# Wikijunior:Solar System/Glossary

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A glossary of words used in this book:

-   **Antimatter**: the opposite of normal matter. Not usually found
    outside of a laboratory. When mixed with matter they cancel each
    other out and release lots of energy.

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-   **Arachnoid**: a scientific term for something shaped like a spider,
    like the legend of the weaving contest.

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-   **Asteroid**: a large rocky object that orbits a star, but is too
    small to be a planet. It is found in space.

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-   **Astronomer**: a person who studies stars and planets. Also a
    person who explores new planets and solar systems.

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-   **Astronaut**: a person who travels beyond the atmosphere of the
    Earth.

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-   **Atmosphere**: a layer of gases around a planet.

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-   **Atom**: a very tiny particle that is the basic building block of
    matter. It is the tiniest thing on Earth.

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-   **Basalt lava**: molten basalt, a kind of rock from a volcano.

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-   **Belt**: A name used for bands of dark-colored cloud layers on
    Jupiter.

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-   **Binoculars**: a folding pair of small telescopes with an eyepiece
    for each eye.

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-   **Carbon dioxide**: a gas that animals breathe out and plants take
    in.

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-   **Carbonaceous chondrite**: A type of meteorite that contains a lot
    of water and organic compounds.

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-   **Centaur**: an icy planetoid that orbits the Sun between Jupiter
    and Neptune.

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-   **Channel**: a groove in the surface of something.

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-   **Comet**: a small icy object orbiting a star.

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-   **Conjunction**: when two objects orbiting the same body come
    closest together.

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-   **Continent**: a huge landmass on a planet, usually made of tectonic
    plates that have locked together.

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-   **Convection**: a type of movement in a gas or liquid that carries
    heat toward a cooler location. When the gas or liquid cools, it
    sinks back down again.

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-   **Core**: the center of a planet or star.

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-   **Corona**: a region of very hot gas that surrounds the photosphere
    of a star.

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-   **Crater**: a dent in a planet\'s surface made by a meteorite
    falling on it.

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-   **Crust**: the outermost layer of a planet\'s surface.

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-   **Dwarf planet**: a rounded body that is in orbit around the Sun. It
    is not a moon and it is not big enough to sweep up the other objects
    along its orbit.

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-   **Eclipse**: the shadow made when one object comes between another
    object and the Sun.

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-   **Energy**: what you use to do work.

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-   **Environment**: the conditions on a planet.

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-   **Equator**: an imaginary line around a planet, perpendicular to the
    axis of rotation.

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-   **Erosion**: the slow wearing away of a
    surface, usually from wind, water, and temperature changes.

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-   **Galaxy**: a huge mix of gas, dust, stars, planets and other
    objects that are held together by their own gravity.

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-   **Gas giant**: one of the four outer planets made out of giant balls
    of gas.

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-   **Gravity**: the force that pulls on anything with mass (see the
    About gravity, mass, and
    weight
    section).

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-   **Hemisphere**: one half of a planet\'s surface.

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-   **Ice cap**: A huge body of ice at the pole of a planet.

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-   **Lagrange point**: the places where
    the gravity from two orbiting objects balance each other.

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-   **Lava**: molten rock above a planet\'s surface.

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-   **Latin**: the language of the Roman Empire that was later used by
    scientists to name things.

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-   **Mantle**: a layer of molten rock below a planet\'s crust.

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-   **Maria**: a large sea of magma that has cooled into solid rock.

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-   **Mass**: the amount of matter that something is made of (see the
    About gravity, mass, and
    weight
    section).

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-   **Matter**: a scientific word for \'stuff\'.

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-   **Meteor**: a small or medium-size rock from space that has entered
    a planet\'s atmosphere but has not reached the ground.

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-   **Meteor shower**: a large number of meteors that enter a planet\'s
    atmosphere at about the same time.

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-   **Meteorite**: A meteorite that made it through a planet\'s
    atmosphere and landed on the ground.

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-   **Methane**: a gas that makes up most of the gas giants.

