An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The Lion. One of the most conspicuous → constellations in the northern hemisphere, at 10h 30m → right ascension, 15° north → declination. Leo is a constellation of the → Zodiac crossed by the Sun from August 10th to September 16th. Leo is visible from February through June. Its brightest star, α Leonis or → Regulus, is of the first magnitude. Abbreviation: Leo; Genitive: Leonis. The neighboring constellations are → Cancer, → Coma Berenices, → Crater, → Hydra, → Leo Minor, → Lynx, → Sextans, → Ursa Major, and → Virgo. Leo contains many bright stars, many of which were individually identified by the ancients. There are four stars of first or second magnitude, which render this constellation especially prominent. Apart from Regulus, the constellation is home to the bright stars → Denebola, the nearby star Wolf 359, and to a number of famous deep sky objects, among them galaxies Messier 65, Messier 66, Messier 95, Messier 96, Messier 105, and NGC 3628. There are two → meteor showers associated with the constellation. The → Leonids usually peak on November 17-18 every year and have a → radiant near the bright star Gamma Leonis. The January Leonids are a minor shower that peaks between January 1 and 7. Leo has 11 stars with known planets.

→ lion.

The Lesser Lion. A faint constellation in the northern hemisphere, at 10h 20m right ascension, 35° north declination. Abbreviation: LMi; genitive: Leonis Minoris.

→ Leo; Minor, from L. minor "lesser, smaller, junior," from PIE base *min- "small."

Šir, → Leo; kucak "small," (Mid.Pers. kucak "small"), related to kutâh "short, small, little," kudak "child, infant," kutulé, → dwarf, Mid.Pers. kôtâh "low," kôtak "small, young; baby;" Av. kutaka- "little, small."

A → dwarf galaxy recently discovered near the Milky Way in → neutral hydrogen → 21-centimeter line observations. Optical imaging observations indicate that it is located between 1.5 and 2.0 Mpc from the Milky Way. This places Leo P in the → Local Volume but beyond the → Local Group. The dwarf galaxy has extreme properties: it is the lowest-mass system known that contains significant amounts of gas and is currently forming stars (Katherine L. Rhode et al. 2013, AJ 145, 149).

→ Leo.

A → meteor shower emanating from an apparent point in the constellation → Leo that occurs from November 14-20, with a maximum on November 17-18. It is due to the annual passage of the Earth through the orbit of the comet → Tempel-Tuttle and encounter with the dust debris from the comet.

From L. Leon, → Leo, + → -ids.

A frequency distribution with a positive → kurtosis, that has a more elevated peak around the mean than the corresponding normal distribution. → platykurtic.

From Gk. lepto-, combining form of leptos "thin, slight" + → kurtosis.

Boland-afrâšté "highly-elevated," from boland "high, tall, elevated, sublime" (variants bâlâ "up, above, high, elevated, height," borz "height, magnitude" (it occurs also in the name of the mountain chain Alborz), Laki dialect berg "hill, mountain;" Mid.Pers. buland "high;" O.Pers. baršan- "height;" Av. barəz- "high, mount," barezan- "height;" cf. Skt. bhrant- "high;" L. fortis "strong" (Fr. and E. force); O.E. burg, burh "castle, fortified place," from P.Gmc. *burgs "fortress;" Ger. Burg "castle," Goth. baurgs "city," E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg; PIE base *bhergh- "high") + afrâšté "raised, elevated, erect," p.p. of afrâštan, → kurtosis.

An → elementary particle that does not participate in the → strong interaction. The Lepton family includes → electrons, → muons, tau leptons, → neutrinos and their → antiparticles. The lepton is a → fermion.

From Gk, lepto-, combining form of leptos "small, slight" + -on a suffix used in the names of subatomic particles (gluon; meson; neutron), quanta (photon; graviton), and other minimal entities or components.

Postulate that the magnitude of the lepton number density is comparable to or larger than the thermal radiation photon number density, so relaxation to equilibrium produces a degenerate sea of neutrinos. Degenerate neutrinos would suppress the number of neutrons relative to protons in the very early Universe; degenerate antineutrinos would suppress the number of protons relative to neutrons. Either case would affect BBNS (Peebles, P. et al., 2009, Finding the Big Bang, Cambridge: UK, Cambridge Univ. Press).

→ lepton; → degeneracy.

The era following the hadronic era, when the Universe consisted mainly of leptons and photons. It began when the temperature dropped below 10¹² degrees kelvin some 10^-4 seconds after the Big Bang, and it lasted until the temperature fell below 10¹⁰ degrees kelvin, at an era of about 1 second.

→ lepton; → era.

