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60 votes

Is there enough matter orbiting the sun to make a second sun?

The vast majority of the stuff in the solar system other than the Sun itself is contained in one body, Jupiter. The total mass of the solar system is estimated to be about 1.0014 solar masses, or ...
David Hammen's user avatar
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28 votes

Is there enough matter orbiting the sun to make a second sun?

No. The total mass of the planets, asteroids, dust etc in the solar system is only about 0.1% of the mass of the sun. There is not nearly enough to make even a small star.
James K's user avatar
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21 votes
Accepted

What is the mechanism through which mass is converted to thermal energy in the accretion disc of a black hole?

The "mass" falling in is the rest mass (at infinity). As the matter falls it gains kinetic energy. Most of the matter cannot fall directly into the black hole because it encounters a ...
ProfRob's user avatar
  • 155k
12 votes
Accepted

What is it like to see a brown dwarf turn into a star?

Exactly what this would look like would depend a great deal on how (fast) the mass is accreted and whether there is a significant amount of energy accreted along with the mass. There are two ...
ProfRob's user avatar
  • 155k
9 votes

Can a brown dwarf accrete enough mass from red giant to become a star?

One scenario that can work is if the wind from the red giant is accreted by the brown dwarf. The brown dwarf can be in quite a wide orbit and still accrete mass because the wind from the red giant, ...
ProfRob's user avatar
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8 votes
Accepted

Where do rocks come from?

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): ...
AtmosphericPrisonEscape's user avatar
7 votes
Accepted

Has gain in mass from accretion onto a black hole been observed?

Unfortunately, the answer is "No", because accretion rates are far too low -- and our ability to measure black hole masses is far too uncertain -- for this to be visible in reasonable times. ...
Peter Erwin's user avatar
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6 votes
Accepted

Why doesn't smashing larger and larger bodies incrementally into a rocky planet create a star?

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 ...
ProfRob's user avatar
  • 155k
4 votes

Degenerate object accretion - what happens after it becomes a PMO?

You are hypothesising that accretion can occur "piece by piece" from a compact object. This may not be the case. In both the situations you have proposed I believe any accretion could be a ...
ProfRob's user avatar
  • 155k
3 votes
Accepted

Can white dwarfs have accretion discs too?

Yes. They are called cataclysmic variables.
ProfRob's user avatar
  • 155k
3 votes
Accepted

Speeds in accretion disks

The same way that in orbital mechanics, slowing down causes you to speed up. For a simple example, consider a Hohmann transfer: A satellite in a high circular orbit makes a short retrograde rocket ...
James K's user avatar
  • 125k
3 votes
Accepted

Spherical Accretion (Bondi Model)

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 ...
HDE 226868's user avatar
  • 36.6k
3 votes

What is the mechanism through which mass is converted to thermal energy in the accretion disc of a black hole?

All else being equal, the same object will produce less far-field gravitational force, the deeper it is in a gravitational well. This is not intuitive if you are used to newtonian gravity, but it’s ...
QuadmasterXLII's user avatar
2 votes

Where do rocks come from?

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 ...
Camille Goudeseune's user avatar
1 vote

Where do rocks come from?

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) ...
bandybabboon's user avatar
  • 4,250

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