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Inhabited black holes

by quasi-quasar
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quasi-quasar
#1
Apr12-03, 05:55 PM
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Black holes have been theorized but never encountered, correct?
Is it true that black holes are vackyooms ?
Could the universe, ever-expanding, be located in a black hole?

Maybe that explains dark matter....

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mathman
#2
Apr12-03, 07:41 PM
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"Black holes have been theorized but never encountered, correct?"

There is strong evidence that black holes have been detected. This is based on events in their vicinity. There is evidence that there is a big one (many millions of suns in mass) at the center of our galaxy.

"Is it true that black holes are vackyooms ? "

I presume you mean vacuum. No, black holes have a lot of stuff - so much mass that light can't escape (that's why they are black).

"Could the universe, ever-expanding, be located in a black hole?"

Maybe.
quasi-quasar
#3
Apr12-03, 08:07 PM
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"Maybe."

Ah! If that made you think as much as it makes me think...

Aren't there laws or something that demonstrate the theory of black holes, perhaps making it impossible for us to reside in one?


russ_watters
#4
Apr13-03, 07:25 PM
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Inhabited black holes

Originally posted by mathman
"Black holes have been theorized but never encountered, correct?"

There is strong evidence that black holes have been detected. This is based on events in their vicinity. There is evidence that there is a big one (many millions of suns in mass) at the center of our galaxy.
I'd go further than that. We have found objects of enourmous mas that have all the properties we would expect black holes to have. So by definition, they ARE black holes.

It seems like an oxymoron that we can learn so much about black holes if we can't see them, but there is so much about them that we CAN measure. Mass is an easy one based on objects orbiting them. Effects such as x-ray radiation are others.
marcus
#5
Apr13-03, 09:46 PM
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Originally posted by russ_watters
I'd go further than that. We have found objects of enourmous mas that have all the properties we would expect black holes to have. So by definition, they ARE black holes.

It seems like an oxymoron that we can learn so much about black holes if we can't see them, but there is so much about them that we CAN measure. Mass is an easy one based on objects orbiting them. Effects such as x-ray radiation are others.
to confirm what russ_watters says about observing them
http://www.eso.org/outreach/press-re.../pr-17-02.html
this is the one at the center of our galaxy
the press release has some good graphics
marcus
#6
Apr14-03, 01:53 AM
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This is maybe routine and not terribly interesting but could somebody please explain how the figure of 2.6 million solar masses is calculated from the orbit. As a rough estimate, the semimajor axis is 950 AU and the orbital period is 15.2 years. Perhaps the semimajor axis is 940 AU but that should not make a big difference. When I calculate it I do not get their figure---I must be doing something wrong.

From the observatory's press release:

http://www.eso.org/outreach/press-r...2/pr-17-02.html

[[The superb data also allow a precise determination of the orbital parameters (shape, size, etc.). It turns out that S2 reached its closest distance to SgrA* in the spring of 2002, at which moment it was only 17 light-hours [5] away from the radio source, or just 3 times the Sun-Pluto distance. It was then moving at more than 5000 km/s, or nearly two hundred times the speed of the Earth in its orbit around the Sun. The orbital period is 15.2 years. The orbit is rather elongated - the eccentricity is 0.87 - indicating that S2 is about 10 light-days away from the central mass at the most distant orbital point [7]....

In fact, model calculations now indicate that the best estimate of the mass of the Black Hole at the centre of the Milky Way is 2.6 ± 0.2 million times the mass of the Sun.]]

A French National Center for Space Research press release:

http://www.cnrs.fr/cw/en/pres/compress/trouNoir.htm


[[An international team (1) has recently observed a star very close to the central object using the Very Large Telescope of the European Southern Observatory (ESO) in Chile. The researchers used the adaptive optics system NAOS (2) equipped with the infrared camera CONICA installed on the telescope whose diameter is 8.2 meters. On the basis of observations made from 1992 to 2001 with the New Technology Telescope (3.6 m in diameter) of the ESO at La Silla, Chile, and of the data obtained with NAOS and CONICA as the star (S2) was passing closest to SgrA*, they have been able to reconstruct its trajectory. The trajectory is an ellipse of 11 light-days by 5.5 light-days, and, when closest to SgrA*, the star is at a distance of 17 light-hours, i.e. 124 astronomical units (three times the distance between the Sun and Pluto; 1 AU = 150 million kilometers). The star completes its orbit in 15.2 years. Analysis of this trajectory would imply that the central object is a 2.6 (±0.2) million solar mass object....


