Earliest time possible for life?

To P.O.

Re evidence for generation III stars being hydrogen and helium

All you need to remember is that when a telescope looks into very, very deep space - 10 billion plus light years away, they are also looking into the past.

By looking at stars and galaxies further and further away, hence further and further into the past, we see the evolution of the cosmos in reverse. Thus, the data gathered, and simple computer models based on that data, shows that generation III stars were hydrogen and helium. Noting, of course, that generation III stars were the first stars.

 

Log in or Sign up to hide all adverts.

Nietzschefan: It might seem a bit weird, but astromers adopted the following (I might have some details wrong):

First Generation stars are those visible prior to the invention of the telescope.

Second Generation stars are those which could be seen with early telescopes: Various stars (not all) in our own galaxy & perhaps some in our local group of galaxies (Or perhaps local galaxies which seemed to be stars when using the early telescopes).

Third Generation stars/galaxies are those viewable using very modern technology.​

There will be no problems if new technology allows the viewing of stars currently beyond current technology. Those stars might be included in the third generation or assigned to a now nonexistent 4th Generation.

The only real problem with the above semantics is that the assignment of stars to generations might be a bit arbitrary. Also, astronomers might quibble a bit over the assignment of some stars/galaxies


Pythagorean Order: The following is a brief summary of the support for the notion that the early universe consisted almost exclusively of hydrogen & helium.

There are methods for determining the composition of stars & interstellar gas clouds. The farther away a star or galaxy is the more distant it is in time. The relative abundance of hydrogen & helium in distant stars/galaxies is greater than in nearby stars/galaxies.

Astrophysicists have sound theories describing the life cycle of stars. The fusion of hydrogen produces helium, a process which lasts for millions or billions of years, depending on the mass of the star (more massive ones use up the hydrogen in millions of years: Smaller stars use it up in billions of years. When that nuclear reaction runs out of fuel (hydrogen), gravity compresses the star increasing the temperature at the core. The increased temperature ignites Helium fusion, creating heavier elements. When the helium is used up, gravity further compresses the star, increasing core temperature & igniting a new fusion process. This process generates heavier elements.

Due to the above description of the life cycle of stars, the relative abundance of hydrogen & helium is decreasing, while the relative abundance of heavier elements is increasing.

Cosmologists using knowledge of nuclear physics have sound theories indicating that the early universe consisted mostly of hydrogen & helium.​

Web sites can be found which go into more detail.

I put posted the above relying on memory & guarantee neither the completeness (very suspect) nor the validity of the descriptions. The basic concepts are correct.

 

Log in or Sign up to hide all adverts.

Mee tooo. What do we do 10 billion years in the future when we have the next generation of stars, call them generation -1. :shrug:

And HTH does one define a "generation" of stars anyway, aren't they really a full-distribution spectrum of various types at various stages.

In any case I vote for Skeptical's answer as the best so far in this thread.

Please Register or Log in to view the hidden image!

 

Log in or Sign up to hide all adverts.

Kenny C: You have not grasped the definition of Gen I, II, III stars. It is a definition established by observational astronomers, not by cosmologists or astrophysicists.

If future technology discovers stars never before known to exist, they will logically be Gen IV stars, not Gen -I

Generation I Star are those which can be seen with the naked eye.

Gen II are those viewable using early telescopes (but not visible to the naked eye).

Gen III are those viewable only if using modern technology beyond that of the early telescopes.

 

No no no ... I'm not talking about past stars but FUTURE stars.

 

The early stars who formmed around 100 million years after the BB are theorized to have been mostly very large stars so they'd have burned off and gone supernova very fast (on a stellar timescale of course), already seeding a fair amount of heavier elements. Seems to me that you might only need a couple more generations (I know, this therm is getting really confusing) to start having the heavy element concentrations necessary to form planets with the right basic ingredients. Adding to that the very early appearance of life on Earth (which although a very inconclusive sample of 1, points toward the direction that life appears pretty mush as soon as it is possible for it to do so), I'd say it could be very early indeed - somewhere between 1 & 2By doesnt sound unreasonable.

 

KennyC: Why would stars discovered in the far future not fit the Observer Astronomer scheme for defining generations?

No no no ... I'm not talking about past stars but FUTURE stars.​

The definition is repeated.

Gen I: Stars visible with the naked eye.

Gen II: Stars visible using early telescope technology, not visible to the naked eye.

Gen III: Stars visible using modern technology, not visible using early telescope technology. For example: Arrays of radio telescopes using computer technology can see stars too distant to be observed with an optical telescope. Radio telescopes hundreds of miles apart are equivalent to an optical telescope with a lens hundreds of miles in diameter.​

If future astronomers use some more advanced technology to see stars not visible with our 21st century technology, they will be Gen IV stars to fit into the above scheme. No problem with the concept, except that it leads to some confusion if you do not understand the definitions used.

 

And since you repeated without apparently understanding what I'm saying, I'll repeat, I'm not friggin talking about existing stars or past stars, but the next FUTURE generation of stars.

You are clearly so bought into the status quo you are not listening.

 

Even stars that havnt formed yet could be included in that nomenclature, depending on the gears required to observe them, or just as gen IV...

 

KennyC: I almost give up. You do not seem to have grasped the definitions used by observational astronomers as opposed to cosmologists & astrophysicists.

One more try at explaining.

1)Suppose that in the far future, there is a new massive star near the Alpha Centauri system (it would now be in the last stage of gravitational collapse). If massive enough, it would be visible to the naked eye & be called a Gen I star, even though it would be billions of years younger than some Gen III stars (which might be non existent now).

2)Suppose this discussion took place circa 1900. At that time there were only Generation I & Generation II stars.

Gen I were those stars visible to the naked eye. Gen II were those not visible to the naked eye, but visible using a telescope.

At that time you might have wondered about stars unobservable using telescopes, but viewable in the future using some technology unkown circa 1900 (We in 2011 can think arrays of radio telescopes using computer technology). They are Gen III stars, unkown cira 1900.

BTW: Gen minus I using the definition of Gen I, II, & III could only be stars observable by blind people (I do not expect there ever to be any Gen minus I Stars).

 

Life is abundant.

All life needs to survive is a few million years co-evolving into something greater on a planet or a rock. Sentient life needs 4.6 billion years to produce humans. First generation stars didn't live that long- it was a firework display of proto-solar systems rearranging themselves.

While it is reasonable to imagine that 8 billion years ago there was a "seed the universe with DNA contest", it is equally reasonable to assume proto life existed one billion years after the big bang.

DNA is mathematical in nature and so is biology.

We are systems built upon systems built upon systems: humans are the new flavor of the month.

It's what we do with the time alloted us as humans that matters.

There is a Great Thinker behind it all-- that's for sure.

 

I understand exactly but that doesn't make it right. The term is being used incorrectly apparently.

Generation has a specific meaning.

Age is a different thing.

:shrug:

 

The reason there wasnt any life around the first start is that there was nothing (or barelly anything) but hydrogen and helium before those first star started blowing up and spreading heavier ellements fused in their core.

You can't say that sentient life needs "4.6 By" to produce intelligent life. That's how long it took here, buts thats a survey with a sample of 1. It could very well have happenned much faster on another world, or not at all, or taken 2 or 3 times that long.

:wallbang: