MIT researchers use galaxy cluster as magnifying lens to see faraway system in a new light

Researchers at MIT used a galaxy cluster as a magnifying lens to see a young galaxy hiding behind it.Illustration by Felice Frankel and Christine Daniloff, MIT

Researchers at the Massachusetts Institute of Technology have used nature’s biggest lens to see the X-rays emitted by a young galaxy 9.4 billion light-years away.

An article on the discovery by lead author Matthew Bayliss was published Monday in the journal Nature Astronomy .

Using data from NASA’s Chandra X-ray Observatory, home to a powerful X-ray telescope, the astronomers studied the Phoenix galaxy cluster 5.7 billion light-years away and were able to see the young galaxy hidden billions of light-years behind it, Bayliss said.

Galaxy clusters are “the big cities of the universe,” astrophysicist Paul Sutter said. They are groups of thousands of galaxies bound together by gravity.

These clusters are so gravitationally powerful that they bend space and time and distort any light that passes through them. This creates nature’s largest lens, said Bayliss, a research scientist in MIT’s Kavli Institute for Astrophysics and Space Research, last week.

Using “gravitational lensing,” astronomers can see things in space too faint to be detected with just a telescope, Bayliss said.

Scientists have used gravitational lensing to obtain images of galaxies at optical wavelengths but never in the X-ray range of the electromagnetic spectrum, according to a statement from MIT.

Scientists previously thought it would be impossible to separate any X-rays coming from background sources from the enormous amount of X-rays coming from the galaxy cluster itself, the statement said.

But Bayliss and his team were able to separate the X-rays coming from the Phoenix cluster from those coming from the new galaxy, allowing them to “see” it.

“We’ve been looking at lensed galaxies for a long time in all sorts of wavelengths, but never in X-ray,” said Sutter, a visiting scholar at the Ohio State University Center for Cosmology and AstroParticle Physics.

Researchers, he said, found “a period of intense star formation in that young galaxy, something that would be impossible to see without this lensing technique.”

The galaxy that Bayliss and his team saw was so deep in space that the X-rays they were deciphering were from 9.4 billion years ago. The images were from a time when the universe was 4.4 billion years old, about one-third of the age it is now, according to MIT.

The galaxy they saw was comparatively small, less than 1 percent of the mass of the Milky Way, Bayliss said. But over time, galaxies consume more stars and grow. Today, 9.4 billion years later, the galaxy would be much larger, he said.

“The way I like to think about how we observe the universe, all we get is a snapshot,” Bayliss said.

Bayliss likened studying the universe to studying the entire human race just from an overhead shot of a stadium. You don’t get to see any of the individual people age, but you do see many different people at different stages in their lives. From that, you can figure out what the lifespan of a person is like.

The snapshot of a young galaxy still in its smaller stages is important to piecing together the lifespan of galaxies, he said.

To Bayliss, the goal of an astronomer is “pushing new techniques to take the best facilities we have on earth and make them more powerful.”

He thinks that this study does just that. Bayliss said it adds another tool to the toolbox for astronomers to study the lives of galaxies and opens the door to examining more faraway space phenomena.