Questions tagged [accretion-discs]

Questions regarding disks of gas, dust, and plasma around a central object, such as a black hole, which takes in the matter.

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How are microlensing events used to constrain the size of innermost stable circular orbits around spinning black holes?

The third paragraph of the introduction to the ArXiv preprint Constraining Quasar Relativistic Reflection Regions and Spins with Microlensing says: Quasar microlensing has significantly improved ...
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Causes of emission of accretion disk

As far as I can see, there are two main sources for the emission of energy from an accretion disk: release of gravitational potential energy of the infalling matter; friction from differential ...
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Why didn't all the iron and heavier elements find their way to the center of the accretion disc in the early solar system?

I guess that's pretty much it. I just heard that that a meteor fragment was found to be solid iron and it just seems inexplicable that it was floating around.
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If a black hole does not emit light, how can one take a picture of the black hole itself?

There's some discussion that the image composed by the Event Horizons Telescope is really just an accretion disk. To "take an image" of something, you need the light reflecting off of the surface of ...
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What is the light source in the black hole images?

What is the light source in the black hole images? I've searched the site before asking, as well as tried to google it. But perhaps the answer is buried due to the recent news. My understanding, is ...
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Mini disk of a blackhole meaning

What is meant by the "mini disk" of a blackhole? Is it the same as accretion disk? If not, whats the difference? Eg: In the abstract of this paper https://arxiv.org/abs/1806.05697 it is mentioned "...
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What is the exact meaning of vicinity of Black hole or a disk? the same as inside?

What is the exact meaning of vicinity of Blackhole or a disk? Is this the same as inside the horizon for black holes? If so, why people don't say inside of BH, simply. What is the difference? I use ...
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How did they make a video of the center of the galaxy, and what is it exactly that's flashing there?

The ESA video ESOcast 173: First Successful Test of Einstein’s General Relativity Near Supermassive Black Hole includes a clip of images of stars at the center of our galaxy orbiting around SgrA*, a ...
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If space was n>3 dimensional, would clouds of particles still turn into 2D disks due to gravity?

I don't fully understand why clouds of particles which turn into galaxies and solar systems usually result in an (approximately) 2D shape, but whatever. Would they still result in an almost 2D shape ...
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What is it exactly about these flares of infrared light from Sgr A* that “confirms” it is a supermassive black hole?

CNET.com's SCI-TECH Scientists confirm a 'supermassive black hole' at the heart of our galaxy It's "mind-boggling", they say. This links to Astronomy.com's Scientists finally confirm the Milky Way ...
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Astrophysical Jet Size?

I am wondering about what is the estimated size of astrophysical jet that shoots out from a black hole, I don’t know if it is determined by the size of a black hole. What would classify a black hole ...
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What defines the plane of an accretion disk around a black hole?

The question Do we know at which angle the Event Horizon Telescope will look at the accretion disk of Sagittarius A*? about just how close to edge-on we would be viewing any accretion disk around the ...
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Quasar mass and accretion rates

This page on Wikipedia -- Quasars mentions that the "The largest known [quasar] is estimated to consume matter equivalent to 600 Earths per minute". However, there is no citation for this comment. How ...
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What stabilizes rings or accretion disks?

We think, more or less, that our Moon was formed from an accretion disk caused by a Mars-sized impactor. Cool. Tidal forces can break apart a moon, causing rings. Ashes to ashes, dust to dust: the ...
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Can matter fly directly into a black hole and avoid the accretion disc?

From what my non-scientifically-trained mind understands, matter typically enters a black hole via getting caught up in the accretion disc going faster and closer to the black hole until it passes the ...
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Did the earth form outside the solar system?

Why isn't it possible that the earth formed outside the solar system and got attracted later by the Sun? I just need arguments to defeat this hypothesis.
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Accretion discs emitting jets [duplicate]

When there are accretion discs jets of particles or radiations will be emitted in the direction parallel to the rotational axis. My beginner level astronomy textbook just says that it is due to ...
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Spherical Accretion (Bondi Model)

I have a question. I studied Bondi's model for spherical accretion. I know the assumptions made in the model are big and that they are rarely representative of what happens in astrophysics. What I ...
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Minimum Mass Solar Nebulae Scaling Factors

I'm attempting to build a MMSN, I've been trying for about... a week to get an intuition on the scaling factors for calculating the mass of the disks, I'm not entirely sure how to think about it. I ...
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Do massive OB stars accrete mass the same way as the black holes they turn into do?

It is often said, in spite of sci fi often having illustrated the opposite, that stellar mass black holes do not gravitationally attract material in their environment into themselves anymore than a ...
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Luminosity of black hole accretion disc

The luminosity of a black hole accretion disc gaining mass at a rate $\mathrm{d}M\over \mathrm{d}t$ can be estimated as $${1\over 12}{\mathrm{d}M\over \mathrm{d}t}c^2$$ That is a substantial ...
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Linear extent of an accretion disk

I have a homework assignment question on accretions discs (essentially an estimation of the number of electron scatterings, but this is just for background). There are a few parameters, one of them ...
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Do the terrestrial planets form later than gas giants in our solar system?

Sorry I forgot where this statements come from, but I also remember the reason behind it is due to young Jupiter moves inwards and destroys the original super earth in inner solar system, and the ...
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When a neutron star accretes matter, will its mass increase?

When a nova gets matter, the outcome is that it may lose more matter because of eruptions. Only some kind of nova's masses can increase stably. A white dwarf may become a supernova after it exceeds ...
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What is the mass limit in a stellar accretion disc?

I became curious about the maximum mass in a star's accretion disc while watching an episode of Star Trek involving a Dyson Sphere. I wondered if some maximum amount of stellar material would limit ...
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Angular momentum in planetary disk formation

Reading about the formation of planetary disks, one of the major problems, it seems like, is the evacuation of angular momentum. Aparently planets can't form with the amount o angular momentum the ...
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Astrochemistry - what does freeze-out mean?

I was recently watching a video on the physics and chemistry in planetary accretion disks, and the speaker at a certain point mentioned 'freeze-out and UV dissociation'. Is freeze-out a purely ...
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What is the temperature of an accretion disc surrounding a supermassive black hole?

What is the temperature of an accretion disc surrounding a supermassive black hole? Is there plasma in the disc?
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The role of gravity during planetesimal accretion

As far as I understand, during the formation of a planetary disc, grains of dust stick together due to collisions and chemical bonding. Considering the size of the grain - say, 1 mm - and the speed - ...
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Accretion disks - why are they disk-shaped, rather than spherical?

So, the theory (briefly) about accretion disks is that stuff falling into the black hole will most likely not fall straight into it but will miss it and go into orbit, perhaps for a long time, perhaps ...
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Torus of the AGN

How much do we know about the structure of the torus surrounding the galactic nuclei? Is the shape defined or still under speculations? And are there different structures for this torus possible i.e., ...
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Pulsars with accreting disk in binary system

Following this line, I am wondering about the following question. Accreting pulsars in binary systems are usually thought to accrete from a prograde disk, so increasing their spin in the process. ...
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Generalised planets?

There is somewhat of an abstract way of generalising the notion of planets. Standard definition of planets is, obviously: "planets are the objects formed from the residual material surrounding a ...
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Stars at near break-up rotation rates

Accretion discs are ubiquitous in astrophisics. As a direct corollary, they are important for the following question. Consider the following model, representing one of the most simple models for ...