A routine survey of the night sky caught the image of a particularly bright image and that image captured the attention of a University of California postdoctoral scholar.
That student’s attention to the image turned into the discovery of an intermediate stage of elliptical galaxy development that is fairly rare, W.M. Keck Observatory Operations Support Manager Bob Goodrich said.
In the image, astronomers found “two massive galaxies, bigger than our Milky Way,” Goodrich said, adding the galaxies are being observed in the process of colliding and merging. The merger will happen in a relatively short time period, at least compared with the time frame in which other astronomical events happen, he said.
Further study revealed something even more unusual, he said. Scientists could see the galaxies are full of gases, and then they realized something about how the gases were being used.
“They’ll use up all the gas in a few hundred million years,” Goodrich said. “That’s a much faster rate than people thought. The rate is so fast, it challenges theoretical models for how quickly gas can be used.”
The situation is so unusual, astronomers estimate only about three dozen such speedily gas-consuming galaxies exist among the billions of galaxies, he added.
The European Space Agency’s Herschel telescope captured the image during a survey. More than a dozen ground-based observatories, including Keck, were used to obtain follow-up images for additional study.
Goodrich likened the discovery to that of the Archaeopteryx, a creature that is understood to show the evolutionary transition from dinosaur to bird.
“It’s exciting because it solves some sort of problem in how we understand how galaxies are formed,” cosmologist Asantha Cooray, the UC Irvine team’s leader. “It gives us some clues in how galaxies are assembled.”
The merger of the galaxies isn’t visible with optical light, Cooray added.
Scientists said the two galaxies collided about 11 billion years ago, and are in the process of forming a massive galaxy 10 times the size of the Milky Way.