Fundamental plane (spherical coordinates)

For the concept in extragalactic astronomy, see Fundamental plane (elliptical galaxies).

The fundamental plane in a spherical coordinate system is a plane of reference that divides the sphere into two hemispheres. The geocentric latitude of a point is then the angle between the fundamental plane and the line joining the point to the centre of the sphere.^[1]

For a geographic coordinate system of the Earth, the fundamental plane is the Equator.

Astronomical coordinate systems have varying fundamental planes:^[2]

• The horizontal coordinate system uses the observer's horizon.
• The Besselian coordinate system uses Earth's terminator (day/night boundary).^[3] This is a Cartesian coordinate system (x, y, z).
• The equatorial coordinate system uses the celestial equator.
• The ecliptic coordinate system uses the ecliptic.
• The galactic coordinate system uses the Milky Way's galactic equator.

See also

• Plane of reference

References

1. Rogers, Lucy (2008), It's ONLY Rocket Science: An Introduction in Plain English, Springer, p. 136, ISBN 9780387753782.
2. Newcomb, Simon (1906). A Compendium of Spherical Astronomy with Its Applications to the Determination and Reduction of Positions of the Fixed Stars. Macmillan. p. 92..
3. "NASA - Besselian Elements of Solar Eclipses". NASA. Retrieved 13 August 2022.