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As if black holes were not mysterious enough, astronomers using NASA's Hubble Space Telescope discovered an unexpected disc of material that was spinning furiously around a supermassive black hole in the heart of the magnificent spiral galaxy NGC 3147, located 130 million light-years away.
The puzzle is that the disc should not be there, based on current astronomical theories. However, the unexpected presence of a disk so close to a black hole offers a unique opportunity to test Albert Einstein's theories of relativity. General relativity describes gravity as the curvature of space and the special relativity describes the relationship between time and space.
"We have never seen the effects of both general relativity and special relativity in visible light with such clarity," said Marco Chiaberge of the European Space Agency, as well as the Space Telescope Science Institute and Johns Hopkins University, both located in Baltimore, Maryland. member of the team that led the Hubble study.
"It's an intriguing look at a record very close to a black hole, so narrow that the velocities and intensity of the gravitational force affect the appearance of photons of light," added Stefano Bianchi, first author of the study, University degli Studi. Roma Tre, Rome, Italy. "We can not understand the data without including the theories of relativity."
Black holes in certain types of galaxies such as NGC 3147 are malnourished because there is not enough material captured by gravitation to feed them regularly. Thus, the fine haze of infalling material swells like a donut instead of flattening into a crepe-shaped disc. Therefore, it is very difficult to understand why a thin disc surrounding a hungry black hole in NGC 3147 mimics much more powerful discs found in highly active galaxies with engorged black monster holes.
"We thought it was the best candidate to confirm that under certain luminosities, the accretion disc no longer exists," explained Ari Laor of the Technion-Israel Institute of Technology located in Haifa, Israel. "What we saw was something completely unexpected. We have discovered that the characteristics of gas production in motion can only be explained by the rotation of a material in a thin disc very close to the black hole. "
Astronomers initially chose this galaxy to validate the accepted models for low-luminosity active galaxies, those with black and lean holes. Models predict the formation of an accretion disk when large amounts of gas are trapped by the gravitational pull of a black hole. This infallible material emits a lot of light, producing a shining beacon called quasar, in the case of the black holes best fed. Once less material is drawn into the disc, it begins to decompose, weaken and change structure.
"The type of disc we see is a reduced quasar that we did not think existed," Bianchi said. "It's the same kind of disk that we see in 1,000 or even 100,000 times brighter objects." The predictions of current gas dynamics models in very weak active galaxies have clearly failed. "
The disk is so deeply embedded in the intense gravitational field of the black hole that the light of the gas disk is altered, according to Einstein's theories of relativity, offering astronomers a unique look at the dynamic processes near the black hole.
The clocked Hubble material swirling around the black hole moves at more than 10% of the speed of light. At these extreme speeds, the gas appears to brighten when it is moving towards Earth on one side and attenuating as it moves away. of our planet on the other side (effect called relativistic beam). Hubble's observations also show that the gas is so ingrained in the gravitational well that the light is barely coming out, and thus seems stretched to shorter wavelengths. The mass of the black hole is about 250 million suns.
The researchers used the Hubble Space Telescope (STIS) Imaging Spectrograph to observe the material swirling inside the disc. A spectrograph is a diagnostic tool that divides the light of an object into its many wavelengths to determine its speed, temperature, and other characteristics with extreme precision. Astronomers needed the sharp resolution of the STIS to isolate the weak light from the black hole region and block the light from the contaminating stars.
"Without Hubble, we would not have been able to see this because the black hole region has poor light," Chiaberge said. "The luminosities of the stars of the galaxy surpass everything in the nucleus, so if you look at it from the ground, you are dominated by the brightness of the stars, which drowns the weak emission of the nucleus."
The team hopes to use Hubble to look for other very compact discs around low wattage black holes in similar active galaxies.
The team's document will be posted online today in the Monthly Notices of the Royal Astronomical Society.
The international team of astronomers participating in this study is composed of Stefano Bianchi (Università degli Studi Roma Tre, Rome, Italy); Robert Antonucci (University of California at Santa Barbara, California); Alessandro Capetti (INAF – Turin Astronomical Observatory, Pino Torinese, Italy); Marco Chiaberge (Institute of Space Telescope Science and Johns Hopkins University, Baltimore, Maryland); Ari Laor (Israel Institute of Technology, Haifa, Israel); Loredana Bassani (INAF / IASF Bologna, Italy); Francisco Carrera (CSIC – University of Cantabria, Santander, Spain); Fabio La Franca, Andrea Marinucci, Giorgio Matt and Riccardo Middei (Università degli Studi Roma Tre, Rome, Italy); and Francesca Panessa (Institute of Astrology and Planetology, INAF, Rome, Italy).
The Hubble Space Telescope is an international cooperation project between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, operates the telescope. The Institute of Space Telescope Sciences (STScI) in Baltimore, Maryland, conducts Hubble's scientific activities. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.