May 30, 2023

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Polarized light reveals the final fate of a star 'Spaghettied' by a black hole

Polarized light reveals the final fate of a star ‘Spaghettied’ by a black hole

Zoom / If a star (red trail) wanders too close to a black hole (left), it can be torn or shredded by intense gravity. Some of the star’s material orbits the black hole, like water in a sewer, and emits copious (blue) X-rays.


When astronomers first observed a star shredded, or “spaghetti,” after getting very close to a supermassive black hole in 2019, they determined that a large portion of the star’s material was being shot outward in strong winds of optical light emitted by the explosion. . Now, astronomers from the University of California, Berkeley (UCB) have analyzed the polarization of that light to determine that the cloud was likely spherically symmetric, adding more evidence for those strong winds.

“This is the first time anyone has deduced the shape of a gas cloud around a tidal star,” he said. Co-author Alex Filippenko said:, UCB astronomer. The most recent results appeared in last paper Published in Monthly Notices of the Royal Astronomical Society.

as we are I mentioned earlier, an object passing beyond the event horizon of a black hole – including light – is swallowed up and cannot escape, even though black holes are also chaotic eaters. This means that part of the body substance is already expelled in a strong jet. If this object is a star, then the process of its tearing (or “ripping”) by the black hole’s strong gravitational forces occurs outside the event horizon, and a portion of the star’s original mass is violently ejected outward. This can be shaped rotating ring of the material (aka Accumulation disk) around the black hole emitting powerful X-rays and visible light. Jets are one way astronomers can indirectly infer the existence of a black hole.

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In 2018, astronomers announced first live photo A fallout from the ripping of a star by a black hole 20 million times the mass of our sun into a pair of colliding galaxies called Arp 299 150 million light-years from Earth. A year later, astronomers recorded Final death throes A star torn apart by a supermassive black hole in such a “tidal disturbance event(TDE), aka AT 2019qiz. The star with roughly half its mass fed – or accumulated – ruptured into a black hole a million times the mass of the Sun, and the other half was ejected outward.

These powerful bursts of light are often hidden behind a veil of interstellar dust and debris, making it difficult for astronomers to study them in more detail. But in 2019, qiz was discovered shortly after the star was torn apart last year, making it easier to study in detail, before the curtain of dust and debris was fully formed. The astronomers made follow-up observations across the electromagnetic spectrum over the next six months, using multiple telescopes around the world. These observations provided the first direct evidence that gas flowing during turbulence and accumulation produces strong light and radio emissions previously observed.

Artist's impression of a star gradually disrupted by the strong gravitational pull of a supermassive black hole.
Zoom / Artist’s impression of a star gradually disrupted by the strong gravitational pull of a supermassive black hole.

Astronomers know that the optical light emitted has a slight polarization of 1 percent based on observations from the 3-meter Shin Telescope at the Lake Observatory near San Jose, California. The observatory includes a spectrometer to determine the polarization of optical light. The light may become polarized after the electrons are scattered in the gas cloud. Due to how remote this TDE is, it usually appears as only a point of light, and polarization is one of the few properties that hint at the shapes of objects.

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according to Co-author Kishore Patra, much of the light emitted by the accretion disk would have started in the X-ray system, but as it passed through the gas cloud, this light continued to lose energy thanks to various scattering, absorption and re-emission, which eventually resulted in it appearing in the photosystem governing. “The final scattering then determines the photon’s polarization state,” Batra said. “So, by measuring the polarization, we can infer the surface geometry where the final scattering occurs.”

Based on polarization measurements in October 2019 that showed zero polarization, the Berkeley scientists calculated that the light came from a spherical cloud with a surface radius of about 100 astronomical units (au), or about 100 times larger than Earth’s orbit. However, measurements made a month later revealed a 1 percent polarization of the light, indicating that the cloud had weakened and taken on a slight asymmetry.

“This observation excludes a class of solutions that have been theoretically proposed and gives us stronger constraints on what happens to the gas around the black hole,” Batra said. ‚ÄúPeople have seen other evidence of wind coming out of these events, and I think this study of polarization definitely makes that evidence even stronger, in the sense that you won’t get a spherical geometry without enough wind. The interesting fact here is that a large part of the matter in A star that’s spiraling inward doesn’t eventually fall into the black hole – it just explodes away from the black hole.”

DOI: Monthly Notices of the Royal Astronomical Society, 2022. 10.1093/Manras/Stack 1727 (About DOIs).

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