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Fraser
2005-Oct-05, 06:33 PM
SUMMARY: An international team of astronomers think they've solved the mystery of short gamma-ray bursts. These powerful explosions shine brighter than a billion suns for only a few milliseconds and fade away quickly. But now, thanks to NASA's Swift satellite, which can detect and analyze these blasts anywhere in the sky, astronomers were able to measure short bursts. The evidence now points to the theory that these bursts occur when a black hole consumes a neutron star, or two neutron stars collide together.

View full article (http://www.universetoday.com/am/publish/grb_mystery_solved.html)
What do you think about this story? post your comments below.

publiusr
2005-Oct-05, 08:56 PM
The gravity of a neutron star pulls material toward its center. So when a black hole really gets its hooks into one--there will be a point between the black hole and the center of the neutron star that might enjoy a near weightless state. The degen. matter blows apart, and releases energy the energy as the rest gets sucked in. This might produce a more directional blast, where two neutron stars slamming together may make a different explosion.

snowflakeuniverse
2005-Oct-06, 01:50 AM
After one of these events, is there any evidence of highly rotating matter?

Snowflake

Greg
2005-Oct-06, 03:22 AM
These results are nicely confirming the most popular theory on how these short grbs formed. The cooperative efforts of Swift, HETE, and soon LIGO are and will continue to produce very valuable astronomical discoveries with far reaching implications for cosmology in the next few years. It is a very exciting time for this field of research.

iantresman
2005-Oct-06, 07:17 AM
Do I understand the paper correctly:

Hypothesis: Gamma rays bursts are caused by black holes colliding with a neutron star.
Evidence: No supernova was detected.
Conclusion: Hypothesis proved.

I must be incorrect because this is garbage science. Indeed, according to this logic, any hypothesis is proved.

Regards,
Ian Tresman

iantresman
2005-Oct-06, 07:26 AM
Do I understand the paper correctly:

Hypothesis: Gamma rays bursts are caused by black holes colliding with a neutron star.
Evidence: No supernova was detected.
Conclusion: Hypothesis proved.

I must be incorrect because this is garbage science. Indeed, according to this logic, any hypothesis is proved.

Regards,
Ian Tresman
Here's the actual evidence:

Fox's team discovered the X-ray afterglow of the July 9 burst with NASA's Chandra X-ray Observatory. [..] The X-ray signals, in the minutes to hours that followed, could be crumbs of neutron star material falling into the black hole, a bit like dessert.

Terrestrial lighting gives off x-rays and gamma rays, so why black holes and neutron stars?

Regards,
Ian Tresman

bigsplit
2005-Oct-06, 01:20 PM
The dessert explaination is the one of which I am not so fond. I find publisers explaination much better. When any body (particularily something with the density of a neutron star or another black hole) interfaces with a BH there will be a disturbance to both bodies. These disturbances will continue after the body crosses the event horizon generating a level of gravitational chaos within the BH causing fluctuation to the event horizon....These fluctuations allow the system to release some energy until it stabalizes.

biknewb
2005-Oct-06, 02:21 PM
...These disturbances will continue after the body crosses the event horizon generating a level of gravitational chaos within the BH causing fluctuation to the event horizon....
Does this chaos cause detectable gravity waves?

VanderL
2005-Oct-06, 02:21 PM
Doesn't this explanation of colliding/merging black holes and neutron stars mean the Universe must be awash in strong gravitational waves that go currently undetected?

I' think black holes/neutron stars as high density objects remains to be proven, what hubris of these investigators to use their theoretical properties to solve a mystery.

Cheers.

blueshift
2005-Oct-06, 02:43 PM
There is a lot more data available once you open up the NASA News Release link at the bottom of the article and open up more links thereafter..The article was incomplete.

bigsplit
2005-Oct-06, 02:47 PM
Does this chaos cause detectable gravity waves?

I can't even speculate on that.

Duane
2005-Oct-06, 07:12 PM
Does this chaos cause detectable gravity waves?

According to theory, yes it should.



I' think black holes/neutron stars as high density objects remains to be proven, what hubris of these investigators to use their theoretical properties to solve a mystery.



