J Our Solar System Mr. Harpers science Mini lesson with audio Click on the speaker icon to hear the words

j Most of the gas began to come together and form a ball in the center of the cloud. Long, long ago there was a great spinning cloud of gas and dust in space.

J j As the ball of gas got bigger and heavier, its gravity got stronger. The heat and pressure in the center of it became so great that the whole ball suddenly caught on fire.

J Most of the gas from the cloud was pulled by gravity to become part of the burning star.

j Some of the left over gas and dust that was still moving around the star came together to form planets.

J j The four inner planets (closest to the star ) are rocky. Mercury Earth Venus Mars

J The outer four planets are bigger and made of gas. Jupiter Neptune Uranus Saturn

Some planets that orbit the sun have moons orbiting them. Earth has one moon Mars has 2 moons Jupiter has more than 60 moons.

j Thats how our solar system was formed.

J The sun is the center of our space neighborhood. It is a ball of burning hydrogen gas that constantly releases great amounts of light energy, just like every star does.

J The four inner planets are rocky.

J The four outer planets are gas.

J Between the rocky inner planets and outer gas planets is a big rings of millions of pieces of rock called asteroids.

J The area between Mars and Jupiter is called The Asteroid Belt.

Astronomers have named some of the bigger asteroids. Asteroids can be as small as pebbles or as big as 500 miles across. But they are still the smallest objects in our solar system.

J Way out past the gas planets in the Kuiper Belt there are objects that orbit the sun but are not really planets.

J Pluto was considered a planet until recently. But Pluto has an orbit path that is not like the eight planets.

J Astronomers are still discovering new objects orbiting the sun way out in the Kuiper Belt. If Pluto is considered a planet, then the others should too.

Today most astronomers agree that there are 8 true planets in our solar system.

J There are other objects in the solar system that have strange orbits paths. Comets go far out into space then race close to the sun and back out into space again for many years.

J Comets are made of ice, dust and rock particles. The biggest comets are about ten miles across. The orbit periods of these dirty snowballs vary from tens of years to millions of years.

J When comets come near the sun they can sometimes be seen bright in the sky for weeks if they pass near Earth.

This is because radiation from the sun causes a tail of gas and dust when the comet gets close. This makes the comet look like its on fire but it isnt.

j But comets dont come very often. Mr. Harper is pretty old and hes never seen a comet.

J The most famous comet is Halleys Comet, which comes near the sun every 76 years. These photos were taken in May The comet could be seen in the night sky for several weeks as it passed near Earth. When it came again in 1986 it wasnt close enough for people on Earth to see. Maybe you will see Halleys Comet the next time it comes in August 2061.

J OK, lets review the things that all fifth graders should know about the solar system.

J The sun is made mostly of hydrogen gas with some helium gas.

J Gravity is responsible for keeping the planets orbiting the sun. Gravity also keeps the moon orbiting around Earth.

J Asteroids are the smallest objects in our solar system

j The sun is the largest object in the solar system.

But thats easy if you know the trick. And fifth graders are expected to know the names of the planets, in order.

The trick is…… My very educated mother just served us nachos.

The trick is…… My Mercury Very Venus Educated Earth Mother Mars Just Jupiter Served Saturn Us Uranus Nachos Neptune

Some people get Mercury and Mars mixed up because they both start with M. So just remember that the silver liquid in some thermometers is called mercury…… ….. and the planet Mercury is really hot because its closest to the sun.

J j

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