Using Parallax to Determine the Distance to and
Brightness of Stars
As discussed many places in
your book, the idea behind annual parallax of stars is that if the Earth is in
fact circling the sun then our view of the stars should change as the year goes
by and the Earth moves from being on one side of the sun to another. Stars should change their positions against
other stars, for example, if viewed in winter when the Earth is on one side of
the sun, and viewed in summer when Earth is on the other side.
Below are two (simulated)
views of the same field of stars -- one the star field as viewed in winter; the
other the same star field as viewed in summer.
In these simulations, a larger dot means the star appears brighter. Look closely and you will see they are not exactly
the same.
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Winter view |
Summer view |
Which stars show measurable
stellar parallax, and what can that tell us about the stars? Chapter 12 (and our “parallax of the thumb”
example in class) tells us that the closer a star is, the greater its parallax. Click
here to continue.