the Hubble Space Telescope It's like an old dog that constantly teaches the astronomical community new tricks. Throughout its almost thirty years of operation, it has revealed vital data on the expansion of the Universe, its age, the Milky Way, supermassive black holes (SMBH), other star systems and exoplanets, and the planets of the Solar System. .
More recently, an international team of researchers using the Hubble made a discovery that was not only fascinating but also completely unexpected. In the heart of the spiral galaxy NGC 3147, they spotted a thin disk of swirling gas that was precariously near a rear hole that has approximately 250 million solar masses. The finding was a complete surprise, since the black hole was considered too small to have a structure around it.
Located approximately 130 million light-years from Earth, NGC 3147 is a spiral galaxy with a relatively small SMBH at its core. Things
Like Stefano Bianchi, researcher at the Università.
"This is an intriguing look at a disk very close to a black hole, so close that the speeds and intensity of the gravitational force affect the appearance of light photons. We can not understand the data unless we include the theories of relativity. "
In smaller galaxies such as NGC 3147, it is not assumed that there is enough material gravitationally captured to feed their SMBHs regularly, which makes them "malnourished black holes". As such, it is likely that the small amount of inflation material they consume inflates and forms a donut-shaped bull, instead of flattening it into a thin disk.
Therefore, it was quite surprising to see a disk surrounding the black hole in NGC 3147 that looks like the most powerful ones around SMBH that are much larger at the center of extremely active galaxies. As explained by Ari Laor of Technion-Israel Institute of Technology:
"We thought that this was the best candidate to confirm that below certain luminosities, the accretion disk no longer exists, what we saw was something completely unexpected." We found that gas in motion produces characteristics that we can only explain as produced by material which rotates on a thin disc very close to the black hole. "
These observations were particularly surprising since the research team initially selected NGC 3147 to validate accepted models of galaxies. These models predict that the accretion discs form when the gas is trapped by a gravitational pull SMBH. As the discs gain speed from the rotatonal speed of the black hole, they begin to emit an intense light, producing a bright nuclear known as a quasar.
However, once less material is introduced into the disk, it begins to break and becomes weaker. When the team observed NGC 3147, they expected to see an active galaxy of lower luminosity with a malnourished black hole. As Bianchi explained:
"The type of disk we see is a small quasar that we did not expect to exist. It's the same kind of disk we see in objects that are 1,000 or even 100,000 times brighter. The predictions of current models for the dynamics of gases in very weak active galaxies clearly failed. "
As noted, because the disk is so deeply integrated into the intense gravitational field of the black hole, the light of the gas disk is modified according to Einstein's Theory of General Relativity. This theory describes how the curvature of space-time is altered in the presence of a gravitational field, which can even affect the behavior of light (described in Einstein's Special Theory of Relativity).
Based on their observations with the Hubble Space Telescope Imaging Spectrograph (STIS), the team determined that the material on the disk was moving at more than 10% of the speed of light. At these extreme speeds, the material on the disk seemed to glow as it traveled to Earth on one side and attenuated as it accelerated on the other (an effect known as relativistic transmission).
The Hubble observations also showed that the gas is so embedded in the gravitational well of the black hole that the wavelength of the light stretches, making it appear more red. Thanks to the sharp resolution of STIS, the team was able to isolate the dim light coming from the black hole region and block the polluting light. As Chiaberge said:
"Without Hubble, we would not have been able to see this because the black hole region has a low luminosity, 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 the stars, which drowns the weak emission of the nucleus. "
The team hopes to take advantage of this latest discovery by using Hubble to search for similar compact discs around black holes of low luminosity. If successful, the resulting discoveries will provide astronomers with additional opportunities to see relativity in action.
The study describing the team's observations recently appeared in the Monthly notices from the Royal Astronomical Society.
Additional reading: Hubble, MNRAS