Why study Astronomy?



1) Science requirement



2) Curiosity



3) Origins



4) Nature of the Physical Universe



5) Applications to Earth



6) Are we alone?





An observational science



1. What is it?



2. How does it work?



3. How will (has) it evolve(d) ?





Metric System



Length: meter (m) 40 inch

kilometer (km) 1000 m

centimeter (cm) .01 m = .4 in.

Mass: gram (g) .04 oz



kilogram (kg) 1000 g = 2.2 lb





Scientific Notation



Distance Earth to Sun 150,000,000 km



= 15 x 107 km



= 1.5 x 108 km



1000 = 1 x 103 = 103



10 = 1 x 101 = 101



129437= 1.29437 x 105



.1 = 1 x 10-1 = 10-1



.01 = 1 x 10-2 = 10-2



.00278 = 2.78 x 10-3

Mass hydrogen atom:



.00000000000000000000000000167



= 1.67 x 10-27 kg



Our Place in the Universe



Earth: diameter 12,800 km



Moon: 3.84 x 105 km distant



The Sun - typical star



Generates energy



Diameter: 1.4 x 106 km



Distance: 1.50 x 108 km =

1 astronomical unit (AU)



Solar System: Sun, 9 planets, moons around planets, asteroids, meteors, comets



Mercury: 0.39 AU from Sun



Pluto: 39.5 AU from Sun (average)



Terrestrial planets - similar to earth



Jovian planets - similar to Jupiter



Cosmic junk



Nearby stars - solar neighborhood



light-year: distance light travels in one year (ly)



speed of light: 3 x 105 km/s

1013 km/yr



look-back time (light travel time)

Nearest star is 4.2 light-years away

Constellations - patterns on sky, not physically related or close in space



Star clusters - physically associated groups

e.g. Pleiades



Stars - differ widely in size and brightness



Interstellar matter - gas and dust between stars



Galaxies - groups of 1011 -1012 stars



Diameters about 105 light year



Milky Way Galaxy - spiral arms, bulge at center





Galaxies - spirals, ellipticals, irregulars



Local Group - our group of galaxies



3 large spirals



~ 40 dwarf galaxies



Groups, Clusters of Galaxies

Range from small groups to hundreds or thousands of galaxies

Millions of light years in diameter



Superclusters - loose groups of clusters of galaxies



Up to 108 ly in size



Quasars - centers of active galaxies

Billions of light-years distant



Expansion of the Universe

Big Bang - 13-14 x109 years ago