Death Spiral First Evidence Of Black Hole

Porfiry writes "NASA's Hubble Space Telescope may have, for the first time, provided direct evidence for the existence of black holes by observing the disappearance of matter as it falls beyond the "event horizon." An event horizon is the mysterious region surrounding a black hole that forever traps light and matter straying nearby. By definition, no astronomical object other than a black hole can possess an event horizon. The discovery comes from a detailed statistical analysis of a 1992 observation of one of the first black holes ever discovered, Cygnus XR-1, which lies 6,000 light-years from Earth in the summer constellation Cygnus the Swan."

And Tackhead sends in this related information: "The folks at the Chandra X-Ray Observatory appear to have detected event horizons by comparing the X-ray luminosity of the accretion discs surrounding black-hole-based X-ray novae versus neutron-star-based X-ray novae during their phases of dormancy. X-ray novae are caused by ignition of fusion in the accretion discs of hot gas drawn from companion stars near black holes or neutron stars. While the novae were dormant, the discs surrounding black hole companions were observed and found to be 100 to 1000 times fainter than those surrounding neutron star companions. The conclusion: 'something' must be consuming the energy that would otherwise be expected from the disc; the most likely candidate being an event horizon."

Comments

Re:Still more indirect "evidence"

[sachsmachine]

I'm not entirely sure this isn't a troll,but... it's either this or finish an essay on Bertrand Russell.

What is your criterion for direct evidence? Part of the idea of a black hole is that I can't really see it in front of me, since it's black. Any good view of evidence would treat visual perceptions as different in degree, rather than kind, from evidence of the sort that these telescopes have turned up. I see tables in front of me all the time, but the way by which I should argue for the existence of tables and the way by which I should argue for the existence of black holes is precisely the same.

What you say about laws applying everywhere is absolutely meaningless. I can create a list of laws for *any* universe that I can describe, no matter how chaotic it may appear -- there may be a whole lot of non-computable functions in those laws, and the list might not be finite, but that doesn't mean that universe is any less bound by laws.

What's unusual about the laws in this universe is that there seem to be relatively few of them, and they're relatively simple -- at least compared to what they might be. There's no reason, though, why they *must* be so simple, or must be equally simple everywhere; the fact that we expect them to be is merely more evidence of the simplicity.

Fusion is marginal in X-ray novae

[Caid Raspa]

X-ray novae are caused by ignition of fusion in the accretion discs

[Kwatz!]

Fusion is not an important factor in X-ray novae. Hydrogen-to-Helium fusion yields about 0.7% of the rest mass (E = mc2). Dropping something to a neutron star yields about 20% of rest mass, or about 280 times more energy than fusion. For black holes the yield is about 10%, as there is no solid surface to slam against.

X-ray novae are ignited when the accretion disk gets ionised. This makes the gas more viscous, leading to a faster lose of angular momentum and thus a faster infall. Eventually, most of the disk falls on the neutron star, producing an X-ray nova outburst.

Re:What does Yogi Bear have to do with this?

[BLAMM!]

But they don't do they? Because if black holes existed then we'd end up with singularities at their centre which would violate physical laws by producing infinite discontinuities. Any theory which breaks itself cannot be a valid theory outside of esoteric mathematical journals.

But yes, they do. Our failure to understand the nature of those laws does not mean they don't exist. They violate *our* laws, the ones based on observation, experimentation and speculation, but that is not the same thing. You have to be smarter than the phenomenon you're trying to explain. We aren't yet.

Naeser's Law:

Hail the mighty Astronomer!

[jayhawk88]

Astronomers never cease to amaze me. This guy found an event that happened for 0.2 seconds, approximately 35,194,176,000,000,000 miles away, that happened 6000 years ago. And could actually recognize the significance of the event.

"as it falls beyond the event horizon"?????

[mozkill]

From our perspective outside a black hole, matter never quite passes through a black hole's event horizon. That is because time slows down near the event horizon and it takes an infinite amount of our time for the matter to pass through the event horizon. From the perspective of the matter falling through the event horizon, the passage is uneventful; the matter experiences no sudden changes as it passes through that surface of no return. Instead, the matter continues to accelerate toward the singularity at the center of the black hole to a point of infinite density and infinitely small size. Its approach to the singularity completely destroys the matter's structure. The gravitational tidal forces caused by the differences in gravity at different locations in space tear the matter apart so that it contributes only mass, charge, momentum, and angular momentum to the singularity. The black hole is usual identified with the event horizon rather than the singularity contained inside it. Passage through that event horizon erases any memory of the structure of the matter, leaving only its mass, charge, momentum, and angular momentum observable in the properties of the black hole.