（精）行星及月球英文版.ppt

Planets and Moons Overview This online lessons consists of the chapters The Solar System The Planets Moons Planets of other stars More information: Links The Solar System What is the Solar System? In the Universe,the Solar System is our homeland,and the Earth is our hometown. The Solar System The Solar System consists of the sun in its centre nine planets,circling around the sun moons asteroids and comets. The Solar System How did the Solar System evolve? Scientists are quite sure, that in the beginning of our Solar System there was a huge disc of dirt, rocks, gas, ice etc. In the middle of this disc, the Sun formed itself and began to glow. In some distances from the centre, the planets emerged from these rings of dirt, rocks and gas. The Solar System How large is our Solar System? The orbit on which Pluto (the farthest planet) circles the sun, has an average diameter of 5.910.000.000 km (Pluto‘s orbit is rather non-circular). The sun itself, the largest object in our Solar System has a diameter of 1.392.520 km. The Solar System How can I imagine these sizes and distances? Imagine the Solar System being a soccer ground (about 100 m long). The sun would be a glaring orange in the centre. Pluto would encircle the sun at the edge of the soccer ground, having the size of a dust particle. The Earth would be 1,30m away from the “orange“, having the size of a sesame seed. The Solar System The Planets Mercury is the planet that is closest to our Sun. Pluto is the farthest. Remember the order of the planets like this: My Very Educated Mother Just Showed Us Nine Planets which means Mercury Venus Earth Mars Jupiter Saturn Uranus Neptun Pluto Mercury What are Mercury‘s features? second smallest planet nearest to the sun one Mercury-year is a quarter Earth-year Mercury is very difficult to be spotted with the naked eye Mercury has no moons Venus What are Venus‘ features? it is a medium sized planet, 2.5 times as large as Mercury second nearest to the sun Venus