The Universe

The Inner Planets

 A solar system is made up of a star and the objects that orbit around it.  Our solar system has 8 planets orbiting the Sun.

 The planets in order from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.  Inner Planets  Mercury, Venus, Earth, and Mars  Called terrestrial planets because their surface is made of rock  Outer Planets  Jupiter, Saturn, Uranus, and Neptune  Surfaces are made out of gas

 An asteroid is a rock that revolves around the Sun.  Most asteroids in our solar system are located in between Mars and Jupiter in the asteroid belt.

RRevolution – how long it takes an object to circle around another object. PPlanets revolve around the Sun and the moon revolves around the Earth. RRotation – one complete spin on its axis. EEarth rotates around causing day and night.

 Smallest planet  Has a large nickel-iron core  88 Earth days to make one revolution around the Sun  Takes 59 Earth days to make one rotation on its axis  Has no true atmosphere so the temperatures at night are extremely low

 Almost the same size as Earth (called Earth’s twin)  Surface is covered in plains, lava flows, volcanoes, huge mountains, and craters.  Venus rotation – 243 Earth Days  Venus revolution – 225 Earth Days  So its day is longer than its year!

 Has a dense atmosphere of carbon dioxide and is covered in a layer of thick clouds  Has extremely high temperatures (900 F)  So close to Earth, it is the brightest planet in our sky

 Rotation – 24 hours  Revolution – 365 days  Largest inner planet  Only planet known to support life  Atmosphere keeps it from getting too hot or too cold

FFourth planet RRotation – 24.6 hours RRevolution – twice as long as Earth’s (about 730 days) AAlso has seasons HHas huge volcanoes; the largest is Olympus Mons VVery thin atmosphere

 Surface of Mars is red because of the iron oxide (rust) in the dust on its surface.  Known as the Red Planet.  Frozen water has been found at both of the poles.

The Outer Planets

LLargest planet 11,000 Earths could fit inside Jupiter RRevolution – 4,333 Earth days or almost 12 years RRotation – 9 hours and 56 minutes GGreat Red Spot is a storm on the surface of Jupiter. Twice the size of Earth!

 Jupiter largest moons are called Galilean moons.  They are named after Galileo Galilei who discovered them with his telescope in  The biggest moons are Ganymede, Callisto, Io, and Europa.  Io has several active volcanoes.  Europa has a possibility of life.

 Second largest planet  Revolution – 29.5 years  Rotation – 10 hours and 39 minutes  Saturn has rings around it that are made up of pieces of ice and rock.  Some of these rocks are pieces of comets.  A comet is a mixture of frozen gases, ice, dust, and rock that move in an orbit around the Sun.

 First planet to be discovered with a telescope  Revolution – 84 Earth years  It is tilted on its side, so the North and South poles are not up and down.  Blue-green color is from methane gas  It has at least 27 moons which are mostly named after William Shakespeare’s work.

RRevolution – 165 years RRotation – 16 hours BBlue color is from methane gas. HHas strong winds up to 1,250 mph HHas at least 5 rings IIt has 13 moons.

 A dwarf planet is an object that is spherical in shape, orbits the Sun, and does not clear its orbit of smaller debris.  Pluto was classified as a dwarf planet in  Two other dwarf planets are Eris and Ceres.

Stars

 A star is an object that produces its own light and heat.  Stars go through cycles.  Stars form out of nebulas.  Nebula – a huge cloud of gases and dust

GGravity pulls in the hydrogen atoms together. TThey begin to run into each other producing a lot of heat until they begin sticking together. TThis becomes a protostar. TThe star expands until the outside of the star cools and turns red. This stage is called a red giant.

 When the helium is gone, the star will cool and shrink.  Final stage for a medium star is a white dwarf which is a small and very dense star that shines with a cooler white light.  Sometimes after the red giant phase, the star gets too much energy and explodes.  The exploding star is called a supernova.  A supernova will form a new nebula.

 They are characterized by their size, color, and temperature.  Color tells the surface temperature.  From coolest to hottest: Red, Orange, Yellow, White, and Blue  Red supergiants are the largest stars.  Neutron stars are the smallest stars.

 A star’s appearance depends on how bright it is and how close to Earth it is.  A star could look very faint because it is not a bright star or it is not very close to Earth.  Sirius is one of the brightest stars in the sky.  How bright a star looks in Earth’s night sky is its apparent magnitude.  A star’s actual brightness is called its absolute magnitude.

 Constellations are patterns of stars.  Constellations are very useful to travelers.  Polaris – the North Star (end of the Little Dipper)  If you follow Polaris you will always be headed north.

 Astronomers divide the sky into 88 constellations.  The stars that you see depend on your latitude on Earth.

SStar charts are maps of the night sky. TThey are used to help you locate a star or constellation. CClick here to see what stars you will see tonight!

 Use lines of declination and right ascension.  Declination is how far north or south a star is from the equator.  Right ascension is how far around the map the star is  Stars are represented as dots.  The size of the dot represents how bright the star is.

 During the night, the constellations in the northern sky circle around Polaris.  As the Earth revolves around the Sun, we see different constellations because we are in a different location.