An Etymological Dictionary of Astronomy and Astrophysics

1. General: A person of abnormally small height owing to a pathological condition; an animal or plant much smaller than the average of its kind or species.
   

2. Astro.: An adjective characterizing a particular type of object, as in → dwarf star, → dwarf galaxy, → dwarf planet.
   

See also:
→ blue compact dwarf galaxy, → brown dwarf, → brown dwarfcooling, → brown dwarfdesert, → DA white dwarf, → DB white dwarf, → DC white dwarf, → DO white dwarf, → double white dwarf, → DQ white dwarf, → Draco Dwarf, → dwarf Cepheid, → dwarf elliptical galaxy, → dwarf irregular galaxy, → dwarf nova, → dwarf spheroidal galaxy, → dwarf spiral galaxy, → dwarf starburst galaxy, → DZ white dwarf, → L dwarf, → M dwarf, → OB subdwarf, → red dwarf, → Sagittarius Dwarf Elliptical Galaxy, → Sagittarius Dwarf Irregular Galaxy, → Sculptor Dwarf Elliptical Galaxy, → subdwarf, → T dwarf, → tidal dwarf galaxy, → white dwarf, → white dwarf cooling track, → white dwarf crystallization, → Y dwarf.

Etymology (EN): Dwarf, from ME dwerg, dwerf, O.E. dweorg, dweorh, O.H.G. twerg “dwarf,” from P.Gmc. *dweraz.

Etymology (PE): Kutulé, from kut “small, short” + Pers. diminutive suffix -ulé, → -ula. The first component kut is the base of kutâh “short, small, little,” kudak “child, infant,” Mid.Pers. kôtâh “low,” kôtak “small, young; baby;” the Mid/Mod.Pers. kucak “small,” belongs to this fammily; Av. kutaka- “little, small.”

1. General: A person of abnormally small height owing to a pathological condition; an animal or plant much smaller than the average of its kind or species.
   

2. Astro.: An adjective characterizing a particular type of object, as in → dwarf star, → dwarf galaxy, → dwarf planet.
   

See also:
→ blue compact dwarf galaxy, → brown dwarf, → brown dwarfcooling, → brown dwarfdesert, → DA white dwarf, → DB white dwarf, → DC white dwarf, → DO white dwarf, → double white dwarf, → DQ white dwarf, → Draco Dwarf, → dwarf Cepheid, → dwarf elliptical galaxy, → dwarf irregular galaxy, → dwarf nova, → dwarf spheroidal galaxy, → dwarf spiral galaxy, → dwarf starburst galaxy, → DZ white dwarf, → L dwarf, → M dwarf, → OB subdwarf, → red dwarf, → Sagittarius Dwarf Elliptical Galaxy, → Sagittarius Dwarf Irregular Galaxy, → Sculptor Dwarf Elliptical Galaxy, → subdwarf, → T dwarf, → tidal dwarf galaxy, → white dwarf, → white dwarf cooling track, → white dwarf crystallization, → Y dwarf.

Etymology (EN): Dwarf, from ME dwerg, dwerf, O.E. dweorg, dweorh, O.H.G. twerg “dwarf,” from P.Gmc. *dweraz.

Etymology (PE): Kutulé, from kut “small, short” + Pers. diminutive suffix -ulé, → -ula. The first component kut is the base of kutâh “short, small, little,” kudak “child, infant,” Mid.Pers. kôtâh “low,” kôtak “small, young; baby;” the Mid/Mod.Pers. kucak “small,” belongs to this fammily; Av. kutaka- “little, small.”

An old name for a class of pulsating variable stars with small variations in amplitude, also called an AI Velae star or delta Scuti star. They lie in the lower part of the Cepheid instability strip.

See also: → dwarf; → Cepheid.

An old name for a class of pulsating variable stars with small variations in amplitude, also called an AI Velae star or delta Scuti star. They lie in the lower part of the Cepheid instability strip.

See also: → dwarf; → Cepheid.

A galaxy that is much smaller than other members of the elliptical class; it is designated as dE. A subtype of dwarf ellipticals is called a → dwarf spheroidal galaxy (dSph). The basic characteristics of the class are low surface brightness and smooth light distribution. They range in luminosity from that of the faintest dSph galaies M_V ~ -9 to about -17. In the → Local Group there are 19 known dEs. They are very common in → galaxy clusters.

