equinox Hear it!

equinox Definition

equi·nox (ē′kwi näks′, ek′wə näks)

noun

  1. the time when the sun in its apparent annual movement along the ecliptic crosses the celestial equator, making night and day of equal length in all parts of the earth: in the Northern Hemisphere the vernal equinox occurs about March 21 and marks the beginning of spring, and the autumnal equinox occurs about September 22 and marks the beginning of autumn
  2. either of the two points on the celestial sphere where the sun's path crosses the celestial equator

Etymology: ME < OFr equinoxe < ML aequinoxium < L aequinoctium < aequus (see equal) + nox, night

equinox Usage Examples

Preposition: of

position: The original equinox of the position as supplied to the HEASARC was 2000.

Converse of object

  • specify: Specify the equinox of the input coordinates, all coords are output as J2000.
  • use: Note that the coordinates in the file use the 1975 equinox.
  • call: We choose a fixed point on the celestial equator, called the vernal equinox, or the First Point of Aries.
  • request: RA The nominal right ascension of the XMM-Newton pointing, in the requested equinox.
  • mark: Around March 21, the sun is in the middle of its swing and will rise at due east, marking the vernal equinox.

Adjective modifier

  • vernal: The same happens at the spring or vernal equinox on the 21st March.
  • autumnal: September 21 was the " official " date of the autumnal equinox.
  • selected: Dec The declination of the object in the selected equinox.
  • specified: Ra The RA of the supernova in the specified equinox.
  • mean: Ecliptic and equatorial co-ordinates are referred to the mean equinox of a given epoch.

Modifies a noun

  • j2000: RA The Right Ascension ( equinox J2000 ) of the EUV source.
  • point: The Galaxy itself connects to our zodiac at the equinox points, in an angle of 60 deg - a sextile!
  • condition: The coupled model was run for equinox conditions during Solar Minimum.
  • year: RA Source RA ( displayed at the current equinox year ).

Noun used with modifier

  • autumn: From the autumn equinox the setting sun moves gradually south along the western horizon.
  • default: Dec The declination of the target in the default equinox.
  • fall: In fact, on the days of the spring and fall equinox the length of daylight is actually longer than darkness by several minutes.
  • output: Output equinox: Give stellar co-ordinates in J2000 or B1950 epoch.