In our solar system, the moon orbits around Earth. Earth – and the other planets – orbit around the Sun. The stars also orbit around the Sun. Have you ever wondered why the Earth, the other planets, the moons and the stars just don’t go flying off on their own into space? What keeps them on their track?
Orbit Facts For Kids
- Orbit: a path an object takes around another.
- Earth orbits the Sun in 365.25 days.
- Moons orbit planets.
- Satellites can be man-made or natural.
- Geosynchronous orbit matches Earth’s rotation.
- ISS orbits Earth at ~28,000 kph.
- Halley’s Comet orbits the Sun every 76 years.
- Elliptical orbits look like stretched circles.
- Orbits can decay, pulling objects closer.
- Tidal forces can change an object’s orbit.
Satellite
Satellites, whether natural like the moon or artificial as those propelled by humans, navigate carefully calculated paths around the Earth known as orbits to maintain their positions without plummeting back to Earth or straying into space.
The trajectory of these orbits can be either circular or elliptical, akin to an elongated circle. The satellite is in a constant state of falling towards Earth but due to the Earth’s round shape, it continually misses it, which enables it to stay in orbit. These orbits can be in close proximity to Earth, termed as low Earth orbits, or significantly farther, akin to the geostationary satellites’ orbit that remain stationary in the sky in relation to the Earth.
Gravity
Gravity, an intriguing force, dictates the movement of celestial objects and is paramount in maintaining the order of our solar system. This force is exemplified in the phenomenon of orbit, where smaller celestial bodies like planets or satellites, such as Earth and Moon respectively, revolve around larger entities like the Sun.
The invisible gravitational pull acts like an unseen tether, anchoring these bodies in their orbits and preventing them from veering off into space. It is this gravitational ‘rope’ that ensures the Earth continues its path around the Sun and the Moon around the Earth. Therefore, the importance of gravity in preserving the structure of our solar system cannot be overstated.
Spacecraft
The idea of spacecraft circling the Earth on an unseen pathway is an intriguing topic for children. The path, or orbit, is an unseen track comparable to a roller coaster that encircles the Earth. To maintain its orbit, a spacecraft must reach a staggering speed of over 17,500 miles per hour, which is over 25 times the speed of sound.
This incredible velocity, coupled with the Earth’s gravitational force, ensures the spacecraft remains in a constant loop around our planet. It is also worth noting that astronauts within the orbiting spacecraft experience a sensation of weightlessness, as if they’re perpetually falling.
Kepler’s laws
Johannes Kepler, a 17th-century scientist, formulated three seminal laws that elucidate the orbital patterns of planets around the sun. His first law identifies the path of these orbits as elliptical, akin to an elongated circle, rather than a perfect circle.
The second law proposes that a planet’s speed in its orbit is contingent on its proximity to the sun, moving faster when closer and slower when further away. The final law establishes a unique correlation between the duration of a planet’s orbit, or its ‘year’, and its distance from the sun, with a longer orbit associated with greater distances. Collectively, these laws provide invaluable insight into the mechanics of our solar system.
Geostationary
A geostationary orbit is an exclusive category of orbital pattern employed by satellites to maintain a static position above Earth’s equator. This can be visualized as a ball being spun on a string above one’s head, with the Earth serving as the central pivot. Unlike other satellites that traverse across the sky, the satellites in geostationary orbit rotate synchronously with the Earth, creating an illusion of being stationary when observed from the ground.
Their constant position over the Earth is beneficial for various applications such as weather prediction, television broadcasting, and communication systems, as it facilitates seamless transmission and reception of signals due to the consistent location of the satellite.
Low Earth Orbit (LEO)
Low Earth Orbit (LEO), located approximately 1,200 miles above Earth, is the nearest orbital region to our planet and home to numerous satellites and space stations, including the International Space Station. Its proximity to Earth enables satellites in this region to capture high-resolution images, making it an optimal location for weather monitoring and spy satellites.
