Astronomy Chapter 2

Geocentric A description of the solar system that involves all of the planets revolving around the Earth.

Heliocentric A description of the solar system in which all planets revolve around the sun.

Ellipse An oval shape, or an elongated circle which is the shape of a planet’s orbit.

Inertia The tendency of a moving object to stay in a straight line or a stationary object to remain in place.

Gas Giants The name given to the first four outer planets Neptune, Uranus, Saturn and Jupiter.

Terrestrial Planets The name given to the four inner planets, Mercury, Earth, Venus and Mars.

Core The center of the sun, where nuclear fusion takes place. Core

Nuclear Fusion The production of energy as hydrogen atoms combine to form helium. Hydrogen Energy Helium

Photosphere The inner layer of the sun’s atmosphere. This sphere is the light that we see from Earth as we look at the sun. Photosphere

Chromosphere The middle layer of the sun’s atmosphere. The chromosphere is  ˚C. The chromosphere is the “color sphere”. Chromosphere

Corona The corona is the outer layer of the sun’s atmosphere, it is 2,000,000 ˚C. Corona

Solar Wind A stream of electrically charged particles made by the sun’s corona.

Sunspot A dark area of gas on the sun that is cooler than surrounding gases.

Prominence A loop of gas from one sunspot region to another.

Solar Flare An explosion of hydrogen gas on the sun’s surface that is caused by connecting loops in sunspot regions.

Retrograde Rotation The spinning in the opposite direction of most planets and moons, from east to west.

Greenhouse Effect The trapping of heat by a planet’s atmosphere.

Comet A ball of dust and ice that orbits in an long narrow ellipse.

Asteroid Objects that are revolving around the sun, but are too numerous and too small to be considered planets.

Asteroid Belt The area in the solar system between the orbits of Mars and Jupiter; this is where many asteroids are found.

Meteoroid A chunk of rock or dust in space.

Meteor A streak of light in the sky that is produced by the burning of a meteoroid in the Earth’s atmosphere.

Meteorite A meteor that has hit Earth’s surface.

Extraterrestrial Life Life that comes from outside of the Earth.