New Sopernovae

Comments and questions about the APOD on the main view screen.
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New Sopernovae

Post by ta152h0 » Tue Mar 07, 2006 11:55 pm

what elements must be detected prior to this thing being called a " supernovae " as opposed to the run of the mill " novae " ??????? :lol:
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Post by l3p3r » Sat Mar 11, 2006 2:44 am

what is the actual difference between the two ?

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Post by Pete » Sat Mar 11, 2006 6:15 am

Both a nova and a supernova would be observed from Earth as a large and sudden brightening of a star followed by fading back to its original luminosity.

Novae are caused by the fusion of matter (namely hydrogen) that accreted onto a white dwarf from a binary companion. Some novae, appropriately called recurring novae, well, recur, on the order of a few years, IIRC...

The nova Velorum 1999, which reached magnitude 3 (easily visible to the naked eye):
The remnants of Nova Cygni (1992), the brightest nova in recent history:

Supernovae are caused by a different process. A supernova is basically an explosive star death - that's putting it mildly - which can briefly outshine its host galaxy (!). Typical supernovae are about a million times brighter (luminosity-wise) than typical novae.

There are two types of supernovae. Basically, Type II supernovae are caused by massive stars using up their nuclear fuels, collapsing in on themselves, and rebounding into space.

Type I supernovae can be related to novae: some of the matter that accretes onto a white dwarf and explodes causing a nova remains on the white dwarf. Repeated novae increase the white dwarf's mass until it exceeds about 1.4 solar masses (the Chandrasekhar limit). This limit is set by a quantum effect called electron degeneracy pressure. Past the Chandrasekhar limit, the white dwarf collapses, temperatures skyrocket, carbon fuses, and the white dwarf explodes. Type I supernovae can also occur when two white dwarfs collide, forming an unstable star with a mass greater than 1.4 suns.

Search the net for the above or consult a textbook for more details. And point out any mistakes in the above writing.