An Etymological Dictionary of Astronomy and Astrophysics
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The flowing out of mass through various processes from an object, for example in a star forming region or in a close binary.

→ mass; → outflow.

A consequence of the → dynamical relaxation process in a gravitationally → bound system, such as a → star cluster or a → globular cluster, where massive and low-mass members occupy different volumes. Massive members sink toward the center, while less massive members tend to move farther away from the center.

→ mass; → segregation.

The portion of the isotope shift which results from the difference between the nuclear masses of different isotopes.

→ mass; → shift.

An analytical technique for identification of chemical structures, determination of mixtures, and quantitative elemental analysis, in which ions are separated according to the mass/charge ratio and detected by a suitable detector.

→ mass; → spectrometry.

A spectrum of charged particles, arranged in order of mass or mass-to-charge ratios. → mass spectrometry.

→ mass; → spectrum.

The process in which the evolved member of a close binary system passes gaseous material to its companion star.

→ mass; → transfer.

In fluid mechanics, the motion of a given amount of material carried by a fluid from one point to another.

→ mass; → transfer.

The principle of interconversion of mass and energy, described by the → mass-energy relation.

→ mass; → energy; → equivalence.

The famous equation proposed by Einstein as a consequence of his special theory of relativity describing the equivalence of mass and energy: E = mc², where E is energy, m is the equivalent amount of mass, and c is the velocity of light.

→ mass; → energy; → relation.

The ratio of the mass of a system, expressed in solar masses, to its visual luminosity, expressed in solar luminosities. The Milky Way Galaxy has a mass-luminosity ratio in its inner regions of about 10, whereas a rich cluster of galaxies such as the Coma Cluster has a mass-luminosity ratio of about 200, indicating the presence of a considerable amount of dark matter.

→ mass; → luminosity; → ratio.

A relationship between luminosity and mass for stars that are on the main sequence, specifying how bright a star of a given mass will be. Averaged over the whole main sequence, it has been found that L = M^3.5, where both L and M are in solar units. This means, for example, that if the mass is doubled, the luminosity increases more than 10-fold.

→ mass; → luminosity; → relation.

A correlation between the → stellar mass (or → luminosity) and the → gas metallicity of → star-forming galaxies (Lequeux et al. 1979) according to which massive galaxies have higher gas metallicities. Several large galaxy surveys, such as the → Sloan Digital Sky Survey (SDSS), have confirmed that galaxies at all → redshifts with higher stellar masses retain more metals than galaxies with lower stellar masses. Besides the dependence on stellar mass, other studies have found further dependences of gas metallicity on other physical properties at a given mass, such as → specific star formation rate, → star formation rate, and stellar age. These higher dimensional relations could provide additional constraints to the processes that regulate the metal enrichment in galaxies. In addition to gas metallicity, also the → stellar metallicity of galaxies is found to correlate with the stellar mass, suggesting the mass-metallicity relation already existed at early epochs of galaxy evolution (Lian et al., 2017, MNRAS 474, 1143, and references therein).

→ mass; → metallicity; → relation.

The relation between the → stellar mass and the physical size of a galaxy. Studies show that the sizes increase with stellar mass, but that the relation weakens with increasing → redshift. Separating galaxies by their → star formation rate, model simulations show that → passive galaxies are typically smaller than → active galaxies at a fixed stellar mass. These trends are consistent with those found in observations; the level of agreement between the predicted and observed size-mass relations is of the order of 0.1 dex for redshifts < 1 and 0.2-0.3 dex from redshift 1 to 2. Known also as the → luminosity-size relation (Furlong et al., 2016, MNRAS 465, 722, and references therein).

→ mass; → size; → relation.

Consisting of or forming a large mass.

From M.Fr. massif (feminine massive) "bulky, solid," from O.Fr. masse "lump."

Porjerm, from por "full, much, very, too much," (Mid.Pers. purr "full;" O.Pers. paru- "much, many;" Av. parav-, pauru-, pouru-, from par- "to fill;" PIE base *pelu- "full," from *pel- "to be full;" cf. Skt. puru- "much, abundant;" Gk. polus "many," plethos "great number, multitude;" O.E. full) + jerm, → mass.

A black hole with a mass between millions and billions of solar masses residing in galactic nuclei. The mass of this type of black holes represents about 0.2% of the bulge mass. When matter is swallowed by the black hole, this gives rise to the tremendous energetic phenomena observed in quasars and active galactic nuclei.

→ massive; → black hole.

A → close binary system composed of two → massive stars.

→ massive; → close binary star.

Spheroidal distribution of dark matter surrounding a galaxy.

→ massive; → halo.

A star whose mass is larger than approximately 10 → solar masses. The → spectral types of massive stars range from about B3 (→ B star) to O2 (→ O star) and include → Wolf-Rayet stars as well as → Luminous Blue Variables. Massive stars are very rare; for each star of 20 solar masses there are some 100,000 stars of 1 solar mass. Despite this rarity, they play a key role in astrophysics. They are major sites of → nucleosynthesis beyond oxygen and, therefore, are mainly responsible for the → chemical evolution of galaxies. Due to their high ultraviolet flux and powerful → stellar winds, they bring about interesting phenomena in the → interstellar medium, like → H II regions, → turbulence, → shocks, → bubbles, and so on. Massive stars are progenitors of → supernovae (→ type Ia, → type Ic and → type II), → neutron stars, and → black holes. The formation processes of massive stars is still an unresolved problem. For massive stars the → accretion time scale is larger than the → Kelvin-Helmholtz time scale. This means that massive stars reach the → main sequence while → accretion is still going on.

→ massive; → star.

1) A person with the ability or power to use, control, or dispose of something.
2) An employer of workers or servants.
3) The male head of a household (Dictionary.com).

M.E. maistre, maister, from O.E. magister, from L. magister "chief, head, director, teacher," ultimately from PIE root *meg- "great," cf. Pers. meh-, as below.

(Aftari) Mastar "elder; larger," (Dari Kermân) mastar "leader, guide," variants (Aftari, Tafreši) mester "elder; great," massar "large, great, high," from (Nâini, Sangesari, Dari Yazd, Kermâni) mas "great, large," variant of meh "great, large, principal," cognate with L. magister "chief, head, director, teacher;" → Big Bang, + comparative suffix -tar.

A game or contest in which two or more contestants or teams oppose each other (Dictionary.com).

Originally "one of a pair, an equal;" O.E mæcca, "companion, mate, one of a pair, wife, husband, an equal," from gemæcca; cf. O.S. gimaco "fellow, equal," O.H.G. gimah "comfort, ease," M.H.G. gemach "comfortable, quiet," Ger. gemach "easy, leisurely."

Kâd, from Mid.Pers. kâdag "game," Sogd. kâtak "game, play;" cf. Kurd. (Sorani) kâya "game," Zazaki kây, Abyâneyi, Anâraki, Nâini kâye, Qohrudi kâda, Shamerzâdi ke, Zefrehi kê "game, play;" Av. kā- "to take pleasure, desire;" Skt. kā- "to desire, wish."