First glimpse of black hole swallowing star, ejecting flare

Washington: Scientists have for the first time witnessed a black hole swallowing a star in a galaxy 300 million light years away and ejecting a flare of matter moving at nearly the speed of light.

The finding tracks the star – about the size of our Sun – as it shifts from its customary path, slips into the gravitational pull of a super massive black hole and is sucked in, said Sjoert van Velzen, a Hubble fellow at the Johns Hopkins University in US. “It’s the first time we see everything from the stellar destruction followed by the launch of a conical outflow, also called a jet, and we watched it unfold over several months,” van Velzen said.

Black holes are areas of space so dense that irresistible gravitational force stops the escape of matter, gas and even light, rendering them invisible and creating the effect of a void in the fabric of space. Astrophysicists had predicted that when a black hole is force-fed a large amount of gas, in this case a whole star, then a fast-moving jet of plasma – elementary particles in a magnetic field – can escape from near the black hole rim. This study suggests this prediction was correct, the scientists said.

Super massive black holes, the largest of black holes, are believed to exist at the centre of most massive galaxies. This particular one lies at the lighter end of the super massive black hole spectrum, at only about a million times the mass of our Sun, but still packing the force to gobble a star. The first observation of the star being destroyed was made in December last year. Researchers used radio telescopes to follow up as fast as possible. They were just in time to catch the action.

By the time it was done, the team had data from satellites and ground-based telescopes that gathered X-ray, radio and optical signals, providing a stunning “multi-wavelength” portrait of this event. It helped that the galaxy in question is closer to Earth than those studied previously in hopes of tracking a jet emerging after the destruction of a star. This galaxy is about 300 million light years away, while the others were at least three times farther away.

The first step for the international team was to rule out the possibility that the light was from a pre-existing expansive swirling mass called an “accretion disk” that forms when a black hole is sucking in matter from space. That helped to confirm that the sudden increase of light from the galaxy was due to a newly trapped star.

“From our observations, we learn the streams of stellar debris can organise and make a jet rather quickly, which is valuable input for constructing a complete theory of these events,” van Velzen said. The study was published in the journal Science.