Origin of Universe Evidence All galaxies in universe appear to be moving away from one another (Red Shift in Starlight) The greater their distance the faster they are receding The temperature of interstellar space is not 0 o K but 2.7 o K Big Bang Theory
Origin of Solar System Evidence Astronomical observations of stars beyond solar system Observations of structure & composition of solar system Internal structure and composition of Earth
Star Formation in a Dust and Gas Cloud in Scorpius
The Sun Sun makes up 99.9% of Solar System Sun is mainly made of: Hydrogen (element #1, simplest and most abundant element in universe) Helium (element #2, second most abundant) Solar energy produced by nuclear fusion 4 Hydrogen nuclei = 2 Helium nuclei + energy
The Solar System With exception of Pluto, all planets occupy sub-circular orbits All orbit in the same plane (ecliptic) and in same direction Nearly all rotate in same direction about axes that are nearly perpendicular to ecliptic
The Planets Inner Planets Mercury, Venus, Earth, Mars Small, dense, rocky. Few moons Outer Planets Jupiter, Saturn, Uranus, Neptune Large, low density, icy. Many moons Pluto
Nebular Theory Star systems are formed by the gravitational collapse of diffuse clouds of dust and gas (nebulae) Cold clouds of dust and gas (mainly hydrogen) are most abundant constituents of universe Gravitational collapse always leads to rising temperatures.