how do we know?

I have a question I can't seam to find an answer to. I've read what kind of star ours is etc, but how are we sure our sun isn't already in the shrinking faze of its life? Mars seaman like it could have or did maybe have life at one time or another(not saying intelligent). How do we know ours isn't going white dwarf? Help answers please.

Originally posted by ExCloud
I have a question I can't seam to find an answer to. I've read what kind of star ours is etc, but how are we sure our sun isn't already in the shrinking faze of its life?

our "kind of star" will expand before it shrinks. Also if Mars has "seaman", life is inevitable!

No one can answer that question. Because no one knows. Everything is a theory. A best guess. Just have to deal with it.

Originally posted by ExCloud
I have a question I can't seam to find an answer to. I've read what kind of star ours is etc, but how are we sure our sun isn't already in the shrinking faze of its life? Mars seaman like it could have or did maybe have life at one time or another(not saying intelligent). How do we know ours isn't going white dwarf? Help answers please.

That is odd. I can only guess how that word got there.

reply to post by wingsfan


That's why I said how do we know we are not in the shrinking stage already? The mars reference was because maybe it shrinks at such a rate that it dried up and now here we are to dry up. Who's to say as the star shrinks and gets farther away that our magnetic feild doesn't decrease from that the the heat of the sun seams more?

reply to post by emberscott


Yea I have come to that everything is theory. I'm wondering why most theories say our sun will expand or get larger when it could have done this already.

Originally posted by emberscott
No one can answer that question. Because no one knows. Everything is a theory. A best guess. Just have to deal with it.

Originally posted by ExCloud
I have a question I can't seam to find an answer to. I've read what kind of star ours is etc, but how are we sure our sun isn't already in the shrinking faze of its life? Mars seaman like it could have or did maybe have life at one time or another(not saying intelligent). How do we know ours isn't going white dwarf? Help answers please.

That is odd. I can only guess how that word got there.

Yeah, me too.

Damn You, Autocorrect

reply to post by Ex_CT2


Wow didn't notice. I'm using my phone haha so its hard to see everything and correct. That's great! Haha

reply to post by ExCloud


Hi!

A very good, not hard to understand podcast about the lifecycle of our sun can be found here: AstronomyCast.
People that don't have audio or enough bandwith will find a transscript at the site if you scroll down.

Highly recommended podcast in general if you are looking for info or news on astronomy, cosmology, spaceflight etc.

Bye

Stellar Evolution - Read all about it.

The principles are pretty easy:
- Mass causes gravity, which compresses the Sun's gasses.
- Compression causes heat to build-up.
- Sufficient heat & pressure cause the hydrogen to fuse in the Sun's core to helium.
- Fusion energy pushes outward against the inward force of gravity.

If the fusion pressure was more than the gravitational pressure, then the star would expand. However, that would take the pressure off of the core and the fusion would stop. If that happened, gravity would become the dominant force and the star would start to collapse in on itself. But then this collapse would again cause compression & heat and restart the fusion.

Our sun is a stable, main-sequence star because it has found the balance-point between these two opposing forces.

You can read what happens next in the above link.

This brings us back to the OP's question: "How do we know?"

For starters, this statement...

Originally posted by emberscott
No one can answer that question. Because no one knows. Everything is a theory. A best guess. Just have to deal with it.

...is utter bunk, bollocks and Bovine Scatology.

Someone was asleep in school when the teacher explained the scientific definition of the word "theory":

A scientific theory is "a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment."...
Scientific theories are the most reliable, rigorous, and comprehensive form of scientific knowledge. This is significantly different from the word "theory" in common usage, which implies that something is unproven or speculative.

(Emphasis mine)

Gravity is a theory, but even the most apathetic slacker understands what will happen if he steps off a cliff. It's not a "guess". Over 165 years ago, astronomers were able to use precise mathematical calculations of gravity to determine the existence and position of a previously undiscovered planet and thus found Neptune. Today we can use the same equations to plot the paths of planetary probes with exquisite precision, and calculate the masses of planets, stars and galaxies countless light-years away.

Quantum mechanics is a theory. No one has ever seen an electron or a hydrogen atom; yet for more than 60 years physicists & chemists have been able to correctly predict the behavior of elements and subatomic particles decades before they are actually discovered. Without an excellent knowledge of quantum phenomena (as opposed to a "best guess"), the computer on which you are reading these words could never have been invented.

Do we know everything? Hell no! But that doesn't mean we know nothing. From a dynamic standpoint, your computer is much more complex than a star. Our understanding of gravity and quantum mechanics is quite adequate for understanding the life cycle of our Sun.

I hope this helps.

Don't sound so worried.

It'll be BILLIONS of years before anything of note or real interest happens to our happy star.

reply to post by Druscilla


This is true in just wondering for my own thought. I know we will all be dead before we find all these answers. Unless we do get a space intervention from some alien race.

reply to post by Saint Exupery


I get this, but how are we sure this is correct. We know the earth is expanding. We know the sun is heating up. We know Mars has some form of water. We know titan has oceans. Even with this how do we know our sun isn't shrinking? In my opinion as you release gas and solar flares you get smaller.

Originally posted by ExCloud
reply to post by Saint Exupery

 

I get this, but how are we sure this is correct. We know the earth is expanding. We know the sun is heating up. We know Mars has some form of water. We know titan has oceans. Even with this how do we know our sun isn't shrinking? In my opinion as you release gas and solar flares you get smaller.

Let me introduce you to Nucleocosmochronology.

Nucleocosmochronology, also known as cosmochronology, is a relatively new technique used to determine timescales for astrophysical objects and events. This technique employs the abundances of heavy radioactive nuclides to calculate the age of formation of astronomical objects in a similar fashion to the dating of rocks in the field of geochronology. Nucleocosmochronology has already been successfully employed to determine the age of the Sun (4.57±0.02 billion years) and of the Galactic thin disk (8.8±1.8×109 y), among others. It has also been used to estimate the age of the Milky Way itself, as exemplified by recent study of Cayrel's Star in the Galactic halo. Limiting factors in its precision are the quality of observations of faint stars, and perhaps more importantly, the uncertainty of the primordial abundances of r-process elements.

Our sun's chemical composition is 74.9% hydrogen and 23.8% helium. The last 2% is heavier elements. We know this through spectrum analysis of the sun.
Because of how nuclear fusion works we know that that the sun will continue to make other elements through it's nuclear fusion. The amount of hydrogen the sun still has means it's only gone through about half of it's life cycle as a main sequence star. It will have to fuse a lot more of that hydrogen into helium to get to the red giant expansion stage.

Please understand the our sun doesn't "shrink" in the way you are thinking. Our sun will become a white dwarf because after the expansion into a red giant, it will fuse the helium into more and more heavier elements. It is during this stage that the sun will begin to throw off material from itself, forming a planetary nebula, until all that remains is it's core. It's that core that will be the white dwarf.

There are stars that do "shrink" after they've expanded, but those are stars that are much, much bigger than our star, and that "shrinking" is actually the star collapsing to produce a nova. Our star is simply not big enough to do that.

A good example of a star that is going to do that, and you can see with your naked eye quite well is Betelgeuse

reply to post by eriktheawful


Starred thank you. Now it makes more sense.

Originally posted by emberscott
No one can answer that question. Because no one knows. Everything is a theory. A best guess. Just have to deal with it.

That statement only applies to the Terran scientists and their fanbase.