A small tail-like structure on a comet that, unlike most comet tails, seems to point toward the Sun. This rare event is an optical illusion due to larger dust particles left along the comet's orbit. And typically occurs when the Earth crosses the plane of the comet's orbit. It seen when the observer is in the plane of the cometary orbit.
Pâddom, from pâd-, → anti-, + dom "tail."
Fr.: queue de comète
A formation of → gas and/or → dust that streams away from the → coma of many comets under the influence of the Sun's → radiation pressure and the → solar wind. See also: → dust tail, → gas tail, → ion tail, → plasma tail, → sodium tail, → Type I tail, → Type II tail, → antitail.
1) pâzé; 2) pâzidan
Fr.: 1) détail; 2) détailler
1) An individual or minute part; an item or → particular.
From Fr. détail, from O.Fr. detail "small piece or quantity," literally "a cutting in pieces," from detaillier "to cut in pieces," from → de- "entirely" + taillier "to cut in pieces," from L. taliare "to split."
Pâzé, from Sogd. pâzê "portion, bit;" Kurd. pâž "part of a whole;" related to Mod.Pers. baxš "part, division," bâž "tribute, toll, impost;" ultimately from Proto-Ir. *baj- "to bestow, divide, have a share;" cf. Av. baž- (baxš-) "to divide, bestow, give a share;" O.Pers. bāji- "tribute, tax;" Mid.Pers. bâj, bâž "tribute, tax," baxtan "to distribute," baxt "luck, fate;" Skt. bhaj- "to share, distribute, apportion," Gk. phagein "to eat (to have a share of food)"; PIE base *bhag- "to share out, apportion;" → division.
1) Having many details.
Adjective from → detail.
donbâle-ye qobâri (#)
Fr.: queue de poussière
Fr.: queue de gaz
Fr.: galaxie tête-queue, ~ têtard
A member of the class of radio galaxies (→ radio galaxy) that have a strong radio emission coming from a bright "head" and a more diffuse emission from a "tail." They are often found in clusters.
donbâle-ye yoni (#)
Fr.: queue d'ions
Of a comet, same as → gas tail.
Fr.: queue magnétique
The portion of a planet's → magnetosphere which is pushed away from the Sun by the solar wind. Earth's magnetosphere extends about 65,000 km on the day-side but more than 10 times further.
Fr.: queue de Mercure
A narrow and elongated structure of glowing → sodium gas associated with Mercury. Mercury's thin atmosphere contains small amounts of sodium that glow when excited by radiation from the Sun. Solar photons also liberate these molecules from Mercury's surface and pushes them away. Because Mercury's gravity is too weak to hold a permanent atmosphere, when atoms are evaporated from the planet's surface, some of the atoms form a tail that points away from the Sun. In particular, the yellow glow from sodium → D line is relatively bright. First predicted in the 1980s, the tail was first discovered in 2001 (A.E. Potter et al., 2001). Many tail details were revealed in multiple observations by NASA's robotic → MESSENGER spacecraft that orbited Mercury between 2011 and 2015.
dom-e natâr, donbâle-ye ~
Fr.: queue neutre
Same as → sodium tail.
Fr.: queue de plasma
The ionized component of a comet's tail, driven nearly straight away from the Sun by the solar wind. Also called ion tail and gas tail.
Fr.: queue de sodium
1) A kind of → cometary tail appearing in some
→ comets, such as → Hale-Bopp.
Sodium tails arise from the very strong → fluorescence
of their sodium atom → D lines
in the visible. They are rapidly accelerated
to high velocities by the Sun, forming a very straight tail distinct from the
→ ion tail.
The release mechanism of sodium from comets is still a matter of debate.
Also called → neutral tail.
sodium tail of the Moon
donbâle-ye sodiomi-ye Mâng
Fr.: queue de sodium de la Lune
A comet-like tail of the Moon comprised of → sodium (Na) atoms and invisible to the naked eye. The lunar surface is constantly bombarded by the → solar wind, → photons, and → meteoroids, which can liberate Na atoms from the → regolith. These atoms are subsequently accelerated by solar → radiation pressure to form a long comet-like tail opposite the Sun. Near → new moon, this diffuse cloud of Na atoms encounters the Earth's gravity and is "pinched" into a beam of enhanced density. This beam appears as the ~3° diameter Sodium Moon Spot (SMS) seen in the sky opposite the Sun. The spot is about five times the diameter of the → full moon, and is 50 times fainter than can be seen with the unaided eye. The spot is reflected light from millions of Na atoms that two days earlier were on the surface of the Moon. This spot is visible to sensitive cameras equipped with filters tuned to the orange light emitted by Na atoms near 589.3 nm (Baumgardner et al., 2021 Journal of Geophysical Research: Planets DOI: 10.1029/2020je006671).
dom (#), donbâlé (#)
1) The part that sticks out at the back of an animal's body, and that it can move.
M.E.; O.E. tægl, from P.Gmc. *tagla- (cf. O.H.G. zagal, Ger. Zagel "tail," O.N. tagl "horse's tail").
Dom, variant domb, "tail;" Mid.Pers. dumb "tail;" Av. duma- "tail"; donbâlé, from domb + -âlé, -âl resemblance suffix, → -al.
Fr.: queue de marée
A long stream of stars and gas, often in the form of a spectacular tail, thrown off a galaxy when it collides with another galaxy. → interacting galaxies; → merger. Two tidal tails form in each galaxy, and they are more spectacular when the masses of the two galaxies are comparable, and when their relative orbit is in the same sense as the rotation inside each spiral galaxy.
Type I tail
dom-e gune-ye I
Fr.: queue de type I
The → gas tail of of a comet.
Type II tail
dom-e gune-ye II
Fr.: queue de type II