Lesson 4: Comets and Meteoroids – We learned about comets which are made up of rocks, ice, and dust. Gravity between the particles in a comet hold it together. They orbit the Sun in long elliptical orbits. As a comet approaches the Sun, a bright tail can develop on the comet. The solid, inner part of a comet is called the nucleus. As a comet approaches the sun, it heats, changing some ice in the nucleus into a gas. Energy from the Sun pushes gas and dust particles away from the nucleus and makes it glow. A short-period comet takes less than 200 years to orbit the Sun and they usually come from the Kuiper belt. Long-period comets take more than 200 years to orbit the Sun and they come from the Oort cloud. Next we learned about meteoroids which are small, rocky particles that move through space. As it passes through Earth’s atmosphere friction with the air makes a meteoroid and the air around it glow. A streak of light in the atmosphere made by a glowing meteoroid is a meteor. Most meteoroids burn up in the atmosphere but a meteoroid that strikes the surface of a planet or a moon is called a meteorite. A meteorite can form a bowl-shaped depression called an impact crater in the surface it strikes. Next we added notes on dwarf planets, asteroids, comets, and meteoroids to our science notebook.
Discussion Question:
Why was Pluto reclassified as a dwarf planet instead of a planet?
Pluto orbits the Sun and is spherical, similar to a planet, but it is not significantly larger than other objects around it. For example, one of Pluto’s moons is about half as large as Pluto.