New Type of Supernova Found

But..But... I thought helium was inert!

G'day StandardsGuy,

Helium is only chemically inert and in this instance we are not talking about a chemical reaction but rather thermonuclear reaction.

Regards masu.

Hi masu,

In a thermonuclear reaction, helium is what is created, it is not the fuel! I think they meant hydrogen, not helium.

-S

So excluding hydrogen and helium where do you think the remaining 90 naturally occuring elements come from?

Yes the primary nuclear fusion process taking place in the vast quantity of stars over the bulk of their lives is the fusion of four hydrogen nuclei (four protons) into helium nuclei (two protons two neutrons and lots energy).

However as the star gets towards the end of its life and the hydrogen starts to diminish the nucleus of the star becomes saturated with helium nuclei. At this stage you can now get helium fusing with hydrogen to form Lithium and more commonly helium fusing with helium to form beryllium. In fact up until the point the star goes nova you will get nuclei all the way up the nickel and iron forming. The reason you cant get past nickel or iron is that atoms after them on the periodic table require more energy to fuse than is released in the fusion process therefore they are unstainable in the core of a star as they would result in it cooling down.

So, how do we get nuclei that are heavier than nickel and iron?

Current theory believes that as a super massive star starts to run out of fuel and go past the red giant stage (that's the helium, helium fusion stage) it collapses back in on itself and then explodes in a supernova releasing more energy in a few seconds that all the stars in the average galaxy and yes supernova do outshine their parent galaxies for a couple of weeks or so. This massive release of energy produces nuclei that are energetic enough to from everything from copper to uranium. In fact and as the late Carl Segan often said that as we contain elements that could only have been formed in a supernova we are really made of star stuff. Personally I prefer to think we are made from star dust but regardless of what you call it life as we know it could not exist if the atoms we are made of didn't go through one of the universe's most violent reactions the supernova.

For readers that are less than 31 degrees north of the equator you might want to have a look at a star called η Carinae (eta Carinae). The image on the right shows eta Carinae in relation to the Southern Cross and Rigel Kentaurus.

η Carinae is a super giant star that is right at the end of its life and likely to go supernovae at any time. Considering it is only 7,500 to 8,000 light years away we are going to be in for one spectacular show when it does go. To start with the southern hemisphere will have no night for at lease a few weeks and probable a couple of months and if the level of gamma radiation is high enough we could be in serious trouble indeed.