View Full Version : Hypothetical calculation - can it be done?

gfellow

2009-May-18, 04:01 PM

I'm hoping to commission some calculations, but before tossing my dosh to the winds, I'd be glad of some feedback from my fellow astronomy enthusiasts.

Please let me know if you think it is possible to base calculations on the following parameters and or if not, why.

It might help if you think of this as an abstract exercise, rather than something actual.

1. Calculate the mass necessary to inaugurate nuclear fusion in a classic proto-sun model. (Sliding parameters, if necessary)

2. For a template, place the proto-sun in the center of our solar system.

3. Extrapolate the speed of proto-sun's angular momentum, determining its rotation using Saturn's (10 h 32 – 47 min) and Jupiter's rotations (9.925 h) as benchmarks. (Sliding parameters, if necessary)

4. Distributing the mass of the proto-sun in an expanding shell, "inflate" the proto-sun until its angular momentum matches that of our Sun (25-30 days)

5. The expanded proto-sun size required.

Let me know if you think this calculation is possible, in advance, thank you.

hhEb09'1

2009-May-18, 05:09 PM

4. Distributing the mass of the proto-sun in an expanding shell, "inflate" the proto-sun until its angular momentum matches that of our Sun (25-30 days) Do you want the angular momentum to match, or the rotation period to match?

gfellow

2009-May-19, 01:21 PM

Hi hhEb09'1,

Do you want the angular momentum to match, or the rotation period to match?

Rotation period.

gfellow

2009-May-21, 01:12 PM

No opinions?

Cougar

2009-May-22, 04:13 AM

Please let me know if you think it is possible to base calculations on the following parameters and or if not, why.

1. Calculate the mass necessary to inaugurate nuclear fusion in a classic proto-sun model. (Sliding parameters, if necessary)

Gee, gfellow, stars come in quite a large range of sizes. So you're talking about the minimum amount of mass that, upon gravitational collapse, will light up due to fusion?

Star formation is fairly well understood - up to a certain point. But it's a bit more complicated than a recipe: "Take x amount of mass. Mix gravitationally."

PraedSt

2009-May-22, 05:41 AM

Let me know if you think this calculation is possible, in advance, thank you.

Hmm, are you asking if one could do steps 1-5 if one wanted to? Don't see why not.

For example, for no.1, with a quick search I got Protostar (http://en.wikipedia.org/wiki/Protostar), Jeans mass (http://en.wikipedia.org/wiki/Jeans_mass) and the Bonnor-Ebert mass (http://en.wikipedia.org/wiki/Bonnor-Ebert_mass).

The rest don't look all that difficult. I think given enough time, even I could do them, as no relativity seems to be involved. :lol:

korjik

2009-May-22, 06:22 AM

I'm hoping to commission some calculations, but before tossing my dosh to the winds, I'd be glad of some feedback from my fellow astronomy enthusiasts.

Please let me know if you think it is possible to base calculations on the following parameters and or if not, why.

It might help if you think of this as an abstract exercise, rather than something actual.

1. Calculate the mass necessary to inaugurate nuclear fusion in a classic proto-sun model. (Sliding parameters, if necessary)

2. For a template, place the proto-sun in the center of our solar system.

3. Extrapolate the speed of proto-sun's angular momentum, determining its rotation using Saturn's (10 h 32 – 47 min) and Jupiter's rotations (9.925 h) as benchmarks. (Sliding parameters, if necessary)

4. Distributing the mass of the proto-sun in an expanding shell, "inflate" the proto-sun until its angular momentum matches that of our Sun (25-30 days)

5. The expanded proto-sun size required.

Let me know if you think this calculation is possible, in advance, thank you.

Other than finding the rotational inertia of a gas ball with an exponential density dependence, this is actually a pretty trivial calculation.

You should end up with a spherical shell with a radius a few times that of Jupiter.

Hmm, are you asking if one could do steps 1-5 if one wanted to? Don't see why not.

For example, for no.1, with a quick search I got Protostar (http://en.wikipedia.org/wiki/Protostar), Jeans mass (http://en.wikipedia.org/wiki/Jeans_mass) and the Bonnor-Ebert mass (http://en.wikipedia.org/wiki/Bonnor-Ebert_mass).

The rest don't look all that difficult. I think given enough time, even I could do them, as no relativity seems to be involved. :lol:

Neither the Jeans mass nor the Bonnor-Ebert mass are relevant to problem one though. They are relevant to whether the object will collapse, but an object can collapse and still be far too small to undergo fusion.

PraedSt

2009-May-22, 04:49 PM

Neither the Jeans mass nor the Bonnor-Ebert mass are relevant to problem one though. They are relevant to whether the object will collapse, but an object can collapse and still be far too small to undergo fusion.

That's right. Collapse is a necessary condition, but not a sufficient one. The mass of the clump/core also needs to be >~0.08 solar masses. Otherwise you get a brown dwarf. At least that's what I understand so far.

orionjim

2009-May-22, 10:54 PM

I looked at your website and have a pretty good idea what you are trying to calculate. I think if you searched google for Lennard Fisk, Thomas Zurbuchen and Nathan Schwadron and looked at their work you will be pleasantly surprised. They are all from the University of Michigan and are developing a solar vortex model. I also think that any one of them would explain that the physics (I think) you’re looking for isn’t possible. I say that based on what I know about the sun; but then I’m not a physicist.

I don’t know if you know the history of Rene Descarte, he had a vortex model of the universe around 1630. Newton politely dismissed it in his Mathematical Principles General Scholium. And he also slammed it in letter he wrote about it. The letter shows the flaws he saw in Descarte thinking. You can find the letter using Google. You might find it interesting.

As far as a solar model, I think if you search for a “solar dynamo” model you might do better. Also if you search for “NASA solar dynamo Hathaway” (don’t use the quotes) you will find some very useful information.

I would be very interested in knowing how you came up with the model you have, and made the connection to the sun. I would suggest doing it using private mail or this thread will end up in the ATM section.

Jim

gfellow

2009-May-27, 03:09 PM

All who posted to this thread, thank you! I have gleaned several sources and leads which I intend to pursue.

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