Detecting Unusual Stellar Shapes: Looking for Perturbed Planets

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Discussion Overview

The discussion revolves around the detection of planets around stars and the potential complications arising from the assumption that stars are perfect spheres. Participants explore the implications of stellar shape on planet detection methods, particularly in the context of gravitational perturbations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the assumption that stars are perfect spheres and suggests that a gravitating body could create an illusion of perturbation.
  • Another participant argues that while stars are not perfect spheres, their shapes are well understood, and the oblate nature of stars due to rotation is a minor factor in the context of planet detection.
  • It is noted that pulsations in stars can affect measurements, but these pulsations can be distinguished from the effects of orbiting planets.
  • A question is raised regarding the methods of detection, specifically whether the concern pertains to the transit method or the Doppler method.

Areas of Agreement / Disagreement

Participants express differing views on the significance of stellar shape in planet detection, with some asserting that it is a minor issue while others raise concerns about its implications. The discussion remains unresolved regarding the impact of stellar pulsations and the methods of detection.

Contextual Notes

Participants acknowledge that the shape of stars and their pulsations may introduce complexities in measurements, but the extent of these effects and their implications for detection methods are not fully resolved.

wolram
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How can we be sure that when looking for planets there sun is not a perfect sphere and just looks like it is being perturbed by a gravitating body?
 
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The star is usually not assumed to be a perfect sphere ... the shape of stars is determined by physics that are well known.
Most stars would be oblate due to their rotation ... but only slightly so a sphere is a very good approximation - especially considering the distances involved.
We can be sure of this for distant stars the same way we can be sure of anything - we check for nearby stars, and assume that the laws of physics are pretty much the same everywhere.

However the shape of the star is not important for detecting bodies orbiting it.

http://www.planetary.org/explore/sp...anets.html?referrer=https://www.google.co.nz/
You can have a go working out how far off spherical the star would have to be to give it the appearance of the kinds of wobbles measured.
 
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Pulsations of stars are indeed something that can mess up radial velocity and intensity measurements, but those pulsations don't have the same structure as influences of planets, so it is possible to separate them. In the worst case you just stop looking for planets around a star that is too chaotic.
 
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wolram said:
How can we be sure that when looking for planets there sun is not a perfect sphere and just looks like it is being perturbed by a gravitating body?
Are you referring to detection by the transit or Doppler method?
 

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