An Etymological Dictionary of Astronomy and Astrophysics

Of limited size; of comparatively restricted dimensions; not large. → method of small perturbations; → Small Magellanic Cloud (SMC).

Etymology (EN): M.E. smale; O.E. smæl “slender, narrow, small;” cf. Dan., Swed., M.Du., Du., O.H.G. smal, O.Fris. smel, Ger. schmal “narrow,” Goth. smalista “smallest.”

Etymology (PE): Kucak “small;” Mid.Pers. kucak “small,” related to kutâh “short, small, little,” kudak “child, infant,” kutulé, → dwarf; Mid.Pers. kôtâh “low,” kôtak “small, young; baby;” Av. kutaka- “little, small.”
Kam “little, few; deficient, wanting; scarce,” from Mid.Pers. kam “little, small, few,” O.Pers./Av. kamna- “small, few.”

Of limited size; of comparatively restricted dimensions; not large. → method of small perturbations; → Small Magellanic Cloud (SMC).

Etymology (EN): M.E. smale; O.E. smæl “slender, narrow, small;” cf. Dan., Swed., M.Du., Du., O.H.G. smal, O.Fris. smel, Ger. schmal “narrow,” Goth. smalista “smallest.”

Etymology (PE): Kucak “small;” Mid.Pers. kucak “small,” related to kutâh “short, small, little,” kudak “child, infant,” kutulé, → dwarf; Mid.Pers. kôtâh “low,” kôtak “small, young; baby;” Av. kutaka- “little, small.”
Kam “little, few; deficient, wanting; scarce,” from Mid.Pers. kam “little, small, few,” O.Pers./Av. kamna- “small, few.”

Same as → Little Dipper.

See also: → small; → Little Dipper.

Same as → Little Dipper.

See also: → small; → Little Dipper.

An irregular galaxy, the smaller of the two → Magellanic Clouds that are satellites of our own Galaxy, lying in the southern constellation → Tucana about 20 degrees from the → south celestial pole. The SMC covers an area roughly 3 by 5 degrees in dimension and has an overall → visual magnitude about +2.7. The SMC is about 10,000 → light-years in diameter and some 210,000 light-years (61 → kpc) away. It has a visible mass of about 1/50-th that of our Galaxy and 1/10-th of that of the → Large Magellanic Cloud (LMC). Its → heavy element content is about a factor 5 smaller than that of the Galaxy. The SMC is the third-nearest external galaxy after the → Sagittarius Dwarf Elliptical Galaxy and the LMC.

See also: → small; → Magellanic; → cloud.

An irregular galaxy, the smaller of the two → Magellanic Clouds that are satellites of our own Galaxy, lying in the southern constellation → Tucana about 20 degrees from the → south celestial pole. The SMC covers an area roughly 3 by 5 degrees in dimension and has an overall → visual magnitude about +2.7. The SMC is about 10,000 → light-years in diameter and some 210,000 light-years (61 → kpc) away. It has a visible mass of about 1/50-th that of our Galaxy and 1/10-th of that of the → Large Magellanic Cloud (LMC). Its → heavy element content is about a factor 5 smaller than that of the Galaxy. The SMC is the third-nearest external galaxy after the → Sagittarius Dwarf Elliptical Galaxy and the LMC.

See also: → small; → Magellanic; → cloud.

A term introduced by the → International Astronomical Union (August 2006) to name the → solar system bodies other than → planets and → dwarf planets. Small solar system bodies include → asteroids, → comets, and → meteoroids.

See also: → small; → solar; → system; → body.

A term introduced by the → International Astronomical Union (August 2006) to name the → solar system bodies other than → planets and → dwarf planets. Small solar system bodies include → asteroids, → comets, and → meteoroids.

See also: → small; → solar; → system; → body.

An asteroid taxonomy built on the → Tholen classification but based on the presence or absence of → absorption features in the visible part of the spectrum. In many cases the two classifications are the same, but the Tholen C and S classes are subdivided in the SMASS classification.

See also: SMASS stands for the Small Main-belt Asteroid Spectroscopic Survey, → small; → main belt; → asteroid; → spectroscopic; → survey; → classification.

