Comets and Asteroids

by Taja Brown


  • "A celestial object consisting of a nucleus of ice and dust and, when near the sun, a “tail” of gas and dust particles pointing away from the sun."
  • Comets are leftover material from the formation of other planets in the solar system. Our whole solar system was created by the collapse of a giant diffuse cloud of gas and dust about 4.6 billion years ago. Most of the matter formed into other planets, but some didn't and we're left to form lumps of frozen dust and gas in the outermost, cooler region of our solar system.
  • Both planets and comets orbit the sun. Planets of our solar system orbit the sun in a circular motion. But comets orbit in a way that's called an elliptical orbit. This means that instead of going around the sun in a circle, the comets orbit is more oval-shaped. The comet reaches a point where is it closest to the sun called perihelion, and a point where it's farthest away from the sun called aphelion.
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  • Comets are just clouds of iced gas and black dust but they only look like something more when you can see them from earth. From earth, they can be seen with 2 tails, as they fly by.
  • Comets only have tails when they are closest to the sun, or at aphelion. With the heat from the sun, some of the ice starts to melt, and it transforms straight to a vapor from ice. The solar wind sweeps the particles back making two long tails.


  • A small rocky body orbiting the sun.
  • Meteoroids are small pieces of interplanetary matter that are usually less than a millimeter in size. Meteor refers to the flash of light caused by meteorites. Asteroids are bigger rocks that come from the asteroid belt in between the orbits of Mars and Jupiter.
  • Near earth asteroids are asteroids that have been nudged by the gravity of other planets into orbits that make them enter earth's neighborhood.
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An asteroid hit earth about 65 million years ago and made the dinosaur population become extinct. Dinosaurs might still be around if the asteroid had hit maybe 5million years earlier.
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This is asteroid Itokawa, taken by Japan Aerospace Exploration Agency.
The above article by society for science explains what would happen if an asteroid actually hit earth, how to avoid it, and craters caused by past asteroids. A crater is, by definition, "a large, bowl-shaped cavity in the ground or on the surface of a planet or the moon, typically one caused by an explosion or the impact of a meteorite or other celestial body".


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