Solving for the Speed of a Star in a Binary System | Physics Wave Question

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Homework Help Overview

The problem involves determining the speed of a star in a binary system based on the observed and laboratory wavelengths of a spectral line. The context is rooted in the Doppler effect as it applies to astrophysics.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants suggest looking into the Doppler effect and its applications, with some mentioning both classical and relativistic approaches. There are discussions about the implications of the observed wavelength shift and how it relates to the star's motion relative to Earth.

Discussion Status

Some participants have offered guidance on exploring the Doppler effect, while others have raised the possibility of using different formulations, indicating a variety of approaches being considered. There is no explicit consensus on a single method or solution yet.

Contextual Notes

Participants note that there may not be enough information provided in the problem to apply certain advanced concepts, such as general relativity corrections.

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Homework Statement



a spectral line coming from a star in a binary system has a wavelength of 515.2 nm. in the lab the same spectral line would have a wavelength of 518.6 nm. what is the speed of the star in relation to earth?

Homework Equations


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The Attempt at a Solution


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look up doppler effect, I'm not going to propose solution, because once you learn it for yourself -- I'm sure you'll figure it out in an instant (at least in a classical sense, not accounting the general relativity corrections -- there's not enough info in the problem to use that anyway).
 
Or you could try relativistic doppler effect.
 
Use the Dopple formula:

f'=f.V/(V+Vs)

V=c=3.10^8 m/s :speed of the radio wave.
Vs: velocity of the star (source).

U should find Vs, if it's positive then the star is moving away from the earth, otherwise it's moving closer.
 

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