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

A region on the surface of the → Moon where the → gravitational attraction is slightly higher than normal due to the presence of dense rock.

Short for mass concentration; → mass; → concentration.

1) Having qualities appropriate to or usually associated with a man.
2) Of, relating to, or constituting the gender that ordinarily includes most words or grammatical forms referring to males (Merriam-Webster.com).

M.E. masculin, from O.Fr. masculin "of the male sex," from L. masculinus "male, of masculine gender," from masculus "male, masculine; worthy of a man," diminutive of mas "male person, male," of unknown origin.

Narin, from nar, → male.

1) A source of very intense, narrow-band, coherent microwave radiation involving → stimulated emission, as in the → laser.
2) A device that generates such radiation.
3) In astronomy, maser emission detected from a number of molecules and associated with several environments: the vicinity of newly forming stars and → H II regions (OH, water, SiO, and methanol masers); the circumstellar shells of evolved stars, i.e. red giants and supergiants (OH, water, and SiO masers); the shocked regions where supernova remnants are expanding into an adjacent molecular cloud (OH masers); and the nuclei and jets of active galaxies (OH and water masers). The hydroxyl radical (OH) was the first interstellar maser detected (Weinreb et al. 1963).

Maser stands for Microwave Amplification by Stimulated Emission of Radiation; → laser.

An emission arising from the → maser process.

→ maser; → emission.

1) Something that serves to cover or conceal.
Electronics: A pattern used to control the configuration of conducting material deposited or etched onto a semiconductor chip.
2) Electronics: To override one signal with a stronger one.

From M.Fr. masque "covering to hide or guard the face," from It. maschera, from M.L. masca "mask, specter, nightmare," of uncertain origin.

1) Mâsk, loan from Fr., as above; 2) with verb zadan "to make, to do," originally "to strike, beat; to do; to play an instrument" (Mid.Pers. zatan, žatan; O.Pers./Av. jan-, gan- "to strike, hit, smite, kill" (jantar- "smiter"); cf. Skt. han- "to strike, beat" (hantar- "smiter, killer"); Gk. theinein "to strike;" L. fendere "to strike, push;" Gmc. *gundjo "war, battle;" PIE *g^when- "to strike, kill").

1) A method of improving → spatial resolution of images. → pupil masking; → unsharp masking.
2) Computers: The process of specifying a number of values that allow extracting desired information from a set of characters or bits while suppressing the undesired information.

Verbal noun of → mask.

1) A measure of the amount of material in an object, defined either by the inertial properties of the object or by its gravitational influence on other bodies. See also → inertial mass, → gravitational mass.
2) A considerable assemblage, number, or quantity.

From O.Fr. masse "lump," from L. massa "kneaded dough, lump," from Gk. maza "barley cake, lump, mass, ball," related to massein "to knead."

Jerm, from Ar. jirm.
Qond "assembled, collected; a crowd," related to gondé "coarse, thick; big;" Mid.Pers. gund "troop, group, gathering;" loaned into Arm. gund and Ar. jund.
Tudé "heap, stack, tumulus;" cf. Kurd. tavda "all, total;" Tati tâya "heap, mass;" Sogd. tuδē "heap, mass." Perhaps related to PIE *teuta- "people, tribe;" cf. Lith. tauta, Oscan touto, O.Irish tuath, Goth. þiuda, O.E. þeod "people, folk, race."
Anbuh "numerous, abundant," from Proto-Iranian *ham-buH- "to come together," from ham- "together," → com- + *buH- "to be , become," Av. ham.bauu- "to come together, unite," from ham- as above + bauu-, bu- "to be, become," O.Pers. bav- "to be, become," Mod.Pers. budan "to be," Skt. bhavati "becomes, happens," PIE base *bheu-, *bhu- "to grow, become;" cf. Gk. phu- "become," P.Gmc. *beo-, *beu-, E. be.

