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