1.  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.

2.  The Sun  Planets  Dwarf Planets  Satellites/Moons  Comets  Asteroids  Meteoroids

3. Distance and size NOT to scale

5.  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

6.  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

7. Terrestrial Inner Planets Jovian Outer Planets  “Earth-like” ◦ Mercury ◦ Venus ◦ Earth ◦ Mars  “Jupiter-like” ◦ Jupiter ◦ Saturn ◦ Uranus ◦ Neptune Gas Giants Ice Giants

8.  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

9. Feb. 2015 – NASA image

10.  Further from the sun  Very massive  Gas Giants and Ice Giants  Lower average density than terrestrial planets  All have rings

11.  2006 image from Keck Observatory

12.  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

13.  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

14.  Bright spot?  More to come, as Dawn mission approaches Ceres this month

15.  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

16. Explorers’ Guide to the Solar System16

17.  Many smaller objects also orbit the sun ◦ Asteroids ◦ Comets ◦ Meteoroids

18.  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

19.  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

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

21.  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

22.  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

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

24. Explorers’ Guide to the Solar System24