A measure of the rate of absorption of radiation, expressed as the linear absorption coefficient divided by the density of the medium through which radiation is passing.

→ mass; → absorption; → coefficient.

The difference between the rest mass of an atomic nucleus (made up of protons and neutrons) and the sum of the masses of its individual protons and neutrons. The mass difference is equal to the released binding energy. Also called mass deficiency

→ mass; → defect.

The mass per unit area of the ring material, integrated through the thickness of the ring. Sometimes called → surface density (Ellis et al., 2007, Planetary Ring Systems, Springer).

→ mass; → density.

1) For → massive stars and → supergiants, the difference between the → spectroscopic mass and the → evolutionary mass. Early studies found that the spectroscopic mass was systematically less than the evolutionary mass by as much as a factor of 2 for supergiants. Improvements in the stellar atmosphere models (taking into account → line blanketing) have decreased or eliminated the size of the discrepancy for Galactic stars. There is still a mass discrepancy for the hottest → O stars in the → Magellanic Clouds (See, e.g. Massey et al. 2009, ApJ 692, 618).
2) For a → cluster of galaxies, the apparent difference between the mass of the cluster obtained by using the → virial theorem, and the mass inferred from the total luminosities of the member galaxies.

→ mass; → discrepancy.

The energy (E) associated with a mass (m), as specified by the → mass-energy equivalence  E = mc², where c is the → speed of light. For a moving body the total energy of the particle is expressed by: E² = m²c⁴ + p²c², where m is → rest mass and p → momentum.

→ mass; → energy.

An event in the history of life on Earth in which large numbers of species (sometimes more than 90% of some species) vanish in a relatively short period of time. In spite of controversy, it is generally recognized that there have been at least six major mass extinctions. These occurred in the late Cambrian (500 million years ago), in the late Ordovician (440 million years ago), in the late Devonian (365 million years ago), at the end of the Permian (245 million years ago), in the late Triassic (208 million years ago), and at the end of the Cretaceous (65 million years ago).

→ mass; → extinction.

The mass of a fluid that passes a specified unit area in a unit amount of time.

→ mass; → flow.

An → equation expressing the → atomic mass of a → nuclide as a function of its → mass number and the → atomic mass unit.

→ mass; → formula.

The fractional amount (by mass) of a given → chemical element or → nuclide in a given → chemical composition. In chemical composition studies of astrophysical objects the mass fractions of → hydrogen, → helium, and all the remaining chemical elements are usually denoted by the parameter X, Y, and Z, respectively. Their sum is defined as X + Y + Z = 1. The parameter Z is usually referred to as → heavy elements or → metals.

→ mass; → fraction.

1) The number of a class of objects as a function of their mass. → initial mass function (IMF); → present-day mass function (PDMF).
2) A numerical relation between the masses of the two components of a → spectroscopic binary that provides information on the relative masses of the two stars when the spectral lines of only one component can be seen. If M_p is the mass of primary (whose spectrum is known), M_s is the mass of secondary, and i the → angle of inclination of the orbit, the mass function is given by: (M_s³. sin³i) / (M_p + M_s)².

→ mass; → function.

The outpouring of particles and gas from a star, occurring at varying rates and by a variety of processes throughout a star's lifetime. → Bipolar flows are believed to be due to mass loss by forming → protostars, while → massive stars lose their mass through powerful → stellar winds.

→ mass; → loss.

The rate with which the → mass loss process takes place, usually expressed in → solar mass per year. → radiation-driven mass loss. The mass loss rate and the → terminal velocity are anti-correlated, since the → wind momentum is constant, → bi-stability jump.

→ mass loss; → rate.

The total number of → protons and → neutrons in the → atomic nucleus (symbol A). The mass number is written either after the → chemical element name or as a superscript to the left of an element's symbol. For example, the most common isotope of oxygen is oxygen-16, or ¹⁶O, which has 8 protons and 8 neutrons.

→ mass; → number.