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The Planets and the Solar System Where we’re going today… • Solar System By the end of this class, you should be able to… 1. Define planet and solar system. 2. Describe the difference between rotation and revolution. What does each movement cause? 3. Describe the difference between the inner planets and the outer planets. 4. Briefly describe all the planets. The Planets and the Solar System The Solar System Planet – is a celestial body that orbits one or more stars. Planets only reflect light radiated by its star, they do NOT generate their own energy. Solar System – a group of planets circling one or more stars Each galaxy spins around a central nucleus. Within our spinning galaxy (Milky Way) our solar system is also rotating (250 km/s) Within our solar system, all the planets are in motion too, including Earth… …around itself and around the sun… The Planets and the Solar System …around itself… Rotation- motion of a planet as it spins on its axis (imaginary line from north to south) Earth moves from west to east at 1670 km/h or 0.5 km/s …around the sun… Revolution – motion of a planet as it orbits the Sun (Earth = 30 km/s) The Earth and other planets follow an elliptical path around the Sun. The Planets and the Solar System The Formation of the Solar System Our solar system was formed more than 4.5 billion years ago. Left over material from our Sun’s formation combined to form eight planets and numerous other smaller bodies (moons, asteroids, comets) Not all the planets formed at the same time or in the same way… The Planets and the Solar System In the first 100 million years or so, the material closest to the young Sun developed into planets – Mercury, Venus, Earth and Mars. These are called the inner planets or terrestrial (Earth-like) planets They have relatively small, solid cores and rocky crusts The Planets and the Solar System Further away, large clumps of gas, ice and dust formed Jupiter, Saturn, Uranus and Neptune. These are called the outer planets or jovian planets They have large gaseous bands and cold temperatures The inner and outer planets are separated by an asteroid belt The Planets and the Solar System The Planets and the Solar System The Planets A planet is… …a body that orbits one or more stars …large enough that its own gravity holds it in a spherical shape …the only body occupying its orbital path Planets are very far apart. So far that we don’t use km’s, astronomers have devised another unit. Astronomical Unit (AU) It is equal to the average distance between the Sun and Earth (150 million km) Therefore the Earth is 1 AU from the Sun The Planets and the Solar System Mercury ⅓ the size of the Earth (slightly larger than the moon) No significant atmosphere Experiences extraordinary temperature differences (night (-143°C) to day (400°C)) Temp differences causes rock to form immense cracks (due to hot/cold) The Planets and the Solar System Venus Similar in size and composition to Earth (sister planet) Atmosphere is different (completely CO2) Thick clouds cover the planet. (Sulphur mixes to from acid rain) The Planets and the Solar System Earth Only place known to have water in three phases (liquid, solid, and gas) Water covers nearly three-quarters of the Earth’s surface Atmosphere is composed mainly of N and O The Planets and the Solar System Mars Called the red planet (Fe in its surface) Half the size of Earth but same amount of surface area (volcanoes and deep canyons) Very thin atmosphere of CO2 and winds of more than 900km/h The Planets and the Solar System Jupiter Largest planet in the solar system (mass about 2.5 times greater than all other planets combined) Has a “great red spot” the size of three Earths that is a storm raging in the clouds Composed mainly of H and He Despite size, Jupiter has the shortest day of all planets (10 hours) The Planets and the Solar System Saturn Elaborate system of rings (formed from ice particles and dust) Rings are 250 000 km wide & as thin as 10 m Composed mainly of H and He The Planets and the Solar System Uranus Fourth most massive planet Similar composition to Jupiter and Saturn Includes a ring system composed of ice and dust Blue colour comes from methane gas in atmosphere Unusual rotation – flipped on its side (appears to roll through orbit) The Planets and the Solar System Neptune Outermost planet (third most massive) Composition similar to that of Uranus and same dark blue colour Has a ring system like other three gas giants Has large, blue, earth like patch – likely a storm in the clouds of Neptune (like the red spot of Jupiter) The Planets and the Solar System Did we get there… Can you… 1. Define planet and solar system. 2. Describe the difference between rotation and revolution. What does each movement cause? 3. Describe the difference between the inner planets and the outer planets. 4. Briefly describe all the planets. Assignment: Planet Profile