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Space Rocks

Asteroids, Meteors, Comets, & Dwarf Planets

Unit 3: Our Solar System

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Space Rocks Overview

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Asteroids

  • Asteroids are small, rocky, irregularly-shaped objects that orbit the sun
  • Most asteroids (thousands) lie in the asteroid belt, a region between the orbits of Mars and Jupiter
  • The combined mass of all the asteroids is probably less than 1/1000 the mass of the Earth

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The Asteroid Belt

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Ceres

  • Ceres is the largest object in the asteroid belt
  • Now classified as a dwarf planet

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Meteoroids

  • Meteoroids are space rocks that are bigger than a piece of dust but smaller than an asteroid
  • Meteoroids come from the asteroid belt, Mars, the moon, and comets

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Meteor

  • A meteor is a meteoroid that enters the earth’s atmosphere
  • It appears as a streak of light as it enters the atmosphere and begins burning up
  • Often called “shooting stars”

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Meteorite

  • Meteors that don’t completely burn up in Earth’s atmosphere and land on the surface are called meteorites

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Comets

  • A comet is a small body of ice, rock, and dust that follows a highly elliptical orbit around the sun
  • All comets have a nucleus that is composed of ice and rock
  • A coma is a spherical cloud of gas and dust that comes off the nucleus
  • Comets have two tails: a dust tail and an ion/gas tail
  • Most come from the Oort cloud

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Comet Leonard – December 2021

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RIP January 3, 2022

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Comet vs Meteor

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What about Pluto?

It’s not a planet, asteroid, comet, OR meteoroid?

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Dwarf Planets

  • A dwarf planet is a celestial body that orbits the sun and is round because of its own gravity
  • A dwarf planet does not have the mass to have cleared other bodies out of its orbit around the sun
  • Five dwarf planets have been identified: Ceres, Pluto, Eris, Haumea, and Makemake
    • Ceres is in the Asteroid Belt, the others are in the Kuiper Belt

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The Dwarf Planets

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Pluto: From Planet to KBO

  • Pluto was once considered to be the ninth planet in the solar system
  • Beginning in 1992, Kuiper belt objects began to be discovered beyond Neptune’s orbit, some of which had similar size and composition as Pluto
  • In 2006, Pluto was redefined as a “dwarf planet” by the International Astronomical Union

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Why isn’t Pluto a Planet?