Posts tagged supernova

A new type of supernova?

SN 2006gy

This one exploding star outshines an entire galaxy! The NGC 1260 core is the dimmer object.

Ok, I thought I was all on the up and up with these things and how they worked.  Ok, that is, as much as a layman can be on the up and up.  I am not an astrophysicist (yet)!

So get this: a few years ago we witnessed a strange supernova.  Actually, a little back story first.  The general idea I always had was that stars with several solar masses went supernova.  Reason being, they burned through their fuel at a greater rate.  Once the fuel at the core was gone or fusion wasn’t adequate enough to resist the inward pressure (gravity) the whole thing collapsed.  This releases a tremendous amount of energy and essentially the star explodes.  You get left with a huge amount of ‘stuff’ being blown out into space and you’re left with either a neutron star or black hole at what used to be the core of the star.

That was a super basic overview and back story.  So what is this new supernova?  It is being called a Pair-instability Supernova.  What the what?!  If the name sounds bizarre then wait until you hear about how it works.

So here is how it goes.  First, you need a supermassive star.  A star of 130-250 solar masses seems to be the “zone”.  Instinctively, one thinks “the more massive the star, the more massive the black hole it leaves behind”.  Well, not really.  At least, not in the case of this kind of star.  See, these supermassive stars have low metallicity.  I believe that means they’re almost entirely Hydrogen and Helium with very little other elements present…

…and well, I’m going to just post what Wiki says because I’m feeling lazy:

A pair instability supernova occurs when pair production, the production of free electrons and positrons in the collision between atomic nuclei and energetic gamma rays, reduces thermal pressure inside a supermassive star‘s core. This pressure drop leads to a partial collapse, then greatly accelerated burning in a runaway thermonuclear explosion which blows the star completely apart without leaving a black hole remnant behind.[1][2] Pair instability supernovae can only happen in stars with a mass range from around 130 to 250 solar masses and low to moderate metallicity (low abundance of elements other than hydrogen and helium, a situation common in Population III stars). The recently observed objects SN 2006gy and SN 2007bi[3] are hypothesized to have been pair instability supernovae.

So there, you have it.  The star goes kablooey and leaves nothing but the fresh scent of brute.  Ok maybe not.  Incredible though, that a star can completely obliterate itself and leave nothing behind.

With that said, the star SN 2006gy is in a galaxy some 240 million light  years away (ie the light we saw originated 240 million years ago).  There is a star nearer to us, Eta Carinae that might go supernova much in the same way.  If it does, it will likely be brilliantly bright.  Visible during the day and able to be read by at night.

Fact is stranger than fiction, once again.

More info here

And here (this site has multiple links at the bottom)

Supernova witnessed by satellite

A supernova is a cataclysmic ending to the life of a large star.  The reason these stars explode (supernova) is due to the fact they are too large to sustain equilibrium for very long.  Our Sun is calm middle sized star that should last 5 billion more years or so.  Massive stars lifespans can be measured in millions of years.

Well recently we’ve witnessed a star going supernova.  One scientist compared it to winning the lottery.  I’d say it’s probably more probable to win the lottery.  People win lotteries every week!  We’ve only ever witnessed a supernova the moment it happened just this once, so far.

NASA’s Swift satellite caught the exploding star in action.  As stated in the article, we’re used to seeing stars after they explode, never the moment they do explode.  A comparison the article makes is it would be like seeing fireworks a couple of seconds after exploding.  It’s still cool to see but, if astronomers are anything like me, they like things that go BOOM!

Why do large stars supernova?

Long story short:
Huge stars burn their fuel at an amazing rate.  This fuel is what keeps stars in equilibrium.  This means that the outward force of nuclear fusion reactions is equal to the inward force of gravity.  One tries to blow it up, the other tries to crunch it down. 

It looks something like this:
>>>><<<omg it’s hot in here>>><<<<
(like my diagram?)

As a massive star runs low on fuel the inward force overpowers the outward force.  Once the balance is lost, the star collapses.  Once the collapse begins an unstoppable chain reaction occurs that rips the star apart in spectacular fashion.  The star is blown apart and it’s outer layes are hurled into space.  Whatever is left of the interior might possibly become a neutron star or a black hole, depending on the original mass of the star.

CNN Article
NASA Article

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