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

A branch of astrophysics that deals with objects emitting highly energetic radiation, such as X-ray astronomy, gamma-ray astronomy, and extreme ultraviolet astronomy, as well as neutrinos and cosmic rays.

→ high; → energy; → astrophysics.

Cosmic rays which typically have energies in the range 10¹⁵ to 10²⁰ electron volts. For the most part, they are protons and other atomic nuclei, and come from distant cosmos, perhaps even from outside our own Galaxy.

→ high; → energy; → cosmic; → ray.

A neutrino produced in high-energy particle collisions, such as those occurring when → cosmic rays strike atoms in the Earth's → atmosphere. Their energy range expands from a few → MeVs up to tenths of a → peta- (P) → electron-volts.

→ high; → energy; → neutrino.

A system consisting of a dominant → spiral galaxy associated with → dwarf satellite galaxies and intergalactic matter. Examples in the → Local Group are our Galaxy and the → Andromeda galaxy.

→ hyper- + → galaxy.

A high luminosity star with absolute visual magnitude around -10, about 10⁶ times as luminous as the Sun. Hypergiant stars are evolved → massive stars belonging to the luminosity class Ia+ or Ia0. Their spectra show very broadened emission and absorption lines resulting from the high luminosity and low surface gravity which favor strong → stellar wind. See also → Humphreys-Davidson limit; → yellow hypergiant.

→ hyper-; → giant.

A large mass of floating or stranded ice that has broken away from a glacier; usually more than 5 m above sea level.

Iceberg, half Anglicization, half adoption of Du. ijsberg "ice mountain," from ijs, → ice, + berg "mountain" (cf. Ger. Eisberg, Sw. isberg), from P.Gmc. *bergaz; cf. M.H.G. berc, O.H.G. berg "mountain;" cognate with Pers. boland, borz, berg, as below; PIE base *bheregh- "high, elevated."

Yaxberg, from yax, → ice, + berg "mountain, hill," in Laki dialect, related to Pers. boland "high," 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. & 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."

To plunge into or place under a liquid; dip; sink (Dictionary.com).

→ in- + merge, → submerge.

Of, existing, or occurring in the space between galaxies. → intergalactic absorption, → intergalactic cloud, → intergalactic matter , → intergalactic medium , → warm-hot intergalactic medium.

→ inter-; → galactic.

→ Absorption features in the spectra of bright sources like → quasars attributed to a tenuous matter filling the medium between galaxies.

→ intergalactic; → absorption.

→ Intergalactic matter in the form of clouds.

→ intergalactic; → cloud.

Very low density material found indirectly in the space between galaxies. → intergalactic absorption.

→ intergalactic; → matter.

The matter or environment between the galaxies of a → cluster.

→ intergalactic; → medium.

The difference between the energy added to a system and the energy given up by the system in performing work.

→ internal; → energy.

Same as → ionization potential.

→ ionization; → energy.

The energy which a body possesses as a consequence of its motion, defined as one-half the product of its mass m and the square of its speed v, i.e. 1/2 mv².

→ kinetic; → energy.

The energy required to separate an ion from a → crystal to an infinite distance. In other words, the energy released when one → mole of a crystal is formed from gaseous ions.

→ lattice; → energy.

A neutrino which is mainly produced in → nuclear processes, such as the ones in the → Sun (→ solar neutrino), or in the center of an exploding → supernova. Such neutrinos are, however, more energetic than those making up the → cosmic neutrino background.

→ low; → energy; → neutrino.

The energy stored in a magnetic field. It is the → work that must be done to establish a magnetic field in terms of the → magnetic induction. Magnetic energy varies as the square of the magnetic induction. It can be expressed in several other ways, for example in terms of the current and of the magnetic flux, or in terms of the current density and vector potential.

→ magnetic; → energy.

The → merging of two spiral galaxies with roughly equal masses colliding at appropriate angles. The dynamical friction is so efficient that the galaxies merge after only a few perigalactic passages.

→ major; → merger.

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.