An asteroid taxonomy built on the → Tholen classification but based on the presence or absence of → absorption features in the visible part of the spectrum. In many cases the two classifications are the same, but the Tholen C and S classes are subdivided in the SMASS classification.

See also: SMASS stands for the Small Main-belt Asteroid Spectroscopic Survey, → small; → main belt; → asteroid; → spectroscopic; → survey; → classification.

A huge, → high-velocity cloud of hydrogen gas that measures some 9,800 × 3,300 → light-years. It is located between 36,000 and 45,000 light-years away from Earth in the northern constellation of → Aquila. It has a mass of at least 10⁶ → solar masses. It is now moving toward the disk of the → Milky Way at 73 ± 26 km/s and is expected to hit the disk of our Galaxy in about 27 million years, at an angle of approximately 45° at a point in the → Perseus Arm, one of two major → spiral arms of the Galaxy.

See also: Named after Gail Bieger, née Smith, who discovered the cloud in 1963,
when she was an astronomy student at Leiden University in the Netherlands; → cloud.

A huge, → high-velocity cloud of hydrogen gas that measures some 9,800 × 3,300 → light-years. It is located between 36,000 and 45,000 light-years away from Earth in the northern constellation of → Aquila. It has a mass of at least 10⁶ → solar masses. It is now moving toward the disk of the → Milky Way at 73 ± 26 km/s and is expected to hit the disk of our Galaxy in about 27 million years, at an angle of approximately 45° at a point in the → Perseus Arm, one of two major → spiral arms of the Galaxy.

See also: Named after Gail Bieger, née Smith, who discovered the cloud in 1963,
when she was an astronomy student at Leiden University in the Netherlands; → cloud.

A fog combined with smoke or other forms of atmospheric pollutants in an unhealthy or irritating mixture.

Etymology (EN): From sm(oke) + (f)og; → smoke; → fog.

Etymology (PE): Dudmeh, from dud, → smoke,

• meh, → fog.

A fog combined with smoke or other forms of atmospheric pollutants in an unhealthy or irritating mixture.

Etymology (EN): From sm(oke) + (f)og; → smoke; → fog.

Etymology (PE): Dudmeh, from dud, → smoke,

• meh, → fog.

A mass of tiny particles in the air that rises up from something burning.

Etymology (EN): M.E., O.E. smoca, related to smeocan “give off smoke;” cf. M.Du. smooc, Du. smook, M.H.G. smouch, Ger. Schmauch; PIE base *smeug(h)- “smoke” (cf. Arm. mux “smoke,” Gk. smukho “to burn in a smoldering fire,” O.Ir. much, Welsh mwg “smoke”).

Etymology (PE): Dud, from Mid.Pers. dût, dûd “smoke;” Av. dunman- “cloud,” duuan- “to fly;” cf. Skt. dhvan- “to smoke;” Hittite tuhhae- “to prouce smoke;” PIE base *dheu- “to blow, reel; smoke, dark.”

A mass of tiny particles in the air that rises up from something burning.

Etymology (EN): M.E., O.E. smoca, related to smeocan “give off smoke;” cf. M.Du. smooc, Du. smook, M.H.G. smouch, Ger. Schmauch; PIE base *smeug(h)- “smoke” (cf. Arm. mux “smoke,” Gk. smukho “to burn in a smoldering fire,” O.Ir. much, Welsh mwg “smoke”).

Etymology (PE): Dud, from Mid.Pers. dût, dûd “smoke;” Av. dunman- “cloud,” duuan- “to fly;” cf. Skt. dhvan- “to smoke;” Hittite tuhhae- “to prouce smoke;” PIE base *dheu- “to blow, reel; smoke, dark.”

1. Of a curve, free from bumps or abrupt irregularities.
   
2. To modify a sequential set of numerical data by reducing the differences in magnitude between adjacent values.

Etymology (EN): O.E. smoð “free from roughness, not harsh,” of unknown origin.