In particle physics, a quantum number attributed to elementary particles which is conserved in nuclear reactions. It is +1 for a lepton, -1 for an antilepton and 0 for other particles.

→ lepton; → number.

The Hare. A small → constellation in the southern hemisphere at about 6h right ascension, 20° south declination. Abbreviation: Lep; genitive: Leporis.

L. lepus "hare."

Xarguš "rabbit, hare," literally "ass-ear," Mid.Pers. xargôš, from xar "donkey, ass" (Mid.Pers. xar "donkey;" Av. xara- "donkey;" cf. Skt. khára- "donkey, mule") + guš, → ear.

A bright blue star of → apparent visual magnitudeV = 2.70, that with → Shaula (Lambda Scorpii) makes up the Scorpion's stinger. Among its other designations: HR 6508 and HIP 85696. Lesath is 580 → light-years away. Lesath and Shaula appear very close on the sky (less than a degree apart), but they are not physically related. Lesath is a → subgiant of → spectral type B2 IV with a → luminosity of about 7,380 Msun. It has a radius of about 6 Rsun, and a → surface temperature of about 22,000 K.

Lesath, from Ar. al-Las'ah (اللسعه) "the sting."

1) A symbol or character representing a sound of which words are formed used in writing and printing a language.
2) A written or printed communication addressed to a person or organization.

M.E., from O.Fr. letre "character, letter; missive," from L. littera "letter of the alphabet," litterae (plural) "epistle, literature"

1) Vât "letter, word," from vat- "to speak, say;" cf. (Kurd.) wittin "to speak, say," → article, (Nâyin) vâte, (Qohrud) vâta, (Sangesar) -vât-/vân, (Zazaki) vâtiš, (Awromani) wâtay/wâc-, (Farizand) -vât/-vaj, (Gaz) vâ-/vât, related to Pers. vâžé "word;" Mid.Pers. vâc, vâcak "word, speech;" âva "voice, sound," âvâz "voice, sound, song," bâng "voice, sound, clamour" (Mid.Pers. vâng); Av. vacah- "word," vaocanghê "to decalre" (by means of speech), from vac- "to speak, say;" cf. Skt. vakti "speaks, says," vacas- "word;" Gk. epos "word;" L. vox "voice;" PIE base *wek- "to speak."
2) Nâmé, → book.

A position with respect to a given or specified base. → energy level.

From O.Fr. livel, from L. libella "a balance, level," diminutive of libra "balance, scale."

Tarâz "level; a level," from tarâzu "balance, scales," Mid.Pers. tarâzên-, taraênidan "to weigh," Proto-Iranian *tarāz-, from *tarā- "balance, scale" ( cf. Skt. tulā- "scales, balance, weight," from tul- "to weigh, make equal in weight, equal," tolayati "weighs, balances," L. tollere "to raise," Gk. talanton "balance, weight," Atlas "the Bearer" of Heaven," Lith. tiltas "bridge;" PIE base telə- "to lift, weigh") + Av. az- "to convey, conduct, drive," azaiti drives" (cf. Skt. aj- "to dive, sling," ájati "drives," ajirá- "agile, quick," Gk. agein "to lead, guide, drive, carry off," L. agere "to do, set in motion, drive," from PIE root *ag- "to drive, move," → act).

Same as → significance level.

→ level; → significance.

A rigid bar that pivots about a point and is used to move or lift a load at one end by applying force to the other end. → lever arm.

M.E. levere, levour; O.Fr. levier "a lifter, a lever," agent noun from lever "to raise," from L. levare "to raise," from levis "light" in weight.

Ahrom, of unknown etymology.

The distance between the point of application of a → force and the → axis around which the object could → rotate.

→ lever; → arm.

1) To rise or float in the air, especially by means of supposed magical powers.
2) To cause to rise or float in the air.

From L. levitas "lightness," from levis "light."

Bâlâ kardan, literally "to raise, uplift," from bâlâ "high, up," → high, + kardan "to do, perform, make," → effect; bâlâ šodan, from bâlâ + šodan "to go, to pass, to become," → set.

1) The action of rising or causing something to rise and float in the air, typically by means of supposed magical powers.
2) → radiative levitation.

→ levitate; → -tion.

A combining form meaning "left" and "counterclockwise," used in the formation of compound words, such as → levorotation, levocardia, levoglucose, etc. The variant lev- occurs before vowels. Compare → dextro-.

From L. laevo-, from laevus, cf. Gk. laios, Russ. levyj, + epenthetic vowel -o-.

Cap-, from cap "left," of unknown etymology.

The counterclockwise rotation of the → plane of polarization of light (as observed when looking straight through the incoming light) by certain substances.

Adj. related to → levorotation.