ASTR 3 Lecture Notes - Lecture 4: Galilean Moons, Lunar Eclipse, Nicolaus Copernicus
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New moon phase only, and with the correct distance, angle. (lunar eclipse: full moon only. ) An annular eclipse: a circle hoop shape of solar eclipse. Stars do not move relative to each other throughout the year. Plan(cid:28664)ts: r(cid:28668)s(cid:28664) (cid:28668)n t(cid:28667)(cid:28664) (cid:28664)ast an(cid:28663) s(cid:28664)t (cid:28668)n t(cid:28667)(cid:28664) w(cid:28664)st, always r(cid:28664)ma(cid:28668)n (cid:28662)los(cid:28664) to t(cid:28667)(cid:28664) (cid:28664)(cid:28662)l(cid:28668)pt(cid:28668)(cid:28662). Usually move east to west relative to the background stars like the sun, but sometimes move west to east: retrograde motion by ptolemy. Epicycle: planets are moving in small circles as they orbit the earth. This is made to explain the retrograde motions. Ptolemy needed 80 epicycles to explain orbits: a mathematically sophisticated model, but accurately predicted the phenomenon. Nicholas copernicus: earth orbit the sun once a year. The parallax (arcsec)= 1/distance (parsec); 1 parsec=3. 2 light years. The biggest parallax one can get from a star is 1 arcsec. The angles in the parallax were so small that they be observed.