Researcher contact:
Daniel Rouan
Laboratoire d'études spatiales et d'instrumentation en astrophysique
(CNRS-Observatoire de Paris -CNES)
e-mail: daniel.rouan@obspm.fr]]
steppenwolf
#7
Apr14-03, 05:28 AM
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Originally posted by quasi-quasar
Black holes have been theorized but never encountered, correct?
...
Could the universe, ever-expanding, be located in a black hole?
black holes were indeed theorised but many scientists consider they don't actually exist for many reasons, an alternative was even offered that would fit observations but avoid all the theoretical nastiness that can't be ignored but often is. some craxy new type of star, i will go flick through dusty mags...

technically the laws of physics would break down in a black hole, it would then be quite paradoxical for the/a universe to exist in one as by definition the 'laws of physics' are the laws within this universe.

Maybe that explains dark matter....
how?
kyle_soule
#8
Apr14-03, 09:53 AM
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Pertaining to the original post: I think it needs to be noted that black holes are theorized, not hypothesized. Gravity, too, is only a theory.
marcus
#9
Apr14-03, 09:54 AM
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I looked in Astrophysics Abstracts

http://arxiv.org/abs/astro-ph/0210426

It has a link to the PDF file of the original journal article.

http://arxiv.org/PS_cache/astro-ph/pdf/0210/0210426.pdf

The journal article says 3.7 +- million solar masses within the pericenter distance of 124 AU. However it estimates that 2.6 of this is the black hole itself and the remaining 1.1 is a visible cluster of stars and stuff around the black hole.


(That 3.7 million was essentially what I got using semimajor 950 AU and period 15.2 years.)

both the press releases and the article mention other weird possibilities for the concentration of mass----a giant ball of bosons, a great heap of fermions (eg. neutrinos) sustained by degeneracy pressure, a cluster of neutron stars. They argue against these possibilities mainly by reasoning from the observed density. Maybe these possibilities have by now been laid to rest?
russ_watters
#10
Apr14-03, 03:48 PM
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Originally posted by marcus
This is maybe routine and not terribly interesting but could somebody please explain how the figure of 2.6 million solar masses is calculated from the orbit. As a rough estimate, the semimajor axis is 950 AU and the orbital period is 15.2 years. Perhaps the semimajor axis is 940 AU but that should not make a big difference. When I calculate it I do not get their figure---I must be doing something wrong.
Do your calculations take into account the fact that the orbit isn't circular?
marcus
#11
Apr14-03, 04:57 PM
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Originally posted by russ_watters
Do your calculations take into account the fact that the orbit isn't circular?
Yes. Indeed it is highly elliptical----eccentricity 0.87. I used that fact as a check in some of my calculations.

when I looked at the original journal article it turned out I had gotten the same answer as they did----3.7 million solar masses----for what the star was orbiting.

So there was no contradiction after all.


However they can see a cluster of material around the hole, which they estimate at around 1.1 million
So they assign a figure of 2.6 million to the hole
and 1.1 million to the other stuff, for a total of 3.7

This is discussed in
http://arxiv.org/PS_cache/astro-ph/pdf/0210/0210426.pdf
and explains the discrepancy.

All in all it is a pretty intimate look at a black hole.

cheers
Royce
#12
May5-03, 10:18 AM
P: 1,476
"Could the universe, ever-expanding, be located in a black hole?"

In his book; "In the Begining" John Gibbins speculates about that.
If the universe did start out as a singularity, blackhole, then the entire universe as we know it still is contained in an expanding singularity or blackhole.


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