9

There is a limit to how quickly a black hole can accrete matter. As a star gets close to a black hole it may be tidally disrupted and pulled apart. The material from the star will then fall toward the black hole and as it does so, the gravitational potential energy will go into heating it up. Now the stellar material would not normally be able to fall ...


7

In general, solids are made from from atoms that originate naturally in stellar nucleosynthesis, see for example the composition of our sun's atmosphere from an older paper of Asplund et al (2005): Here you see for example, that silicon (Si), an important rock-forming element, has an abundance relative to hydrogen of $10^{-3}$, or for every 1000 hydrogen ...


6

Who can say for sure? I guess the physics in Universe Sandbox is not good enough. What I would say though is that if you have a "protostar" that contains a higher proportion of heavy elements than a usual star, then the threshold for ignition of hydrogen will be lower than 75 Jupiter masses (e.g. How large can a ball of water be without fusion ...


3

One example is that of the core of a Thorne–Żytkow object, or TŻO. It consists of a high-metallicity M class red giant or supergiant with a neutron star at its core. Generally, TŻOs form when a neutron star collides with a suitable red giant/supergiant. The neutron star settles into the center of the other star. Eventually, the main source of energy for the ...


3

I read that a black hole can sometime "choke" on a star: "...the disrupted stellar matter was generating so much radiation that it pushed back on the infall. The black hole was choking on the rapidly infalling matter." I read the report and thought it was reasonable, and in line with Rob's answer. But note that there's no certainty that this is what ...


3

Yes. They are called cataclysmic variables.


2

The physical difference between high- and low-mass X-ray binaries is that the latter has a donor star that fills its Roche lobe. Usually, the compact object is more massive than the donor star. Mass transfer occurs via Roche lobe overflow. In high-mass X-ray binaries usually the donor star is more massive than the compact object and mass transfer is via a ...


2

Micrometer-sized dust condenses in red-giant atmospheres, then interacts with gas around young stars to grow to mm, then overcomes the bouncing barrier to reach cm to m sized "pebbles." (Answer derived from comments by A.P.E.; sadly, theirs links are dead. Edit: A.P.E. reposted an answer that I could accept.)


1

The initial seeding of rocks is thought to be a rapid and energetic event resulting in the formation of chondrules which are millimeter-sized spherules that form as molten (or partially molten) droplets in space before coalescing to their parent asteroids. Recent evidence suggests that the solar system comes from the hottest stars devoid of hydrogen at the ...


1

$10^{8} M_{\odot}$ SMBH. Eddington Luminosity (dodgy estimate, since assumes spherical accretion) is $ L/L_{\odot} \simeq 3\times 10^{4} (M/M_{\odot}) = 3\times 10^{12} L_{\odot}$. Let's assume we are seeing all this emerge from the face of a flat disc of total area (front and back) $\pi R^2$ and temperature $T \simeq 10^{5}$ K. Assume black body emission,...


1

I think the outer edge of an accretion disk is not well-defined, and observationally the radius will depend on which wavelength you consider, since the farther you get from the BH, the softer the radiation will be. But if you look in the UV, then Morgan et al. (2010) find the following relation between $R_{2500}$ (the radius when observed at $\lambda = 2500$ ...


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