“These stellar tidal disruption events are one of very few ways astronomers know the existence of supermassive black holes at the centers of galaxies and measure their properties. , UC Berkeley assistant professor of astronomy. “One of the craziest things a supermassive black hole can do is to shred a star by its enormous tidal forces,” said team member This was not observed for this tidal disruption event. Many theorists have hypothesized that the stellar debris forms an eccentric, asymmetric disk after disruption, but an eccentric disk is expected to show a relatively high degree of polarization, which would mean that perhaps several percent of the total light is polarized. The interesting fact here is that a significant fraction of the material in the star that is spiraling inward doesn’t eventually fall into the black hole - it’s blown away from the black hole.” “People have been seeing other evidence of wind coming out of these events, and I think this polarization study definitely makes that evidence stronger, in the sense that you wouldn’t get a spherical geometry without having a sufficient amount of wind. “This observation rules out a class of solutions that have been proposed theoretically and gives us a stronger constraint on what happens to gas around a black hole,” said UC Berkeley graduate student The results support one answer to why astronomers don’t see high-energy radiation, such as X-rays, from many of the dozens of tidal disruption events observed to date: The X-rays, which are produced by material ripped from the star and dragged into an accretion disk around the black hole before falling inward, are obscured from view by the gas blown outward by powerful winds from the black hole. , UC Berkeley professor of astronomy and a member of the research team. “This is the first time anyone has deduced the shape of the gas cloud around a tidally spaghetiffied star,” said But the new data on the light’s polarization, which was essentially zero at visible or optical wavelengths when the event was at its brightest, tells astronomers that the cloud was likely spherically symmetric. 8, 2019, suggest that a lot of the star’s material was blown away at high speed - up to 10,000 kilometers per second - and formed a spherical cloud of gas that blocked most of the high-energy emissions produced as the black hole gobbled up the remainder of the star.Įarlier, other observations of optical light from the blast, called AT2019qiz, revealed that much of the star’s matter was launched outward in a powerful wind. Luckily, this was the first such event bright enough that astronomers from the University of California, Berkeley, could study the optical light from the stellar death, specifically the light’s polarization, to learn more about what happened after the star was torn apart. That tidal disruption of a sun-like star by a black hole 1 million times more massive than itself took place 215 million light years from Earth. In 2019, astronomers observed the nearest example to date of a star that was shredded, or “spaghettified,” after approaching too close to a massive black hole. Recent studies of these so-called tidal disruption events suggest that a significant fraction of the star’s gas is also blown outward by intense winds from the black hole, in some cases creating a cloud that obscures the accretion disk and the high-energy events happening within. Some of the star’s matter swirls around the black hole, like water down a drain, emitting copious X-rays (blue). If a star (red trail) wanders too close to a black hole (left), it can be shredded, or spaghettified, by the intense gravity.
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