See also: → dwarf; → elliptical; → galaxy.

A galaxy that is much smaller than other members of the elliptical class; it is designated as dE. A subtype of dwarf ellipticals is called a → dwarf spheroidal galaxy (dSph). The basic characteristics of the class are low surface brightness and smooth light distribution. They range in luminosity from that of the faintest dSph galaies M_V ~ -9 to about -17. In the → Local Group there are 19 known dEs. They are very common in → galaxy clusters.

See also: → dwarf; → elliptical; → galaxy.

A small, low luminosity galaxy that is associated with a larger spiral galaxy and may make up part of a galactic halo. There are many of them in the Local Group, and often orbit around larger galaxies such as the Milky Way and the Andromeda Galaxy. There are three main types of them: → dwarf elliptical galaxy (dE), → dwarf irregular galaxy (dI), and → dwarf spiral galaxy (dSA).

See also: → dwarf; → galaxy.

A small, low luminosity galaxy that is associated with a larger spiral galaxy and may make up part of a galactic halo. There are many of them in the Local Group, and often orbit around larger galaxies such as the Milky Way and the Andromeda Galaxy. There are three main types of them: → dwarf elliptical galaxy (dE), → dwarf irregular galaxy (dI), and → dwarf spiral galaxy (dSA).

See also: → dwarf; → galaxy.

An irregular galaxy that is much smaller than other irregulars. Dwarf irregulars are generally metal poor and have relatively high fractions of gas. They are thought to be similar to the earliest galaxies that populated the Universe, and are therefore important to understand the overall evolution of galaxies.

See also: → dwarf; → irregular; → galaxy.

An irregular galaxy that is much smaller than other irregulars. Dwarf irregulars are generally metal poor and have relatively high fractions of gas. They are thought to be similar to the earliest galaxies that populated the Universe, and are therefore important to understand the overall evolution of galaxies.

See also: → dwarf; → irregular; → galaxy.

A class of → novae and → cataclysmic variables that have multiple observed → eruptions. Their prototype is → U Geminorum star. Optically, dwarf nova eruptions have amplitudes
of 2-6 mag in V, a duration of a few to 20 days and a recurrence time-scale of weeks to years. Dwarf novae are thought to be → semidetached binary stars consisting of a → white dwarf  → primary accreting via → Roche lobe overflow from a → companion which is usually a → late-type, generally → main-sequence star. DN outbursts are usually attributed to the release of gravitational energy resulting from an → instability in the → accretion disk or by sudden mass transfers through the disk.

See also: → dwarf; → nova.

A class of → novae and → cataclysmic variables that have multiple observed → eruptions. Their prototype is → U Geminorum star. Optically, dwarf nova eruptions have amplitudes
of 2-6 mag in V, a duration of a few to 20 days and a recurrence time-scale of weeks to years. Dwarf novae are thought to be → semidetached binary stars consisting of a → white dwarf  → primary accreting via → Roche lobe overflow from a → companion which is usually a → late-type, generally → main-sequence star. DN outbursts are usually attributed to the release of gravitational energy resulting from an → instability in the → accretion disk or by sudden mass transfers through the disk.

See also: → dwarf; → nova.

A new category of → astronomical objects in the → solar system introduced in a resolution by the 26th General Assembly of the → International Astronomical Union (IAU) on August 24, 2006. The characterizing properties are as follows:

1. It is in orbit around the Sun;
2. It has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a → hydrostatic equilibrium (nearly round) shape;
3. It has not “cleared the neighbourhood” around its orbit; and
4. It is not a → satellite of a → planet, or other non-stellar body. The property 3 reclassified → Pluto from a planet to a dwarf planet because it has not cleared the neighborhood of its orbit (the → Kuiper Belt). The largest known dwarf planets are: → Eris, → Pluto,
   → Ceres, → Makemake, and → 2015 RR245.

See also: → dwarf; → planet.

