Orbit
Astronauts on a space shuttle
mission can see planet Earth below. They see different parts of Earth as the
shuttle goes around the planet. The shuttle is in orbit above Earth. An orbit is
a curved path going around something in space.
WHAT KINDS OF THINGS ORBIT IN SPACE?
The Moon orbits Earth. Space
shuttles and artificial satellites also orbit Earth.
Spacecraft sent to explore distant
planets sometimes go into orbit. A spacecraft orbits a planet and takes pictures
and measurements.
Everything in our solar system
orbits around the Sun. All the planets orbit the Sun. Pieces of rock called
asteroids orbit the Sun. Balls of ice and rock called comets orbit the Sun.
Moons orbit planets, which orbit the Sun.
Our Sun is a star in the Milky Way
Galaxy. A galaxy is a group of stars. All the stars in the Milky Way orbit the
center of the Galaxy.
HOW ARE ORBITS SHAPED?
An orbit can be shaped like a
circle. Most orbits are oval-shaped like a racetrack. Planets, asteroids, and
comets in our solar system have oval-shaped orbits. Another name for the oval
shapes of orbits is ellipse.
Some orbits are bigger ovals than
others. The bigger the oval, the longer it takes something to orbit the Sun. It
takes Earth one year, or 365 days, to go around the Sun. It takes Pluto 248
years to orbit the Sun. Pluto has an orbit that takes it very far from the
Sun.
Most comets orbit the Sun in huge
oval paths. Sometimes the orbital paths of these comets take them close to the
Sun in the center of our solar system. Sometimes their paths take them out to
the edge of our solar system.
HOW DO SATELLITES ORBIT EARTH?
Weather satellites, communications
satellites, and other types of satellites take different paths around Earth.
Some satellites orbit directly above Earth’s equator. The equator is an
imaginary line around the middle of the planet. The orbits of other satellites
take them over the North and South poles.
Some communications satellites
orbit at the same speed that Earth turns. They look like they are not moving. A
satellite has to move at just the right speed to stay in its orbit above
Earth.
WHAT KEEPS THINGS IN ORBIT?
The force of gravity holds
satellites, moons, planets, and stars in orbit. Gravity is a force that pulls
one thing toward another. When you throw a ball up in the air, Earth’s gravity
pulls it back down to the ground. The bigger something is, the stronger is its
force of gravity.
The Sun is very large and its
gravity pulls on planets and everything else in the solar system. The Sun’s
gravity makes the planets travel in a curved path around the Sun. Earth’s
gravity holds the Moon and artificial satellites in curved paths around
Earth.
When a spacecraft goes fast enough,
it can overcome the pull of Earth’s gravity. Rockets can make spacecraft move
fast enough to head toward distant planets.
Sometimes satellites in low orbits
around Earth slow down. This happens when the satellites brush against faint
wisps of air. Earth’s gravity pulls slow-moving satellites down. The satellites
fall toward Earth. Sometimes the satellites burn up in the air. Sometimes the
satellites crash into the ocean.
Tags
Space
