PROPER MOTION - degrees in a year). What is happening in...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
PROPER MOTION We've seen that diurnal motion of stars is due to the rotation of the earth on its axis. Annual motion of stars is due to the revolution of the earth around the sun. And the motion of planets is due to the actual orbits of the planets around the sun. It was finally discovered, in the eigtheenth century, that the stars do have real motion, called proper motion . We see this as a very small angular displacement, over time, relative to other stars. In telescope it would look as Figure 1 below, with one star displaced after, say, a year relative to a pattern among other stars. This figure looks similar to the one we saw earlier showing the wandering of a planet. The difference is that the angular shift of a star is very much less, typically about 1/1000 of a degree per year (whereas for a planet it might be 90 degrees or 180
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: degrees in a year). What is happening in space is shown in Figure 2. Seen against a background of 7 distant stars, the near star is first at point P, aligned with star 2, then at later time (years later) at point Q, aligned with star 6. The stars that exhibit proper motion are always those that are relatively near to us, and their motion seen relative to distant stars. "Near" in this context means from a few light years out to a few tens of light years. The distant stars may be millions of light years away. Great patience and diligence is required to study this motion. One must be assured that the telescope is in exactly the same position and orientation consistently over a period of years, even decades....
View Full Document

This note was uploaded on 12/15/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.

Page1 / 2

PROPER MOTION - degrees in a year). What is happening in...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online