Astrophysicists At OU Detect Planets In Another Galaxy

Feb 7, 2018

Researchers at the University of Oklahoma believe they have detected planets outside the Milky Way.

Professor Xinya Dai and postdoctoral researcher Eduardo Guerras say they have detected the presence of a population of planets in a galaxy 3.8 billion light years away from Earth. It’s the first time planets have been detected in another galaxy.

Their research is published in Astrophysical Journal Letters.

“We again expanded the boundary, the frontier, into the extragalactic regime. And I hope this will trigger many new studies from this new frontier,” Dai said.

Dai says the mass of the planets range from the mass of the moon to the mass of Jupiter, and the faraway galaxy has a ratio of 2,000 planets per each star.

Guerras says the planets were indirectly detected because no instrument is strong enough to see an object that is so far away. Dai and Guerras used microlensing to detect them.

In this case, the galaxy sits within the line of sight of a quasar.

When an object, like a galaxy, moves in front of a very bright object, like a quasar, the foreground object’s gravity distorts the light of the background object, making it appear brighter. The same technique has been used to discover some exoplanets in the Milky Way.

“There’s physics involved in all of this and you have to fit all the pieces together,” Guerras said. “The composition of the quasar, what is happening in different wavelengths of the light. And there was something that didn’t fit. In order to explain that anomaly, we had to introduce this population of planets. Now with the planets, everything fits together.”

The planets are floating, which means they do not orbit a star. Guerras thinks there might be many floating planets in our own galaxy.

“They are not bounded to any star. It’s not like the planets that we are used to in the solar system that orbit around the sun. These are planets that wander around between the stars in the dark,” Guerras said.

The researchers used data from NASA’s Chandra X-ray Observatory, a telescope that is orbiting the Earth. Chandra is controlled by the Smithsonian Astrophysical Observatory. The OU Supercomputing Center for Education and Research calculated the microlensing models.


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