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 2 years ago
The star Wold 359 has a parallax angle of 0.419 arcseconds. Describe how this parallax angle is measured.
 2 years ago
The star Wold 359 has a parallax angle of 0.419 arcseconds. Describe how this parallax angle is measured.

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Vandreigan
 2 years ago
Best ResponseYou've already chosen the best response.1Well, the easiest way to describe it is that the star is photographed throughout the year. The photographs are then compared to find the two that show the greatest change in position with respect to the background stars (the furthest background stars will not have appeared to move at all). From this, you can find an angle. Half of that angle is the parallax angle.

Schrodinger
 2 years ago
Best ResponseYou've already chosen the best response.0Thanks! It's fine if I don't get it but could you elaborate a little just to see what I can or can't get?

Vandreigan
 2 years ago
Best ResponseYou've already chosen the best response.1What do you mean, exactly?

Schrodinger
 2 years ago
Best ResponseYou've already chosen the best response.0I dunno, I assumed by "the easiest way" you meant there was probably a more technical or mathematical way to put it in terms. I've always sucked with understanding parallax so I just kind of see what I can do to get it.

Vandreigan
 2 years ago
Best ResponseYou've already chosen the best response.1Well, the exact definition is more along the lines of "Using imagery of the star from Earth, while the triangle formed between the star, the sun, and the earth, at two different times of the year (6 months apart), the angular displacement of the star with respect to the background stars can be easily measured. Half of this angular displacement is the parallax angle, which may be used to calculate the distance of the star from the sun"

Vandreigan
 2 years ago
Best ResponseYou've already chosen the best response.1oops, while the triangle formed by the star, sun and earth is a right triangle, from two different times of the year.

Vandreigan
 2 years ago
Best ResponseYou've already chosen the best response.1Basically, we use the two pictures that give us the greatest angular displacement of the star with respect to more distant stars (which will appear not to move at all, because they are so far away). These correspond to being at the vertex of the two right triangles.

Vandreigan
 2 years ago
Best ResponseYou've already chosen the best response.1From this, it's a rather simple matter to measure that angular displacement. Divide it by two, and you have the parallax angle!

Vandreigan
 2 years ago
Best ResponseYou've already chosen the best response.1I suppose I should ask what level of school is this for? I can make things a little more clear if needed.

Schrodinger
 2 years ago
Best ResponseYou've already chosen the best response.0High School, senior year Physics. Thanks so much! Right now i'm just reading everything you said, lol.

Vandreigan
 2 years ago
Best ResponseYou've already chosen the best response.1There's a picture of how to find parallax on wikipedia, which may make things a little more clear. http://en.wikipedia.org/wiki/File:Stellarparallax2.svg

Vandreigan
 2 years ago
Best ResponseYou've already chosen the best response.1Since it's high school physics, you'll assume the earth's orbit is perfectly circular. So just take one picture. 6 months later take another picture. Measure the angular displacement with respect to the background stars. Divide that by two. Done!

Schrodinger
 2 years ago
Best ResponseYou've already chosen the best response.0Since the Earth has an elliptical orbit, is our ability to measure the distance (but the parallax angle) of a star affected by where the star lies relative to our orbit? Like, ifoh, lol, just read

Vandreigan
 2 years ago
Best ResponseYou've already chosen the best response.1It is, but the effect is small. Usually we just do the measurements at certain times to try to squeeze a little more out of this method. It has a limit on it, as you can see by the parallax of the stars you're given. They are in arcseconds, which is an EXTREMELY small angle.

Vandreigan
 2 years ago
Best ResponseYou've already chosen the best response.1If the star is too far away, it doesn't appear to move at all. We just can't resolve or measure the parallax angles of some stars (most of the stars, in fact).
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