Is the Cloud of Hydrogen Gas Likely to Collapse?

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Homework Help Overview

The discussion revolves around the stability of a cloud of hydrogen gas, specifically a cloud with 8 solar masses, a temperature of 20 K, and a radius of 0.6 light years. Participants are exploring whether this cloud is likely to collapse based on the Jeans mass concept.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to apply the Jeans mass formula to determine the stability of the hydrogen cloud. There are questions regarding the application of the formula and the interpretation of results. Some participants express confusion over the calculations and the significance of the derived values.

Discussion Status

The discussion is ongoing, with participants sharing their calculations and questioning each other's logic. There is no explicit consensus on the outcome, as different interpretations of the Jeans mass and its implications are being explored.

Contextual Notes

Some participants note potential typos and misunderstandings in the application of the formulas. There is also uncertainty regarding the definitions of terms like Jeans length and whether it refers to radius or diameter, which may affect the conclusions drawn about the cloud's stability.

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Homework Statement


A cloud consists of 8 solar masses of hydrogen gas (H2). Its temperature is 20 K and its radius is 0.6 light years. Will it collapse?


Homework Equations


jeans mass


3. The Attempt at a Solution [/b
I've tried to use jeans mass to solve this however I am finding the formula difficult to understand
 
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Show your work.
 
So far I'm using the formula
3/2kT <GMm/R
And (3KT/2Gm) x k >mj

I'm substituting m=2.167x10^-27
G=6.67x10^-11
K=1.38x10^-23
T=20
R=0.6

However I'm not sure what it is exactly that I'm gaining from using these formulae?
I'm getting that (3kT/2Gm) x R = 1.115011357 x 10^15 ?
I'm aiming to get an answer of
Jeans mass = 1.05 x 10^31 kg
Which is less than 8 solar masses (1.6 x 10 ^31) so it will collapse?
 
I struggled to follow your logic above. Seem to be a few typos:
(3KT/2Gm) x k >mj
(3kT/2Gm) x R = Mj ?
(3kT/2Gm) x R = 1.115011357 x 10^15
√((3kT/2Gm) x R) = 1.115011357 x 10^15 ?
Also, I don't see online a formula with that 3/2 factor. I see one with 15/4pi, another that approximates that to 1. Anyway, using your 3/2 I get that the Jeans length/radius = 0.84, which suggests to me it won't collapse. (I'm a bit confused over whether the Jeans length is a radius or a diameter, but if it's a diameter then the actual radius is much too large to collapse.)
 

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