Glossary - A journey through the universe

Galaxies: Groups of stars, celestial bodies, gases and cosmic dust that are in a specific place in the universe.

Nebulae: Accumulations of gases and star dust that are between the stars of a Galaxy. They look like a cloud and some of them emit light, while others absorb it.

Stars: Celestial bodies of spherical shape formed by gases inside which thermonuclear reactions that release light and heat occur.

Planetary systems: A group formed by a star and all the planets, satellites, asteroids and comets that orbit around it. The planetary system where we live is called the Solar System.

Planets: Spherical celestial bodies that orbit around a star and that do not emit their own light.

Satellites: Solid celestial bodies that orbit around a planet and have a smaller size than it.

Asteroids: Irregular bodies formed by rock and metal that revolve around a star. When they measure less than 50 meters they are called meteoroids.

Meteorites: Meteoroids that reach the surface of a planet. When entering the planet's atmosphere, they heat up and get partially disintegrated, leaving a bright vapor trail that is called a meteor or shooting star. 

Comets: Celestial bodies of small size that orbit around a star. They are formed by ice, dust and rocky material that sublimate when passing through a star, leaving a bright and luminous trail in their path. 

Orbit: Closed path that a celestial body travels in space around a star. 

Earth's rotation: Movement that the Earth makes when it rotates on itself around an imaginary axis that passes through its poles. 

Earth's revolution: movement of the Earth along its orbit around the Sun. 

Eclipse: The partial or total blocking of light of one celestial object by another. In a solar eclipse the Moon comes between the Sun and the Earth. In a lunar eclipse the Earth comes between the Sun and the Moon. 

Equinox: The time of the year when the Sun's rays falls perpendicular to the Equator. The Sun illuminates both hemispheres same number of hours. There are two equinoxes: the spring equinox and the fall equinox. 

Solstice: The time of the year when the Sun's rays fall perpendicular to one of the tropics. There are two solstices: the summer solstice and the winter solstice.

You can read the Spanish version of this glossary here.