Stellar aberration

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Offline Vorador

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Stellar aberration
« on: 18/10/2013 09:47:39 »
Hello everyone,

Stellar aberration is taken as one of the strongest observational evidence for heliocentric model of the solar system. I wanted to know why this phenomenon can not be explained by the geocentric model (since it is caused by relative motion of stars and earth)?

Thank you! :)

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Offline BartLeplae

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Re: Stellar aberration
« Reply #1 on: 19/10/2013 19:15:16 »
The direction and magnitude of stellar aberration is determined by:
- the rotation speed of the Earth at the place of the observer (diurnal aberration)
- the speed of the Earth relative to the Solar System (annual aberration)
- the speed of the Solar System relative to the Milky Way (secular aberration)

In other words: the direction and magnitude of stellar aberration is not determined by the motion relative to the observed stars but to the motion relative to Solar System, Milky Way, ... . The annual aberration for any star in a given direction is the same, independent of the motion of the observed star.

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Offline evan_au

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Re: Stellar aberration
« Reply #2 on: 20/10/2013 10:20:26 »
In the days when the structure of the solar system was in hot dispute, it was thought that the stars were unmoving and unchanging*, all at the same distance. So they would have expected no motion from the stars.

So the observation of stellar aberration that light from the stars appeared at a slightly different angle on a yearly cycle indicated that the Earth was moving around the Sun every year; the Earth was not stationary at the center of the universe, with the Sun orbiting around the Earth every day.

*Some known exceptions included the star Algol, "the ghoul", a short-term eclipsing binary; and the occasional appearance of a Nova (meaning "new star", but we now know it represents the death of a star).

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Offline Vorador

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Re: Stellar aberration
« Reply #3 on: 09/12/2013 16:01:49 »
In the days when the structure of the solar system was in hot dispute, it was thought that the stars were unmoving and unchanging*, all at the same distance. So they would have expected no motion from the stars.

So the observation of stellar aberration that light from the stars appeared at a slightly different angle on a yearly cycle indicated that the Earth was moving around the Sun every year; the Earth was not stationary at the center of the universe, with the Sun orbiting around the Earth every day.

*Some known exceptions included the star Algol, "the ghoul", a short-term eclipsing binary; and the occasional appearance of a Nova (meaning "new star", but we now know it represents the death of a star).
I see. So stellar aberration alone isn't evidence enough that earth circles the sun.

Thank you for your answers and sorry for such a late response.