#5 Introduction to the Solar System

Just one star  Not studying galaxies (billions of stars) or star clusters (millions of stars) yet, only our own solar system.  Solar means “sun” so solar system = sun system  Sun is a star, and is our only one!

How to measure something so large?  The distance between stars (and galaxies) is HUGE so we measure it in light years.  Light Years is the distance light will travel in a year **very important**: a light year is not a time, but a distance! **very important**: a light year is not a time, but a distance!

Astronomical Units  Planets in our solar system are closer together, so we can use AU (Astronomical units)  1 AU=Average distance between the Earth and the sun (lazy scientists)  Ex) Mercury is closer to sun (.39 AU)  Ex) Pluto is further from sun (39.5 AU)

The Planets  Now have 8 planets orbiting the Sun  Orbits are elliptical An ellipse is a shape that can be thought of as a "stretched out" circle or an ovalAn ellipse is a shape that can be thought of as a "stretched out" circle or an oval

Two major planet groups  The planets are divided into two major groups 1. Terrestrial Planets (Inner Planets)1. Terrestrial Planets (Inner Planets) 2. Gas Giants (Outer Planets)2. Gas Giants (Outer Planets)  These two groups are separated in the middle by the asteroid belt

Inner Planets Gas Giants Asteroid Belt

Terrestrial Planets IIIInner Planets (closest to the sun) Mercury, Venus, Earth, Mars ““““Terrestrial” = “Land” Rocky (dirt-like and metal materials) Small Dense Few moons No Rings

Mercury Venus Earth Mars

MercuryThe Speediest Planet- Travels at 29.7 miles/sec. VenusThe Twin Planet- roughly the same size as Earth and visible from Earth without a telescope EarthThe Home Planet - only planet known to have an atmosphere that sustains life MarsThe Red Planet - an iron surface is blown around by storms Terrestrial Planets

The Gas Giants OOOOuter Planets (Farthest from sun) Jupiter, Saturn, Uranus, Neptune MMMMade of gas and liquid HUGE Low densities (Saturn floats in water) Lots of moons All of them have rings

JupiterThe Giant Planet- All the other planets could be squeezed inside of it! SaturnThe Ringed Planet- has the most (and the largest) rings UranusThe Tilted Planet- orbits on its side NeptuneThe Windy Planet- fiercest winds blowing up to 1400 mi/hr. Blue color, Named for the Roman God of the Sea

What about poor Pluto?  Now considered a dwarf planet  2 nd largest dwarf planet we know of Eris is bigger, Ceres is anotherEris is bigger, Ceres is another  Mass is about 1/5 that of our moon  Made of Ice and Rock (Very Cold)  Orbit is highly elliptical and sometimes dips into Neptune’s orbit

The Dwarf Planets

Here’s our solar system

So putting it all together.....