Holy man, VanderL, what more "proof" has to be provided for you to accept that these objects exist? There are quite a few images now of highly compact extremely massive objects with accretion discs around them, unequivocal measurements of highly compact, extremely massive objects orbiting companion stars, and excellent images of stars screaming around the massive, compact object at the centre of our own galaxy. I think that there is more than enough evidence that these objects exist.

Fortunate
2005-Oct-06, 07:57 PM
Do I understand the paper correctly
No, you do not understand the paper correctly.

Hypothesis: Gamma rays bursts are caused by black holes colliding with a neutron star.
Just the short ones.

Evidence: No supernova was detected.
There is other evidence also. You can read about it if you wish.

Conclusion: Hypothesis proved.
No scientific hypothesis is ever considered incontrovertably proved. They are all to some degree tentative. That doesn't mean, however, that they are all equally plausible.
In the case of the short gamma ray bursts, on the one hand, the observations are all consistent with the merger theory. On the other hand, they seem incompatible with a supernova theory. These were, apparently, the only two hypotheses that had seemed plausible in the light of what we knew previously. Remember that to be credible a theory has to work quantitatively as well as "qualitatively," so any thorough assessment involves mathematics.
Perhaps somebody really smart will propose another reasonable explanation. If that happens, further investigations will attempt to decide between this new hypothesis and the one involving mergers. Right now, we seem to have run out of promising alternative conjectures, and the one that remains seems correct. In any case, we will observe more and more bursts in as many ways as we can. These new observations will strengthen our faith in the merger scenario if they seem to support it, or, if they reveal discrepancies, will cast doubt upon that theory. Ultimately, there are plenty of people with clever minds and pencils, but the accumulation of more and better data provides a corrective to mind spinning. Hopefully, if our theories are wrong. we will recognize that they are.

galacsi
2005-Oct-06, 08:02 PM
Great and colourfull artist illustration ! You can see the black hole is also white , yellow and mostly pink ! Poor neutron star is in flames , you could think it could escape but no it is doomed ! What a cruel universe !

VanderL
2005-Oct-06, 08:32 PM
Holy man, VanderL, what more "proof" has to be provided for you to accept that these objects exist? There are quite a few images now of highly compact extremely massive objects with accretion discs around them, unequivocal measurements of highly compact, extremely massive objects orbiting companion stars, and excellent images of stars screaming around the massive, compact object at the centre of our own galaxy. I think that there is more than enough evidence that these objects exist.

Don't put words in my mouth Duane, I don't deny that these objects exist and their behaviour seems to be consistent with the theory of high density objects, but not on all counts. It took a large number of adjustments before we had an object emitting large amounts of energy in a confined space instead of an object absorbing matter. Until we have a high enough resolution to actually see this matter being "sucked in" I'm unconvinced. And don't try the "this is the best evidence you can get" approach, if it isn't proven (yeah I know proof is relative) we need to be careful. The fact that most people believe black holes are deep gravitational wells containing a singularity, doesn't make it true. Within a few years we will be able to image them in much better detail, we'll see what happens.

Cheers.

Duane
2005-Oct-06, 08:53 PM
Don't put words in my mouth Duane

Um, pardon me, but you said:



I' think black holes/neutron stars as high density objects remains to be proven,


So how am I putting words in your mouth?

Duane
2005-Oct-06, 09:08 PM
[snip]
don't deny that these objects exist and their behaviour seems to be consistent with the theory of high density objects, but not on all counts.

And which counts are those?


Until we have a high enough resolution to actually see this matter being "sucked in" I'm unconvinced.


Hmmm, well how about:

Star eats companion (http://www.physorg.com/news6248.html)

or: Supermassive Black Hole Eats a Star (http://www.williams.edu/Astronomy/jay/chapter31_etu6.html)

Now, just how "sucked in" do you need it to be? Are you convinced? :wall:

biknewb
2005-Oct-07, 07:12 AM
Hmmm, well how about:

Star eats companion (http://www.physorg.com/news6248.html)

or: Supermassive Black Hole Eats a Star (http://www.williams.edu/Astronomy/jay/chapter31_etu6.html)

Now, just how "sucked in" do you need it to be? Are you convinced? :wall:

This does not really convince me. All I see are artist's renderings of ideas about interpretations of observations.
I can't find the actual images/observations at the Chandra website (probably because I don't know how to search for them).

