Supermassive black holes sit at the centers of most large galaxies and usually weigh millions or billions of times the mass of the Sun. At the center of the Milky Way lies Sagittarius A*, with a mass of about four million Suns. Because black holes do not emit light, astronomers infer them from the motion of nearby stars and gas.
A new study in The Astrophysical Journal Letters by Eric Coughlin of Syracuse University and colleagues explains the fate of a star that wanders too close. The black hole’s gravity stretches the star into a long, thin debris stream. That stream wraps around the black hole as a result of Einstein’s General Theory of Relativity rather than simple Newtonian gravity.
Parts of the circling stream can collide and release a burst of energy. After collisions, gas slowly spirals into the hole by accretion, producing intense radiation that can briefly outshine the whole galaxy. Astronomers call these tidal disruption events, or TDEs, and they are one of the few ways to study hidden supermassive black holes in other galaxies. New high-resolution simulations, using tens of billions of particles and GPUs on powerful supercomputers, now show a narrow, coherent stream that later collides with itself. Earlier low-resolution models had given a more sprayed debris pattern and too much dissipation; the new work supports long-standing theoretical predictions and clarifies why TDEs vary from case to case.
Difficult words
- supermassive — Extremely large in mass compared with ordinary objects.
- infer — Decide something from indirect evidence or information.
- debris — Pieces or remains left after something breaks.
- relativity — Theory that describes gravity using space and time.
- accretion — Slow process of gas falling and joining a body.
- tidal disruption event — Moment when a star is torn apart by gravity.tidal disruption events
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Discussion questions
- Why are tidal disruption events useful for astronomers studying hidden supermassive black holes in other galaxies?
- How might better, higher-resolution simulations change our understanding of tidal disruption events?
- Would you prefer to study black holes by observing the sky or by running computer simulations? Why?
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