# Distant and luminous stars using parallax angles?

Star A has a measured parallax angle of 0.1 arcseconds, while Star B has a parallax angle of 1.0 arcseconds. From the Earth, both stars are measured to have the same apparent brightness.

How do I find which star is more distant?

And how do I find which star is more luminous?

TIA!

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By definition a star which has a parallax angle of 1 arc second is at a distance of 1 parsec. A parsec is the commonly used distance measure in Astronomy. It is approximately equal to 19 trillion mines. Think of a triangle formed by the earth, the sun and the star. Its a very thin triangle. The angle at the star tip is the parallax angle - 1 arc second. The base of the triangle is the distance between the earth and the sun.

Star A at a parallax of 0.1 seconds is at a distance of 1/0.1 = 10 parsecs.

Star B is at 1 parsec.

Since Star A is more distant but appears just as bright, it must be more luminous.

Incidentally, there are no stars known within 1 parsec of earth. The closest star is the triple star system Alpha Centaurus at a distance of 1.26 parsecs.

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• By measuring the parallax-tic displacement. You have make two measurements exactly one year apart (like Sept. and March). This way you are measuring from two different location and you will know the distance between the sightings. The difference in "apparent" location of the star are recorder and this distance is the displacement. The one with the largest displacement is the closest. If you want to make a specific distance, you will have to refer to tables in astronomy measurements. Or you can record the p. displacement of the moon and do a proportion from that data. Since we know the exact distance to the moon from laser measurement that would be a good frame of reference.

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• the respond they are finding for is probably d. although the Hipparcos satellite tv for pc measured the parallax of greater effective than 2.5 million stars. this is plenty greater effective than are seen to the bare eye, in spite of the reality that of course basically a tiny share of the full stars interior the Universe.

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