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.
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.
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.
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.
Any of the planets Jupiter, Saturn, Uranus, and
Neptune, whose orbits lie beyond the asteroid
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.
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
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.
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.
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.
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.
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
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.
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
NASA has made many discoveries and accomplishments involving space exploration.