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-   **Near Earth asteroid**: an
    asteroid that has an orbit that brings it very close to the earth.

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-   **Newton**: a unit of measurement the describes how hard gravity is
    pulling you down (see the About gravity, mass, and
    weight
    section).

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-   **Observatory**: A special building where astronomers keep their
    telescopes ready for use.

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-   **Orbit**: the path that an object takes around a larger object.

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-   **Orbit System**: a planet and its moons rotating around a star.

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-   **Organic compounds**: compounds (collections of atoms) containing
    carbon.

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-   **Phase**: how a planet or moon looks to us at some part of its
    orbit, when it is lit by the Sun.

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-   **Planet**: the celestial body that has a greater mass than all
    other objects of the same orbit system together and that describes a
    well-defined, special orbit around a star.

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-   **Planetary nebula**: a great cloud of gas that was blown off by an
    old star.

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-   **Photosphere**: the layer of a star that releases light and other
    energy into space.

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-   **Prominence**: an eruption of hot gas at the surface of the Sun.

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-   **Provisional designation**: a temporary name given to a newly-found
    object. Later a permanent name may be picked.

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-   **Radar**: radio waves used to find distances to and make maps of
    things.

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-   **Regolith**: loose soil on the Moon created by rocks hitting the
    surface at very high speed.

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-   **Retrograde motion**: a rotation that is the opposite way from the
    rotation of most of the Solar System.

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-   **Retrograde orbit**: an orbit that is the opposite way from the
    orbit of most of the planets and moons in the Solar System.

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-   **Ring**: A flat, circular band of many small, loose objects that
    orbit a planet.

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-   **Rotate**: to spin around on an axis.

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-   **Satellite**: an object in a stable orbit around a much larger
    object.

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-   **Scarp**: a type of cliff.

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-   **Sidereal day**: the time for a planet or moon to rotate so that a
    distant star overhead is again overhead.

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-   **Silicate**: an object composed mostly of
    the element silicon, which makes rocks.

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-   **Shooting star**: another name for a meteor.

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-   **Solar day**: the time for a planet or moon to rotate so that the
    Sun is again overhead.

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-   **Solar wind**: a very hot gas that is being blown away from the Sun
    at a high speed.

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-   **Spacesuit**: A special sealed suit that protects an astronaut. It
    has its own air supply so the astronaut can breath, and is insulated
    against the cold of space.

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-   **Spectrum**: the colored band of light made when white light passes
    through a prism.

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-   **Star**: a huge ball of gas that is so heavy that it causes nuclear
    reactions inside itself. This produces heat and light.

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-   **Sulfuric acid**: a strong type of acid that is used in car
    batteries, and contains the element sulphur.

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-   **Supergiant**: a star near the end of its life that puffs out into
    a huge body many times larger than a normal star.

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-   **Surface area**: the area on the outside of something.

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-   **Tectonic Plate**: a solid part of
    the crust that very slowly moves across the surface of a planet

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-   **Telescope**: a system of lenses or mirrors that are used to see
    distant objects.

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-   **Terrestrial planets**: the four planets closest to the Sun.

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-   **Tether**: A cord that is used to keep two things attached to each
    other, such as an astronaut to a spaceship.

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-   **Tide**: the rise in the surface caused by gravity from another
    object, such as the Moon or Sun.

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-   **Tidal lock**: when tides have slowed rotation so that a moon or
    planet is always facing the same side toward the planet or star.

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-   **Transit**: When astronomers observe one object pass in front of a
    larger object.

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-   **Trojan asteroid**: an asteroid in
    the same orbit as a planet or moon that always stays the same
    distance ahead or behind.

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-   **Volcanic**: something that relates to volcanoes.

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-   **Volume**: the size of a three-dimensional object.

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-   **White dwarf**: a star that has run out of fuel to burn and is
    slowly cooling off.

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-   **Zone**: A name used for bands of light-colored cloud layers on
    Jupiter.

it:Wikijunior Il sistema
solare/Glossario
de:Wikijunior Sonnensystem/
Glossar
fr:Wikijunior:Système
solaire/Glossaire
