An Etymological Dictionary of Astronomy and Astrophysics

A version of the → H-R diagram displaying stellar gravities (→ gravity, log g) against the corresponding → effective temperatures (T_eff).

See also: Named after the group of astrophysicists (W.-R. Hamann, W. Schmutz, U. Wessolowski) working at Kiel University (Germany), who introduced the diagram in 1980s; → diagram.

A version of the → H-R diagram displaying stellar gravities (→ gravity, log g) against the corresponding → effective temperatures (T_eff).

See also: Named after the group of astrophysicists (W.-R. Hamann, W. Schmutz, U. Wessolowski) working at Kiel University (Germany), who introduced the diagram in 1980s; → diagram.

A → vector field on a → Riemannian manifold (or → pseudo-Riemannian manifold) that preserves the → metric. In other words, the → derivative of the metric with respect to this vector field is null.

See also: Named after the German mathematician Wilhelm Killing (1847-1923); → vector.

A → vector field on a → Riemannian manifold (or → pseudo-Riemannian manifold) that preserves the → metric. In other words, the → derivative of the metric with respect to this vector field is null.

See also: Named after the German mathematician Wilhelm Killing (1847-1923); → vector.

A prefix meaning 10³.

See also: Introduced in France in 1795, when the → metric system was officially adopted, from Gk. khilioi “thousand,” of unknown origin.

A prefix meaning 10³.

See also: Introduced in France in 1795, when the → metric system was officially adopted, from Gk. khilioi “thousand,” of unknown origin.

The basic unit of mass in the
→ International System of Units (SI) and → MKS versions of the → metric system, equal to 1,000 → grams. The kilogram was until 2019 defined as the mass of the standard (international prototype) kilogram, a platinum-iridium cylinder kept at the International Bureau of Weights and Measures (BIPM), at Sèvre, near Paris, France. Copies of this prototype are kept by the standards agencies of all the major industrial nations.
A kilogram is equal to the mass of 1,000 cubic cm of water at 4°C (→ maximum density).

According to the new (2019) definition, the kilogram is defined by taking the fixed numerical value of the → Planck constant (h) to be 6.62607015 × 10^-34 when expressed in the unit J.s, which is equal to kg m² s^-1, where the meter and the second are defined in terms of c and Δν Cs.

See also: → kilo-; → gram.

The basic unit of mass in the
→ International System of Units (SI) and → MKS versions of the → metric system, equal to 1,000 → grams. The kilogram was until 2019 defined as the mass of the standard (international prototype) kilogram, a platinum-iridium cylinder kept at the International Bureau of Weights and Measures (BIPM), at Sèvre, near Paris, France. Copies of this prototype are kept by the standards agencies of all the major industrial nations.
A kilogram is equal to the mass of 1,000 cubic cm of water at 4°C (→ maximum density).

According to the new (2019) definition, the kilogram is defined by taking the fixed numerical value of the → Planck constant (h) to be 6.62607015 × 10^-34 when expressed in the unit J.s, which is equal to kg m² s^-1, where the meter and the second are defined in terms of c and Δν Cs.

See also: → kilo-; → gram.

A metric unit of force which is equal to a mass of one kilogram multiplied by the standard acceleration due to gravity on Earth (9.80665 m sec^-2). Therefore one (1) kilogram-force is equal to 1 kg × 9.80665 m sec^-2 = 9.80665 → newtons.

See also: → kilogram; → force.

A metric unit of force which is equal to a mass of one kilogram multiplied by the standard acceleration due to gravity on Earth (9.80665 m sec^-2). Therefore one (1) kilogram-force is equal to 1 kg × 9.80665 m sec^-2 = 9.80665 → newtons.

See also: → kilogram; → force.

A unit of → frequency, equal to 10³ Hz.

See also: → kilo-; → hertz.

A unit of → frequency, equal to 10³ Hz.

See also: → kilo-; → hertz.

A unit of length, equal to 1000 meters.,

See also: → kilo-; → meter.

