Astronomers Report Biggest Stellar Explosion

[glenc (Glen)]

By DENNIS OVERBYE
Published: May 7, 2007
Kaboom, indeed.
In a cascade of superlatives that belies the traditional cerebral reserve of their profession, astronomers reported today that they had seen the brightest and most powerful stellar explosion ever recorded.
The cataclysm — a monster more than a hundred times as energetic as the typical supernova in which the more massive stars end their lives — might be an example of a completely new type of explosion, astronomers said. Such a blast — proposed but never seen — would explain how the earliest and most massive stars in the universe ended their lives and strewed new elements across space to fertilize future stars and planets...

Eta Carinae could blow up sooner than we thought, Dr. Smith said, noting that it could be tomorrow, it could be thousands of years from now. Astronomers have no way of telling.
Even if it did blow as the new supernova did last fall, at a distance of around 7,500 light years, Eta Carinae would be unlikely to cause any serious harm to Earth, astronomers said. The explosion would be visible in the daylight and at night you would be able to read a book by its light.

http://www.nytimes.com/2007/05/07/sc...ml?ref=science

The SN was in NGC 1260.
http://www.associatedcontent.com/art...supernova.html

Would be hard to see the local DSO if eta Car blew up!

[Rodstar (Rod)]

Glen, I am imagining the difficult situation where one would have to find times in the month/ year when BOTH the moon and Eta Carinae are below the horizon to have decently dark conditions. Very troubling....

I hope Eta hangs in there for at least another 50 years....by which time I should have seen enough to be content.

[robagar]

Rod, your glass is half empty isn't it

[Karls48 (Karl)]

Then I hope Eta Carinae will wait bit longer before it goes supernova. That would stuff up observing for some time. Full Moon is bad enough.

[Ric]

It would be an awesome sight indeed but I fear we would all have to move to the northern hemisphere for any decent viewing.

[sheeny (Al)]

Here's the news @ nature release on the same story:

http://www.nature.com/news/2007/0705.../070508-1.html

Al.

[bojan]

This latest article is a good example of insufficient and even wrong information supplied... excellent wayto create confusion.
Pay attention to a mechanism of this explosion, they are described differently... If reader is not careful, and reads only last one of them, he/she may conclude that somehow photons could be splitted itn two?!
"In stars as massive as the parent to SN 2006gy, the inside is predicted to have been hot enough to split photons apart. This equates to a loss in radiation energy, and so to a loss in the internal energy source that stabilizes the star against the effect of gravity. The result is that the whole thing explodes. "
What is worse, there is a contradiction: loss of internal pressure causes the star to explode!

Popularization of science is really a hard wok... rarely done properly.

[robagar]

actually, saying that photons are split in two isn't far off the truth - in a really hot star the a photon has enough energy to make an electron and a positron. The photon hits a nucleus and is absorbed, and then the electron and positron are emitted immediately afterwards.

So a photon goes in and an electron-positron pair comes out, so you could say the photon has been split into two parts.

[robagar]

Oh, and the decrease in radiation pressure does cause the explosion! Heavy stars are balanced between gravity pulling and pressure from the photons pushing, and while there's enough pressure to counteract the gravity, the star lives. Electron/positron pair production takes high energy photons out of the system, reducing the pressure. Take out enough photons and the whole thing goes bang.

[robagar]

Come to think of it, the electron and positrons will go on to hit each other and annihilate, producing two more photons, each with half the energy of the original one. So the photon does literally split in two, in an indirect kind of way.

(Conservation of energy and momentum prevents them from combining back into one photon. In the first interaction where one photon becomes two particles, the nucleus takes the left over momentum.)

[bojan]

Rob,
I still insist this is not correct presentation of facts.
Reduced radiation pressure will cause the star to collapse, not to explode.
Then, possibly some other mechanism can cause a sudden increase in internal pressure, which may tear the star apart, but this is not even suggested, and definitely not explained in this article.
"Splitting" photons in two is also not the correct description of what is going on here. It is a creation of positron-electron pairs in certain circumstances, yes, but this is not splitting, to my understanding of plain English :-)
I have quite a lot of experience in presentation of scientific fact to the public (I was involved in this on one astronomical observatory in Europe during public days) and I know very well how easy it is to confuse people.. one wrong word during explanation and next week I was hearing from other people how someone said this-and-that to his or her friend a week before... and I was horrified because I realized that I was the source of that mis-information :-)

[robagar]

I guess it's a fine line between simplification and over-simplification. I did a double take at the photon-splitting in the article too, but I wonder if it's not a reasonable way of summing up a fairly complicated process?

After all, collapse is the first stage of a supernova explosion, and a high energy photon does become two lower energy photons via pair production. Perhaps going into too much detail is as confusing as anything else.

[bojan]

Originally Posted by robagar

Come to think of it, the electron and positrons will go on to hit each other and annihilate, producing two more photons, each with half the energy of the original one. So the photon does literally split in two, in an indirect kind of way.

(Conservation of energy and momentum prevents them from combining back into one photon. In the first interaction where one photon becomes two particles, the nucleus takes the left over momentum.)

See, how much you have to guess to get it eventually right...
Here it is also not clear why double number of half-energy photons would have lower radiation pressure than the higher energy photons.. This way of presentation implies a much higher level of previous knowledge about those things, and general public simply does not have this. I bet that not many people even noticed those nuances we are talking about here..... and perhaps went on searching wikipedia, for example. And I am by nmo means an expert here, I am just an amateur :-)
No, mate, I am not convinced that this is a good way of presenting scientific facts :-)

[robagar]

Well, I think the author did a good job in a short article without getting bogged down in details. Though maybe for us the details are the interesting bits

[bojan]

[xelasnave]

So what should one be reading to get the correct message.
Is it possible for a layperson to get an reasonable understanding or is it a matter that anything less than a degree in particle physics or should that be nuclear physics (or indeed more education still) will leave one uninformed at best or mislead at the worst.
alex

[robagar]

For my money you can't beat the Feynman Lectures on Physics books. They're degree level physics, but very readable and highly intuitive.

[xelasnave]

He sounds good and a bongo player to boot.
Thank you Rob
alex

[iceman (Mike)]

I listened to more about this on the StarStuff podcast this afternoon. Pretty amazing, really - the size of it! Only 3 or 4 stars in our galaxy of 100's of billions of stars get big enough to produce an explosion this size!

[xelasnave]

I think we may find common ground...other than love of music

Science alone of all the subjects contains within itself the lesson of the danger of belief in the infallibility of the greatest teachers in the preceding generation . . .Learn from science that you must doubt the experts. As a matter of fact, I can also define science another way: Science is the belief in the ignorance of experts.

(Richard Feynman, The Pleasure of Finding Things Out (1999) p. 186-187. This work is based on transcriptions from an interview made in 1981.)

alex