Physics and the Universe 1-14-08

Physics and the Universe 1-14-08 - constellation& the...

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Physics and the Universe: Monday January 14, 2008 Cyclic Motions in the Sky Speed of light= C C=3x10^8m/s Distance= Speed x Time = 3x10^8m/s x 1 year = 3x10^8m/s (3x10^7sec/ 1 year) = 9x10^15m = 10^16m 10^16m x 1km/1000m 10^13km = 10 trillion Constellations In ancient times, constellations only referred to the brightest stars that appeared to form groups, representing mythological figures Today, Constellations are well-defined regions of the sky, irrespective of the presence or absence of bright stars in those regions The stars of a constellation appear to be close to one another. The constellation Orion is composed of stars (named how?) (Betelgeuse & Rigel) Stars are named by a Greek letter (α,β,γ,etc.) according to their relative brightness within a given
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Unformatted text preview: constellation & the possessive form of the name of the constellation The Magnitude Scale First introduced by Hipparchus (160 – 127B.C.) : • Brightest stars: ~1 st magnitude • Faintest stars(unaided eye): 6 th magnitude One magnitude difference is quantitatively defined=2.512 1 st magnitude stars are 100 times brighter than 6 th magnitude stars ΔM12=1= 2.512 ΔM13=2=2.512^2=6.3 ΔM14=3=2.512^3=16 ΔM15=4=2.512^4=40 ΔM16=5=2.512^5=100 The Celestial Sphere • Zenith= Point on celestial sphere directly overhead • Nadir= Point on the c.s directly underneath (not visible!) • Celestial equator= projection of Earth’s equator onto the c.s • North Celestial Pole= Projection of Earth’s north pole on the c.s....
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