Astronomers using the NASA / ESA Hubble Space Telescope have observed an unexpected thin material disk surrounding a supermassive black hole in the heart of the spiral galaxy NGC 3147 , 130 million light-years away.
The presence of the black disk in such a weakly glowing active galaxy has surprised astronomers. Black holes in certain types of galaxies, such as NGC 3147, are said to be starving, as gravity-trapped material is insufficient to supply them regularly. It is therefore surprising that there is a thin slice surrounding a starving black hole, mimicking the much larger slices in extremely active galaxies.
Of particular interest is that this disc of material orbiting the black hole provides a unique opportunity to test Albert Einstein's theories of relativity. 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 these theories, allowing astronomers to cast a unique view of the dynamic processes near a black hole.
"We have never seen the effects of the general and special theory of relativity in the visible light so clearly," said team member Marco Chiaberge of AURA for ESA, STScI and Johns Hopkins University.
It was measured by Hubble that the material of the disk swirls around the black hole at more than 10% of the speed of light. At such extreme speeds, the gas appears to brighten as it approaches one side of the earth, and it darkens as it moves away from our planet on the other side. This effect is called relativistic rays. Hubble's observations also show that the gas is so deeply embedded in a gravitational well that it is difficult for the light to escape and therefore extends to redder wavelengths. The mass of the black hole is about 250 million times that of the sun.
"This is a fascinating view of a disk that is very close to a black hole, so close that the speed and intensity of the force of gravity have an impact on how we see the photons of the light," he explained First author of the study, Stefano Bianchi, the Università degli Studi Roma Tre in Italy.
Artistic representation of the peculiar thin material disk orbiting a supermassive black hole in the heart of the spiral galaxy NGC 3147, 130 million light-years distant. Credit: ESA / Hubble, M. Kornmesser
To study the matter swirling deep in this disk, researchers used the Hubble Space Telescope Imaging Spectrograph (STIS) instrument. This diagnostic tool divides the light of an object into its many individual wavelengths to determine the speed, temperature and other properties of the object with very high accuracy. STIS was an integral part of the effective observation of the region of low luminosity around the black hole, which the brilliant light of the galaxy was hidden.
Astronomers initially selected this galaxy to validate recognized models for lower luminosity active galaxies: those with malnourished black holes. These models predict that material disks should form when abundant gas is trapped by the strong gravitational force of a black hole, which then emits much light and produces a brilliant beacon called quasar.
Top view of an artist's impression of the peculiarly thin disk of material orbiting a supermassive black hole in the heart of the spiral galaxy NGC 3147 and 130 million points of light away. Years away. Credit: ESA / Hubble, M. Kornmesser
"The type of disc we see is a downsized quasar that we did not expect," Bianchi explained. "It's the same type of disk we see in objects that are 1000 or even 100,000 times brighter, and the predictions of current models for very weak active galaxies have clearly failed."
The team hopes Hubble to search for other very compact disks to use low-luminosity black holes in similar active galaxies.
Publication: Stefano Bianchi, et al., "HST reveals a compact, slightly relativistic broad-line region in the candidate True Type 2 NGC 3147", MNRAS , 2019; doi: 10.1093 / mnrasl / slz080