Aren't black holes/dark matter really super massive Black stars?

[CelestialDNA]

I am having a terrible time understanding or accepting Dark Matter or Black Holes over Dark/Black-Stars. Why are scientists hunting for dark matter to account for the added mass in the galaxies when this could be perfectly explained by darkstars or black stars? A star so massive that its escape velocity is bigger than the speed of light? (485 times the suns mass) Couldnt these stars not be detectable by our instruments and account for the added mass in the galaxies? What eliminates these objects from existing in the universe? Also...why are blackholes so widely accepted but dark/black stars are not? Black holes form from a dying star...dark/black stars are just super massive stars. Given the nature and laws of gravity I do not see why a star of such massive porportions could not exist. I have posted this question on several astronomy forums hoping to get a clear answer or perhaps one from real astrophysists.

[KeithBC]

I have no idea what you mean by "black stars". Black holes are one of the candidates for dark matter. My understanding is that they are not a particularly good candidate, for a number of reasons, one of which is that they typically aren't very black: in-falling matter lights them up like a searchlight.

Dark matter has not yet been characterized. They know it's there because of its gravitational effect, and they know it's dark because they can't see it. Beyond that, it's up for grabs. My understanding is that current explanations tend to favour subatomic particles rather than large objects (i.e. WIMPS rather than MACHOS), but I'll leave it to someone else to explain why.

[CelestialDNA]

A black star is a super massive star with an escape velocity equal to the speed of light. It is "black" because the light cannot escape it's surface. Our suns escape velocity is approx 670 km/sec. X 485 = c- the speed of light. Meaning a star 485 more massive than our sun would have such properties.

[Joe Lalumia]

The definition of a black hole is any object having sufficient mass so that the escape velocity is equal to or greater than the speed of light.

For example if you crushed the Earth down to the size of a marble it would become a black hole.

[KeithBC]

A black star is a super massive star with an escape velocity equal to the speed of light. It is "black" because the light cannot escape it's surface.

In other words a black hole. If you are going to draw a distinction between the two, then please define what you consider the difference to be.

[CelestialDNA]

In other words a black hole. If you are going to draw a distinction between the two, then please define what you consider the difference to be.

A black hole is a remanant of a dying star. A black star would be just like any other star just massive. Also a black hole creates a singularity in the fabric of space-time. A black star warps space but isn't causing a singularity as it's mass is disbursed across a larger area.

[KeithBC]

A black hole is a remanant of a dying star. A black star would be just like any other star just massive. Also a black hole creates a singularity in the fabric of space-time. A black star warps space but isn't causing a singularity as it's mass is disbursed across a larger area.

Is there any evidence that such an object can exist, and is there any evidence that such objects do exist? What is the mass range at which such an object becomes a possibility, if indeed it does at all?

[CelestialDNA]

Is there any evidence that such an object can exist, and is there any evidence that such objects do exist? What is the mass range at which such an object becomes a possibility, if indeed it does at all?

That's what I have been trying to figure out all along. Somehow scientists are obsessed about blackholes and string theory none of which can be truly proven. A black star on the other hand could definately exist. As mentioned several times in my previous posts such a star needs to have at least 485 times the mass of our sun. I derived that number by taking our suns escape velocity and dividing it by the speed of light.

[dcbrown73]

I know of no "black star" unless you are talking about a black hole. A black hole is a star that runs out of fuel and collapses in on itself. A star is bigger than it normally would be due to the outward force created during the fusion process. (nuclear reaction) Once the star runs out of fuel, that outward force no longer exists and it collapses in on itself. If it does not contain enough mass per volume after collapsing to become a black hole, then it becomes a neutron star or white dwarf.

Can a star with fuel exists yet still be massive enough to create an event horizon? I don't know. If it could, it sure wouldn't last very long as the fusion would be come so extreme that it would burn all of it's fuel rather quickly and turn into a black hole anyway.

VY Canis Majoris which I believe is the largest known star is estimated (with some disagreements) between 600 and 2,100 times the size of our sun. Our sun is over 4 billion years old, yet VY Canis Majoris probably has a life span of only 1 million years due to it's immense size. So, even if a black star could exist, it would be short lived and become a black hole anyhow.

...whatever a black hole actually is.

[newman]

I'm not exactly sure but wouldn't too much mass cause a star to collapse in on itself and form a black hole? If true this would preclude the possibility of your "dark stars", since anything that reached enough mass to have gravity strong enough to prevent even light from escaping it would by definition collapse into a black hole. I'm by no means an astrophysicist but from what I can gather that should be along the lines of why they don't expect such supermassive objects out there - they'd all collapse into black holes anyway.