Matter falling toward a black hole collects into a spinning accretion disk, where it becomes compressed and heated before eventually spilling over the black hole’s event horizon, the point beyond which nothing can escape and astronomers cannot observe. Astronomers call this a tidal disruption event. When a star passes too close to a black hole with 10,000 or more times the sun’s mass, tidal forces outstrip the star’s own gravity, converting the star into a stream of debris. For comparison, the event horizon of a black hole like this is about 13 times bigger than the sun, and the accretion disk formed by the disrupted star could extend to more than twice Earth’s distance from the sun.
“We think this means the optical and UV emission arose far from the black hole, where elliptical streams of orbiting matter crashed into each other.”Īstronomers think ASASSN-14li was produced when a sun-like star wandered too close to a 3-million-solar-mass black hole similar to the one at the center of our own galaxy.
“We discovered brightness changes in X-rays that occurred about a month after similar changes were observed in visible and UV light,” said Dheeraj Pasham, an astrophysicist at the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts, and the lead researcher of the study. Now, a team of scientists using observations from NASA’s Swift satellite have mapped out how and where these different wavelengths were produced in the event, named ASASSN-14li, as the shattered star’s debris circled the black hole. Intense tides tore the star apart, which produced an eruption of optical, ultraviolet and X-ray light that first reached Earth in 2014. Some 290 million years ago, a star much like the sun wandered too close to the central black hole of its galaxy. Credit: NASA’s Goddard Space Flight Center New data from NASA’s Swift satellite show that the initial formation of the disk was shaped by interactions among incoming and outgoing streams of tidal debris. The debris gathered into an accretion disk around the black hole. This artist’s rendering shows the tidal disruption event named ASASSN-14li, where a star wandering too close to a 3-million-solar-mass black hole was torn apart.
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