### Schuster-Schwarzschild model

**(Schuster-Schwarzschild approximation)**
(simplified model of a star's production of absorption lines)

The **Schuster-Schwarzschild model** is a simplified model of the Sun's
mechanism for producing absorption lines, treating the
Sun as if a distinct outer layer (termed a **reversing layer**)
produces the lines through opacity
at specific wavelengths, which surrounds a
black body producing a continuum emission.
It was inspired by Kirchhoff's laws.
The method has been refined and can still be used,
e.g., for calculating a curve of growth.
It can be considered an example of a
**two-stream approximation**.

It is a simplification because real stars do not have such neat
distinction between the source of the continuum emission and
of the spectral lines.
A more complex model of line formation that does not make this
artificial distinction is the **Milne-Eddington model**.
These were early-twentieth century models and today's
computation capabilities make more complex
and realistic models practical.

The original model simplifies by ignoring details of a ray's travel
through the reversing layer such as the ray's angle and
the thickness of the layer,
effectively making it an early **two stream approximation**,
and sometimes the term *Schuster-Schwarzschild model* is used
for that aspect of the model even in cases where modeling
absorption-line formation is not the goal.
This is common in some (non-astrophysics) branches of applied science.

(*physics,EMR,stars*)
**Further reading:**

http://en.wikipedia.org/wiki/Two-stream_approximation

http://www.astro.wisc.edu/~townsend/resource/teaching/astro-310-F08/17-line-profiles-2.pdf

http://ads.harvard.edu/books/1989fsa..book/AbookC13.pdf

http://users.metu.edu.tr/itari/me508/CHAPTER13.pdf

https://ui.adsabs.harvard.edu/abs/1905ApJ....21....1S/abstract

https://gdz.sub.uni-goettingen.de/id/PPN252457811_1906

**Referenced by pages:**

two-stream approximation

Index