Point where an orbit crosses a plane of reference to which it is inclined
An
orbital node
is either of the two points where an
orbit
intersects
a
plane of reference
to which it is inclined.
[1]
A
non-inclined orbit
, which is
contained
in the reference plane, has no nodes.
Planes of reference
[
edit
]
Common
planes of reference
include the following:
Node distinction
[
edit
]
If a reference direction from one side of the plane of reference to the other is defined, the two nodes can be distinguished. For geocentric and heliocentric orbits, the
ascending node
(or
north node
) is where the orbiting object moves north through the plane of reference, and the
descending node
(or
south node
) is where it moves south through the plane.
[4]
In the case of objects outside the Solar System, the ascending node is the node where the orbiting secondary passes away from the observer, and the descending node is the node where it moves towards the observer.
[5]
, p. 137.
The position of the node may be used as one of a set of parameters, called
orbital elements
, which describe the orbit. This is done by specifying the
longitude of the ascending node
(or, sometimes, the
longitude of the node
.)
The
line of nodes
is the straight line resulting from the intersection of the object's orbital plane with the plane of reference; it passes through the two nodes.
[2]
Symbols and nomenclature
[
edit
]
Look up
anabibazon
in Wiktionary, the free dictionary.
Look up
catabibazon
in Wiktionary, the free dictionary.
The symbol of the ascending node is
(
Unicode
: U+260A, ?), and the symbol of the descending node is
(
Unicode
: U+260B, ?).
In medieval and early modern times, the ascending and descending nodes of the Moon in the ecliptic plane were called the "dragon's head" (
Latin
:
caput draconis
,
Arabic
:
??? ???????
) and "dragon's tail" (
Latin
:
cauda draconis
), respectively.
[6]
: p.141,
[7]
: p.245
These terms originally referred to the times when the
Moon
crossed the apparent path of the sun in the sky (as in a
solar eclipse
). Also, corruptions of the Arabic term such as
ganzaar
,
genzahar
,
geuzaar
and
zeuzahar
were used in the medieval West to denote either of the nodes.
[8]
: pp.196?197,
[9]
: p.65,
[10]
: pp.95?96
The
Koine Greek
terms
αναβιβ?ζων
and
καταβιβ?ζων
were also used for the ascending and descending nodes, giving rise to the English terms
anabibazon
and
catabibazon
.
[11]
[12]
: ¶27
Lunar nodes
[
edit
]
For the
orbit of the Moon
around
Earth
, the
plane
is taken to be the
ecliptic
, not the
equatorial plane
. The
gravitational
pull of the
Sun
upon the Moon causes
its nodes
to gradually
precess
westward, completing a cycle in approximately 18.6 years.
[1]
[13]
Use in astrology
[
edit
]
The image of the ascending and descending orbital nodes as the head and tail of a dragon, 180 degrees apart in the sky, goes back to the Chaldeans; it was used by the Zoroastrians, and then by Arabic astronomers and astrologers. In Middle Persian, its head and tail were respectively called
g?zihr sar
and
g?zihr dumb
; in Arabic,
al-ra's al-jawzihr
and
al-dhanab al-jawzihr
? or in the case of the Moon, ___
al-tennin
.
[14]
Among the arguments against astrologers made by
Ibn Qayyim al-Jawziyya
(1292?1350), in his
Miftah Dar al-SaCadah:
"Why is it that you have given an influence to
al-Ra's
[the head] and
al-Dhanab
[the tail], which are two imaginary points [ascending and descending nodes]?"
[15]
See also
[
edit
]
References
[
edit
]
- ^
a
b
"node"
.
Columbia Encyclopedia
(6th ed.). New York:
Columbia University Press
. 2004. Archived from
the original
on March 9, 2007
. Retrieved
May 17,
2007
.
- ^
a
b
c
Darling, David.
"line of nodes"
.
The Encyclopedia of Astrobiology, Astronomy, and Spaceflight
. Retrieved
May 17,
2007
.
- ^
Tatum, Jeremy B.
"Chapter 17"
.
Celestial Mechanics
. Retrieved
May 17,
2007
.
- ^
ascending node
, entry in
The Encyclopedia of Astrobiology, Astronomy, and Spaceflight
, David Darling, on line, accessed May 17, 2007.
- ^
The Binary Stars
, R. G. Aitken, New York: Semi-Centennial Publications of the University of California, 1918.
- ^
Survey of Islamic Astronomical Tables
, E. S. Kennedy,
Transactions of the American Philosophical Society
, new series,
46
, #2 (1956), pp. 123–177.
- ^
Cyclopædia, or, An universal dictionary of arts and sciences
Archived
2008-12-02 at the
Wayback Machine
, Ephraim Chambers, London: Printed for J. and J. Knapton [and 18 others], 1728, vol. 1.
- ^
Planetary Latitudes, the Theorica Gerardi, and Regiomontanus
, Claudia Kren,
Isis
,
68
, #2 (June 1977), pp. 194–205.
- ^
Prophatius Judaeus and the Medieval Astronomical Tables
, Richard I. Harper,
Isis
62
, #1 (Spring, 1971), pp. 61–68.
- ^
Lexicographical Gleanings from the Philobiblon of Richard de Bury
, Andrew F. West,
Transactions of the American Philological Association
(1869-1896),
22
(1891), pp. 93–104.
- ^
anabibazon, entry in
Webster's third new international dictionary of the English language unabridged: with seven language dictionary
, Chicago: Encyclopædia Britannica, 1986.
ISBN
0-85229-503-0
.
- ^
New thoughts on the genesis of the mysteries of Mithras
, Roger Beck,
Topoi
11
, #1 (2001), pp. 59–76.
- ^
Marcia Rieke.
"Introduction: Coordinates, Seasons, Eclipses (lecture notes)"
.
Astronomy 250
.
University of Arizona
. Archived from
the original
on August 26, 2016
. Retrieved
May 17,
2007
.
- ^
"G?zihr"
.
Encyclopædia Iranica (iranicaonline.org)
. February 17, 2012. Vol. XI, Fasc. 2, p. 184
. Retrieved
March 28,
2023
.
Cf.
Gochihr (Zoroastrianism)
.
- ^
Livingston, John W. (1971). "Ibn Qayyim al-Jawziyyah: A Fourteenth Century Defense against Astrological Divination and Alchemical Transmutation".
Journal of the American Oriental Society
.
91
(1): 96?103.
doi
:
10.2307/600445
.
JSTOR
600445
.