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At the event horizon, theory holds that escape velocity is equal to the speed of light. Outside the event horizon it would decrease with increasing distance away from the black hole per the inverse square rule; inside the event horizon it is thought to exceed the speed of light; thus nothing can escape.
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JordanI found a reference value of 5,200 km/sec for the case of Sirius B, but I didn't take the trouble to do the calculations. However, obviously the escape velocity depends on the exact mass of the white dwarf. Note that a white dwarf with a larger mass will have a smaller diameter (due to the increased gravitation); both the larger mass and the smaller diameter will contribute to a larger escape velocity.
Yes. Well, we THINK so; we cannot observe anything inside a black hole, and our mathematical understanding of physics breaks down within the "singularity" around a black hole. Literally, the mathematical equations that appear to work in "normal" space break down and give nonsense answers when applied to what we believe are the conditions near a black hole.
Someday, we'll probably figure out what's happening there - but for now, we're just happy that there are no black holes anywhere nearby. At least, not that we know of!
The gravitational force that a black hole has on another object depends on the following:
1. The mass of the black hole
2. The mass of the object
3. The distance between the centres of the black hole and the object (r)
Using Newton's Law of Universal Gravitation, this force can be calculated using the following equation:
F=G*[(m1*m2)/(r2)]
where:
F = force
G = universal gravitational constant = 6.674×10−11 N m2 kg−2
m1 = mass of the first object
m2 = mass of the second object
r = distance between the centres of the objects
If, however, you wish to calculate the surface gravity of a black hole - which refers to the gravitational acceleration that's experienced at its surface (i.e. the event horizon) - then a different equation is used:
k = c4/[4Gm]
Where:
k = surface gravity
c = speed of light in a vacuum = 3x108m/s
G = universal gravitational constant = 6.674×10−11 N m2 kg−2
m = mass of the black hole
It is more appropriate to talk about the mass of a black hole. Read here if you don't know the difference: http://en.wikipedia.org/wiki/Mass_versus_weight. To talk about the weight means that you measure the attraction of the black hole against some other object - and that will vary, depending on the distance and mass of the other object.
The mass of a black hole, then, can vary between a few times the mass of the Sun (stellar black holes), passing through intermediate-mass black holes (a few thousand of times the mass of the Sun, believed to exist in some star clusters), up to the galactic (or "supermassive") black holes, in the centers of galaxies, that have a mass of millions, or even billions, of times the mass of our Sun.
It is also suspected - but not yet confirmed - that during the Big Bang, miniature black holes may have been created, small enough that they might evaporate any time soon.
F= (G x(m1x m2))/r2 The force a black hole has on another object is equal to a constant multiplied by the masses involved, divided by the distance squared. So 2 small objects very close can has the same gravitational pull as 2 huge objects billions of miles apart. The force the black hole has relates to it's size (mass) and the mass of the object being measured against, and the distance between them. The pull of a black hole at a distance is no different than that of a regular star, it's when you get very close that things happen differently.
The gravitational force that a black hole has on another object depends on the following:
1. The mass of the black hole
2. The mass of the object
3. The distance between the centres of the black hole and the object (r)
Using Newton's Law of Universal Gravitation, this force can be calculated using the following equation:
F=G*[(m1*m2)/(r2)]
where:
F = force
G = universal gravitational constant = 6.674
About a third, or half, the speed of light. The exact escape velocity really depends on the mass and diameter of the neutron star. Note that a more massive neutron star would be smaller, due to the increase in gravitation. If a certain limit is reached, the neutron star becomes a black hole. Before that limit is reached, pressumably the escape velocity could reach any value up to (almost) the speed of light.
Matter falling upon the dark hole reaches such a large speed (the escape velocity), that it is utterly destroyed; individual atoms don't remain whole, but rather, become part of the neutron soup of the neutron star.
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What is a rapidly spinning neutron star called?
A young neutron star. Really - that is what a neutron star is. If the neutron star's magnetic field is pointed towards Earth, then it is referred to as a pulsar - because of it's rapid pulsations [See related question] but it is still a neutron star.
Is the density of a pulsar greater than the density of a neutron star?
Yes, the density of a pulsar is generally higher than that of a typical neutron star. Pulsars are a type of neutron star that emit beams of radiation, often resulting from rapid rotation, making them more compact and dense compared to other neutron stars.
How does a neutron star differ from a main sequence star?
A neutron star is a stellar remnant
Is a pulsar a neutron star?
Yes. A pulsar is a rapidly spinning neutron star.
what star is smaller neutron star or white dwarf star?
A neutron star is smaller, but has a greater mass. A typical white dwarf is about the size of a terrestrial planet. A typical neutron star is a few miles across.
