As if the black holes were not mysterious enough, astronomers using NASA's Hubble Space Telescope have found an unexpectedly thin disk of material that swirls furiously around a supermbadive 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, according to 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 special relativity describes the relationship between time and space.
"We have never seen the effects of general and special relativity on visible light so clearly," said Marco Chiaberge of the European Space Agency and the Space Telescope Science Institute and Johns Hopkins University, both in Baltimore, Maryland. , Member of the team that carried out the Hubble study.
"This is an intriguing look at a disk very close to a black hole, so close that the velocities and intensity of the gravitational force affect the appearance of photons of light," added the study's first author, Stefano Bianchi, of the Università degli Studi. Roma Tre, in Rome, Italy. "We can not understand the data unless we include the theories of relativity."
Black holes in certain types of galaxies such as NGC 3147 are malnourished because there is not enough material gravitationally captured to feed them regularly. Then, the fine mist of the inflated material is inflated like a donut instead of being flattened into a pancake-shaped disk. Therefore, it is very puzzling why there is a thin disk surrounding a hungry black hole in NGC 3147 that imitates much more powerful discs found in extremely active galaxies with black holes of engorged monsters.
"We thought that this was the best candidate to confirm that below certain luminosities, the accretion disk 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 found a gas in motion that produces characteristics that we can only explain as produced by material that rotates in a thin disc very close to the black hole."
Astronomers initially selected this galaxy to validate accepted models of active low-luminosity galaxies, those with black holes found in a poor diet of material. The models predict that an accretion disk forms when large amounts of gas are trapped by the strong gravitational force of a black hole. This inflatable material emits a lot of light, producing a bright beacon called quasar, in the case of well-fed black holes. Once less material is introduced into the disk, it begins to break, becomes weaker and changes structure.
"The kind of disk we see is a small quasar that we did not expect to exist," Bianchi said. "It's the same kind of disk we see in objects that are 1,000 or even 100,000 times brighter." Predictions of current models for the dynamics of gases in very weak active galaxies failed.
The disk is so deeply embedded in the intense gravitational field of the black hole that the light of the gas disk is modified, according to Einstein's theories of relativity, giving astronomers a unique view of the dynamic processes near a hole black.
The material of the Hubble clock revolves around the black hole moving at more than 10% of the speed of light. At those extreme speeds, the gas seems to glow as it travels towards Earth on one side, and it dims as it moves away from our planet on the other side (an effect called relativistic emission). The Hubble observations also show that the gas is so ingrained in the gravitational well that the light is struggling to get out, and therefore seems stretched at redder wavelengths. The mbad of the black hole is around 250 million soles.
The researchers used the Hubble Space Telescope (STIS) imaging spectrograph to observe the matter swirling deep inside the disk. A spectrograph is a diagnostic tool that divides the light of an object into its many individual wavelengths to determine its speed, temperature, and other characteristics with very high precision. Astronomers needed the sharp resolution of STIS to isolate the dim light from the black hole region and block light from contaminating stars.
"Without Hubble, we would not have been able to see this because the black hole region has a low luminosity," said Chiaberge. "The luminosities of the stars in the galaxy eclipse anything in the nucleus, so if you look at it from the ground, you are dominated by the brightness of the stars, which drowns out the weak emission of the nucleus."
The team hopes to use Hubble to find other very compact discs around low-wattage black holes in similar active galaxies.
The team article will appear online today at the Monthly notices from the Royal Astronomical Society.
The international team of astronomers in this study is formed by Stefano Bianchi (Università degli Studi Rome Tre, Rome, Italy); Robert Antonucci (University of California, Santa Barbara, California); Alessandro Capetti (INAF – Osservatorio Astrofisico di Torino, Pino Torinese, Italy); Marco Chiaberge (Space Telescope Science Institute and Johns Hopkins University, Baltimore, Maryland); Ari Laor (Israel Institute of Technology, Haifa, Israel); Loredana Bbadani (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 Rome Tre, Rome, Italy); and Francesca Panessa (INAF Istituto di Astrofisica and Planetologia Spaziali, Rome, Italy).