Gamma Ray Burst

Cackmobile writes "The Sydney Morning Herald is reporting that some Australian scientists have been watching a gamma-ray burst. The article makes some good points about the origins of these." Update: 03/21 03:27 GMT by T : MickDownUnder writes with a link to NASA's press-releasy version, with story, pictures and animations.

Comments

Re:What is the news??

[Ashtray_Waterloo]

It's the birth of a black whole. Have a cigar!

Here's a link to an article on Yahoo!News:

LINK

SWIFT

[little1973]

Nasa is building a satellite capable of catching gamma-ray burst on the fly. Here's the link.

Not much here

[bzcpcfj]

From the article: "They could be the birth cry of black holes formed from the ruins of a supernova or the result of colliding black holes or neutron stars." Those are hardly new theories. The article doesn't say how the observers happened to catch the burst as it happened, what observers were able to see in the "weeks" (which is a long time for a gamma ray burst) that followed, or what the artist's conception of a Wolf-Rayet star has to do with any of this. On the whole, a very disappointing article. This story, published last October 8 by NASA is much more informative.

Re:Not much here

[golo]

Coincidentally yesterday NASA came out with this article about the October event. HETE satellite catched a gamma-ray burst "[it] spotted the burst, nailed down a location, and notified observers worldwide within a few seconds, while the gamma rays were still pouring in". It turns out that there is a "Gamma-ray burst Coordinates Network", and an Automated Telescope in Japan that started observing just 193 after the burst was detected. cool story.

Weeks is appropriate

[barakn]

what observers were able to see in the "weeks" (which is a long time for a gamma ray burst)

The gamma rays themselves persist anywhere from .01 to 1000 s. Even with HETE-2, we have almost no chance of pinpointing the location of the short GRBs. But the long ones last long enough to pinpoint their location with X-ray telescopes. If that happens, then the GRB can be observed across the energy spectrum from X-rays to radio waves. They often take weeks before they dim to the point they can't be distinguished from their host galaxies. The misperception that gamma rays bursts are fleeting comes from the days before the BeppoSAX satellite launch in 1996, when positions could not be located precisely enough for follow up observations in other regions of the spectrum.

Long GRBs (such as the one lst October) are probably caused by hypernovae or collapsars, where a massive star (at least 20x our sun's mass, not the 10-15 solar mass star mentioned in the Sydney Morning Herald) has its core collapse into a black hole, perhaps after collapsing into an intermediate neutron star. The short GRBs are probably the result of mergers between massive compact objects like white dwarfs, neutron stars, and black holes.

Re:Weeks is appropriate

[barakn]

I think the conventional 0.01s to 1000s figures are how long they last in gamma rays. Do the bursts last longer in other forms of light?

That was exactly the point in my last post. When the gamma rays are gone the show isn't over.

From this one might assume Wolf-Rayet stars might already have undergone an event which might have caused a GRB (gamma ray burst)?

No. These massive stars have (usually) burned through most of their supply of hydrogen and are furiously burning helum. They are losing their outer layers in a fierce wind, rather than an explosion, which will continue for years. Their mass loss is driven by the absorption of light by C,N, and O that they have cooked up. Super- and hypernovae lose mass due to the sudden collapse of their cores; the explosive energy comes from gravitational potential energy, mostly. Two different processes. I should note that Wolf- Rayet stars are generally close to blowing up as supernovae, or if we're lucky, a hypernova with its jet pointed at us (a.k.a. a GRB). This link for another over-simplified answer.

Science Daily

[Alizarin Erythrosin]

Science Daily has an article about it too, saying "Scientists arriving on the scene of a gamma-ray burst just moments after the explosion, have witnessed the death of a gigantic star and the birth of something monstrous in its place, quite possibly a brand new, spinning black hole."

This is exciting, seems like we have a first hand look at the formation of a black hole!