Other Objects in the Solar System Comets Structure

Other Objects in the Solar System

Comets: Structure

Comets: Structure • As a comet approaches the Sun ices of water, methane, and ammonia vaporize because of the heat from the sun. – This releases dust and jets of gas. – The gases and released dust for a bright cloud called a coma around the nucleus of the comet. – Solar wind pushes on the gases and dust in the coma, causing the particles to form separate tails that always point away from the sun.

Comets: Where do they come from? • Astronomer Jan Oort proposed the idea that billions of comets surround the solar system. • This cloud of comets, called the Oort Cloud, is located beyond the orbit of Pluto.

Meteoroids, Meteors, and Meteorites • After comets vaporize and break up after they have passed close to the Sun many times the small pieces from the comet’s nucleus spread out into a loose group within the orbit of the comet. • These pieces of dust and rock , along with others from other sources are called meteoroids.

Meteoroids, Meteors, and Meteorites • When the path of a meteoroid crosses the position of Earth they can enter Earth’s atmosphere at speeds of 15 -70 km/s. • Most meteoroids are so small that they completely burn up in Earth’s atmosphere. • A meteoroid that burns up in Earth’s atmosphere is called a meteor.

Meteoroids, Meteors, and Meteorites • When a meteoroid is large enough it might not burn up completely in the atmosphere. – If it strikes Earth, it is called a meteorite. – Most meteorites are debris from asteroid collision or broken-up comets. Barringer Crater – 1. 2 km in diameter – 200 m deep

Asteroids • Most asteroids are located in an area between the orbits of Mars and Jupiter called the asteroid belt. • The sizes of the asteroids in the asteroid belt range from tiny particles to objects 940 km in diameter. – Ceres (940 km in diameter) is the largest and the first one discovered. – Vesta (530 km in diameter) – Pallas (522 km in diameter) – 10 Hygiea (430 km in diameter)

Asteroids

Asteroids • Comets, asteroids, and most meteorites formed early in the history of the solar system. • Scientists study these space objects to learn what the solar system might have been like long ago.

Dwarf Planets

What is a dwarf planet? • The definition of a planet was revised again in 2006. According to NASA, the International Astronomical Union (IAU) most recently defines a planet as a celestial body that: • Is in orbit around a star, but is not itself a satellite* • Has sufficient mass so it is nearly spherical in shape* • Has cleared the neighborhood around its orbit*