Planets are round like spheres. All planets spin on an axis and orbit the sun.
Nine planets are in our solar system as well as the sun and the planet's moons
or satellites. All nine planets are completely solid or have a solid core in the
center of the planet. Six out of nine planets orbit the sun in the same direction.
The planets nearest the sun such as Mercury and Venus receive more heat
than those far away from the sun such as Neptune and Pluto. The temperature
on the planets are estimated from measurements of infrared radiation or heat
waves and what the planets send out which are radio waves . The atmosphere
of these planets are a mixture of gas that surrounds the planet. Some planet's
atmospheres are made of carbon dioxide and nitrogen, the others are made of
mainly helium, hydrogen, methane, and ammonia. A planet quite like earth
would have surface features such as mountains, valleys, lakes, rivers, flat areas,
and craters. A planet's surface is shaped partly by collisions with meteorites
and partly by conditions on the
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