Etymology (PE): Hamvâr “level, equal, an even place or thing,” from ham- “same, equally, even; together, with” (Mid.Pers. ham-, like L. com- and Gk. syn- with neither of which it is cognate. O.Pers./Av. ham-, Skt. sam-; also O.Pers./Av. hama- “one and the same,” Skt. sama-, Gk. homos-;
originally identical with PIE numeral *sam- “one,” from *som-. The Av. ham- appears in various forms: han- (before gutturals, palatals, dentals) and also hem-, hen-) + -vâr similarity suffix.

1. Of a curve, free from bumps or abrupt irregularities.
   
2. To modify a sequential set of numerical data by reducing the differences in magnitude between adjacent values.

Etymology (EN): O.E. smoð “free from roughness, not harsh,” of unknown origin.

Etymology (PE): Hamvâr “level, equal, an even place or thing,” from ham- “same, equally, even; together, with” (Mid.Pers. ham-, like L. com- and Gk. syn- with neither of which it is cognate. O.Pers./Av. ham-, Skt. sam-; also O.Pers./Av. hama- “one and the same,” Skt. sama-, Gk. homos-;
originally identical with PIE numeral *sam- “one,” from *som-. The Av. ham- appears in various forms: han- (before gutturals, palatals, dentals) and also hem-, hen-) + -vâr similarity suffix.

1. A curve which is free from abrupt fluctuations.
   

2. A curve if it has tangents at all points and the angle of inclination of the tangent is a continuous function of the arc length.

See also: → smooth; → curve.

1. A curve which is free from abrupt fluctuations.
   

2. A curve if it has tangents at all points and the angle of inclination of the tangent is a continuous function of the arc length.

See also: → smooth; → curve.

A numerical method for modeling → compressible hydrodynamic flows, which uses particles to simulate a continuous fluid flow. Because the system of hydrodynamical basic equations can be analytically solved only for few exceptional cases, the SPH method provides a numerical algorithm to solve systems of coupled → partial differential equations for continuous field quantities. The main advantage of the method is that it does not require a computational grid to calculate spatial → derivatives and that it is a Lagrangian method, which automatically focuses attention on fluid elements. The equations of motion and continuity are expressed in terms of ordinary differential equations where the body forces become classical forces between particles. This method was first independently developed by Lucy (1977, AJ 82, 1013) and Gingold & Monaghan (1977, MNRAS 181, 375).

See also: Smoothed Particle Hydrodynamics, first used by Gingold & Monaghan (1977); → smooth; → particle; → hydrodynamics.

A numerical method for modeling → compressible hydrodynamic flows, which uses particles to simulate a continuous fluid flow. Because the system of hydrodynamical basic equations can be analytically solved only for few exceptional cases, the SPH method provides a numerical algorithm to solve systems of coupled → partial differential equations for continuous field quantities. The main advantage of the method is that it does not require a computational grid to calculate spatial → derivatives and that it is a Lagrangian method, which automatically focuses attention on fluid elements. The equations of motion and continuity are expressed in terms of ordinary differential equations where the body forces become classical forces between particles. This method was first independently developed by Lucy (1977, AJ 82, 1013) and Gingold & Monaghan (1977, MNRAS 181, 375).

See also: Smoothed Particle Hydrodynamics, first used by Gingold & Monaghan (1977); → smooth; → particle; → hydrodynamics.

An average of 13 monthly → sunspot numbers, centered on the month of concern. The 1st and 13th months are given a weight of 0.5.

See also: → smooth; → sunspot; → number.

An average of 13 monthly → sunspot numbers, centered on the month of concern. The 1st and 13th months are given a weight of 0.5.

See also: → smooth; → sunspot; → number.

The mathematical process that makes a curve smooth.

See also: Verbal noun of → smooth.

The mathematical process that makes a curve smooth.

See also: Verbal noun of → smooth.

A low-pass filter designed to reduce the amplitude of a ripple while freely passing the direct current obtained from a rectifier or direct-current generator. Also known as smoothing filter.

See also: → smoothing; → circuit.

A low-pass filter designed to reduce the amplitude of a ripple while freely passing the direct current obtained from a rectifier or direct-current generator. Also known as smoothing filter.

See also: → smoothing; → circuit.