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  2. Earth radius - Wikipedia

    en.wikipedia.org/wiki/Earth_radius

    Earth radius (denoted as R 🜨 or R E) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid (an oblate ellipsoid), the radius ranges from a maximum (equatorial radius, denoted a) of nearly 6,378 km (3,963 mi) to a minimum (polar radius, denoted b) of nearly 6,357 km (3,950 mi).

  3. List of common astronomy symbols - Wikipedia

    en.wikipedia.org/wiki/List_of_common_astronomy...

    R E, R 🜨 - Radius compared to Earth; R J, R ... Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; additional terms may apply.

  4. Mean radius (astronomy) - Wikipedia

    en.wikipedia.org/wiki/Mean_radius_(astronomy)

    For planet Earth, which can be approximated as an oblate spheroid with radii 6 378.1 km and 6 356.8 km, the mean radius is = (( ) ) / = . The equatorial and polar radii of a planet are often denoted r e {\displaystyle r_{e}} and r p {\displaystyle r_{p}} , respectively.

  5. Glossary of astronomy - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_astronomy

    A-type star In the Harvard spectral classification system, a class of main-sequence star having spectra dominated by Balmer absorption lines of hydrogen. Stars of spectral class A are typically blue-white or white in color, measure between 1.4 and 2.1 times the mass of the Sun, and have surface temperatures of 7,600–10,000 kelvin.

  6. Gravity of Earth - Wikipedia

    en.wikipedia.org/wiki/Gravity_of_Earth

    The gravity g′ at depth d is given by g′ = g(1 − d/R) where g is acceleration due to gravity on the surface of the Earth, d is depth and R is the radius of the Earth. If the density decreased linearly with increasing radius from a density ρ 0 at the center to ρ 1 at the surface, then ρ(r) = ρ 0 − (ρ 0 − ρ 1) r / R, and the ...

  7. Lunar distance - Wikipedia

    en.wikipedia.org/wiki/Lunar_distance

    Geostationary Earth Orbit is 42,164 km (26,199 mi) from Earth center, or ⁠ 1 / 9.117 ⁠ LD = 0.109 68 LD (or 0.109 68 LDEO [19]) Distance between the Earth and Moon ( mean value ) – sizes and distance to scale – with travel time at speed of light animated Photo of Earth and Moon , taken by the OSIRIS-REx probe Lunar distance to scale ...

  8. Spherical coordinate system - Wikipedia

    en.wikipedia.org/wiki/Spherical_coordinate_system

    The physics convention.Spherical coordinates (r, θ, φ) as commonly used: (ISO 80000-2:2019): radial distance r (slant distance to origin), polar angle θ (angle with respect to positive polar axis), and azimuthal angle φ (angle of rotation from the initial meridian plane).

  9. Earth-centered, Earth-fixed coordinate system - Wikipedia

    en.wikipedia.org/wiki/Earth-centered,_Earth...

    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.