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Earth: 12,756.2 km (equatorial) 1.28×10 4: 4.11: Measurement comprises just the solid part of the Earth; there is no agreed upper boundary for Earth's atmosphere. The geocorona, a layer of UV-luminescent hydrogen atoms, lies at 100,000 km. The Kármán line, defined as the boundary of space for astronautics, lies at 100 km. [12] [13] [14] [15]
In astronomy, coordinate systems are used for specifying positions of celestial objects (satellites, planets, stars, galaxies, etc.) relative to a given reference frame, based on physical reference points available to a situated observer (e.g. the true horizon and north to an observer on Earth's surface). [1] Coordinate systems in astronomy can ...
It is convenient to define the orientation of an ECI frame using the Earth's orbit plane and the orientation of the Earth's rotational axis in space. [3] The Earth's orbit plane is called the ecliptic, and it does not coincide with the Earth's equatorial plane. The angle between the Earth's equatorial plane and the ecliptic, ε, is called the ...
The Earth-centered, Earth-fixed coordinate system (acronym ECEF), also known as the geocentric coordinate system, is a cartesian spatial reference system that represents locations in the vicinity of the Earth (including its surface, interior, atmosphere, and surrounding outer space) as X, Y, and Z measurements from its center of mass.
A number of different coordinate systems, each differing by a few degrees, were used until 1932, when Lund Observatory assembled a set of conversion tables that defined a standard galactic coordinate system based on a galactic north pole at RA 12 h 40 m, dec +28° (in the B1900.0 epoch convention) and a 0° longitude at the point where the ...
The extra pull of Earth's gravity decreases the object's orbital period, and at the L 2 point, that orbital period becomes equal to Earth's. Like L 1, L 2 is about 1.5 million kilometers or 0.01 au from Earth (away from the sun). An example of a spacecraft designed to operate near the Earth–Sun L 2 is the James Webb Space Telescope. [8]
The barycentric celestial reference system (BCRS) is a coordinate system used in astrometry to specify the location and motions of astronomical objects. It was created in 2000 by the International Astronomical Union (IAU) to be the global standard reference system for objects located outside the gravitational vicinity of Earth: [1] planets, moons, and other Solar System bodies, stars and other ...
The origin at the centre of Earth means the coordinates are geocentric, that is, as seen from the centre of Earth as if it were transparent. [3] The fundamental plane and the primary direction mean that the coordinate system, while aligned with Earth's equator and pole , does not rotate with the Earth, but remains relatively fixed against the ...