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Fraser
2005-Dec-21, 09:33 PM
SUMMARY: Even though they explode in an instant, the after effects of supernovae can be seen for hundreds of years. Astronomers have observed the remains of three supernovae that flashed in our skies hundreds of years ago. Careful image analysis found concentric arcs of light moving outwards from where the supernovae exploded. Light from these explosions has bounced off of clouds of interstellar gas, and is now visible to astronomers like an echo can be heard when sound bounces off a distant object.

View full article (http://www.universetoday.com/am/publish/cfa_old_supernova.html)
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trinitree88
2005-Dec-23, 02:48 PM
Hmm. The light echo surrounding distant supernovae predicted by Zwicky, and confirmed is interesting. Assuming a uniform density ISM, it should drop off as inverse square law, too. But it suggests something else. At a distance of 160,000 light-years, SN1987a deposited ~20 neutrinos in detectors here. A neutrino of several Mev loses about ~ 10 % of it's energy in a forward scatter...say, 700-800 kev. Enough energy here to generate a diffuse x-ray background (whose origin remains controversial)...with some energy left over to heat dust grains, that then reradiate it away, until equilibrium is reached. That surface of last scattering, from the still expanding event horizon of the Local Bubble's last supernova, would appear as a diffuse microwave background, oriented in a polarization seemingly aligned with the magnetic axis of the star cluster it originated in... the Local Group. The Large Magellanic Cloud at 160,000 lt-yrs...the most recent supernova the Lost Pleiade at 3800 light-years (possibly an even closer one)....1600 times stronger than 20 neutrinos per total detector mass (a few million gallons of water, here)..32,000 events, and microwaves from every ~4 million kgs. of dust, that would otherwise be invisible.:)

trinitree88
2005-Dec-23, 02:52 PM
Hmm. The light echo surrounding distant supernovae predicted by Zwicky, and confirmed is interesting. Assuming a uniform density ISM, it should drop off as inverse square law, too. But it suggests something else. At a distance of 160,000 light-years, SN1987a deposited ~20 neutrinos in detectors here. A neutrino of several Mev loses about ~ 10 % of it's energy in a foraward scatter...say, 700-800 kev. Enough energy here to generate a diffuse x-ray background (whose origin remains controversial)...with some energy left over to heat dust grains, that then reradiate it away, until equilibrium is reached. That surface of last scattering, from the still expanding event horizon of the Local Bubble's last supernova, would appear as a diffuse microwave background, oriented in a polarization seemingly aligned with the magnetic axis of the star cluster it originated in... the Local Group. The Large Magellanic Cloud at 160,000 lt-yrs...the most recent supernova the Lost Pleiade at 3800 light-years [(1800 yrs BC. + ~ 2000 till now) to possibly an even closer one) ]....1600 times stronger than 20 neutrinos per total detector mass (a few million gallons of water, here)..32,000 events, and microwaves from every ~4 million kgs. of dust, that would otherwise be invisible.:) :cool: