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# Star Formation (Star Condensation)

Author Topic:   Star Formation (Star Condensation)
Taz
Member (Idle past 2522 days)
Posts: 5069
From: Zerus
Joined: 07-18-2006

 (1)
 Message 4 of 33 (390811) 03-22-2007 2:01 AM Reply to: Message 1 by Hoof Hearted03-20-2007 8:28 AM

Well, let us look at the mathematics behind all the theoretical mumble jumbles, shall we?

Ideal gas law PV = nRT = NkT
P = pressure
V = volume
n = number of moles
R = universal gas constant (8.3145 J/mol K )
T = temperature
N = number of molecules
k = boltzmann constant (1.38066 * 10-23 J/K)

Our sun is an average star and has about 10^57 atoms of hydrogen and helium. A typical stellar cloud is about 20K, which is about -250 degrees celcius. A typical interstellar cloud is about .1 LY across, which is about 9.46 * 10^14 meters. Volume of a sphere is 4/3*pi*r^3. Therefore...

k=1.38066 * 10-23 J/K
T=20K
N=10^57
V=4.41*10^44 m^3

P = (NkT)/V = 6.26*10^-10 J/m^3 which by the way is 6.26*10^-10 N/m^2

Now, the gravitational force on each hydrogen atom on the outer rim can be calculated roughly by the following equation.

F = (G*M*m)/r^2

F = force
G = universal gravitation constant (6.67 * 10^âˆ’11 N m^2 /kg^2)
M = mass of an object (1.7*10^30 kg)
m = mass of the other object (1.7*10^-27 kg)
a = surface area of hydrogen atom(3.52*10^-20 m^2)

Therefore, F/a = 1.16*10^-2 N/m^2

So, the pressure on each atom on the outer rim of the gas cloud is 6.26*10^-10 N/m^2 while the gravitational force on each atom's surface is 1.16*10^-2 N/m^2. As you can see, gravity clearly wins out on this one.

 This message is a reply to: Message 1 by Hoof Hearted, posted 03-20-2007 8:28 AM Hoof Hearted has replied

 Replies to this message: Message 5 by Minnemooseus, posted 03-22-2007 2:07 AM Taz has replied Message 7 by Hoof Hearted, posted 03-22-2007 4:11 AM Taz has taken no action Message 9 by CTD, posted 03-23-2007 6:28 AM Taz has replied

Taz
Member (Idle past 2522 days)
Posts: 5069
From: Zerus
Joined: 07-18-2006

 Message 6 of 33 (390813) 03-22-2007 2:12 AM Reply to: Message 5 by Minnemooseus03-22-2007 2:07 AM

Re: Need anything more be said?
You know, I have 3 dogs. My dogs would own your smiling cat there.

{Are you threatening my cat??? - ADMINNEMOOSEUS}

Edited by Adminnemooseus, : I love my yawning cat.

 This message is a reply to: Message 5 by Minnemooseus, posted 03-22-2007 2:07 AM Minnemooseus has taken no action

Taz
Member (Idle past 2522 days)
Posts: 5069
From: Zerus
Joined: 07-18-2006

 Message 11 of 33 (391166) 03-23-2007 6:23 PM Reply to: Message 9 by CTD03-23-2007 6:28 AM

 CTD writes:These calculations assume the "typical stellar cloud" has the same mass as our sun, occupying a spherical space "about .1 LY across". Perhaps this is why your results are the first I've seen that indicate gravity is sufficient to form stars from these clouds.

You misunderstood me. I made that calculation off the top of my head to disprove the assumption that the tendency of a gas to expand is stronger than gravity. Clearly, a quick look at the some actual math says otherwise.

But on the other hand, our sun make up the bulk of the mass of our solar system. Why can't I use the sun's mass to calculate the initial gravitational force?

Edited by Tazmanian Devil, : No reason given.

 This message is a reply to: Message 9 by CTD, posted 03-23-2007 6:28 AM CTD has replied

 Replies to this message: Message 14 by CTD, posted 03-24-2007 12:31 AM Taz has replied

Taz
Member (Idle past 2522 days)
Posts: 5069
From: Zerus
Joined: 07-18-2006

 Message 15 of 33 (391308) 03-24-2007 1:01 PM Reply to: Message 14 by CTD03-24-2007 12:31 AM

Re: Sorry
 CTD writes:If the gas is sufficiently "pre-condensed" at the start of the calculation, gravity alone should suffice; but then how does one account for the "pre-condensed" state?

Pre condensed? If you haven't noticed, 20K is a very low temperature.

The volume of a typical interstellar cloud is 4.43*10^44 m^3. Divide that by 10^57 and you get 4.43*10^-13 m^3. Each hydrogen gas takes up a volume of 6.2*10^-31 m^3. I'd hardly call that condensed.

 If you were to take the mass of the sun, translate it to gas, and calculate the volume it prefers to occupy at a given temperature, I think your results would probably match most models.

I think you've read too much creationist misinformation. You seem to think that there is a predetermined volume for gas at certain temperature.

But let me ask you this. How the hell do you calculate it's prefered volume at a given temperature? At least give me that much to go on.

