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symesie04

Proverbial Candle (Type 1A)

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Ok i have a query over type 1a classification.

Now I understand that all type 1a supernova produce the same luminosity due to the physics that produce them. I also understand that given this information that they can thus be used to estimate distances to objects whenever they are seen. A dimmer or brighter type 1a would indicate a further or closer event, simples. However what i fail to understand is how can they determine that what they are looking at is in fact a type 1a and not another type of supernova event? Especially when observed at extreme ranges of observation? How can they tell that what they are observing is in fact not a type II at a distance that what appear to resemble a type 1a?

Am i missing something?

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Not all 1a's are quite the same, so there is still some tweaking to do to get a good luminosity reading.

However all 1a's have a characteristic spectroscopic signature, so by looking at the spectra you can determine what sort it is.

This is why there is a 1a,1b,1c etc - they looked sort of similar, spectroscopically but have different lines in them. It turns out 1b & 1c are produced by a completely different mechanism (core collapse), but that's where hindsight is so useful :)

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Ah yes spectrophotometry I hadnt considered that. But that must be very difficult to determine as most type 1a's are usually inbedded deep with galaxies and therefore the light must get contaminated with light from that?

Just out of interest as type 1a's are a result of a companion white dwarf munching on material from a healthy neighbour and not core collapse is it thought that they still produce the heavy elements at supernova and do they still result in the dense neutron star remnants?

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Ah yes spectrophotometry I hadnt considered that. But that must be very difficult to determine as most type 1a's are usually inbedded deep with galaxies and therefore the light must get contaminated with light from that?

No, because the SN1a is giving out light, so you see emission bands, and the light is enough to outshine the galaxy. Some of it may get absorbed in gas and dust on it's way out of the galaxy, but that would come out as absorption.

Just out of interest as type 1a's are a result of a companion white dwarf munching on material from a healthy neighbour and not core collapse is it thought that they still produce the heavy elements at supernova and do they still result in the dense neutron star remnants?

 

Yes lots of heavy elements are produced from SN1a, but a different set from the core collapse type. SN2 tend to produce more of some elements called alpha elements, such as magnesium, whereas SN1a tend to produce more iron. This is a useful way to let you date galaxy formation events.

As to whats left over, I suspect it would be in the white dwarf category. The star wasn't big enough to form a neutron star in the first place, so formed the white dwarf that went SN> As it looses a lot of mass and bts in the explosion, whatever is left must be smaller than it started, so can't really be a neutron star. This is just my thinking though without any evidence, I'll see if I can find out!

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Thanks Julian, a wealth of knowledge as always.

Thats interesting to know about the heavy elements, do you know why different elements are formed in the different types? As i thought everything heavier than Iron were created in the supernova itself do the type 1a and other types differ in intensity therefore producing different elements? And do all the different types of supernova all produce a different range of elements?

Oh ok i wasnt sure if the stealing of material led to a rapidly and massively increased core density hence the supernova and therefore left a neutron star.

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Thanks Julian, a wealth of knowledge as always.

Thats interesting to know about the heavy elements, do you know why different elements are formed in the different types? As i thought everything heavier than Iron were created in the supernova itself do the type 1a and other types differ in intensity therefore producing different elements? And do all the different types of supernova all produce a different range of elements?

Oh ok i wasnt sure if the stealing of material led to a rapidly and massively increased core density hence the supernova and therefore left a neutron star.

I think the stealing of material is a relatively slow process - remember it has to gather a significant mass to go supernova, maybe a tenth of a Sun, so it's probably not a quick process.

I don't know in detail why they produce different elements, but its probably because of the way they go off.

In a type 1a, they are tipped over the limit and suddenly the oxygen and helium which is in a degenerate state starts to burn. As degenerate matter is not much affected by heat, it doesn't explode immediately, but burns as a wave across the dwarf and then explodes. Strong silicon lines show up in a SN1a explosion, which is how they are identified (and no H lines). After a few weeks, strong Iron lines show up, so we know they make a lot of iron.

So - its basically a wave of burning zooming across a very hot cinder that causes a type 1a

A type 2 is caused by the star collapsing in on itself, imploding. A lot of the elements it has made are destroyed in this process by photodisintegration, so it almost starts from scratch. It crushes down to a neutron star and then bounces somehow (not well understood) and explodes outwards. Most of the energy is lost as neutrinos, but the remainder drives the nuclear reactions that make heavy elements. As the collapse sort of resets the state somewhat, I guess it makes more of the light elements than the heavy ones.

Should say I'm not an expert on this stuff!

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