Objects of similar mass orbit each other with neither object at the centre, whilst small objects orbit around larger objects. In our Solar System, the Moon orbits Earth, and Earth orbits the Sun, but that does not mean the larger object remains completely still.

A satellite is anything that orbits around a larger object. A natural satellite is any celestial body in space that orbits around a larger body. Moons are called natural satellites because they orbit planets.

Orbits are the result of a perfect balance between the forward motion of a body in space, such as a planet or moon, and the pull of gravity on it from another body in space, such as a large planet or star. These forces of inertia and gravity have to be perfectly balanced for an orbit to happen.

Gravity attracts all things towards each other

• Gravity holds the atmosphere in place around the Earth.
• Gravity keeps people on the Earth’s surface.
• Gravity keeps the International Space Station in orbit around the Earth.
• Gravity keeps the Moon orbiting around the Earth.
• Gravity keeps the Earth orbiting around the Sun.

Explanation of how objects under the influence of gravity move in orbits. A body in uniform circular motion undergoes at all times a centripetal acceleration given by equation (40). According to Newton’s second law, a force is required to produce this acceleration.

Orbital Motion: Newton concluded that two factors—inertia and gravity– combine to keep Earth in orbit around the sun, and the moon in orbit around Earth.

1.62 m/s²

So as the mass of either object increases, the force of gravitational attraction between them also increases. If the mass of one of the objects is doubled, then the force of gravity between them is doubled. If the mass of one of the objects is tripled, then the force of gravity between them is tripled.

Mercury

By the order of the 14 Planet Theory, the planets were Mercury and the Moon, Venus, Mondas, Earth, Mars, Asteris, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon and Planet 14.

In classical antiquity, the seven classical planets or seven sacred luminaries are the seven moving astronomical objects in the sky visible to the naked eye: the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and Saturn.

Biggest Planets In Our Solar System

To begin with planets, as that is the easiest question to answer, there are no planets bigger than the Sun or even close to the size of the Sun. At about 13 times the mass of Jupiter a planet becomes what is referred to as a “brown dwarf”.

Uranus

Venus

1.3 million Earths

Is Earth the Fifth Smallest Planet?

• Mercury (Average diameter: 4879.4 km, or about 2/5 the size of Earth)
• Mars (Average diameter: 6772 km, or about 1/2 the size of Earth)
• Venus (Average diameter: 12,104 km, or about 9/10 the size of Earth)
• Earth (Average diameter: 12,735 km)

As the authority on the naming and classification of celestial objects, the International Astronomical Union officially recognizes five dwarf planets in the solar system:

• Pluto.
• Eris.
• Ceres.
• Makemake.
• Haumea.

Currently, there are six dwarf planets officially designated by the IAU: Pluto, Ceres, Eris, Makemake, Haumea, and 2015 RR245, discovered in July.

That means that according to the definition of the International Astronomical Union, the Earth cannot technically be considered as a planet and that it is, in fact, a dwarf-planet. There were seven earth sized objects discovered in orbit around an ultracool dwarf star forty light years away using this method.

Dwarf planets of the solar system

• Meet the dwarf planets of our solar system, Pluto Eris, Haumea, Makemake and Ceres. (
• The dwarf planet Ceres, also the largest asteroid in the solar system, is seen here in an amazing view from the Hubble Space Telescope.