Formation of the Solar System and The Universe

Our Solar System Sun is the center of a huge rotating system of: Planets Their satellites Smaller bodies Most of the mass of solar system is the sun (99.85%)

Our Solar System Planets move in elliptical orbit All in same direction Terrestrial planets = small and rocky Mercury, Venus, Earth, Mars Jovian planets = huge gas giants Jupiter, Saturn, Uranus, Neptune

Formation of the Solar System Between stars = gas and dust Nebula = cloud of gas and dust Hydrogen, helium, heavier elements Nebula begin rotating slowly and contract because of gravity Clouds contract --> spin faster

Nebular Theory Nebular theory states that the sun and all bodies in the solar system formed from a rotating disk of interstellar gas and dust. 4.6 billion years ago This cloud is roughly spherical and so dense that it begins to collapse under its own gravity

Nebular Theory As the speed of rotation increased, the center of the disk flattened. The dense center formed the sun and planets formed along the flattened, nebular cloud Nebular theory

Planetesimals Planetesimals = small, irregularly shaped bodies Solid bits of matter collided and clumped together = accretion Planetesimals grew larger Enough mass --> exert a gravitational pull on other objects Grew into planets

Birth of Planets Inner solar system = close to sun Temperatures high Only metals and silicate minerals Too hot for ices of water, carbon dioxide Outer solar system = cold enough for ices of water Accumulations of solid bits of material and large quantities of ices Large enough to capture gases (hydrogen and helium) --> grew into giants

Galaxies Galaxies = groups of stars, dust, and gases held together by gravity Our galaxy = Milky Way More than 100 billion stars in Milky Way Looks milky because the solar system is located within a flat disk We view it from inside and see stars in every direction

The Milky Way Galaxy Interstellar matter blocks our vision Radio telescopes Size = large spiral galaxy Disk = 100,000 light-years wide Nucleus = 10,000 light-years thick Milky Way = taken by a camera mounted on a satellite

The Milky Way Galaxy Structure At least 3 spiral arms Sun is in one of these arms about 2/3 of the way from the center Stars in arms rotate around the nucleus Outermost arms move slowest

Types of Galaxies Spiral Galaxies Elliptical Galaxies Irregular Galaxies

Spiral Galaxies Disk-shaped Greater concentration of stars near center Arms extend from nucleus Both young and old stars Youngest in arms 20% of all galaxies Barred spiral = stars arranged in shape of bar Milky Way? 10% of all galaxies

Elliptical Galaxies Round to oval Most are small No spiral arms Contain old stars 60% of all galaxies

Irregular Galaxies Irregular shapes Made up of mostly young stars 10% of all galaxies

Galaxy Clusters Galaxies grouped in clusters May contain thousands of galaxies Our cluster contains 28 + galaxies Galaxy clusters make up superclusters

The Expanding Universe Doppler Effect = perceived change of wavelength of a wave that is emitted from a source that is moving away or toward an object Wave appears to be “stretched” as source moves away from you Wave appears to be “squished” as source moves toward you

The Doppler Effect Light from a source moving away from you appears redder Waves are lengthened Moving toward you appears bluer Waves are shortened

How are Doppler shifts measured? From dark lines in spectrum Comparing them with standard spectrum We’ll talk about this more in depth when we discuss stars

Doppler Effect in Astronomy Determines whether a body in space is moving way from or toward Earth Large Doppler shifts = higher speeds Small Doppler shifts = slower speeds

Red Shift Most galaxies have Doppler shifts toward red end of spectrum Earth and source are moving away from each other

Hubble’s Law Greater red shifts = faster speeds Hubble’s Law = more distant galaxies have greater red shifts --> they must be moving away from us at a speed that is proportional to their distance Red shifts of distant galaxies tell us that the universe is expanding

The Big Bang Remember…all galaxies are moving away from us We are not at the center of the universe Big Bang = the universe began as a violent explosion from which the universe continues to expand, evolve, and cool Universe was a dense, hot, supermassive ball 13.7 billion years ago --> violent explosion --> material hurled in all directions All matter and space created Atoms formed Gases cooled and condensed --> formed the stars

Evidence for the Big Bang Red shift of galaxies Universe is still expanding Cosmic background radiation = energy Coming from every direction in space Produced during big bang

How will the universe end? Will it last forever? Stars slowly burn out Invisible matter, black holes, dark and cold universe The Big Crunch? Galaxies stop moving away Gravity pulls back in (critical density) Combine into high-density, high-energy mass Fiery death