#active galactic nucleus

[colorpicked-pride-flags-jwst]

Asexual flag colorpicked from quasar J0100+2802

[zespaceblog]

Supermassive Switch On

Looking out at supermassive black holes around us, we noticed that some are quiet, like our own Sag A*, and others like the one sat at the heart of Centaurus A are incredibly active, sending out huge jets of particles at near the speed of light.

More recently it was discovered that these states are not set in stone, these objects seem to switch on and off, and even our own Milky Way's Sag A* has had past moments of being an AGN (Active Galactic Nucleus).

So imagine scientists surprise when one was triggered while being observed, the first instance of this ever occurring.

The galaxy in question is probably one you'll not be too familiar with 1ES 1927+654, and has a supermassive black hole around 1.4 million times the mass of our sun, and lies 270 million light years from us.

Back in 2018 it was quiet, then suddenly for a short time seemed to turn on, then off again. Again in 2022 it began again.

By studying this galaxy, the outburst jets, we hope to understand why and how AGN's occur, and how we could predict if our own galaxy is due to turn on, particularly important as 26,000 light years from us, Sag A* sits with one of it's poles pointing in our general direction. Nobody knows how far that jet will go, but if it makes it here, it won't be a great day for the inhabitants of planet Earth.

[netmassimo]

An article published in the journal 'Nature' reports the observation of very strong winds coming from the supermassive black hole at the cen

An article published in the journal "Nature" reports the observation of very strong winds coming from the supermassive black hole at the center of the galaxy Cosmos-11142 which inhibited star formation within it. A team of researchers led by Professor Sirio Belli of the University of Bologna, Italy, used the James Webb Space Telescope to detect the movement of cold neutral gas pushed at such a speed that it swept away the gas in the galaxy and thus prevented the formation of new stars. This is the first evidence of how a supermassive black hole can have that effect on a galaxy.

[astraiox]

unified AGN model

[quasarlasar]

Some diagrams I hand-drew to use in the AGN planetarium show. My digital art software has been non-functional lately so I figured I might as well go back to colored pencil. The first page is just a diagram of all the structures associated with accreting supermassive black holes (AGN stands for active galactic nucleus which is how the actively feeding black hole manifests from the outside...as a bunch of weird activity in the center of a galaxy). The latter diagram shows the name of different astrophysical phenomena that are all thought to be due to accreting supermassive black holes.

For those that don’t know...

The supermassive black hole feeds from a whirlpool of plasma called an accretion disk. The accretion disk emits a lot of high-intensity ultraviolet light, which ionizes the galaxy in a broad swath called the ionization cone. The two main regions of ionized gas that are observed by astronomers are the broad line region (BLR) and narrow line region (NLR). The BLR is gas that is located close to the accretion disk in the center of the galaxy, and is thought to be moving rapidly, but observations are mixed as to whether the motion is an outflow (shown here), inflow, or simply rotation. The NLR is much more rarefied gas that occupies the ionization cone, and such extends through length scales comparable to the galaxy itself. All of these portions of the AGN features emit in optical light.

Sometimes astronomers can see the BLR and accretion disk light, but most of the time they cannot. To explain this, the AGN unification hypothesis posits that a thick ‘donut’ of cooler gas and dust--the torus--surrounds the BLR. When our line of sight is intercepted by the torus it blocks the BLR from view (”obscuration”). The torus radiates in the mid-infrared.

Just above and below the accretion disk is the corona, which is where UV photons from the accretion disk are boosted up to X-ray energies (hence why I have depicted them as the stereotypical radioactive green). The corona lies at the base of relativstic jets, powerful beams of fast-moving particles that extend out from the center of the galaxy and sometimes go on to punch into intergalactic space. When they do, they can carve enormous cavities into the gas that surrounds galaxies as they gradually slow down and pool into clouds of radio-emitting plasma called radio lobes. The jets are prominent in radio, but emit across the whole electromagnetic spectrum.

The weird thing about jets is that while AGN are famous for them most AGN do not have visible jets. This is why I have chosen to call the powerful AGN QSOs (”quasi-stellar objects”) rather than the more famous quasar. The word quasar comes from “quasi-stellar radio source” and was coined because the first discovered quasar had a prominent radio jet, but most quasars discovered since don’t emit in radio prominently. 

The reason for this is unknown. It could be an orientation effect (similar to how we cannot see the BLR in most AGN), but it might also be an intrinsic difference since theoretical models show jets form only at certain accretion levels.

The other big AGN unification mystery is what the source of the obscuration of the BLR really is. Based on the vanilla torus explanation, one would not expect say, AGN in merging galaxies to be more heavily obscured than AGN in isolated galaxies, but this nonetheless is the case. Astronomers currently think obscuration can also be due to random dust clouds in the galaxy, not just the torus. And we don’t exactly know what the torus is either. Does it condense out of the material flowing into the supermassive black hole? Or out of it? Or is it some sort of ‘food reservoir” that the black hole can accrete from?

[wigmund]

From SpaceTelescope.Org Picture of the Week; June 4, 2018:

Threads of Blue

A ripple of bright blue threads through this galaxy like a misshapen lake system. The foreground of this image is littered with nearby stars with their gleaming diffraction spikes. A keen eye can also spot a few other galaxies that, while masquerading as stars at first glance, reveal their true nature on closer inspection.

The central galaxy streaked with color, IC 4870, was discovered by DeLisle Stewart in 1900 and is located approximately 28 million light-years away. It contains an active galactic nucleus, or AGN: an extremely luminous central region so alight with radiation that it can outshine the rest of the galaxy put together. AGNs emit radiation across the complete electromagnetic spectrum, from radio waves to gamma-rays, produced by the action of a central supermassive black hole that is devouring material getting too close to it. IC 4870 is also a Seyfert galaxy, a particular kind of AGN with characteristic emission lines.

IC 4870 has been imaged by Hubble for several studies of nearby active galaxies. By using Hubble to explore the small-scale structures of AGN in nearby galaxies, astronomers can observe the traces of collisions and mergers, central galactic bars, nuclear starbursts, jets or outflows, and other interactions between a galactic nucleus and its surrounding environment. Images such as this can help astronomers understand more about the true nature of the galaxies we see throughout the cosmos.

Credit: ESA/Hubble & NASA

[colorpicked-pride-flags-jwst]

Could you do an Aegosexual one please? ❤️❤️

(p.s i love your posts they're so cool)

Aegosexual flag colorpicked from Circinus Galaxy

[colorpicked-pride-flags-jwst]

Pocketgender flag colorpicked from artist’s concept of the Circinus galaxy’s center, hosting a supermassive black hole with two relativistic jets coming from its poles