Lecture02 - Observing the Stars Stellar Positions:...

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Observing the Stars Stellar Positions: Astrometry Instrumentation Transit Telescopes (groundbased) Photographic Plates Electronic imagers Hipparcos and Hubble space telescopes Careful positional observations over a series of years reveal two types of motions: parallax and proper motion
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Parallax Apparent motion of an object due to the real motion of the observer Astronomical parallax arises from Earth’s orbital motion about the Sun 1 year periodic oscillation of star’s position Parallax is the fundamental distance measurement tool for stars no theoretical uncertainties
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Parallax
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Parallax (continued) p = ½ total parallax angle (’’) d = distance to star (pc) au = astronomical unit = Earth-Sun distance = 1.49 x 10 11 m then tan(p) p = 1au / d d = 1 / p 1 parsec = 206,265 au = 3.09 x 10 16 m 3.25 light-years
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Measuring Parallaxes First successful measurement: Friedrich Bessel, 1838 star 61 Cyg p = 0.3” d = 3.3 pc = 11 ly
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This note was uploaded on 10/01/2009 for the course ASTRO 109 taught by Professor Piatek during the Spring '07 term at Rutgers.

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Lecture02 - Observing the Stars Stellar Positions:...

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