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

An instrument designed to observe objects when they cross the meridian.

→ meridian; → observation.

The observation of a star when it crosses an observer's meridian.

→ meridian; → observation.

The moment when a celestial object crosses an observer's meridian. Same as meridian transit.

→ meridian; → passage.

Of, pertaining to, or resembling a meridian.

→ meridian + → -al.

From nimruzân, → meridian, + -i adj. suffix.

The mass motion of material within a → rotating star generated by the star's departure from spherical symmetry. For a rotating star in which → centrifugal forces are not negligible, → radiative equilibrium and → hydrostatic equilibrium cannot be satisfied. In this condition energy transfer is accomplished by means of the physical motion of material. According to → von Zeipel theorem, the heating on an → equipotential surface is generally higher in the polar direction than in the equatorial direction, which drives a large scale circulation current rising at the pole and descending at the equator. As a consequence, → mixing of material takes place in the stellar interior; see also → Eddington-Sweet time scale. The meridional circulation plays an important role in the evolution of → massive stars. The circulation current was first suggested by Arthur S. Eddington in 1926 (The Internal Constitution of the Stars, Dover Pub. Inc., New York) and subsequently quantified by P. A. Sweet (1950, MNRAS 110, 548).

→ meridional; → circulation.

Meteo.: A flow between the poles, or between the equator and the poles. A positive value indicates flow away from the equator; a negative value, flow toward the equator.

→ meridional; → flow.

In the → solar dynamo model, a magnetic field that points from the north to south or south to north.

→ meridional; → magnetic; → field.

One of the stars in the Pleiades with a visual magnitude 4.17. It is a giant of spectral type B6 lying at a distance of about 1400 light-years.

Merope was one of the seven Pleiades, daughters of the Titan Atlas.

A → prime number of the form 2^p - 1, where p is a prime. As of February 2013, 48 Mersenne primes are known. The largest known prime number is 2^57,885,161 - 1. Each prime gives rise to an even → perfect number.

Marin Mersenne (1588-1648), French theologian, philosopher, mathematician and music theorist; → prime.

A star of visual magnitude 4.8 lying 204 light-years away in the constellation → Aries. It is in fact a triple star system.

The origin of Mesarthim (or Mesartim) is a matter of controversy. Some scholars have related it to the Ar. methartim (مثرطم) "very fat (animal)," but the connection is not obvious although the words are apparently similar. The original Ar. name was Šaratayn (الشرطین) "the two marks" denoting the current β and γ stars in Aries. It was also the name of the lunar mansion of which these two stars were members. Johann Bayer (1572-1625) erroneously related Šaratayn to the Hebrew Sartai, a current term in the astrological literature of his time. Subsequently, others figured that Sartai was related to Hebrew Mesartim "servants." The Latin transliteration and alteration Mesarthim found much success in establishing itself as the proper name for star γ Arietis.

1) One of the open spaces between the cords or ropes of a net.
2) Any knit, woven, or knotted fabric of open texture.
3) An interwoven or intertwined structure; network.
4) Electricity: A set of branches that forms a closed path in a network so that removal of a branch results in an open path. (Dictionary.com).

M.E. mesche "open space in a net," apparently from O.E. max "net," earlier mæscre (cf. Dan. maske, Sw. maska, M.Du. maessce, Du. maas "mesh," O.H.G. masca, Ger. Masche "mesh").

Bâncé "aperture, opening, window" in (Kermânšâhi) Kurd., ultimately from Proto-Ir. *banaka-, from *baH- "to shine," cf. Av. bāmya- "light, bright;" Pers. bâm "morning, dawn; splendor, light," Ossetic bon "day," probably related to bezel "opening, aperture," in several dialects of the Fârs province (Lâr, Gerâš, Xonj, Fišvar), → morning.

A combining form meaning "middle," used in the formation of compound words; e.g. → meson; → mesosphere.

From Gk. mesos "middle, in the middle;" akin to L. medius, Pers. miyân, → middle; → medium.

Meso-, loan from Gk.

A nuclear particle with a mass intermediate between that of a proton and an electron, which is believed to be responsible for the strong nuclear force. In contrast to the case of baryons or leptons, meson number is not conserved: like photons, mesons can be created or destroyed in arbitrary numbers. Their charge can be positive, negative, or zero.

From mes-, meso-, from Gk. mesos "middle," akin to L. medius, Pers. miyân, → medium, → middle, + -on a suffix used in the names of subatomic particles.

A class of → meteorites that is → brecciated→ stony-iron with nearly equal amounts of → metal and → silicates.

→ meso-; → siderite.

The layer of the atmosphere located between the → stratosphere and the → ionosphere, where temperature drops rapidly with increasing height. It extends between 17 to 80 kilometers above the Earth's surface.

→ meso-; → sphere.

1) General: A piece of information (written, spoken, or by signals).
2) Computer science: A defined amount of information, coded or not, between machines or machines and men. → information theory.

M.E., from O.Fr. message "message, news, embassy," from M.L. missaticum, from L. missus "a sending away, dispatching," from mittere "to send," → mission.

Payâm, variants payqâm, peyqâm, Mid.Pers. paygâm, ultimately from *patigam-, literally "arriving, newcomer," from *pati- "to, toward, at, in," → ad hoc, + *gam- "to come," → heliosheath.

One who brings → messages.

From M.E. messengere, messingere, messangere, from O.Fr. messanger, a variant of messagier, from → message + → -er.

Payâmbar "messenger," from payâm, → message, + bar "carrier," from bordan "carry," → vector.

A NASA robotic spacecraft that orbited the planet → Mercury for more than four years, between 2011 and 2015. Among its accomplishments, the mission determined Mercury's surface composition, revealed its geological history, discovered details about its internal magnetic field, and verified its polar deposits are dominantly water-ice. → Mercury's tail.

Messenger, short for "MErcury Surface, Space ENvironment, GEochemistry, and Ranging", a reference to the → messenger god Mercury from Roman mythology; → spacecraft.

A catalog of more than 100 nebulous-appearing astronomical objects, initially established to avoid confusion with comets. These objects are now well known to be among the brightest and most striking gaseous nebulae, star clusters, and galaxies. The designations of the catalog are still used in identification; e.g. M1 is the Crab Nebula (in Taurus).

In honor of the French astronomer Charles Messier (1730-1817), who compiled the list between 1760 and 1784 in order to avoid confusion with comets; → catalog.

Any of the nebulous-looking → astronomical objects listed in the → Messier catalog.

→ Messier catalog; → object.