Mysterious black hole type perplexes, bewilders
Billions of times the mass of our own sun, so-called massive black holes present a baffling mystery with clues hidden at the very dawn of existence.
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In the next few years, a variety of telescopes may help answer this question by providing a better look at black holes in multiple wavelengths of light, from radio, infrared and visible light to X-rays and gamma rays, Volonteri said.Skip to next paragraph
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It is difficult to study the evolution of massive black holes because they take so much time to develop. However, stellar-mass black holes may help shed light on their larger cousins, since they evolve on humanly accessible time-scales and because as many as 100 million stellar-mass black holes may be scattered throughout the Milky Way.
Stellar-mass black holes are often paired with normal stars in systems known as X-ray binaries. In the past decade, X-ray observatories have helped scientists learn much about how stellar-mass black holes pull matter from their partner stars. In turn, these findings are helping astrophysicists understand how massive black holes do the same thing, said study co-author Rob Fender at the University of Southampton in England.
X-ray binaries apparently can emit bright outbursts of radiation lasting months to years. Researchers suspect the temperature of the disk of matter accreting onto black holes rises as its mass grows, eventually ionizing the hydrogen within. This increases the viscosity of material in the accretion disk, making it easier for it to slow down and get dragged into the black hole. This increased rush of matter into the black hole is apparently what causes the outbursts of radiation from these systems. Eventually the flow of matter into the black hole slows as the accretion disk runs out of material, which makes the disk cool down, resetting the cycle.
This cycle of activity seen with stellar-mass black holes in X-ray binaries is providing insight into the formation and power of the jets and bursts seen from massive black holes. This titanic activity releases energy that shapes their surrounding galaxies.
An accretion disk was recently detected swirling tightly around a massive black hole — apparently the remnant of a star that wandered too close. Intriguingly, this material seems to be very near the black hole's event horizon, the boundary beyond which nothing escapes. "By analyzing signals from this material, we can test the predictions of Einstein's theory of general relativity, which is quite exciting," said Rubens Reis, an astrophysicist at the University of Michigan, who authored another study in the same issue of Science.
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