The discussion revolves around the possibility of a black hole existing within 20 light years of the Solar System, particularly between us and nearby stars like Alpha Centauri or Barnard's Star. Participants explore the implications of such a black hole's gravitational influence and the detectability of its effects.
Participants express a range of views, with some agreeing on the nature of gravitational effects from black holes, while others remain skeptical about the existence of nearby black holes. The discussion does not reach a consensus on the detectability of such objects or the implications of their gravitational fields.
Participants reference various assumptions about the nature of black holes, gravitational fields, and the limitations of current observational techniques, but these assumptions remain unresolved.
Not so. I forgot the "size" that our sun would have for an EH if compressed to a black hole, but it is very small. For example, for a star with a mass of 19.9 x 10^30Kg (A mass of about 10 times that of our Sun) would have a Schwarzschild radius of about 30 kilometers. That's only about 18.6 miles!Dr.Brain said:Black Holes's gravitational field is nothing special.If a black hole has an event horizon radius same as that of sun , its gravitational field would be same as that of sun
This is true, it is just another source of gravity that we may, or may not, detect.Dr.Brain said:I doubt that Gravitational field of a BH at such a distance would make a major impact on field around us , and may go undetected unless BH is itself massive.
If the Sun were somehow compressed enough to become a black hole, it would be less than 6 kilometers (well under 4 miles) across.
Labguy said:Not so. I forgot the "size" that our sun would have for an EH if compressed to a black hole, but it is very small. For example, for a star with a mass of 19.9 x 10^30Kg (A mass of about 10 times that of our Sun) would have a Schwarzschild radius of about 30 kilometers. That's only about 18.6 miles!.
Your description is correct, but I took his statement to mean an EH radius equal to the sun's radius, which would mean a massive BH. Not sure that's what he meant.George Jones said:I think you and Dr. Brain are saying the same thing. The Schwarzschild radius for any (spherically symmetric) massive object can be calculated. If the the Schwarzschild radius lies within the object (i.e., the object has mass outside), then the object is not a black hole; if all the mass lies inside its Schwarzschild radius, then the object is a black hole. By Birkhoff's theorem, a distant observer cannot use gravity to tell the difference between equal mass (spherically symmetric) objects, be they stars, black holes, or even stars collapsing (spherically symmetrically) to form black holes.
Regards,
George
Labguy said:Not so. I forgot the "size" that our sun would have for an EH if compressed to a black hole, but it is very small. For example, for a star with a mass of 19.9 x 10^30Kg (A mass of about 10 times that of our Sun) would have a Schwarzschild radius of about 30 kilometers. That's only about 18.6 miles!
This is true, it is just another source of gravity that we may, or may not, detect.
EDIT: Found it (too lazy to calculate)
I agree, but you said size instead of mass. Mass would be a more accurate description as size implies a measure of distance and mass is "a quantity of matter", regardless of size.Dr.Brain said:I was trying to imply that whenever you are outside a black hole having a size of some star A, its gravitational field would be no different from that star . I mean that if the poster above had asked me if a star's gravitational field between us and alpha centauri could be detected , the answer would have been the same.
Concluding that as long as you are outside a black hole , it can be treated as just another body carrying massive mass just like a star.
BJ