Furthermore, the relatively short distance to LEO makes it the most accessible and cost-effective region in space, which has resulted in it becoming densely populated with thousands of satellites.
However, this convenience does not come without challenges; to counter Earth’s gravitational pull and maintain their orbit, objects in LEO must travel at high speeds of around 17,500 miles per hour.
Planetary motion
Planetary motion is a term that describes how planets travel in unique orbits around the sun, influenced by the sun’s gravitational pull. These orbits are either circular or elliptical, resembling the shapes of a circle or an oval.
The proximity of a planet to the sun determines the strength of the gravitational pull, thereby influencing the speed of its orbit. For instance, Mercury, being the closest planet to the sun, experiences a strong gravity that makes it orbit the sun in a short span of 88 days.
On the other hand, Neptune, the furthest planet from the sun, takes a staggering 165 years to complete its orbit due to a weaker gravitational pull.
Ellipse
The elliptical nature of orbits, which are not perfect circles due to the gravitational pull between two celestial bodies, notably influences our daily lives. This interesting shape is exemplified by the Earth’s orbit around the Sun, where the Sun’s strong gravity pulls the Earth closer at certain points in its orbital path, thus creating an elliptical shape.
This phenomenon is the reason behind the change of seasons. During the Earth’s closer proximity to the Sun, we experience summer, while its farther distance leads to winter. Therefore, the elliptical shape of orbits significantly impacts our everyday life.
Space station
It’s fascinating to know that space stations, including the International Space Station (ISS), orbit the Earth just as the Earth orbits the sun. They follow a unique path, constantly revolving around our planet at an astounding speed of roughly 17,500 miles per hour.
This rapid speed allows the ISS to complete an orbit around the Earth every 90 minutes, which is swift enough to travel to the moon and back within a day’s time. Consequently, astronauts aboard the ISS are treated to the remarkable sight of experiencing 16 sunrises and sunsets daily.
Escape velocity
The intriguing concept of escape velocity, crucial in discussions about orbits, refers to the requisite speed an object must attain in order to overcome the gravitational pull of a planet or moon and venture into space.
Take, for instance, a rocket departing Earth, which must reach a staggering 25,000 miles per hour to accumulate sufficient energy to break away from Earth’s gravitational force and successfully enter orbit. It’s important to understand that gravity, the force anchoring us to the ground and preventing aimless floating, must be countered with considerable speed to facilitate space travel, thereby illustrating the critical role of escape velocity.
The answer is gravitational forces. The Sun, as well as the planets, has a magnetic field that attracts smaller objects and holds them in place. But, you ask, why don’t the planets fall into the Sun? When you point a magnet at a paper clip, the paper clip becomes attached to the magnet. Why don’t the planets do the same thing?
The planets and stars travel on an elliptical path around the Sun, which keeps them from falling into the Sun. Here’s a useful explanation from Cornell University. Say Superman threw a ball across the sky. The ball would go a long way, but eventually it would begin to fall. Because Superman threw it with such force, the ball would go all the way to the horizon, or the rounded edge of the Earth. Because the Earth is turning, the ball falls, but it never actually drops to the ground. It simply travels around the Earth. This is how orbit works. The moon orbits around the Earth, while the Earth orbits around the Sun.
Orbit Vocabulary
- Solar system: a system of celestial bodies that orbit or gather around one large body; galaxy
- Magnetic field: An area that is magnetic, or that has the power to attract and hold other objects
- Elliptical: egg-shaped
- Horizon: the place where the eye can see no further because the Earth’s surface is rounded
Learn More All About Orbit
Watch this cool video about satellite orbit:
A video explaining how satellites orbit the Earth.
Orbit Q&A
Question: What else orbits in space besides the planets, moons and stars?
Answer: Lots of things orbit in space that were put there by man. Satellites orbit the Earth, taking photos, regulating cell phone use or reporting weather patterns. Rocks, dust and debris also orbit the planets or the Sun.
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