A star and all of the objects that travel in orbit around it

The area of space that is influenced by the gravity of a star

Our solar system is just one of many others.

What is a Solar System?

The Sun Planets Dwarf Planets Satellites/Moons Comets Asteroids Meteoroids

Objects in Our Solar System

Layout of Our Solar System

Distance and size NOT to scale

Relative Sizes in our Solar System

All planets orbit the sun in almost-circular elliptical orbits on approximately the same plane (the ecliptic).

Dwarf Planets, comets, asteroids, and meteoroids also orbit the sun

Most Satellites/Moons orbit planets (some orbit dwarf planets or even asteroids)

Almost all planets, dwarf planets, and moons rotate and revolve counter-clockwise

Motions of our Solar System

In 2006, the IAU defined a planet as a celestial body that:◦Is in orbit around the sun◦Has sufficient mass to assume a (nearly)

round shape◦Has cleared the neighborhood around its

orbit

What is a Planet?

Two kinds of planets:Terrestrial Inner Planets Jovian Outer Planets

“Earth-like”◦Mercury◦Venus◦Earth◦Mars

“Jupiter-like”◦Jupiter◦Saturn◦Uranus◦Neptune

Gas Giants

Ice Giants

Terrestrial (Inner) Planets

Closer to the sun Relatively small size and mass as compared to

outer planets

Rocky surface Craters present to some degree on all inner

planets

Curiosity Rover’s Selfie on Mars

Feb. 2015 – NASA image

Jovian (Outer) Planets Further from the sun Very massive Gas Giants and Ice Giants Lower average density than terrestrial planets All have rings

2006 image from Keck Observatory

Jupiter

In 2006, the IAU defined a dwarf planet as a celestial body that:◦Is in orbit around the sun◦Has sufficient mass that it assumes a

(nearly) round shape◦Has NOT cleared the neighborhood

around its orbit◦Is NOT a satellite

What is a Dwarf Planet?

Smaller than planets Have “company” in their orbital areas Can have moons Most are located in

the Kuiper Belt, but Ceres is in the Asteroid Belt

Dwarf Planets

Bright spot? More to come,

as Dawn mission approaches Ceres this month

Ceres image taken by Dawn Spacecraft Feb. 19, 2015

A satellite (AKA-moon) is an object that revolves around a planet or dwarf planet (or an asteroid)

As of 2008, there are 176 confirmed moons in our solar system

Most are located around the outer planets

What is a Satellite?

Explorers’ Guide to the Solar System 16

Jupiter’s moon Io

Image taken by Galileo spacecraft in 2002

Small Bodies Many smaller objects also orbit the sun◦Asteroids◦Comets◦Meteoroids

Asteroids are small, rocky, and irregular (up to 1000 km)

Sometimes called “minor planets”

Most orbit in a region between the orbits of Mars and Jupiter known as the Asteroid Belt

Combined, they would be about half the size of Earth’s moon

Asteroids

Comets An ice and rock core

(nucleus) that melts as it approaches the sun and gets blown into space by solar wind pressure (coma and tail).

Highly elliptical orbits originate in deep space

Kitt Peak telescope imageof comet NEAT in 2004(NASA, NOAO, NSF, T. Rector, Z.Levay and L.Frattare)

Rosetta Mission to Comet On 12 November

2014, ESA's Rosetta mission soft-landed its Philae probe on comet 67P/ Churyumov-Gerasimenko

During the next phase of the mission, Rosetta will accompany the comet through perihelion in August 2015

Image taken by Rosetta 165 km from the center of Comet 67P, April 15, 2015

Meteoroids are small irregular grains of rock, most are asteroid pieces and comet dust (up to a few meters in diameter)◦If they collide with Earth’s atmosphere, they

form visible streaks of light as they burn up and are called meteors (shooting stars)

◦If a meteor reaches Earth’s surface, it is then classified as a meteorite

MeteoroidMeteorMeteorite

Their location ◦Meteoroid= space◦Meteor= Earth’s atmosphere◦Meteorite= Earth’s surface

What’s the only difference between a meteoroid, a meteor, and a meteorite?

Explorers’ Guide to the Solar System 24