 Sun- center and largest body of solar system  Eight planets and their moons revolve around the sun  Comets- smaller bodies  Asteroids- chunks of rocks  Comets and asteroids revolve around the sun

 Revolve: travel around  Orbit: path  Gravity: pull that holds the bodies of the solar system together  Ellipse: oval path that a planet orbits

 Is an average sized star  Sun and its solar system are part of the Milky Way galaxy  Composed of hydrogen and helium gases  Has sunspots- dark spots that appear on the surface

 Has solar flares- violent bursts of energy from the surface  Solar flares can cause auroras- spectacular light shows

 Galaxy- huge system of stars, dust, and gas held together by gravity  Majority of galaxies are spiral galaxies  Other types:  Elliptical  Irregular

 Constellation- group of stars that forms a pattern  Knowing which constellation a star is in lets you know which part of the sky to look at to find that star

 Stars appear to move across the sky just like the sun because of the Earth’s rotation  Some constellations can only be seen during certain times of the year  Constellations change with the seasons because Earth is traveling around the sun  Everything in the universe moves- stars move in various directions and at various speeds

 Earth rotates on its axis  Axis- imaginary line between the North and South Poles and the Earth’s center  Rotates from west to east  Earths rotation causes daytime and nighttime

 A day is a complete rotation and takes 24 hours  Time is based on Earth’s rotation  Earth is divided into 24 time zones  Earth’s moon takes about 28 days to revolve around Earth- we only see one side of moon

 Earth’s axis is tilted- this causes axis to be pointed toward the sun during parts of orbit, and away from sun during other parts  Earth takes 365 and a fourth days (one year) to orbit once around the sun  During the year, the Northern and Southern Hemispheres experience seasons

 Seasons- change in the number of daylight hours and average daily temperatures  December 21- Northern Hemisphere has fewest daylight hours  June 21- Northern Hemisphere has most daylight hours

 The side of Earth facing the sun gets more direct sunlight- Northern Hemisphere gets the most solar energy during the summer  Southern Hemisphere has opposite seasons as Northern Hemisphere

 Eight planets revolve around sun in elliptical orbits  Order from sun outward: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune

 Four planets closest to the sun: Mercury, Venus, Earth, and Mars  Much smaller than outer planets  Have solid rocky surfaces with mountains, plains, canyons, and craters

 Four planets that are furthest from Sun starting after Mars  Jupiter, Saturn, Uranus, and Neptune  Very large and made of gases  They are often called gas giants

 Have no solid surface  Jupiter- banded appearance and large red spot  Saturn- ring system  Uranus- blue color and rotates on side

 Neptune- appears blue  Asteroid belt- lies in the space between the inner planets and outer planets  Asteroids orbit sun in same area

 Moon does not give off light, it reflects sun’s light  Changing of the moon’s shape during the month is the moon’s phases  As moon moves through its orbit, its position is sky changes relative to the positions of the sun and moon

 The portion of the sunlit side of the moon changes during the month  Full moon- round circle- when Earth I between the moon and the sun  Waning moon- grows smaller  New moon- cannot see- sunlit side facing away from Earth

 Waxing moon- seems to grow larger  Eclipse: one thing in space blocks the view of another  Solar eclipse: moon passes between the sun and Earth- blocks view of the sun  Lunar eclipse: Earth comes between the moon and sun- casts a shadow on the moon

 Moon:  surface has plains, mountain ranges, valleys, and craters ▪ Craters- formed when objects from space hit the moon’s surface  No running water/no atmosphere

 No weathering/erosion/earthquakes/volcanoes  Surface changes from being hit by objects from space  Rotation(length of day): almost 28 Earth days  Revolution(Length of year): Almost 28 Earth days

 Earth:  Has liquid water  Surface has plains, mountain ranges, valleys, and few craters  Has earthquakes/erosion/volcanoes

 Has atmosphere to burn up objects from space before they hit Earth and form craters  Rotation (length of day): Almost 24 hours  Revolution ( length of year): 365 and ¼ days