Units used in Stellar Distances

# Units used in Stellar Distances - to 1° every 350...

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Units used in Stellar Distances 1. Parsecs - parallax of one Arc sec. One parsec is or 3.26 light years (Ly) 2. Light year – The distance light travels in one year or 3. The speed of light (c) = 3.0 X 10m/s or 186,000 miles/sec Calculating Parsecs 1 pc = p = arc seconds Example 1 Given: Vega distance = 8 pc Find: Parallax d (parsecs) = (seconds of arc) so 8 pc = or p = = .125 arcsec. Motion of the Stars 1. Proper Motion – discover by Edmund Haley in 1718, it is the change in position of a star that is perpendicular to the Earth or “The rate at which a star appears to move across the celestial sphere with respect to very distant objects. i. The star with the largest proper motion is Barnard’s Star the second closest known star. ii. Barnard’s Star has a proper motion of 10.25″ per year which corresponds

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Unformatted text preview: to 1° every 350 years. <Would the proper of stars affect what the constellations will look like in the future?> 2. Solar Motion – The motion of the Sun with respect to the stars i. The direction toward which the Sun is moving is called the apex. ii. The direction the Sun came from is called the antapex. iii. 1 st measurement of solar motion was made by William Herschel in 1783 3. Radial Motion or Radial Velocity – motion of a star towards or away form us. This motion causes a Doppler Shift in the light coming from a star. If a star is moving towards us the light from the star is shifted to the blue in of the electro-magnetic spectrum, if a star is moving away from us then the light from the star is shifted to the red end of the spectrum....
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## This note was uploaded on 12/15/2011 for the course BIO BSC1010 taught by Professor Gwenhauner during the Fall '10 term at Broward College.

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Units used in Stellar Distances - to 1° every 350...

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