On November 22, 2014, a burst of X-rays was detected by the All-Sky Automated Survey for SuperNovae (ASAS-SN) coming from a galaxy 290 million light years away. Initially thought to be a supernova, it was later determined to be a tidal disruption event where a star came too close to a supermassive black hole and was consumed. The event was rare, occurring maybe once every 10,000 to 100,000 years in a galaxy, and transformed a dormant black hole into an observable one.
Scientists trained three X-ray telescopes on the galaxy and observed a strong and regular pulse of X-rays every 131 seconds, which maintained its rhythm over 450 days. The pulse was likely caused by a white dwarf star orbiting the black hole, which was cloaked in glowing matter after a tidal disruption event.
By analyzing the pulse, scientists were able to measure the spin of the black hole, which was found to be at least 0.7 and possibly as high as the theoretical maximum of 0.998. This is the first measurement of spin made possible by a tidal disruption event, and it could provide a method for determining the spin of black holes, particularly dormant ones.
The measurement of spin is important for understanding the origins of black holes. If supermassive black holes grow mainly by feeding on matter from within their own galaxy, their spins would be expected to be very large. However, if they grow predominantly by merging with other black holes, their spins would be lower. By measuring the spins of more black holes, scientists can better understand their growth and the formation and evolution of galaxies over billions of years.
Here are the key facts extracted from the text:
1. On November 22, 2014, a burst of X-rays was detected by the All-Sky Automated Survey for Supernovae (ASAS-SN).
2. The X-ray signal came from the center of a galaxy approximately 290 million light years away.
3. The signal was not a supernova, but rather a star being consumed by a supermassive black hole.
4. The supermassive black hole had a mass millions of times that of the sun.
5. The event was a tidal disruption event, where a star gets too close to a black hole and is torn apart.
6. Tidal disruption events are rare, occurring maybe once every 10 to 100,000 years in a galaxy.
7. The star's matter spiraled into the black hole, forming an accretion disk that emitted visible light, UV, and X-rays.
8. The event transformed a dormant black hole into an observable one.
9. Scientists trained three X-ray telescopes to observe this part of the sky for years after the event.
10. A strong and regular pulse of X-rays was detected, brightening and dimming every 131 seconds.
11. The pulse was observed by all three telescopes over 450 days and maintained its rhythm without weakening.
12. The pulse's relative strength got stronger over time, modulating the X-ray signal by around 40%.
13. Black holes are characterized by only two attributes: mass and spin.
14. Mass is relatively easy to determine, but spin is harder to measure.
15. The spin of a black hole can be measured by observing the innermost stable circular orbit (ISCO) of the accretion disk.
16. The ISCO depends on the spin of the black hole, with faster-spinning black holes having a smaller ISCO.
17. The spin parameter of a black hole is a dimensionless value that ranges from 0 (no spin) to 1 (maximum spin).
18. The maximum real-world spin parameter is thought to be around 0.998.
19. The spin of a black hole can be measured by observing the iron emission line, the periodic oscillations in the data, or the accretion disk's radius.
20. The study's authors proposed that the periodic oscillations were caused by a white dwarf star in orbit around the black hole.
21. The white dwarf star was cloaked in glowing matter, creating an X-ray hotspot that orbited the black hole.
22. The measured spin parameter of the black hole was at least 0.7 and possibly as high as the theoretical maximum of 0.998.
23. The accretion disk's objects were going at least half the speed of light.
24. This is the first measurement of spin made possible by a tidal disruption event.
25. The implication is that this could provide a method for determining the spin of black holes, particularly dormant ones.
26. About 95% of supermassive black holes are dormant.
27. Understanding the spin of supermassive black holes can help us understand their origins and growth.
28. Supermassive black holes lie at the centers of most galaxies, and understanding their growth can help us understand galaxy formation and evolution.