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Does this make sense?


glider
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......The star was 11000 light years away and exploded 350 years ago?


 


When stars explode, it's a messy business. But the massive blasts are also useful, seeding the universe with such key elements as calcium, iron and titanium.


 


And with the help of a new high-energy X-ray telescope, NASA said Wednesday astronomers are closer than ever to seeing just what's going on.


 


"This is helping us untangle the mystery surrounding how stars explode," said Fiona Harrison, principal investigator on NuSTAR, or the Nuclear Spectroscopic Telescope Array.


 


Combined with images from another NASA X-ray observatory, Chandra, NuSTAR has created the "first ever map of radioactive material in the remnants of a star that exploded," she told reporters.


 


One of the biggest surprises was that stars, which are spherical objects, do not explode in a circular manner, she said.


 


Rather, it appears that the blast is more lumpy and distorted from the very beginning.


 


"Prior to the explosion, the core of the star literally sloshed about," said Harrison, a scientist at the California Institute of Technology.


 


Astronomers based their findings on the observations of Cassiopeia A, or Cas A for short, a remnant of a supernova 11,000 light years away.


 


The star exploded around 350 years ago, blowing off outer layers with an extreme heat that created even more elements.


 


........Surely it exploded 11350 years ago?


 


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I think you are right.

The supernova was first observed 350 years ago, but it will have happened roughly 11000 years prior to that.

That's how i'd read it anyway.

Jd

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no, not necessarily. The star may have gone pop 350 years ago as observed from Earth but that doesn't make it 11350 years ago. You have to take into account for the Hubble constant and any redshift in order to figure out exactly how long ago it was. Is Cas A now 11000Ly away right now, or does it appear 11000Ly away now? This will have another influence over the actual amount of time ago it went pop. I am guessing they are saying it went pop 350 yrs ago as observed from Earth.


 


If James hadn't wussed out on the course he'd know how to work it out too, it was covered in week 11 :D


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I'm pretty sure Earth is the reference point for most of us :)

 

Indeed, but there is no fixed point in space or time. We have to assume from this set of facts that Cas A was Observed going pop 350 years ago, not that it actually went pop 350 years ago since there is no way that we are aware of that the light can have reached us yet if it went pop 350 years ago.

 

We need the inverse of  wavelength - observed wavelength plus 1 to give us our redshift factor, then we need the Hubble constant, and distance observed to figure out the actual distance at the time it went pop. Then we can figure out the amount of time it took that light to get to us, this will then tell us how long ago it actually happened. It will not be 11350 years ago, it's more likely to be 10000 years ago or less

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not terribly, but if those figures are correct in any way shape or form it would suggest that Cas A is moving towards us at a greater speed than the universe is expanding by a small amount :)


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Despite the high brow talk above, it must have gone "bang" a lot nearer 11350 years ago than 350 years ago.

So i'm still siding with Noel's interpretation.

Jd

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From me, Bradford is 85 miles away; Leeds 76.6 miles away; so that's not a good analogy since we are talking about an error of a few light years one side or the other of 11350 light years, an error of 5/11350 = 0.097%... If you gave me direction to Bradford and were out by 0.097% you'd get me to within 131 metres which I'd be quite happy about :)


 


[as you all know my maths is not great so don't ask me for directions to Bradford, or Leeds]


 


JD

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From me, Bradford is 85 miles away; Leeds 76.6 miles away; so that's not a good analogy since we are talking about an error of a few light years one side or the other of 11350 light years, an error of 5/11350 = 0.097%... If you gave me direction to Bradford and were out by 0.097% you'd get me to within 131 metres which I'd be quite happy about :)

 

[as you all know my maths is not great so don't ask me for directions to Bradford, or Leeds]

 

JD

 

The figures range between 11350 and 10350 according to the information contained within this thread and associated links, last time I looked it was closer to 9% than 0.09%. As I say, ask a question, expect an answer. :)

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