Nearby supernova risk discussed by Sigurdsson

[marcus]

The preprint on this has not come out yet. What we have is a 5 January blog entry by Sigurdsson.
http://scienceblogs.com/catdynamics/2010/01/has_a_supernova_type_ia_progen.php

The work concerns T Pyxidis
and is by a group at Villanova University led by Prof. Edward Sion.

What I get from this is that T Pyxidis is extremely interesting but far enough away not to pose a material threat to Earth.

The explosion they think T Pyxidis is preparing for for is type Ia.

 

[Arch2008]

I read about this today in an online German magazine. T Pyxidis is something like 1000 ly away, IIRC. The German article described it as a "death star" that "some astronomers feared would destroy the ozone layer". I had read that a GRB was dangerous at that distance if it was pointed at us, but I didn't think that a SN could damage the ozone from three hundred parsecs.

 

[marcus]

Here's some stuff in the media about T Pyxidis:
http://www.spacedaily.com/reports/T_Pyxidis_Soon_To_Be_A_Type_Ia_Supernova_999.html

Here's wikipedia on it:
http://en.wikipedia.org/wiki/T_Pyxidis

 

[marcus]

I read about this today in an online German magazine. T Pyxidis is something like 1000 ly away, IIRC. The German article described it as a "death star" that "some astronomers feared would destroy the ozone layer". I had read that a GRB was dangerous at that distance if it was pointed at us, but I didn't think that a SN could damage the ozone from three hundred parsecs.

My information is not 1000 ly, but more like 1000 parsec.
In other words around 3260 light year.

I suppose, like your German article said, it COULD pose a threat to our ozone layer, by the gammaray causing nitrogen and oxygen in our atmosphere to react to form the oxide NO, which would then eat our ozone.

But the impression I get is that we don't even have a reliable understanding and also the current reports need to be confirmed. So there is no reason for concern. We still must find out more and understand more.

I'm curious to see the German article. if not too much trouble could you give a link?

 

[Frame Dragger]

There is no way in hell, even if the supernova produced a GRB aimed down our throats, that a supernova 3260 ly distant will have ANY effect. The Earth would need to be struck by a GRB within no more than a hundred or so ly to really do massive damage. That damage would come in the form, mostly, of portions of the upper atmosphere being converted to nitric oxide and causing catastrophic climate change. For a really great article by NASA, try this: http://earthobservatory.nasa.gov/Newsroom/view.php?id=22898

 

[turbo]

The NY Daily News loves hot headlines as much as any rag, but they are quoting Edward Sion as saying that "soon" means about 10 million years.

http://www.nydailynews.com/news/world/2010/01/05/2010-01-05_possible_supernova_could_threaten_earth_say_astronomers.html

 

[Frame Dragger]

The NY Daily News loves hot headlines as much as any rag, but they are quoting Edward Sion as saying that "soon" means about 10 million years.

http://www.nydailynews.com/news/world/2010/01/05/2010-01-05_possible_supernova_could_threaten_earth_say_astronomers.html

Well... that's pretty soon in a cosmic sense. LOL... oh man, that article is so funny. I think people have become fear-junkies.

 

[mheslep]

There is no way in hell, even if the supernova produced a GRB aimed down our throats, that a supernova 3260 ly distant will have ANY effect. The Earth would need to be struck by a GRB within no more than a hundred or so ly to really do massive damage. That damage would come in the form, mostly, of portions of the upper atmosphere being converted to nitric oxide and causing catastrophic climate change. For a really great article by NASA, try this: http://earthobservatory.nasa.gov/Newsroom/view.php?id=22898

Well I'd be interested in the calculations. For comparison, the year http://en.wikipedia.org/wiki/SN_1054" was day light visible and was 6300 ly away. Assuming the explosions have similar energies, we should receive, what, 4X the energy on Earth from a T Pyxidis explosion? Even if not a photon or particle of ionizing radiation penetrated the atmosphere, might not a 4X SN1054 be worth another Watt or two on top our current 1366W? Or, might it wreck the night/day biological cycles for a while? What is the likely energy release from a T Pyxidis super nova, as compared to SN1054?

Also, this pop press article cites Sion, Godon and McClain of AAS saying T Pyxidis is already overdue, clear the building.
http://www.thesun.co.uk/sol/homepage/news/2795981/Supernova-may-wipe-out-the-Earth.html

 

[mheslep]

More reading shows that T Pyxidis would be a Type IA, yielding 1–2 × 10^44 joules over 10s per http://en.wikipedia.org/wiki/Supernova#Type_II", and SN1054 was a Type II supernova (9 solar masses) which yields 10^46 joules. Assuming this wiki swag is correct, SN1054 was 50-100x more powerful than T Pyxidis could hope to be, thus all is well and nothing to see here, please disperse.

https://www.youtube.com/watch?v=<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/rSjK2Oqrgic&hl=en_US&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/rSjK2Oqrgic&hl=en_US&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

 

[Frame Dragger]

More reading shows that T Pyxidis would be a Type IA, yielding 1–2 × 10^44 joules over 10s per http://en.wikipedia.org/wiki/Supernova#Type_II", and SN1054 was a Type II supernova (9 solar masses) which yields 10^46 joules. Assuming this wiki swag is correct, SN1054 was 50-100x more powerful than T Pyxidis could hope to be, thus all is well and nothing to see here, please disperse.

This is... yes. Well keep in mind that the power of a supernova has a lot to do with (as you've discovered) the type which is determined by the star's initial mass (when it first was a star so to speak), and its composition when it gravity overwhelmes everything up to and including nuclear forces.

The scenario in which we (people on Earth! lol) have to be concerned requires a vast star collapsing to form a neutron star (or some other more degenerate form of matter) or black hole. In that scenario you could find that when the star collapses it emits a large Gamma Ray Burst (think of extragalactic jets, but a lot briefer and far more energetic) and THAT, which is radiated in two cones from two poles. Even then, the range for a change in atmospheric conditions is within a hundred or hundreds of ly, not thousands.

Finally, this all illustrates another major issue: dying stars do not emit the energy you are talking about in a perfectly homogeneous sphere. This can lead to danger for us (by letting a GRB extend the 'range' of such an event in relation to Earth), but it also means that much of what you might expect to reach a distant object is lost to the remnant (nebula, neutron star, black hole, etc), material ejecta which poses no risk, and high energy gamma rays... but concentrated into (relatively narrow) cones.

For the record however, ANY event that bombards Earth with gamma rays (such as the ongoing existence of Sol) which falls short of converting our ozone layer into a layer of Nitric Oxide would probably just cause some very interesting lightshows. Our atmosphere makes for a dandy shield, which is why we can live within such close proximity to Sol.