Parallax LO to explore the phenomenon of parallax

Parallax L/O to explore the phenomenon of parallax

Determining the distance to a star is difficult because we cannot actually travel to the star and measure the distance directly. Instead, astronomers must be very clever and measure the distance indirectly. One of the ways they do this is by the method of Parallax.

Parallax measurements take advantage of the fact that, as the Earth orbits around the Sun, relatively near-by stars appear to move with respect to the fixed, very distant stars Notice in the cartoon that the closer water seems to move a lot quicker than the background water although they are moving at the same speed

This is the same thing that happens when you look at a close object with first one eye and then the other. For example, hold your thumb at the tip of your nose. Look at your thumb with first your right eye and then your left. Your thumb appears to move because your eyes are not at exactly the same place, so each eye views the thumb from a different angle. Now hold your thumb at arm's length and repeat the experiment. Your thumb will still appear to shift, but will not appear to move as much as it did when it was closer. The same thing happens to stars. The closer stars appear to shift more than the farther stars. The "fixed" background stars are not really fixed; they are just so far away that we cannot distinguish their apparent shift.

Calculating the angle of parallax L b p Now attempt the work sheet questions

The Scale of Things Parallax angles are usually measured in fractions of a second of arc a second of an arc is 1 of a degree. 3600 Astronomers use a unit based on this: the parsec.

An object whose parallax angle is 1 second of arc it is at a distance of 1 parsec Because a smaller angle means it is a bigger distance an object whose parallax angle is 2 seconds of arc is at a distance of 0. 5 parsec. A parsec has a distance of 3. 1 x 1013 km