Matter Rides Black Hole's Space-Time Wave

[Dover]

Matter Rides Black Hole's Space-Time Wave
By Robert Roy Britt
Senior Science Writer
posted: 10 January 2005
01:52 pm ET


SAN DIEGO -- Armed with cosmic speed guns and other high-tech devices, astronomers have witnessed amazing speeds around one black hole and an exotic wave in space-time careening around another.

The findings are among the most convincing ever of the incredible velocities and distortions that occur very close to black holes, and they help provide better estimates of the masses of the black holes. They also showcase a new method for getting an even better handle on these gravitational behemoths.

In one finding, a spinning black hole appears to create an orbiting wave. In a gross oversimplification, the process is similar to the wobble of a spinning top. The other study found evidence of hotspots -- perhaps blobs of hot gas the size of the Sun, or maybe regions lit by magnetic energy -- travelling at 10 percent the speed of light.

The results were presented here Monday at a meeting of the American Astronomical Society....cont'd

http://www.space.com/scienceastronomy/aas_blackhole_050110.html

[burythehatchet]

1. you must have strings on the brane

:)

[On the Road]

2. I Saw This on Yahoo

but I didn't understand what the scientists were looking at when they reported the wave in spacetime. How did it show up?

[pmbryant]

3. My attempt at a brief explanation

This appears to be the abstract that corresponds to the result presented yesterday: http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004AAS...20517202M&db_key=AST

Abstract
In stellar-mass Galactic black hole binaries, broad Fe K-alpha emission lines and X-ray QPOs are thought to be produced in the inner disk. We have found the first direct link between Fe K-alpha emission line strength and QPO phase in an black hole binary. Our analysis of two RXTE observations has revealed that the Fe K-alpha emission line commonly seen in spectra of GRS 1915+105 varies in flux and equivalent width with the phase of 1 Hz and 2 Hz QPOs. If these frequencies are only Keplerian frequencies, they correspond to 85 and 50 Schwarzschild radii; in this region, relativistic shaping of the Fe K-alpha line is inevitable. The Fe K -- QPO connection may be explained by precession at the inner disk (e.g. Lense-Thirring precession), which supports some theories for the origin of low-frequency QPOs in such systems. The Fe K -- QPO connection holds great promise for revealing the innermost environment around black holes in detail.

Jargon:

* "Fe K-alpha" is spectral line of highly-ionized iron that is used commonly by X-ray astronomers because it is very prominent spectral feature at those wavelengths.

* "QPO" apparently is an acronym for "Quasi-periodic oscillation". In this case, the frequency of the changes in the spectral line appears to be 1-2 Hz, or 1-2 times per second.

So these rapid changes in the iron line appear to be what is being observed. (An X-ray satellite, RXTE, was used to make the observations since the atmosphere absorbs most X-rays from space.)

The rest is deduced from this data. As quoted in the article, the author says, "It may be that other explanations turn out to be better, "Miller told SPACE.com. "It is not a shut case."

X-ray astronomy was never my strong point, so I hope I've got the gist of it.

--Peter

EDIT: Added link to RXTE satellite info.

[On the Road]

4. Thanks. So "Relativistic Shaping" is What They're saying?

I guess this would be like Einstein's prediction that the sun would bend the light from stars near the sun's horizon. Which was confirmed during that famous eclipse.

So presumably rather than seeing a circle of Fe K-alpha emission lines, they're seeing some kind of swirling pattern indicating that they travelled through warped space?

[pmbryant]

5. Time variations, not a spatial pattern, I think.

Since the area immediately surrounding a black hole is so small (at least by astronomic scales), I don't think they are seeing any spatial pattern at all. It's just too small to resolve any detail with our telescopes.

I suspect they are measuring an unresolved "blob" of Fe K-alpha emission that goes through rapid changes in brightness.

The leap from that observation to warped space is obviously a large one. No doubt, that is why the author sounds not at all confident that that is the correct explanation.

--Peter

EDIT: slight re-phrasing

[On the Road]

6. I Thought They Were Looking at the Concretion Disk

since nothing can escape from a black hole itslef. That concretion disk is supposed to be spinning at relativistic speeds, something like one tenth the speed of light.

[pmbryant]

7. Yes, the accretion disk

But the region of the accretion disk spinning at relativistic speeds is too small for our telescopes to resolve at the distances involved.

--Peter

[On the Road]

8. That Would Make Sense

Kind of like how they detect extrasolar planets when they're too small to obseve directly.