#5 Introduction to the #5 Introduction to the Solar SystemSolar System

Just one starJust one star

Not studying galaxies (billions of stars) Not studying galaxies (billions of stars) or star clusters (millions of stars) yet, or star clusters (millions of stars) yet, only our own solar system.only our own solar system.

Solar means “sun” so Solar means “sun” so solar solar system = sun systemsystem = sun system

Sun is a star, and is Sun is a star, and is our only one!our only one!

How to measure something so large?How to measure something so large?

The distance between stars (and galaxies) The distance between stars (and galaxies) is HUGE so we measure it in light years.is HUGE so we measure it in light years.

Light Years is Light Years is thethe distancedistance light will light will travel in a year travel in a year

****very importantvery important**: a light year is not a **: a light year is not a time, but a time, but a

distancedistance!!

Astronomical UnitsAstronomical Units Planets in our solar system are closer Planets in our solar system are closer

together, so we can use AU together, so we can use AU (Astronomical units)(Astronomical units)

1 AU=Average distance between 1 AU=Average distance between the Earth and the sun the Earth and the sun (lazy (lazy

scientists)scientists)

Ex) Mercury is closer to sun (.39 AU)Ex) Mercury is closer to sun (.39 AU)

Ex) Pluto is further from sun (39.5 AU)Ex) Pluto is further from sun (39.5 AU)

The PlanetsThe Planets Now have 8 planets orbiting the SunNow have 8 planets orbiting the Sun Orbits are ellipticalOrbits are elliptical

• An ellipse is a shape that can be thought An ellipse is a shape that can be thought of as a "stretched out" circle or an oval of as a "stretched out" circle or an oval

Two major planet groupsTwo major planet groups

The planets are divided into two major The planets are divided into two major groupsgroups• 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 These two groups are separated in the middle by the asteroid beltmiddle by the asteroid belt

Inner Planets

Gas Giants

Asteroid Belt

Terrestrial PlanetsTerrestrial Planets

Inner Planets (closest to the sun)Inner Planets (closest to the sun)• Mercury, Venus, Earth, MarsMercury, Venus, Earth, Mars

““Terrestrial” = “Land”Terrestrial” = “Land”• Rocky (dirt-like and metal materials)Rocky (dirt-like and metal materials)• SmallSmall• DenseDense• Few moonsFew moons• No RingsNo Rings

Mercury Venus Earth Mars

Mercury The Speediest Planet- Travels at 29.7 miles/sec.

Venus The Twin Planet- roughly the same size as Earth and visible from Earth without a telescope

Earth The Home Planet - only planet known to have an atmosphere that sustains life

Mars The Red Planet - an iron surface isblown around by storms

Terrestrial PlanetsTerrestrial Planets

The Gas GiantsThe Gas Giants

Outer Planets (Farthest from sun)Outer Planets (Farthest from sun)• Jupiter, Saturn, Uranus, NeptuneJupiter, Saturn, Uranus, Neptune

Made of gas and liquidMade of gas and liquid• HUGEHUGE• Low densities (Saturn floats in water)Low densities (Saturn floats in water)• Lots of moonsLots of moons• All of them have ringsAll of them have rings

The Gas GiantsThe Gas Giants

Jupiter The Giant Planet- All the other planets could be squeezed inside of it!

Saturn The Ringed Planet- has the most (and the largest) rings

Uranus The Tilted Planet- orbits on its side

Neptune The Windy Planet- fiercest winds blowing up to 1400 mi/hr. Blue color, Named for the Roman God of the Sea

What about poor Pluto?What about poor Pluto? Now considered a dwarf planetNow considered a dwarf planet

22ndnd largest dwarf planet we know of largest dwarf planet we know of• Eris is bigger, Ceres is another Eris is bigger, Ceres is another

Mass is about 1/5 that of our moonMass is about 1/5 that of our moon

Made of Ice and Rock (Very Cold)Made of Ice and Rock (Very Cold)

Orbit is highly elliptical and Orbit is highly elliptical and sometimes dips into Neptune’s orbitsometimes dips into Neptune’s orbit

The Dwarf Planets

Here’s our solar system........

So putting it all together.....So putting it all together.....