A unit of length, equal to 1000 meters.,

See also: → kilo-; → meter.

A fast-evolving → supernova-like phenomenon resulting from the → merger of compact, binary objects such as two → neutron stars or a neutron star and a → black hole. A kilonova represents an → electromagnetic counterpart to → gravitational waves. Also called → macronova. A simple model of the phenomenon was put forward by Li and Paczynski (1998, ApJL 507, L59). The kilonova phenomenon can last between days and weeks following the merger.

Within the small volume of space where a merger occurs, the combination of a huge amount of energy, and a large number of neutrons, is the instigator for the → r-process. The high density favors this rapid → neutron capture by nuclei, leading to the formation of new → chemical elements with high → atomic numbers
and high → atomic weights. Many elements heavier than → iron form in these environments, including many rare elements, most notably → platinum (atomic number 78) and → gold (atomic number 79).

The decay of heavy atomic nuclei leads to the radioactive heating and a release of electromagnetic radiation. The heat cannot easily escape as radiation, because of the high opacity of the ejected material. The heat is radiated thermally, heating up the nearby matter, which can be then seen in the → near-infrared.

It was long thought that the r-process could also occur during core-collapse supernovae, but the density of neutrons within supernovae appears to be too low.

The first indication of a kilonova following a short GRB 
came from the extensive follow-up of GRB 130603B, which was one of the

nearest and brightest short GRBs ever detected, and also the first short GRB with an optical afterglow spectrum.

The first kilonova found to be associated with a gravitational waves was detected in the study of → GW170817.

See also: The term kilonova was introduced by Metzger et al. (2010, MNRAS 406, 2650), who argued that the peak luminosities of neutron star merger transients are typically ~ few × 10⁴¹ erg s^-1, or a factor of ~ 10³ larger than the → Eddington luminosity for a solar mass object. They therefore dubbed these events kilonovae; from → kilo-; → nova.

A fast-evolving → supernova-like phenomenon resulting from the → merger of compact, binary objects such as two → neutron stars or a neutron star and a → black hole. A kilonova represents an → electromagnetic counterpart to → gravitational waves. Also called → macronova. A simple model of the phenomenon was put forward by Li and Paczynski (1998, ApJL 507, L59). The kilonova phenomenon can last between days and weeks following the merger.

Within the small volume of space where a merger occurs, the combination of a huge amount of energy, and a large number of neutrons, is the instigator for the → r-process. The high density favors this rapid → neutron capture by nuclei, leading to the formation of new → chemical elements with high → atomic numbers
and high → atomic weights. Many elements heavier than → iron form in these environments, including many rare elements, most notably → platinum (atomic number 78) and → gold (atomic number 79).

The decay of heavy atomic nuclei leads to the radioactive heating and a release of electromagnetic radiation. The heat cannot easily escape as radiation, because of the high opacity of the ejected material. The heat is radiated thermally, heating up the nearby matter, which can be then seen in the → near-infrared.

It was long thought that the r-process could also occur during core-collapse supernovae, but the density of neutrons within supernovae appears to be too low.

The first indication of a kilonova following a short GRB 
came from the extensive follow-up of GRB 130603B, which was one of the

nearest and brightest short GRBs ever detected, and also the first short GRB with an optical afterglow spectrum.

The first kilonova found to be associated with a gravitational waves was detected in the study of → GW170817.

See also: The term kilonova was introduced by Metzger et al. (2010, MNRAS 406, 2650), who argued that the peak luminosities of neutron star merger transients are typically ~ few × 10⁴¹ erg s^-1, or a factor of ~ 10³ larger than the → Eddington luminosity for a solar mass object. They therefore dubbed these events kilonovae; from → kilo-; → nova.

A unit of distance equal to 1,000 → parsec (pc)s, or 3,260 → light-years.

See also: → kilo-; → parsec.

A unit of distance equal to 1,000 → parsec (pc)s, or 3,260 → light-years.

See also: → kilo-; → parsec.

