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Earth is the third planet from the Sun and the only object in the Universe known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago. Earth's gravity interacts with other objects in space, especially the Sun and the Moon, Earth's only natural satellite. Earth revolves around the Sun in 365.26 days, a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times.


Aphelion is the point in the orbit where the celestial body is farthest from the Sun.

152,100,000 km
94,500,000 miles
1.017 AU (astronomical unit)


The perihelion of any orbit of a celestial body about the Sun is the point where the body comes nearest to the Sun.

147,095,000 km 
91,401,000 miles
0.98327 AU (astronomical unit)

Semi-major axis

The semi-major axis is one half of the major axis, and thus runs from the centre, through a focus, and to the perimeter.

149,598,023 km 
92,955,902 miles
1.00000102 AU (astronomical unit)


The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values between 0 and 1 form an elliptic orbit, 1 is a parabolic escape orbit, and greater than 1 is a hyperbola.


Orbital period

The orbital period is the time a given astronomical object takes to complete one orbit around another object, and applies in astronomy usually to planets or asteroids orbiting the Sun, moons orbiting planets, exoplanets orbiting other stars, or binary stars.

365.256363004 days
1.00001742096 years

Average orbital speed

In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter or, if the object is much less massive than the largest body in the system, its speed relative to that largest body. The speed in this latter case may be relative to the surface of the larger body or relative to its center of mass.

29.78 km/s
107,200 km/h
66,600 mph

Mean anomaly

In celestial mechanics, the mean anomaly is an angle used in calculating the position of a body in an elliptical orbit in the classical two-body problem. It is the angular distance from the pericenter which a fictitious body would have if it moved in a circular orbit, with constant speed, in the same orbital period as the actual body in its elliptical orbit.



Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object.

7.155° to the Sun's equator
1.57869° to invariable plane
0.00005° to J2000 ecliptic

Longitude of the ascending node

The longitude of the ascending node (☊ or Ω) is one of the orbital elements used to specify the orbit of an object in space. It is the angle from a reference direction, called the origin of longitude, to the direction of the ascending node, measured in a reference plane.

−11.26064° to J2000 ecliptic

Argument of perihelion

The argument of perihelion, symbolized as ω, is one of the orbital elements of an orbiting body. Parametrically, ω is the angle from the body's ascending node to its periapsis, measured in the direction of motion.



A natural satellite or moon is, in the most common usage, an astronomical body that orbits a planet or minor planet (or sometimes another small Solar System body).

1 natural satellite: the Moon
5 quasi-satellites
>1,700 operational artificial satellites 
>16,000 space debris

Mean radius

The Earth's mean radius is determined as the average distance from the physical center to the surface, based on a large number of samples.

6,371.0 km
3,958.8 miles

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