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

Old stars with very low metallicities (→ metallicity) found in the → halo of the Galaxy. Also called → population II star.

→ halo; → population.

A faint, wide ring around → Jupiter that has the shape of a doughnut. It is about 22,800 km wide and about 20,000 km thick. This ring starts at 100,000 km from the center of Jupiter. The outer edge of the Halo merges into the → Main ring.

→ halo; → ring.

A member of a group of five chemical elements having closely related and similar properties. The halogens are: fluorine, chlorine, iodine, bromine, and astatine. They make up Group 17 of the → periodic table and can be found on the left-hand side of the → noble gases.

From Gk. halo- prefix from Gk. hals "salt" + → -gen.

The brightest star in the constellation → Aries. Hamal is a cool → giant of → spectral type K2 with a → luminosity about 55 times that of the Sun and lies about 65 light-years away.

Hamal, from Ar., shortened form of Ra's al-Hamal (رأس‌الحمل), "the head of the sheep."

One of a set of equations that describe the motion of a → dynamical system in terms of the → Hamiltonian function and the → generalized coordinates. For a → holonomic system with n degrees of freedom, Hamilton's equations are expressed by: q^._i = ∂H/∂p_i and p^._i = - ∂H/∂q_i, i = 1, ..., n.

→ Hamiltonian function; → equation.

Of all the possible paths along which a → dynamical system can move from one configuration to another within a specified time interval (consistent with any constraints), the actual path followed is that which minimizes the time integral of the → Lagrangian function. Hamilton's principle is often mathematically expressed as δ∫Ldt = 0, where L is the Lagrangian function, the integral summed from t₁ to t₂, and δ denotes the virtual operator of Lagrangian dynamics and the → calculus of variations.

→ Hamiltonian function; → principle.

The study of → dynamical systems in terms of the → Hamilton's equations.

→ Hamiltonian function; → dynamics.

A reformulation of classical mechanics that predicts the same outcomes as classical mechanics. → Hamiltonian dynamics.

→ Hamiltonian; → mechanics.

A function that describes the motion of a → dynamical system in terms of the → Lagrangian function, → generalized coordinates, → generalized momenta, and time. For a → holonomic system having n degrees of freedom, the Hamiltonian function is of the form: H = Σp_iq^._i - L(q_i,q^._i,t) (summed from i = 1 to n), where L is the Lagrangian function. If L does not depend explicitly on time, the system is said to be → conservative and H is the total energy of the system. The Hamiltonian function plays a major role in the study of mechanical systems. Also called → Hamiltonian.

Introduced in 1835 by the Irish mathematician and physicist William Rowan Hamilton (1805-1865); → function.

The dynamical operator in → quantum mechanics that corresponds to the → Hamiltonian function in classical mechanics.

→ Hamiltonian function; → operator.

A small → village.

M.E. hamlet, hamelet, from O.Fr. hamelet "small village," diminutive of O.Fr. hamel "village," itself diminutive of ham "village;" of Germanic origin; cf. E. home, O.E. ham, Du. heem, Ger. Heim; cognate with → city.

Kalâ, from Tabari kalâ "village, borough." Dozens of village names contain kalâ az suffix in Mâzandarân and Gilan.

1) The terminal part of the forelimb in humans and other primates.
2) A part serving the function of or resembling a hand.

M.E. O.E. hond, hand "hand; side; power;" cf. O.S., O.Fris., Du., Ger. hand, O.N. hönd, Goth. handus.

Dast "hand; strength; superiority;" Mid.Pers. dast; O.Pers. dasta-; Av. zasta-; cf. Skt. hásta-; Gk. kheir; L. praesto "at hand;" Arm. jern "hand;" Lith. pa-žastis "arm-pit;" PIE *ghes-to-.

A scholarly book on a specific subject that is conveniently handled.

→ hand; → book.

1) A tendency to use one hand rather than the other.
2) The property of an object (as a molecule) of not being identical with its mirror image. Same as → chirality (Merriam-Webster.com).
See also: → B-mode polarization, → E-mode polarization.

→ hand + -ed + → -ness.

Dastâli, from dast, → hand, + -al, → -al, + noun suffix -i, on the model of → chirality.

The → polarization arising from line scattering in the presence of "weak" magnetic fields. The effect occurs when precession around magnetic field depolarizes and rotates polarization of the scattered light. The Hanle effect is sensitive to ~10³ times smaller field strengths than the → Zeeman effect. It is in particular used to measure the weak magnetic field of the solar → prominences, which is 10^-3 tesla and over 10^-2 tesla for the active prominences.

Named for the German physicist Wilhelm Hanle (1901-1993), who published his his discovery in 1923 (Naturwissenschaften 11, 690); → effect.

Take place; occur; befall.

M.E. hap(pe)nen, from hap "luck, chance" + -en.

Fatidan, variant of oftâdan, fotâdan "to fall; to be fall, occur;" Sistani aft, aftid "to → fall."

An → event or occurrence.

Verbal noun of → happen; → -ing.

To disturb persistently; bother continually. → galaxy harassment.

From M.Fr. harasser "tire out, vex," possibly from O.Fr. harer "set a dog on," and perhaps blended with O.Fr. harier "to harry, draw, drag."

Sotuhidan, infinitive from sotuh, → harassed.

Subject to → harassment.

P.p. of → harass.

Sotuh "afflicted, distressed, helpless," from Mid.Pers. stô "distressed, defeated;" O.Pers. us-tav-, from us- "out, without," ultimately from *ustau- "unable, weak," from *us- "out," → ex-, + *tau- "to be able," → power.

The act or an instance of harassing. → galaxy harassment.

Verbal noun of → harass.