A new category of → astronomical objects in the → solar system introduced in a resolution by the 26th General Assembly of the → International Astronomical Union (IAU) on August 24, 2006. The characterizing properties are as follows:

1. It is in orbit around the Sun;
2. It has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a → hydrostatic equilibrium (nearly round) shape;
3. It has not “cleared the neighbourhood” around its orbit; and
4. It is not a → satellite of a → planet, or other non-stellar body. The property 3 reclassified → Pluto from a planet to a dwarf planet because it has not cleared the neighborhood of its orbit (the → Kuiper Belt). The largest known dwarf planets are: → Eris, → Pluto,
   → Ceres, → Makemake, and → 2015 RR245.

See also: → dwarf; → planet.

A subtype of dwarf ellipticals (→ dwarf elliptical galaxy), which are companion to the → Milky Way and other similar galaxies. The first example of such objects was discovered by Harlow Shapley (1938) in the constellation → Sculptor. 22 such galaxies are known currently to orbit the Milky Way and at least 36 exist in the → Local Group of galaxies.

Nearby → galaxy clusters such as the → Virgo, → Fornax, → Centaurus, and → Coma clusters contain hundreds to thousands of individual dSph galaxies.
These galaxies have very low → surface brightnesses, as low as only 1% that of the → sky background. They are also among the smallest, least luminous galaxies known. Most of the radiation from dSph galaxies is emitted by stars in the optical portion of the → electromagnetic spectrum. The lack of strong → emission lines, → infrared, or → radio emission suggests that these galaxies are generally devoid of → interstellar medium. The velocities of stars within dSph galaxies are so high that them must be disrupting. However, the bulk of mass in these galaxies might be undetected. Dynamical models that include → dark matter do adequately explain the → velocity dispersion of the stars in all dSph systems. In the most extreme cases, only 1% of the mass of the galaxy is visible. Many of the Local Group dSph galaxies show evidence for → star formation more recent than 10 Gyr.

See also: → dwarf; → spheroidal; → galaxy.

A subtype of dwarf ellipticals (→ dwarf elliptical galaxy), which are companion to the → Milky Way and other similar galaxies. The first example of such objects was discovered by Harlow Shapley (1938) in the constellation → Sculptor. 22 such galaxies are known currently to orbit the Milky Way and at least 36 exist in the → Local Group of galaxies.

Nearby → galaxy clusters such as the → Virgo, → Fornax, → Centaurus, and → Coma clusters contain hundreds to thousands of individual dSph galaxies.
These galaxies have very low → surface brightnesses, as low as only 1% that of the → sky background. They are also among the smallest, least luminous galaxies known. Most of the radiation from dSph galaxies is emitted by stars in the optical portion of the → electromagnetic spectrum. The lack of strong → emission lines, → infrared, or → radio emission suggests that these galaxies are generally devoid of → interstellar medium. The velocities of stars within dSph galaxies are so high that them must be disrupting. However, the bulk of mass in these galaxies might be undetected. Dynamical models that include → dark matter do adequately explain the → velocity dispersion of the stars in all dSph systems. In the most extreme cases, only 1% of the mass of the galaxy is visible. Many of the Local Group dSph galaxies show evidence for → star formation more recent than 10 Gyr.

See also: → dwarf; → spheroidal; → galaxy.

A galaxy that belongs to the spiral class but is significantly smaller.

See also: → dwarf; → spiral; → galaxy.

A galaxy that belongs to the spiral class but is significantly smaller.

See also: → dwarf; → spiral; → galaxy.

A star that burns its hydrogen content to produce its energy and therefore belongs
to the main-sequence luminosity class.

See also: → dwarf; → star.

A star that burns its hydrogen content to produce its energy and therefore belongs
to the main-sequence luminosity class.

See also: → dwarf; → star.

A → starburst galaxy that is a → dwarf galaxy. Examples include: the → dwarf irregular galaxy IC 10, the compact dwarf irregular Henize 2-10, and the dwarf irregular galaxy NGC 5253.

See also: → dwarf; → starburst; → galaxy.

A → starburst galaxy that is a → dwarf galaxy. Examples include: the → dwarf irregular galaxy IC 10, the compact dwarf irregular Henize 2-10, and the dwarf irregular galaxy NGC 5253.

See also: → dwarf; → starburst; → galaxy.