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the The Hubble Space Telescope is like an old dog who is constantly teaching new things to the astronomical community. During his almost thirty years of operation, he revealed essential data on the extension of the Universe, its age, the Milky Way, supermassive black holes (SMBH), other star systems and exoplanets and the planets of the solar system. .
Recently, an international team of researchers using Hubble made a fascinating and totally unexpected discovery. At the heart of the spiral galaxy NGC 3147, they spotted a thin disk of swirling gas that was precariously near a bottom hole of about 250 million solar masses. The discovery was a total surprise since the black hole was considered too small to have such a structure around.
Located about 130 million light-years away from Earth, NGC 3147 is a spiral galaxy with a relatively small SMBH at its center. Things
Like Stefano Bianchi – a researcher at Università
"This is an intriguing look at a record very close to a black hole, so close that the velocities and intensity of gravitational attraction affect the appearance of photons of light. We can not understand the data without including the theories of relativity. "
In small galaxies such as NGC 3147, it is not expected to have enough gravitational capture materials to regularly feed their SMBHs, making them "malnourished black holes". As such, the small amount of infalling material that they consume may swell and form a donut-shaped torus, rather than flatten it into a thin disc.
So it was rather surprising to see a disc circling the NGC 3147 black hole that looks like the more powerful discs found around much larger SMBH at the center of extremely active galaxies. As Ari Laor of the Technion-Israel Institute of Technology, explained:
"We thought it was the best candidate to confirm that below some brightness, the accretion disk no longer existed. 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. "
These observations were particularly surprising since the research team had initially selected NGC 3147 to validate accepted galaxy models. These models predict the formation of accretion disks when the gas is trapped by the gravitational attraction of SMBH. As the discs gain rotational velocity from the black hole, they begin to emit intense light, producing a bright nuclear quasar.
However, once less material is sucked into the disc, it begins to break down and become paler. When the team examined NGC 3147, she was expecting to see an active galaxy of lower brightness with a malnourished black hole. As Bianchi explained:
"The type of disc we see is a reduced quasar that we did not expect to exist. This is the same type of disc that we see in 1000 objects, or even 100 000 times brighter. Predictions of current gas dynamics models in very weak active galaxies have clearly failed. "
As we have noted, the disk being deeply integrated into the powerful 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 modified in the presence of a gravitational field that can even influence the behavior of light (described in Einstein's theory of special relativity).
Based on their observations with the Hubble Space Telescope Imaging Spectrograph (STIS), the team determined that the contents of the disk were moving at more than 10% of the speed of light. At these extreme speeds, the material in the disc seemed to brighten as it was heading toward Earth on one side and fading as it s & rsquo; Distance from the other (effect known as relativistic radiation).
Hubble's observations have also shown that the gas is so buried in the gravitational well of the black hole that the wavelength of light stretches, making it redder. Thanks to the clear resolution of the STIS, the team was able to isolate the weak light from the black hole region and block the contaminating light. As Chiaberge said:
"Without Hubble, we would not have been able to see that because the black hole region has low light. The luminosities of the stars of the galaxy surpass all that is in the nucleus. So, if you observe 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 take advantage of this latest discovery by using Hubble to look for similar compact discs around low-light black holes. If successful, the resulting discoveries will provide astronomers with additional opportunities to see relativity in action.
The study that describes the team's observations was recently published in the Monthly Notices from the Royal Astronomical Society.
Further reading: Hubble, MNRAS
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