quadrature
In astronomy, the constellation in which one celestial body has a geocentric angular distance of 90 degrees from another is called quadrature (also square note; astronomical symbol : □) . If the other celestial body is not named, it is usually the quadrature to the sun, i.e. H. the celestial body is just 90 degrees elongated .
The moon is in quadrature with the sun in the first and last quarter . If an upper planet is in quadrature to the sun, it does not appear fully illuminated, but at a certain phase angle . This is the angle at which the earth and sun appear when viewed from the planet. The phase angle is maximum at quadrature. Instead of the term quadrature , the term “ largest phase” is often used . However, this is only noticeable on Mars on the planetary disk itself. It then has a phase shape like the moon about three to four days before or after the full moon.
The lower planets Mercury and Venus can never be in quadrature because their greatest elongation is less than 90 degrees.
Outside the solar system , it is called quadrature when, in a binary star or exoplanet system, the angle between the observer on earth and the companion star is 90 degrees, i.e. measured from the main star.
See also
literature
- Andreas Guthmann: Introduction to celestial mechanics and ephemeris calculus . 2nd Edition. Spektrum Akademischer Verlag, Heidelberg, Berlin 2000, ISBN 3-8274-0574-2 , pp. 191 .
Individual evidence
- ↑ Aspects (lexicon entry). In: Meyers Großes Konversations-Lexikon. 6th edition, Bibliographisches Institut, Leipzig / Vienna 1905-1909. 1909, Retrieved July 23, 2018 .