Hypernovae?

[Wellsi]

Do these events really exist and is there any proof for one existing? or do we have to wait until a massive star really does explode? Even so, what could be the effects on the earth if such an event were to happen (say for example Eta Carinae 8000 light years away?)

[Garth]

Do these events really exist...?

Long Gamma Ray Bursts?

Garth

[Wellsi]

i didnt think they had tied GRB with super/hyper novae? i remember there being one incidence where the GRB was detected along with a supernovae in the same direction... but it was only the one case?

[Garth]

It was just a suggestion in the absence of anything better!

Note it is generally thought that there are two classes of GRBs, short and long. The short GRBs are more intense and shorter in duration. They could be caused by neutron stars or BHs colliding and might be nearer than the long GRBs.

It also depends on what you mean by "Hypernovae", just extra powerful supernovae? One possible use of the term might apply to the demise of extra- massive PopIII stars, which would place them at cosmological distances, z ~ 1, and, if the source of long GRBs, it could explain their isotropic distribution over the sky.

You can find information at the NASA site: Gamma Ray Bursts (http://imagine.gsfc.nasa.gov/docs/science/know_l2/bursts.html) Are the sources of GRBs outside our Galaxy?
Recent observations of apparent counterparts in other parts of the electromagnetic spectrum seem to imply that at least some, if not all, GRB occur in galaxies other than the Milky Way. The observed isotropy is also a necessary requirement of cosmological models. The apparent inhomogeneity would result from redshift effects, and possibly source evolution. If gamma-ray bursts are cosmological, however, their energy release must be gigantic. For the brightest bursts, if the intrinsic emission is isotropic the total energy in gamma-rays must be 1053 to 1054 ergs, which is at least as great as that produced in supernovae. The difference, of course, is that in supernovae only 1051 ergs comes out in kinetic energy and visible light, and almost all of the photons are well below X-ray energies. Cosmological models are being developed which can get all that energy into high-energy photons; they are currently favored by the majority of astrophysicists.

Garth

[Wellsi]

ok the star i was in referance to when thinking about this was Eta Carinae, what is that like 100 times more massive than the sun and 8000 light years away? what could that blowing up do to us here on earth?

[SpaceTiger]

ok the star i was in referance to when thinking about this was Eta Carinae, what is that like 100 times more massive than the sun and 8000 light years away? what could that blowing up do to us here on earth?

Not a whole lot, unless it did give rise to a GRB and the gamma-rays were beamed directly at earth. So far, it seems from our observations that the opening angles of GRB jets vary a good bit, so I couldn't give a precise probability.

[Wellsi]

the gamma rays from an exploding star would "theoretically" be beamed out in all directions no? Sure there would be impurites in the consistancy of the gamma ray intensity like more could go in one direction than another (just like a grenade exploding)
Do we have redshift on eta carinae?

[SpaceTiger]

the gamma rays from an exploding star would "theoretically" be beamed out in all directions no?

No, we think that most gamma-rays from long bursts are channeled along a pair of jets.



Do we have redshift on eta carinae?

Eta Carinae is in our galaxy, so it has a negligible cosmological redshift... or do you mean its Doppler redshift?

[Wellsi]

yeh doppler redshift sorry about that :D
so gamma ray bursts could be emitted like the jets of radiation from a pulsar? just from the poles?

[SpaceTiger]

yeh doppler redshift sorry about that :D

The systemic radial velocity is -8 km/s:

http://www.ingentaconnect.com/content/bsc/mnr/2004/00000351/00000001/art00005

[Wellsi]

so its receding from us at 8km/s?

[SpaceTiger]

so its receding from us at 8km/s?

That's right.

[Wellsi]

is it in another spiral arm of our galaxy or dont we know? 33,000 light years to the galatic centre right?

[SpaceTiger]

is it in another spiral arm of our galaxy or dont we know? 33,000 light years to the galatic centre right?

I don't know if it's in another spiral arm, but the galactic center is closer to 25,000 light years away.