ANTA01H3 Lecture Notes - Lecture 10: Parsec, Radiant Energy, Photon
Document Summary
Finding how far the stars are: d (parsec) = 1/p (arcseconds) A parsec is equal to 206, 265 au or 3. 26 ly. By definition 1 parsec (pc) is the distance of a star subtends an angle equal to one arc second. Note the dependence of parsec to the size of the orbit of the earth. First sucessful measurement of parallax: fredrich bessel was the first person to measure the parallax of the star. In 1838, bessel measured the parallax of cygni-61 to be 0. 313 arc-second: the actual value is closer to 0. 286 arc-second. Distances between the stars: parsec is a natural unit as it turns out that the average distance between two individual stars is about a parsec. Hipparcos (high precision parallax collecting satellite: reminds us of hipparchus, the goal was to measure the parallax of 120, 000 stars with a precision of 2-4 millarcsec.
