Black Hole Found Inside Globular Cluster

acidrain writes "Contrary to the prediction of some computer models, scientists have found a black hole resting peacefully in a dense nest of stars called a globular cluster. Previously discovered black holes are either similar in size to a large star, or super massive holes which are millions of times bigger than a star is able to remain stable. This finding indicates there may be an intermediate size range of holes residing within these star clusters."

Comments

Re:Yet Another Black Hole

[__aaclcg7560]

Black holes will never go out of style until a space dog eats a fleet of space ships. That will be news for the next century.

Re:large black holes?

[odasnac]

IANAAP, but i think it refers to the size of its event horizon; it could refer to its mass, but from what i understand mass and event horizon size are pretty well directionally proportional.

Large by mass

[MillionthMonkey]

The singularity is a point but the Schwarzchild radius around it is directly proportional to mass. One earth mass is equivalent to something like a few cm of Schwarzchild radius.

Inside the Schwarzchild radius everything falls into the hole regardless of velocity, no exceptions.

Re:Large by mass

[Ambitwistor]

The Schwarzschild radius isn't "emitted" from anything. It is simply a location in space, or rather a distance that defines a location. You can define a Schwarzschild radius for any object, even yourself. A black hole (roughly speaking) is a body whose matter has all collapsed into a region smaller than its own Schwarzschild radius. The Earth is not a black hole, because its matter is not contained within a region a centimeter across. Anyway, at a distance of 1 (current) Earth radius, a cm-sized black hole's gravity would not be any stronger than the current Earth's gravity; black holes don't suck things in more strongly than the objects they formed from. (Of course, the reason we are not falling into the center of the Earth is because we are standing on a solid surface; that would not be true for a black hole.)

warning required?

[PTBarnum]

The important question is, does this black hole have a warning label?

WARNING: do not drop spaceship keys into black hole

Re:Yet Another Black Hole

[Guppy06]

"How many black hole discoveries do we need to announce before they no longer become news?"

Black Hole Found Inside New Jersey.

I wonder if time is dilated there...

[Progman3K]

If you lived on a planet of the star closest to the black hole, would the passing of your time be measurably different from ours?

Re:I wonder if time is dilated there...

[shma]

According to General Relativity, the passage of time at a location depends on the gravitational field there. So, for instance, if the sun were to collapse into a black hole, there would be no change in the passage of time here. You would have to pass within a few Schwarzschild radii to see an effect (The Schwarzschild radius for the sun is about 3 kilometers, while Earth is 150 million km from the sum)

Re:I wonder if time is dilated there...

[MillionthMonkey]

If you lived on a planet of the star closest to the black hole, would the passing of your time be measurably different from ours?

Measurably but imperceptibly different from ours. But for the planet, no different than before. The gravity along a planet's orbit would be unchanged by the star's collapse. If it survives the red giant phase or the explosion, a planet's orbit won't be expected to change. By me, anyway.

The interesting spacetime effects that we associate with black holes take plase close to the singularity at the center, in regions of space that were formerly buried under the original star's surface. It would be hard to explain how you could find a planet bound in a stable orbit in there now. In the absence of gravity from a third body, things will either strike the singularity or take a mostly hyperbolic trajectory past it.

And be careful what you mean when you say "would the passing of your time be measurably different from ours" because some people take that to mean that you'll look down at your watch and see the hands moving faster or slower than usual. You'll always experience proper time for your reference frame, which basically means you'll never see that. The difference is with clocks far away from the black hole, which tick more quickly than clocks closer to it.

Re:I wonder if time is dilated there...

[rufty_tufty]

"The article says the black holes are "resting" inside the globular cluster"

Next you'll be telling me its pining for the fyords!

Re:Yet Another Black Hole

[LouisZepher]

To hell with the space dog, I'm more concerned with the mutant space goat.

Re:Yet Another Black Hole

[PsyQo]

I discovered one between the buttcheeks of some guy called Goatse, but that doesn't make slashdot, now does it?

Black hole do not change their mass

[aepervius]

As far as I remmember, black hole have the same mass as the collapsing star (before starting slowly to dissipate). Thus the same gravity as the as the star would be felt at the same distance. There is albeit a difference, within the schwarschild radius, the gravity pull is enough to pull everything without possible escape even light. Normally this radius smaller than the radius of the star itself before collapsing, if the mass would be at a point. In other word if the sun was to suddenly transform in black hole, the earth would happily go wander on the same orbit.

Re:Black hole do not change their mass

[SuiteSisterMary]

(note: this is from memory)

Our sun is defined as 'one solar mass.'

Very basically, a star's tendancy to collapse in on itself is countered by the fact that it's a big old nuclear fireball. As it runs out of hydrogen to burn, it starts to collapse in on itself again, until it starts burning helium. Once the helium is gone, it starts to collapse again.

Any given star of less than 1.4 solar masses will stop collapsing and turn into a white dwarf, due to the fact that it's gravity isn't enough to overcome the repulsion of electrons. (If this white dwarf gets some new material, say, by having a red giant close enough that it can gather material from it, it will explode, giving us a supernova.)

Any given star of greater than 1.4 solar masses but less than 3 solar masses will overcome this, but get halted by inability to squish neutrons together.

Anything bigger than 3 solar masses will overcome neutron degeneracy, and collapse even further into a black hole.

Re:Yet Another Black Hole

[cciRRus]

Actually there is just one; the rest were dupes. =)

Question: Why stars don't fall into the center?

[vbwyrde]

"Globular clusters, which are found in the halo of a galaxy, contain considerably more stars and are much older than the less dense galactic, or open clusters, which are found in the disk." - http://en.wikipedia.org/wiki/Globular_cluster What this makes me wonder is how the Globular Cluster, being much older than other galactic structures neither spins, nor contracts into itself. I would think that a Black Hole at the center would gobble the stars closest to it, increasing its gravitational attraction so that all of the surrounding stars would free fall straight "down" into it. The spin of other galaxies makes it so that stars do not just fall straight down into their own central black holes, but instead fall in a spiral toward it so that it takes a very long time for them to fall into it. But the Globular Cluster, with stars just hanging there in a spherical shape around it... I must ask - how come the stars have not fallen into the center long, long ago? Anyone have a theory on that?