Cosmology Question-What Happens When The Stars All Burn Out?

I was reading a bok about astronomy, and the author was explaining the evolution of stars. According to him, stars like the sun will reach a point when all of their hydrogen will have been converted into helium (vis fusion). When that day comes, the sun will become a red giant, and the helium will begin fusing to form elements like iron, iridium, uranium, etc. If we look into the far future, eventually all the stars will “burn” oout-what then happens-should I worry about this?

I wouldn’t worry too much if I were you Ralph. It’s a looooong-way-away, and besides, we’ve got electricity now…so when it gets all dark and cold, we can turn on the lights and put the heater on. :smiley:

And just think of all the money saved when you don’t have to buy SPF 30+ Sunscreen. :smiley: :smiley:

And of course, our sun is a second generation star, which means that it was formed in the aftermath of the “death” of other stars. Just because the stars around today will be all gone in a few billion years, doesn’t mean more won’t pop up in the mean-time.

Perhaps someone who actually knows something about this field can explain whether or not current models of star death/birth are steady state or not.

everything dies, baby, that’s a fact…

I’m not an “expert” by anyone’s definition, but I have been studying astronomy lately, so maybe I can help a little bit. I won’t be able to go real in-depth, but I think I can give you an idea:

I don’t think we need to worry about the amount of stars ever running out. The universe is constantly expanding and there is a lot of gas and dust out there, and some of it will eventually become stars. Some of that gas and dust is from stars that have already died or from explosions. New stars form from the gas and dust from old stars. The newer stars are more “metal rich” (a “metal” being anything heavier than hydrogen or helium) and are referred to as being more “polluted.” Older stars don’t have as much metal.

So I don’t think we’ll ever run out of stars, we’ll just run out of the stars that are more “metal poor.”

In about 100 trillion (10[sup]14[/sup]) years, give or take a few billion, the last star will flicker out. Don’t wait up.

Our knowledge is based on our current understanding of Physics. It would seem that Thermodynamics tells us entropy will increase, so in an expanding, infinite universe, everything gets spread out and cooler. Here’s one description of what might happen. Of course, we could be wrong about this – it’s entirely possible we can’t apply our results to the universe as a whole, or there’s some mechanism to counteract entropy.

Actually, I think we’ll find out about the stars pretty soon. I just shipped a new IBM computer to Tibet …

How many sleeps is that?

Are we there yet?
Are we there yet?

Don’t make me stop this galaxy and come back there!

Hmmf. Maybe thats what you think.


Hopefully in the afterlife things will work better.
And on a more personal note: Some things just shouldn’t worry about, unless you get. This is one of them.

Just want to point out that star will only create elements up to iron using fusion. Elements with a higher atomic number were created by things such as novas & supernovas. The reason is that iron takes more energy to fuse then it releases.

Thats why we use uranium/plutium in are atomic bombs (fission) and hydrogen in our thermonuclear bombs (fusion).

Also that leads us to the conclusion that all the heavy elements here on earth were created by a nova/supernova at some time. Just goes to show you how big and old this universe is

OK, after about 10[sup]14[/sup] years, there’re no more stars, and nothing left to make new ones. By about 10[sup]100[/sup], the most massive black holes will finish evaporating. Somewhere in between there, most protons will have decayed (we don’t yet know the proton’s lifespan), and the positrons produced will mostly annihilate with electrons. In the long view, eventually, there’s nothing left but photons, gravitons, and neutrinos, all of which are getting colder and lower-energy at an exponential rate (assuming that the current cosmological acceleration continues).

This is the way the world ends: Not in a bang but a whimper.

What will happen in the end depends on the resolution of some ongoing questions today. If the universe is massive enough, then one day it will contract into a ‘big crunch’ that will be the opposite of the big bang.

However, if the Universe keeps on expanding forever, then we’re headed for a ‘cold death’, in which the average temperate of the universe eventually drops below the point where life can be sustained.

If the universe stops expanding, then eventually you’ll wind up with a ‘heat death’. The laws of thermodynamics tell us that if two objects have a differential in heat, energy will flow from one to the other until they are at the same temperature. After that point, no work can be done through the exchange of heat between them. Taken to its ultimate conclusion, that means that eventually, the universe will settle to a situation where there is uniform energy throughout, and no work can be done. That’s the ‘heat death’ - an increase in entropy until you reach stasis. Needless to say, that would suck for us. In fact, all of the possible endings of the universe pretty much suck for us, assuming we can survive for billions of years anyway.

Actually, the ‘heat death’ will happen whether the Universe is expanding or static. But if it expands forever, then the average temperature will continue to decrease. In the static model, it will reach an average value and stay there.

unless you get paid to.


The great Computer will say, “Let there be light!”


It’s worse than you think (isn’t it always?).

The Universe is not only expanding, but it’s accelerating. At some distance, the fabric of space is expanding as fast as light. Any object past this distance is therefore impossible to see; it’s like it’s beyond your horizon.

The problem is, as the Universal expansion increases, the distance to that horizon shrinks. It gets closer. So eventually, after a loooong time, the only things we’ll be able to see are ourselves (the Milky Way), its companion satellite galaxies and the Andromeda Galaxy (which is gravitationally bound to us, I believe, and so will always be inside our horizon).

So even as all the stars burn out, the Universal Curfew will make it impossible to look farther out. The Universe will be dark, and uncomfortably close.

I leave the idea of space moving faster than light to someone else to explain. I fear my joy in this topic is waning quickly.

OK OK, we’ve all (or most of us) read the theorys that the universe will decay or become back holes and that in 10^100 they will have evaporated leaving photons of long wavelengths spreading out until they are too far apart for anything to happen.


What happens in a ring black hole? Specifically, in some of these, they can have TWO event horizons that can actually cancel each other out, leaving just the kerr type black hole. This matter stays a ring, and is not a true singularity since the thickness is close too but not exactly zero. Without its gravitational pull, it would not evaporate since there would be no Hawking radiation. Without having actual particles, it would not evaporate. This is one exotic specimen that might truely stand the test of time.

Also, due to the uncertanty principle, particles can and do pop in and out of existance since space cannot be completely empty. This sea of virtual particles should still be here right?

I’ve never heard of a ring black hole. The closest I can think of is a Kerr (rotating) black hole, where the central singularity is a ring, but there’s still only one event horizon, and it’s still shaped like a (squashed) sphere. Kerr black holes will evaporate just like Schwartzschild ones; in fact, black holes will lose angular momentum (and charge) much faster than they lose mass, so the final stages of a Kerr hole will be Schwartzschild anyway.

I think it’s incredibly cool to reflect that the carbon and oxygen I’m made of, the iron we build with, the gold we make jewelry out of, and the uranium we use to blow things up all came from a star’s life and death.

[Matrix moment]
[/Matrix moment]