What is a satellite? (with pictures)

Manned spacecraft can be called “satellites” when they are in orbit around the Earth.

A satellite can be defined as any object, man-made or naturally occurring, that orbits around something else. For example, the moon orbits around the Earth, therefore it meets this definition. Earth is a satellite of the sun. Other naturally occurring examples include comets, stars, asteroids and other planets.

The orbit is determined by the gravitational pull of the object around which the other body circles. That around which a satellite circles is called the principal object. Primary objects are also affected by their satellites, however, and feel some of their gravitational pull. In some cases, when two objects have similar size and mass and a similar gravitational pull, they can be called binary systems. Some argue that the moon Charon and Pluto represent a binary system rather than a primary object and satellite, since they both have similar mass.

Sputnik, the first artificial satellite, was launched by the Soviet Union in 1957.

Most are more familiar with the term in relation to the many satellites that circle the Earth. Sputnik was the first artificial satellite, launched in 1957 by the Soviet Union. The launch of Sputnik is almost analogous to the start of the Space Race that ensued between the US and the USSR. In today’s climate, however, many countries have found that a cooperative effort is more successful in space exploration and studies. The International Space Station, which orbits Earth, is currently the largest man-made satellite in space and represents the cooperative effort of many countries.

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High-performance fighter jets like the F-22 Raptor can carry ASAT missiles that can target orbiting satellites.

Artificial satellites are classified by types and there are more than ten types. Some of the main types used today include astronomical, communication, earth observation and weather satellites and space stations. Others include those used to monitor Earth from a military standpoint and biosatellites, which can carry animals or other life forms for the purpose of researching terrestrial life forms in space. Navigation satellites are now popular and form a vital part of the global positioning system (GPS) now available in many cars.

Planets like Earth and Mars are satellites of the Sun.

These objects can also be classified by the height at which they orbit the Earth or another body. A satellite in low Earth orbit circles the planet at an altitude of 0 to 1,240 miles (1,995.59 km). High Earth orbits can be as far away as 22,240 miles (35,791.81 km). Medium Earth orbits represent the distance between high and low Earth orbits.

There are other distinctions to describe the type of orbit it has; for example, Pluto has a slightly elliptical orbit. It can also be sorted by the main object it orbits. A satellite circling the Earth has a geocentric orbit, for example. The Earth and planets in this solar system are classified as having a heliocentric orbit, as they revolve around the sun.

Like a satellite, the moon orbits around the Earth.

An artificial satellite can serve many purposes. People use many different systems these days to track things like the weather, to make cell phones work, to figure out how to get somewhere, and to gather more information about Earth and the galaxy. About 5,000 man-made satellites currently orbit Earth, and on clear and dark nights, it’s often possible to see one in the night sky. Of course, planets, stars and comets are also satellites. People should also remember that the Earth is not stationary in the sky as it orbits the sun.

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