Substitute this set of interpretations for another and a completely different artist's rendering pops out.

regards

Thanatos
2005-Oct-07, 07:29 AM
Spectroscopic analysis is the short answer. All known supernova types have characteristic spectral "fingerprints" [and granted there is some overlap]. But GRB spectra [which admittedly are few and of low quality] compared to supernova spectra, it smacks of trying to match dog tracks to human footprints.

Fortunate
2005-Oct-07, 08:37 AM
Doesn't this explanation of colliding/merging black holes and neutron stars mean the Universe must be awash in strong gravitational waves that go currently undetected?
It depends on what you mean by "strong." Articles such as this one
http://www.nasa.gov/mission_pages/swift/bursts/short_burst_oct5.html
indicate that waves from such mergers would be near the limit of LIGO's capability. The amplitude of a gravitational wave decreases proportional to the first power of the distance from the source (it's good for us that it isn't an inverse square law). The article above implies that we might only be able to detect mergers that are close-by and then only if we knew precisely where to look.

Jerry
2005-Oct-10, 05:41 PM
We had a hunch that short gamma-ray bursts came from a neutron star crashing into a black hole or another neutron star, but these new detections leave no doubt,
There is a significant difference between being sucked into a hypothetical Black Hole, and a merger of two Neutron stars - which are known to exist, so this is a pretty broad characterization. One could add "Or something similar somewhere in between." Nothing has been proven, but this is a nice chunk of affirmative data.


This is good news for LIGO," said Dr. Albert Lazzarini, of LIGO Laboratory at Caltech. "The connection between short bursts and mergers firms up projected rates for LIGO, and they appear to be at the high end of previous estimates. Also, observations provide tantalizing hints of black hole - neutron star mergers, which have not been detected before. During LIGO's upcoming yearlong observation we may detect gravitational waves from such an event.
Yes, if good news includes a constraint that basically says we cannot detect gravity waves. "At the high end" includes the probability that a GW event should have been detected by now - Especially since Voyagers 1 seems to be confirming many high energy events are consumed by the helopause. The longer results are nil, the higher the probability they always will be.

Duane
2005-Oct-12, 03:52 PM
Substitute this set of interpretations for another and a completely different artist's rendering pops out.

I really think you should read them again, then go to the first press release from which the stories were written. You may also want to look up the papers, probably in arxive.

The telescope witnessed the star as it was pulled apart while whipping past the BH. Pretty convincing evidence, unless you just do not want to, or cannot, see it.

biknewb
2005-Oct-12, 05:28 PM
I really think you should read them again, then go to the first press release from which the stories were written. You may also want to look up the papers, probably in arxive.

The telescope witnessed the star as it was pulled apart while whipping past the BH. Pretty convincing evidence, unless you just do not want to, or cannot, see it.

Duane, I did read the original Nasa Press release. Several times. I also looked for more detailed pictures. All I found was a Chandra image of a 5x6 pixel bright spot and telescope pictures that do not show much detail either. Obviously this is already a great technological accomplishment. It is nowhere near evidence of the pretty pictures artists made to illustrate the interpretations.
Can someone point me to the image of the star that is devoured by the black hole. I mean the actual recorded image?

Don't get me wrong, I think this interpretation makes perfect sense with the black hole and the neutron star.
But it is only one possible interpretation of the images.
(I don't know if I am alowed to mention the other possibility in this thread with the new strict rules of discussing ATM ideas....:silenced:

regards

Duane
2005-Oct-12, 07:49 PM
(I don't know if I am alowed to mention the other possibility in this thread with the new strict rules of discussing ATM ideas....

Not here, no, but I would be interested in hearing what other possibilities there may be. By all means, please post to the ATM thread to discuss it--or possibly the Q&A thread, depending :)