Space Vocab

by Erin Outen

Celestial Objects

Objects such as planets, moons, and stars that are located in the sky or in space

Celestial objects include the Sun, Earth, the moon, and all the other planets in our solar system.


A group of interacting or interdependent parts forming a complex whole; for example, all the factors or variables in an environment or all the planetary bodies revolving around a star

The solar system is a system because all the planets revolve around the Sun, and all the moons revolve around their planets.

Solar System

The Sun together with the group of planets and other celestial bodies that are held by its gravitational attraction and revolve around it

The solar system includes the Sun, the eight planets and their moons, asteroids, metiors, and dwarf planets.

Orbital Path

A curved path traveled by a satellite as it revolves around an object in space

The orbital path of the planets is not a perfect circle, instead it is slightly oval shaped.


The luminous celestial body around which Earth and other planets revolve and from which they receive heat and light

The Sun is a star made of dense, burning gases. The Sun is gargantuan compared to the other planets.


A ball of gas in space that produces its own light and heat

The Sun is the closest star to Earth. But, there are billions of other stars in the universe.


Any of the large celestial bodies that revolve around the Sun in the solar system

There are eight planets in our solar system, all of which revolve around the Sun.

Inner Planet

Any of the rocky, terrestrial planets of Mercury, Venus, Earth, and Mars, whose orbits are inside the asteroid belt

The inner planets are Mercury, Venus, Earth, and Mars. All of these planets are made out of solid material.

Outer Planet

Any of the planets Jupiter, Saturn, Uranus, and Neptune, whose orbits lie beyond the asteroid belt

Pluto used to be considered an outer planet but in 2006, it was decided that Pluto is a dwarf planet



All of the inner planets are terrestrial planets.


Large and small rocks or metallic masses orbiting the Sun; made up of materials similar to those that formed the planets

Although asteriods orbit the Sun, they are not planets because they often share their orbital path.

Asteroid Belt

The region between the inner and outer planets where most asteroids orbit around the Sun

Most of our solar system's asteroids are located in the asteroid belt.


A natural chunk of rock or dust existing outside of Earth’s atmosphere

Meteoroids only exist outside of Earth's atmosphere.


Small meteoroid that burns upon entry into Earth’s atmosphere

When a meteoroid enters Earth's atmosphere and burns, it becomes a meteor.


Remains of meteoroids that strike the surface of Earth or the Moon

Although meteors are meteoroids that enter Earth's atmosphere, meteorites are meteoroids that strike Earth's surface.


Something that orbits around another object; for example, a moon orbiting a planet or a human-made object orbiting Earth

When you think of a satellite, you think of a man-made object that orbits Earth. But satellites can also be moons.


A celestial body that revolves around a planet

While Earth has one moon, other planets may have many moons

Galilean Moons

The four largest and brightest moons of Jupiter, which were discovered by Galileo Galilei: Ganymede, Io, Callisto, and Europa

Ganymede, Io, Callisto, and Europa are called Galilean moons because they were discovered by Galileo Galilei.


A celestial body of ice, dust, and rock with an elongated and elliptical orbit

Comets orbit the Sun too, but are to small to be called planets.


Glowing, heated dust and vaporized gas that surrounds the icy comet nucleus as it travels near the Sun; solar winds cause heated gases to stream out of the nucleus, forming a tail, which points away from the Sun

What most people call the tail of the comet, is actually the coma.


The force of attraction that pulls objects toward each other; the force that controls the motion of our solar system

Gravity is what keeps the planets in orbit and us on Earth.

Gravitational Attraction

The force that pulls two objects towards each other; the greater the mass of an object, the greater the attraction; the further apart the objects, the weaker the attraction

The gravitational attraction between Earth and the moon is greater than the gravitational attraction between the moon and the Sun, so the moon orbits the Earth.

Newton’s Law of Universal

The law that says that every object in the universe attracts every other object, and that the force is affected by mass and distance: the greater the mass of an object, the greater the attraction; the further apart the objects, the weaker the attraction

Newton's Law of Universal Gravitational says exactly how gravity works.


1) The amount of matter in an object 2) A body or object

Mass is not the same as weight. Mass is the amount of matter in an object.

Space Exploration

The investigation of physical conditions in space and on stars, planets, and other celestial bodies through the use of satellites, space probes, or spacecraft with human crews

Space exploration has improved over the years with the arrival of new technology.


A spacecraft that gets power from an engine full of chemical propellants

People have used rockets to explore space and learn more about it.


A vehicle or device designed for travel or operation outside Earth’s atmosphere

People have used spacecrafts many times to explore space.

Space Shuttle

A reusable spacecraft designed to transport people and cargo between Earth and space

Space shuttles are reusable rockets that can send people into space more than once.

Space Probe

An unmanned spacecraft designed to explore the solar system and transmit data back to Earth

Probes are useful because they can go places that humans can't go and they can stay longer than humans can.


A vehicle for exploring the surface of an extraterrestrial body (such as the Moon and Mars)

There is a rover on Mars called Curiosity. It is gathering information and sending it back to Earth.


Something that orbits around another object; for example, a moon orbiting a planet or a human-made object orbiting Earth

Satellites can be man-made objects, or they can be natural objects such as the moon.


An optical instrument for viewing distant objects

When they were first invented, telescopes were only used for seeing things on Earth. But Galileo was the first one to use them for space exploration.


A building or place given over to or equipped for observation of natural phenomena

Observatories often have large telescopes used to study other planets.

International Space Station

An orbiting space satellite, construction of which began in 2001 with the cooperation of 16 nations; used for scientific and space research

The International Space Station was very expensive to build and launch into space.

Galileo Galilei

The father of modern science; made improvements to the telescope and discovered the four largest moons of Jupiter, among many other scientific accomplishments

Galileo made many important discoveries during his lifetime that have helped us greatly in space exploration.


Scientists who travel into space

Astronauts must go through lots of training before they are ready to travel into space.


National Aeronautics and Space Administration; the American governmental agency dedicated to space exploration

NASA has made many discoveries and accomplishments involving space exploration.