Understanding Parallax Angles in Astronomy: Explained with a Diagram

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Homework Help Overview

The discussion revolves around understanding the concept of parallax in astronomy, specifically how the parallax angle is measured and interpreted in relation to observations of a hypothetical Planet X. The original poster expresses confusion regarding the measurement of the parallax angle, particularly the significance of the value 1.52 arcseconds.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the basic idea of parallax through relatable examples, such as using a thumb at arm's length to illustrate the concept. Questions arise about visualizing the measurement of the angle and the specific interpretation of the 1.52 arcseconds difference. There are requests for diagrams to aid understanding, and some participants discuss the relationship between the measured angles and the geometry involved.

Discussion Status

The discussion is active, with participants sharing analogies and resources to clarify the concept of parallax. While some guidance has been offered, particularly through examples and links to diagrams, there remains a lack of consensus on the interpretation of the angle measurements and their implications.

Contextual Notes

Participants note the challenge of visualizing small angle measurements like 1.52 arcseconds and the precision required in astronomical observations. There is also mention of the difference between measurements taken at different times, which raises questions about how these relate to the parallax angle itself.

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Homework Statement


Can someone please explain to me how parallax works?
I don't understand how the angle of parallax is measured


Question to help: Astronomers measuring the parallax angle to Planet X found that the angle measured after 6 months was 1.52 arcsec different from the initial measurement
http://www.mlahanas.de/Greeks/Astronomy2.htm

Angle theta is angle (Earth-Jan)-Star-(Earth-July)

They then said that angle theta is 1.52 BUT I don't see how, can someone please provide a diagram

Homework Equations


I can complete question knowing the angle theta is 1.52. I just don't understand why it is 1.52


The Attempt at a Solution


as above
 
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Hold your thumb out at arm's length with a distant wall in the background. Close one eye and then the other. See how your thumb seems to move back and forth depending on which eye you are looking through? That's the basic idea of parallax. By measuring how much you thumb moves back and forth, and knowing the distance between your eyes, you can calculate the length of your arm ( I know, big deal!)
 
can you draw the diagram for the Question about planet X
 
the thing I don't get is "1.52 arcsec different"
I can't visualise this in my head
 
jsmith613 said:
the thing I don't get is "1.52 arcsec different"
I can't visualise this in my head
They (the astronomers) measured the angle to be 1.52". To measure an angle this small takes a tremendous amount of skill and care.

For the right triangle they draw, 1.52" corresponds to 2θ .
 
I don't have a problem with the angle they measured BUT the difference between angle in Jan and angle in Jun is 1.52, so surely the paralax angle is 1.52 + original angle
 

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