HEIC: Hubble Discovers Mysterious Black Hole Disc

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HEIC: Hubble Discovers Mysterious Black Hole Disc

Post by bystander » Thu Jul 11, 2019 7:40 pm

Hubble Discovers Mysterious Black Hole Disc
ESA Hubble Science Release | 2019 Jul 11
Astronomers using the NASA/ESA Hubble Space Telescope have observed an unexpected thin disc of material encircling a supermassive black hole at the heart of the spiral galaxy NGC 3147, located 130 million light-years away.

The presence of the black hole disc in such a low-luminosity active galaxy has astronomers surprised. Black holes in certain types of galaxies such as NGC 3147 are considered to be starving as there is insufficient gravitationally captured material to feed them regularly. It is therefore puzzling that there is a thin disc encircling a starving black hole that mimics the much larger discs found in extremely active galaxies.

Of particular interest, this disc of material circling the black hole offers a unique opportunity to test Albert Einstein’s theories of relativity. The disc is so deeply embedded in the black hole’s intense gravitational field that the light from the gas disc is altered, according to these theories, giving astronomers a unique peek at the dynamic processes close to a black hole. ...

The disc’s material was measured by Hubble to be whirling around the black hole at more than 10% of the speed of light. At such extreme velocities, the gas appears to brighten as it travels toward Earth on one side, and dims as it speeds away from our planet on the other. This effect is known as relativistic beaming. Hubble’s observations also show that the gas is embedded so deep in a gravitational well that light is struggling to escape, and therefore appears stretched to redder wavelengths. The black hole’s mass is around 250 million times that of the Sun. ...

Hubble Uncovers Black Hole Disk That Shouldn't Exist
NASA | GSFC | STScI | HubbleSite | 2019 Jul 11

HST Unveils a Compact Mildly Relativistic Broad-Line
Region in the Candidate True Type 2 NGC 3147
~ Stefano Bianchi et al
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UCSB: Scientists Resolve the Nature of Powerful Cosmic Objects

Post by bystander » Wed Aug 07, 2019 10:21 pm

An Identity Problem: Scientists Resolve the Nature of Powerful Cosmic Objects
University of California, Santa Barbara | 2019 Aug 06
cid947_lg.jpg
The black hole in the middle of a Seyfert galaxy is surrounded by a cloud of dust that
blocks the broad emission spectra from the material near the center. Credit: NASA

At the center of certain galaxies are objects of such tremendous brightness they outshine the rest of their galaxy by four orders of magnitude. Our understanding of these active galactic nuclei has progressed by leaps and bounds over the past several decades, though recently debate has centered on the identity of some of these objects.

Now, a team of researchers has settled some questions and exposed exciting new findings about these cosmic phenomena. ...

Quasars, the most powerful active galactic nuclei, shine like lighthouses from their home galaxies. These beams are powered by supermassive black holes millions to billions of times the mass of the sun. ...

The gas around these black holes spins so fast that the color of the light it emits is stretched out. The material approaching us appears bluer, while receding gas appears redder. This stretches the normally sharp spikes in the light spectra into broad peaks.

The radiation from these systems also energizes distant gas clouds, which are less dense. Because these clouds rotate more slowly, the peaks in their light emission stay sharp. And because they are less dense, the atoms have enough time to make slower transitions between energy states without interference from neighboring atoms, so scientists see additional spikes that are due to heat rather than radiation.

A dim quasar is called a Seyfert galaxy, and the debate stems from the distinction between the two types of Seyfert galaxies. Type I galaxies produce both of these spectra, but the light from type II galaxies is missing the broad peaks. Before they knew about the black holes at the center, scientists had thought the two were different entities, and were puzzled over what could be powering them.

Antonucci had proposed that they were actually the same objects, simply seen from different perspectives. Namely, that when the broad regions were missing from the spectra, it was because we were looking at the systems side-on, and a ring of dust was obscuring the inner part of the nucleus from our view. ...

HST unveils a compact mildly relativistic broad-line region in the candidate true type 2 NGC 3147 ~ Stefano Bianchi et al
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Hubble settles an old debate about galaxies with supermassive black holes

Post by Ann » Fri Aug 09, 2019 6:54 pm

Hubble settles an old debate about galaxies with supermassive black holes

NGC 3147.
This galaxy was long thought to be a Seyfert 2 galaxy but is really a Seyfert 1.
ESA/Hubble & NASA, A. Riess et al.
Korey Haynes of Astronomy Magazine wrote:

Every large galaxy has a supermassive black hole at its center. And some of those black holes are actively ejecting huge amounts of high-energy light out into the cosmos.

Astronomers divide some of these active galaxies, which otherwise look like normal spirals, into two types, so-called Seyfert 1 and Seyfert 2 galaxies. Seyfert 1 galaxies have distinctive light signatures that emerge from the fast-moving material just outside the black hole. Seyfert 2s lack these signals.

But for three decades now, astronomers have suspected that these two types of galaxies might in fact be the same, we’re just seeing them from different angles. The thought was that a dusty ring around the black hole could hide certain features, making a Seyfert 1 appear like a Seyfert 2.

However, a few stubborn galaxies persisted in hiding those features apparently without any dust ring. That made some astronomers think there might really be a class of “true Seyfert 2 galaxies,” whose features weren’t hidden but genuinely lacking.

Now, astronomers have ruled out one of the last remaining “true Seyfert 2” stragglers, proving it was a Seyfert 1 after all. This means there’s no such thing as a Seyfert 2, just Seyfert 1 galaxies viewed from different angles. Astronomers led by Stefano Bianchi, from the Università degli Studi Roma Tre in Italy, published their results in Monthly Notices of the Royal Astronomical Society July 11...
Hubble Uncovers Black Hole Disk that Shouldn't Exist

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