Could a Binary Star system create a black hole w/o a singularity?

[Stu Pidasso]

Binary stars orbit each other around a common center of mass. Is it possible that the combined mass of a binary star system be such that an event horizon is created?

Stu

[kerowo]

I'm going to say no. I don't there is a black hole with only twice the density of any single star.

[m_the0ry]

No. Black holes are theoretically formed based on mass density, not net mass. Star A + Star B = some arbitrary mass, but unless the mass is at a high enough density in space it does not create an event horizon.

A rotating black hole does however have an ellipsoid shaped event horizon.

[Duke]

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No. Black holes are theoretically formed based on mass density, not net mass. Star A + Star B = some arbitrary mass, but unless the mass is at a high enough density in space it does not create an event horizon.

A rotating black hole does however have an ellipsoid shaped event horizon.

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Does that necessarily imply 2 singularities? And is that the only way that we can tell that they're rotating?

[kerowo]

I think I came at my 'no' the wrong way. Here are a couple of problems with it the OPs guess.

I think the sub-threshold stars would have to be so close together for the system to cross the threshold into blackhole-dom that they would combine into a single unit.

Isn't part of the blackhole process involve the star turning into a red giant or otherwise "dying?" Some part of that process would seriously [censored] up a star close enough to it to create what he is talking about.

[oe39]

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Does that necessarily imply 2 singularities?

[/ QUOTE ]

i don't think so. don't electrons have a "spin" even though they are considered point particles?

[Borodog]

[ QUOTE ]
Binary stars orbit each other around a common center of mass. Is it possible that the combined mass of a binary star system be such that an event horizon is created?

Stu

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We don't know yet. If it can happen at all, it would involve the collision of two neutron stars. People (Google Doug Swesty) are simulating such collisions, but it is unclear yet whether such a collision can form an event horizon, or just a larger neutron star. It seems at first blush that a larger neutron star is not allowed by the Chandrasekhar limit, but because of the tremendous angular momentum incolved (the neutron stars can be orbiting at of order 60,000 RPM during the collision), a black hole might not form.

In any event, these sorts of collisions, are almost certainly responsible for one class of the most luminous events in the universe, gamma-ray bursts (the majority of them though are due to core-collapse of massive stars into black holes).

[pzhon]

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Binary stars orbit each other around a common center of mass. Is it possible that the combined mass of a binary star system be such that an event horizon is created?

[/ QUOTE ]
A useful consideration is the event horizon radius. For a non-rotating, uncharged black hole, this is linear in the mass, m * 2G/c^2 IIRC. That means if the rotation is not significant, and you can contain the two pieces in disjoint spheres, then for the sum to be a black hole, one of the pieces must be a black hole.

Some rotation is involved. The event horizon of a rotating black hole is smaller than the event horizon of a nonrotating black hole. I don't know whether that allows two pieces to avoid being black holes due to rotation (in opposite directions) while the union is a black hole.

[WiiiiiiMan]

LOL at this thread, as if you guys know anything about the subject besides what you looked up on google to reply and try to make yourself look smart......

[kerowo]

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LOL at this thread, as if you guys know anything about the subject besides what you looked up on google to reply and try to make yourself look smart......

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Where there [censored] do you think knowledge comes from? It's the internet not a research university so get back on your troll-cycle and peddle your ass back to BBV4L.