of Galaxies

First Posted: Aug 27, 2015 11:06 AM EDT

It turns out that galaxies can change their structure over the course of their lifetime. Scientists have taken a closer look at galaxies using the Hubble and Herschel telescopes and have found that a large proportion of galaxies have undergone a major metamorphosis since they were initially formed after the Big Bang.

In this latest study, the researchers observed about 10,000 galaxies currently present in the universe using a survey of the sky created by the Herschel ATLAS and GAMA projects. Then, the scientists classified the galaxies into two main types: flat, rotating, disc-shaped galaxies and large, oval-shaped galaxies with a swarm of disordered stars.

The researchers showed that 83 percent of all the stars formed since the Big Bang were initially located in a disc-shaped galaxy. However, 49 percent of stars that exist in the universe today are located in these disc-shaped galaxies. The remainder, though, are located in oval-shaped galaxies.

The result suggests that there's a massive transformation in which disc-shaped galaxies become oval-shaped galaxies over time. It's possible that two disk-dominated galaxies may stray too close to each other and merge into a single galaxy, creating an oval-shaped galaxy. It's also possible that transformation involves a more gentle process and that stars formed in a disk gradually move to the center of a disk and create a central pile-up of stars.

"Many people have claimed before that this metamorphosis has occurred, but by combining Herschel and Hubble, we have for the first time been able to accurately measure the extent of this transformation," said Steve Eales, one of the researchers, in a news release. "Galaxies are the basic building blocks of the universe, so this metamorphosis really does represent one of the most significant changes in its appearance and properties in the last 8 billion years."

The findings are published in the journal Monthly Notices of the Royal Astronomical Society.

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