What is the Angular Extent of Trigonometric Parallax?

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Discussion Overview

The discussion revolves around the concept of angular extent in relation to trigonometric parallax, particularly in the context of astronomical measurements involving binary stars or orbiting bodies. Participants explore the definitions and implications of these terms as they relate to estimating the size of distant objects based on their angular size observed from Earth.

Discussion Character

  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant seeks clarification on the term "angular extent" and its relationship to trigonometric parallax, specifically in the context of a problem involving a semi-major axis of 7.61".
  • Another participant defines angular extent as the angular size of an object, suggesting it refers to how large the object appears from a given viewpoint.
  • A participant elaborates on the application of parallax, noting that it typically involves measuring distances using the Earth's orbit as a baseline, contrasting this with the concept of angular extent.
  • There is a suggestion that knowing the distance to a binary star or orbiting body allows for the determination of its linear size based on its angular size.

Areas of Agreement / Disagreement

Participants generally agree on the definitions of angular extent and its application in estimating sizes of distant objects, but there is no consensus on the relationship between angular extent and parallax, as the discussion includes varying interpretations and clarifications.

Contextual Notes

The discussion does not resolve the nuances between angular extent and parallax, leaving some assumptions and definitions potentially unaddressed.

mahsa
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Hi
I know the meaning of trigonometric parallax, but what is angular extent?
In a problem, it is stated that the true angular extent of semi major axis of the orbit is 7.61".
Is it different from parallax?
Thanks
 
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The angular extent is simply the angular size---i.e. how big it looks.
 
mahsa said:
Hi
I know the meaning of trigonometric parallax, but what is angular extent?
In a problem, it is stated that the true angular extent of semi major axis of the orbit is 7.61".
Is it different from parallax?
Thanks
the typical application of parallax is where the baseline is provided by OUR orbit around the sun.

It sounds to me as if you have a school problem in which there is a binary star or the star has a planet or something orbiting it.

So you are supposed to estimate the real size of a distant object (an orbit) given its angular size seen from earth.

the picture is turned around, the base of the long skinny triangle is out there.

With parallax the baseline is here at home. We get to look at the object from two different locations along the Earth's orbit.

That seems like a difference.
 
Thank you very much! I got it.
so, if I know the distance to that binary or orbit, I know its linear size.
 
mahsa said:
Thank you very much! I got it.
so, if I know the distance to that binary or orbit, I know its linear size.

Yes!
 

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