 This message is a reply to: Message 14 by CTD, posted 03-24-2007 12:31 AM CTD has replied

 Replies to this message: Message 16 by Parasomnium, posted 03-24-2007 1:23 PM Taz has taken no action Message 17 by CTD, posted 03-24-2007 5:44 PM Taz has replied

Taz
Member (Idle past 2522 days)
Posts: 5069
From: Zerus
Joined: 07-18-2006

 Message 18 of 33 (391439) 03-25-2007 12:49 AM Reply to: Message 17 by CTD03-24-2007 5:44 PM

Re: Sorry again
 CTD writes:Now if it's always been common knowledge that gravity alone could get the job done, why was the supernova model even invented?

Why not both? At the beginning when there were only hydrogen and helium (right after the big bang event), certain already dense regions accumulated into interstellar clouds and gravity eventually contract these gas clouds into newly formed stars. The hydrogen burning (or fusion) that occur within these stars create helium, then helium burning creates heavier elements, and so on and so forth. Eventually, some stars run out of fuel and is massive enough that when they collapse under their own weight they become supernovas. During these short violent events, even heavier elements are created while the explosions themselves send these elements back into the interstellar medium. These materials eventually condense again and form another generation of stars. And so on and so forth.

I'm not trying to pick on you, but so far your responses have been little better than "I heard somewhere that Darwin doubted his own theory, therefore evolution is false..."

I'm sorry, but I have not presented any model to speak of. You are making this harder than it is.

Here's what happened so far. The thread started said that he thought gravity wasn't enough to overcome the gas's tendency to expand. I introduced honest to god math calculations that showed otherwise. You came in and said something like in the great scheme of things I'm wrong. I asked specifically why I was wrong and you answered that you heard somewhere that I was wrong, therefore I was wrong.

It would really help if you could be a little more specific than simply repeating "It is very well known that you're wrong, therefore you're wrong..." I mean, throw me a bone here. Tell me what's wrong?

 Last I knew, it was pretty well agreed that it isn't.

May I propose the following explanation? Please note that it is only a hypothesis.

Is it possible that the community you refer to that "pretty well agreed" about this thing is the very same community that wants the young earth creationist model taught in school?

I know from personal experience that it was pretty well agreed that if the earth was a few miles from its current orbit that all life on earth would end immediately, proving that this razor thin region of space that earth occupies must be proof of divine intervention. To me, this "fact" remained pretty well known until I stopped being a fundamentalist christian and someone pointed out to me that earth is several million miles farther away from the sun during summer than during winter. After that, this pretty well known fact stopped being so well known.

What I'm saying is is it possible that, like me, you've been living a sheltered life?

 This message is a reply to: Message 17 by CTD, posted 03-24-2007 5:44 PM CTD has replied

 Replies to this message: Message 19 by anglagard, posted 03-25-2007 1:01 AM Taz has taken no action Message 21 by CTD, posted 03-25-2007 8:53 AM Taz has replied

Taz
Member (Idle past 2522 days)
Posts: 5069
From: Zerus
Joined: 07-18-2006

 Message 22 of 33 (391560) 03-25-2007 10:03 PM Reply to: Message 21 by CTD03-25-2007 8:53 AM

Re: Nah
 CTD writes:Be sure to take the links to Jeans Length and Jeans Instability while you're there. Good looking short-cuts, if you ask me. How's that for a bone?

quote:
One of Jean's major discoveries, named Jeans length, is a critical radius of an interstellar cloud in space. It depends on the mass, size, temperature, and density of the cloud. A cloud that is smaller than its Jeans length will not have sufficient gravity to overcome the repulsive gas pressure forces and condense to form a star, whereas a cloud that is larger than its Jeans length will collapse.

Here's the calculation...

k = 1.38066 * 10-23 J/K
T = 20K
G = 6.67 * 10âˆ’11 N m2 /kg2
m = 1.7*1030 kg
p = m/((4/3)*pi*r3)
r = 4.73 * 1014 meters = .05 LY

Î» = ((5*k*T*r3)/(G*m2)).5

Which comes out to be 2.75*10-14m

So... what's the problem?

 This message is a reply to: Message 21 by CTD, posted 03-25-2007 8:53 AM CTD has taken no action

 Replies to this message: Message 23 by NosyNed, posted 03-26-2007 12:37 AM Taz has replied

Taz
Member (Idle past 2522 days)
Posts: 5069
From: Zerus
Joined: 07-18-2006

 Message 24 of 33 (391570) 03-26-2007 2:43 AM Reply to: Message 23 by NosyNed03-26-2007 12:37 AM

Re: Surprising Jeans Length
 NosyNed writes:We are discussing intersteller gas clouds and the crucial "length" with resonable parameters comes out to a jillion times less than a billionth of a meter?? This doesn't seem to make sense.

My mistake. I blindly trusted that wiki article, which is wrong. If you know how to edit that wiki, you should do it. m refers to the mass of the particle, not the mass of the whole thing. So, the equation cannot be combined like that.

So, Î» = 8.7*1014 m, which is I guess what he has been talking about. My mistake.

Edited by Tazmanian Devil, : No reason given.

 This message is a reply to: Message 23 by NosyNed, posted 03-26-2007 12:37 AM NosyNed has taken no action

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