The Sun, Solar System and Galaxies Dr. Alan F. Weekes

The Sun A large sphere of gas that gives off light, heat and other electromagnetic energy generated by nuclear fusion in its core. It is a star. The whole solar system is held by the sun’s gravity. The greater the mass of an object the greater its gravitational effect. The gravitational effect lessens with distance. Objects are held in elliptical orbits.

The Core- where fusion takes place Photosphere- the layer of the sun we see Sunspots- cooler, storms on the surface Solar flares- blasts of energy, from sunspots Prominence- loops of gas following magnetic fields Corona- Outer atmosphere of the sun

Effects of the Sun on Earth Light & heat Tides Auroras- from flares, energy excites areas in the magnetic field, radio may be disrupted, power outages

The Sun- Websites Spaceweather Nasa Sun Song

The Inner Solar System- Mercury Closest planet to the Sun Moonlike surface, cratered No atmosphere Cold night side, hot day side No Moon

The Inner Solar System- Venus Twin to Earth, size and density Surface like a dry Earth Volcanoes, “continents”, “ocean basins” Craters, rifts Heavy CO 2 Atmosphere, 90x weight of Earth’s Greenhouse Effect, surface temperature ~470 C or 870 F Sulfuric acid clouds No Moon

The Inner Solar System- Venus

Venus without clouds (Radar Image)

Video Clip: Venus

The Inner Solar System- Earth The only planet we know of that supports life. Pleasant atmosphere of N, O, Ar, CO 2 One moon 71% covered with water Only planet to have water in 3 physical states

Video Clip: Earth

The Inner Solar System- Mars ~1/2 of Earth’s diameter ~1/3 of Earth’s gravity Thin CO 2 atmosphere Wind and dust storms Seasons like Earth, similar tilt Days like Earth, similar rotation Evidence of past water flows, glaciers Large volcanoes, large valleys Two moons, small former asteroids

The Inner Solar System- Mars

The Inner Solar System- Websites spacecraft.html yph-arc.html deshows/mars /index.cfm r /

The Outer Solar System- Jupiter The largest planet. Gas Giant, hydrogen and helium Great Red Spot, large persistent (>300 years) high pressure storm 4 large Galilean Moons Ganymede, Callisto, Io, Europa Io, most volcanically active place in solar system 59 smaller moons (total 63) Explored with the Galileo Spacecraft

The Outer Solar System- Jupiter Io – no craters, many volcanoes Europa- mostly water ice Ganymede- largest moon, ice and rock Galileo Spacecraft PagesJupiter Images

Video Clip Jupiter

The Outer Solar System- Saturn The ringed planet- note all the gas giants have some rings Low density- less than water 34 named moons Titan: only moon with an atmosphere

Welcome to the Planets (NASA)

Video Clip- Saturn

The Outer Solar System- Uranus Twin to Neptune in size and density Axis is almost at 90 o, seasons would be long/odd. Uranus Images

Video Clip- Uranus

The Outer Solar System- Neptune Uranus’ Twin 21 Named moons Neptune Images

Video Clip- Neptune

The Dwarf Planets- Pluto Discovered in 1930 by Clyde W. Tombaugh Very small, 2274 km (Earth’s Moon 3476 km) Large moon Charon (1212 km) Pluto is a double planet system Pluto and Charon always keep the same side toward each other Recently 2 more small moons were found Nix and Hydra New Horizons Spacecraft Timeline and Site ain/index.html ain/index.html

The Dwarf Planets- Ceres Smallest dwarf planet now 950 km Discovered in 1801 First asteroid found between Mars and Jupiter Perhaps as much water as all the fresh water on Earth

The Dwarf Planets- Eris Discovered 2005 Larger than Pluto at 2400 km Has one moon, Dysnomia 150 km

The Dwarf Planets- Makemake It was discovered on March 31, 2005 The name of Makemake, the creator of humanity and god of fertility in the mythos of the Rapanui, the native people of Easter Island, was chosen in part to preserve the object's connection with EasterMakemakeRapanuiEaster Island Diameter from 1,360 to 1480 km

The Dwarf Planets- Family Portrait

Video- Dwarf Planets

Small Solar System Bodies- Asteroids Mostly found between Mars and Jupiter Asteroid belt prevented from being a planet by Jupiter’s gravity

Small Solar System Bodies- Asteroids

Small Solar System Bodies- Comets Bodies of mostly ice and rock “dirty snowballs” Usually very elongated elliptical orbits Form a tail as they approach the sun The tail always points away from the sun

Small Solar System Bodies- Comets Comet Hale-Bopp in 1997 (left) Comet McNaughtComet McNaught as seen from Swift's Creek, Victoria, Australia on 23 January 2007

Video Clip- Comet

Galaxies Galaxies are very large groups of stars held together by gravity We are in the Milky Way Galaxy Named for the band of stars that stretches across the sky.

Galaxies Types of Galaxies Spiral-The largest, usually with spiraling arms. The Milky Way is a spiral type. >200 billion stars 100,000 light years across –Light year- the distance that light would travel in one year –300,000 km/sec or 186,000 miles per second –About 9 trillion km or 6 trillion miles We are about 28,000 light years from the center The galaxy rotates, we revolve around the center about once every 220 million years. We see the band of stars when we look into the disk of the galaxy

Spiral Galaxies

Elliptical Galaxies

Irregular Galaxies

A Matter of Scale From Clusters of Galaxies to the inside of an Atom Scale of Size Powers of 10 How big is big and how small is small? eopticsu/powersof10/ eopticsu/powersof10/ _detail&id_power=25http://powersof10.com/index.php?mod=power _detail&id_power=25