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

A compact stellar remnant (e.g., a → white dwarf, → neutron star, or → black hole) that undergoes → inspiral into a much more massive object (→ supermassive black hole found → galactic centers). EMRIs are potential sources of low-frequency → gravitational waves. Predictions of the EMRI event rates span a wide range, from ~ 10^-9 to 10^-6 yr^-1 per galaxy (Merritt et al. 2011, Physical Review D 84, 044024). See also → resonant relaxation.

→ extreme; → mass; → ratio; → inspiral.

A part of the ultraviolet radiation with wavelengths between 50 and 300 Angstöms.

→ extreme; → ultraviolet.

A star with an iron abundance [Fe/H] < -3 found in a → galactic halo. These stars, whose → metallicity is typically less than one thousandth of the solar value, are believed to have formed shortly after the → Big Bang, 13.7 billion years ago. The number of such stars depends on the primordial → initial mass function. If the IMF were steep, there could, in principle, be a lot of EMPSs formed at high → redshifts. Thus many of them could have ended up in the halos of galaxies. See also → Population III star.

→ extreme; → metal; → poor; → star.

A → microorganism with the ability to thrive in extreme environmental conditions that would kill other species. These conditions include high temperatures, very low temperatures, high pressures, high levels of radiation, and high concentrations of salt in water.

→ extreme; → -phile.

A maximum or minimum value of a function in a specified interval.

From L. extremus, → extreme.

Ostomé, from ostom, → extreme + noun suffix -é, from Mid.Pers. -ag.

In → number theory, the statement that for all → integers, the equation xⁿ + yⁿ = zⁿ has no solution in → positive integer. After 358 years of effort by mathematicians to prove the theorem, a complete proof was found by Andrew Wiles in 1995.

→ Fermat's principle; → last; → theorem.

Any finite periodic motion may be analyzed into components, each of which is a simple harmonic motion of definite and determinable amplitudes and phase.

→ Fourier analysis; → theorem.

The total normal induction over any closed surface drawn in an electric field is equal to 4π times the total charge of electricity inside the closed surface. Gauss's theorem applies also to other vector fields such as magnetic, gravitational, and fluid velocity fields. The theorem can more generally be stated as: the total flux of a vector field through a closed surface is equal to the volume → integral of the vector taken over the enclosed volume. Also known as → divergence theorem, Ostrogradsky's theorem, and Gauss-Ostrogradsky theorem.

→ gauss; → theorem.

A → decomposition theorem, whereby a continuous → vector field, F, can be broken down into the sum of a → gradient and a → curl term: F = -∇φ + ∇ xA, where φ is called the → scalar potential and A the → vector potential.

→ Helmholtz free energy; → theorem.

The amount by which a varying quantity increases between two of its stages. In → calculus, the Greek letter Δ (delta) is used to denote an increment; e.g. Δx is an increment of x, contrasted to → decrement.

Increment, from L. incrementum "growth, increase," from stem of increscere "to grow in or upon" from → in- "in" + crescere "to grow."

Fazâyé, from fazâ shortened present stem of afzudan "to add, increase" (Mid.Pers. abzudan "to increase, grow;" O.Pers. abijav- "to increase, add to, promote," from abi-, aiby- "in addition to; to; against" + root jav- "press forward;" Av. gav- "to hasten, drive;" Skt. jav- "to press forward, impel quickly, excite," javate "hastens") + -y- euphonic infix + -é noun/nuance suffix.

The absorption of a photon by an electron in a strong electric field. → bremsstrahlung.

→ inverse; → bremsstrahlung.

If a system of → charged particles, all having the same ratio of charge to mass (q/m), acted on by their mutual forces, and by a central force toward a common center, is subject in addition to a weak uniform magnetic field (B), its possible motions will be the same as the motions it could perform without the magnetic field, superposed upon a slow → precession of the entire system about the center of force with angular velocity ω = -(q/2mc)B.

→ Larmor frequency; → theorem.

A key theorem in statistical mechanics of classical systems which states that the motion of phase-space points defined by Hamilton's equations conserves phase-space volume.

After Joseph Liouville (1809-1882), a French mathematician; → theorem.

Same as → synchrotron radiation.

→ magnetic; → bremsstrahlung.

Logic: In a → categorical syllogism, the premise containing the → major term.

→ major; → premisse.

1) If f(x) is a continuous function on the interval from a to b, then:
∫ f(x) dx = f(c)(b - a) (summed from a to b) for at least one point in that interval.
2) More generally, If f(x) and g(x) are continuous functions on the interval from a to b and g(x)≥ 0, then:
∫ f(x)g(x) dx = f(c) ∫ g(x) dx (both integrals summed from a to b).

→ mean; → value; → theorem.

1) The act of measuring; a measured quantity.
2) The determination of the magnitude or amount of a quantity by comparison (direct or indirect) with the prototype standards of the system of units employed (IEEE Standard Dictionary of Electrical and Electronics Terms). → absolute measurement, → measurement uncertainty, → Roemer's measurement.

Verbal noun of → measure.

The interval within which lies the actually measured value of a physical quantity and the true value of the same physical quantity.

→ measurement; uncertainty, from negation prefix un- + → certainty.

Logic: In a → categorical syllogism, the premise containing the → minor term.

→ major; → premisse.

The entropy change for chemical reactions involving crystalline solid is zero at the absolute zero of temperature. Also known as the third law of thermodynamics.

→ Nernst effect; → heat; → theorem.