/sci/ - Science & Math

mass

>>1769374
well mass yes, but what about heat? I would assume a star that burns twice as hot would last half the time right? Or do star's burn at constant temperatures relative to their size?

bumpingggg

Mass, pretty much exclusively. Temperature is relative to mass, with exception of metalicity, however the main contributing variable to a star's life is mass.

No star just disintegrates; >10 Solar Masses go black-hole, less than that, supernova, and I cant remember, but it's around <0.6 Solar masses go white dwarf. (Supernova's also form neutron stars).

god decides

>>1769401
so what if a star has a higher percentage of non-hydrogen elements? Like say the star has more "sun spots?" than another of the same size.

what happens then? does the star just burn throung those as well?

Also,

http://en.wikipedia.org/wiki/Star#Formation_and_evolution

>>1769407
Well, a star doesn't burn anything but hydrogen until it becomes a giant. Giants can fuse helium, and subsequent fusions up to iron. A higher percentage of non-hydrogen means that obviously it wont burn as hot because of the dilution of fuel. In addition, this means there is less fuel and the star's life is shortened. All of this is quantified if you're interested in stellar evolution.

okay now i have a question about relativity!

say joe is moving through space in a space suit at .5 the speed of light and jim, also moving through space in a space suit at .5 the speed of light. Joe and Jim are both head in opposite directions towards one another, will Joe see Jim and Jim see Joe? Will Joe or Jim be moving at the speed of light relative to one another?

>>1769413
is there an equation for this? like x(hydrogen mass) * y(non hydrogen mass) = life time?

"If" is purely related to mass of star. "When", a star will start going nova happens if the "iron catastrophe" begins.

All heavier elements are produced when protons and neutrons add together, making heavier elements. This is fusion. Heat is also tearing apart the heavier elements, in fission, but mostly, stuff is being made. A star will create stuff with various atomic reactions until it reaches iron. Iron is special, it is energetically the middle ground between heavier things and lighter stuff. Iron starts accumulating in the core.

Heat no longer creates fusion or fission. However, pressure starts compacting the core of the star. Electrons and protons are squeezed together, and creates neutronium. The core compresses down to a tiny ball of density 10^17 kg/m. This happens incredibly fast... like 1/10 of a second. Stuff will keep falling inward, due to the sudden vacuum, making Neutronium even MORE dense than usual. So it bounces back, like a spring, and creates a supernova.

Now, it only gets to Neutronium when the star is around 8 solar mass or more. After its supernova, a black hole happens if the Neutronium is sufficiently massive to overcome light's speed. This is around 3 solar masses.

>>1769433
i see i see, thank you

>>1769422
Sorta.
http://en.wikipedia.org/wiki/Hertzsprung-Russell_diagram
Color is related to star heat. As a star burns, it will go down the "main sequence" line until is starts going red giant, and starts going to the top right, or petters out into a black dwarf, going to the bottom right.

After red dwarfing, it starts heading the other way, becoming hotter and bluer. It might burn out again, going to white dwarf, then black dwarf... or it goes supernova, and creates a neutron star, maybe a black hole.

Fun fact: the universe is too young to have any black dwarves in it yet. ( age < 100 billions years)

Check this site out:
http://outreach.atnf.csiro.au/education/senior/astrophysics/stellarevolution_mainsequence.html
Scroll down to about 1/3 the way down.
Note that the difference between the masses of the extremes on the chart is a factor of 600, but the difference in their main sequence lifetimes is a factor of 6,000,000,000!