Astro- modelling a white dwarf via polytrope

In summary, the Lane-Emden equation has been solved numerically for the scaled radius and the derivative of scaled pressure with respect to scaled radius. With the given equation of state, n, and mass, the maximum scaled radius can be determined. The central density and radius can be calculated by setting the central temperature and density as free parameters.
  • #1
laam
3
0
have solved the lane - emden eqn numerically for scaled radius, and the derivative of scaled pressure with respect of scaled radius, are given the eqn of state, n, and mass, how would i go about working out the central density and the radius?
thanks
 
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  • #2
Huh? Sorry, but can you restate that a little more clearly? Maybe include the equations you worked with too?
 
  • #3
laam said:
have solved the lane - emden eqn numerically for scaled radius, and the derivative of scaled pressure with respect of scaled radius, are given the eqn of state, n, and mass, how would i go about working out the central density and the radius?
thanks

The Lane-Emden Equation only generates finite "stars" for low Polytropic Indices (0 to 4). For those indices, the maximum Scaled Radius is some constant (eg., Pi or sqrt(6)). Thus, the maximum "actual radius" is just that constant multiple of the Scale Length:
[tex]S_{n} = \sqrt{ \frac{(n+1) k_{B}}{4 \pi G m} \frac{T_{c}}{\rho_{c}} }
[/tex]​
The central density & temperature are Free Parameters*.
* For derivation, see: https://www.physicsforums.com/showthread.php?t=278009 [post #8]
 

Related to Astro- modelling a white dwarf via polytrope

1. What is a white dwarf?

A white dwarf is a type of star that has exhausted all of its nuclear fuel and collapsed under its own gravity. It is composed of degenerate matter, which means the electrons in the star's core are packed so tightly that they are unable to occupy the same energy states, resulting in a compact and incredibly dense object.

2. How is a white dwarf formed?

A white dwarf is formed when a star with a mass less than about 8 times that of our sun runs out of nuclear fuel. As the star's core collapses, the outer layers are expelled in a planetary nebula, leaving behind the hot and dense core, which is the white dwarf.

3. What is astro-modelling?

Astro-modelling is the process of using mathematical and computational models to simulate and study astronomical objects and phenomena. This allows scientists to better understand the physical processes and properties of these objects and make predictions about their behavior.

4. What is a polytrope?

A polytrope is a mathematical model used to describe the internal structure of a star. It assumes that the star's density is a function of its pressure, and allows scientists to study how changes in pressure and temperature affect the star's structure and evolution.

5. How does astro-modelling a white dwarf via polytrope help in understanding these objects?

Astro-modelling a white dwarf via polytrope allows scientists to simulate and study the internal structure and evolution of these objects. By changing the parameters in the model, scientists can see how different factors, such as mass and temperature, affect the white dwarf's behavior. This can provide valuable insights into the properties and behavior of white dwarfs in the universe.

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