Astronomers Discover Small Black Hole Beyond the Milky Way

by Jennifer Shea
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Astronomers using the European Southern Observatory’s Very Large Telescope (VLT) have stumbled across a new black hole. It’s inside a cluster of stars just beyond the borders of our Milky Way galaxy. And it’s the first black hole ever discovered outside the Milky Way using this particular technique.

Black holes soak up light, so you can’t look at them directly through most telescopes. But astronomers have learned to look for a black hole’s gravitational pull on the objects around it in outer space. Through this indirect technique, astronomers tracked down the new black hole, according to Space.com.

The VLT sits on top of a mountain in the desert of northern Chile. It has been watching NGC 1850, a cluster in the Large Magellanic Cloud, which is roughly 160,000 light-years away from our planet. And it showed astronomers a star that’s about five times as big as our sun. The star appeared to be orbiting something.

Eventually, astronomers figured out that it was orbiting a black hole roughly 11 times as big as our sun.

This Is The Youngest Star Cluster Ever Known to Host a Black Hole

NGC 1850, where astronomers found the black hole, is only 100 million years old. That’s pretty young compared to most stars. In fact, scientists have never before found a black hole in a star cluster so young.

The astronomers who found this black hole say their technique may be key to finding other black holes elsewhere. In the past, astronomers have found black holes through the X-rays that result when black holes absorb matter. They’ve also found them through the gravitational waves that result when black holes collide with one another or with neutron stars.

But black holes don’t often give off X-rays or gravitational waves. So these astronomers’ technique – tracking the black hole’s dynamic effect on a nearby star – could be a promising way forward.

“The vast majority [of black holes] can only be unveiled dynamically,” said Stefan Dreizler, a member of the team that found this black hole, in a press release. “When they form a system with a star, they will affect its motion in a subtle but detectable way. So we can find them with sophisticated instruments.”

The ELT Will ‘Revolutionize’ Hunt for Black Holes, Astronomers Say

The team’s research has been published in a paper in Monthly Notices of the Royal Astronomical Society. Astronomers from across Europe, Canada and Australia worked to discover the black hole. They gathered data over the course of two years.

The astronomers mounted the Multi Unit Spectroscopic Explorer (MUSE) on top of the VLT and used it to hone in on the star whose odd motion told them it was orbiting something.

“MUSE allowed us to observe very crowded areas, like the innermost regions of stellar clusters, analyzing the light of every single star in the vicinity,” said co-author Sebastian Kamman, who is based at Liverpool’s Astrophysics Research Institute, in the press release. “The net result is information about thousands of stars in one shot, at least 10 times more than with any other instrument.”

Meanwhile, the Extremely Large Telescope (ELT) is scheduled to launch sometime this decade. And astronomers expect it to “revolutionize” the hunt for black holes, both near our galaxy and at much greater distances from it.

Outsider.com