A unit of energy equivalent to one kilowatt (1 kW) of power expended for one hour (1 h) of time. The kilowatt-hour is not a standard unit in any formal system, but it is commonly used to measure the consumption of electrical energy. To convert to → joules, use:
1 kWh = 3.6 × 10⁶ J = 3.6 × 10¹³→ ergs.

See also: → kilo-; → watt-hour.

A unit of energy equivalent to one kilowatt (1 kW) of power expended for one hour (1 h) of time. The kilowatt-hour is not a standard unit in any formal system, but it is commonly used to measure the consumption of electrical energy. To convert to → joules, use:
1 kWh = 3.6 × 10⁶ J = 3.6 × 10¹³→ ergs.

See also: → kilo-; → watt-hour.

Of or relating to → kinematics. Same as kinematical.

See also: → kinematics.

Of or relating to → kinematics. Same as kinematical.

See also: → kinematics.

A systematic error introduced in a sample of stellar → proper motion data by higher velocity stars that are easier to measure.

See also: → kinematic; → bias.

A systematic error introduced in a sample of stellar → proper motion data by higher velocity stars that are easier to measure.

See also: → kinematic; → bias.

The ratio of the → dynamic viscosity (η)
to the density (ρ) of a fluid: ν = η/ρ. The unit of kinematic viscosity in the → SI system is m²s^-1. In the → cgs system, cm²s^-1, equal to 10^-4 m²s^-1, is called the → stokes (st).

See also: → kinematic; → viscosity.

The ratio of the → dynamic viscosity (η)
to the density (ρ) of a fluid: ν = η/ρ. The unit of kinematic viscosity in the → SI system is m²s^-1. In the → cgs system, cm²s^-1, equal to 10^-4 m²s^-1, is called the → stokes (st).

See also: → kinematic; → viscosity.

Of or relating to → kinematics. → kinematic.

See also: → kinematic; → -al.

Of or relating to → kinematics. → kinematic.

See also: → kinematic; → -al.

A central, tightly bound stellar subsystem observed in some elliptical galaxies which rotates in the opposite direction with respect to the main body of the → elliptical galaxy. Elliptical galaxies are thought to be the result of the → merger of two or more sizable galaxies. A plausible scenario for how counter-rotating cores could form in such a merger is as follows. If at least one of the galaxies has a core region that is fairly tightly bound by the galaxy’s gravity, and the direction in which the two galaxies orbit each other before merging is opposite to the direction of rotation of stars in that tightly bound core,
it is likely that, after the merger, the tightly bound core will end up as the core of the new, larger galaxy, while retaining its original sense of rotation. The surrounding stars, on the other hand, will rotate in a different way dictated by the orbital motion of the galaxies around each other, before the merger.

While this is a plausible scenario, it can only explain some of the counter-rotating cores.

Recently A. Tsatsi et al. (2015, ApJ 802, L3) have shown that although the two → progenitor galaxies are initially following a → prograde orbit, strong reactive forces during the merger can cause a short-lived change of their orbital spin; the two progenitors follow a → retrograde orbit right before their final coalescence. This results in a central kinematic decoupling and the formation of a large-scale (~2 kpc radius) counter-rotating core at the center of the final elliptical-like merger remnant, while its outer parts keep the rotation direction of the initial orbital spin.

See also: → kinematical; → decouple; → core.

A central, tightly bound stellar subsystem observed in some elliptical galaxies which rotates in the opposite direction with respect to the main body of the → elliptical galaxy. Elliptical galaxies are thought to be the result of the → merger of two or more sizable galaxies. A plausible scenario for how counter-rotating cores could form in such a merger is as follows. If at least one of the galaxies has a core region that is fairly tightly bound by the galaxy’s gravity, and the direction in which the two galaxies orbit each other before merging is opposite to the direction of rotation of stars in that tightly bound core,
it is likely that, after the merger, the tightly bound core will end up as the core of the new, larger galaxy, while retaining its original sense of rotation. The surrounding stars, on the other hand, will rotate in a different way dictated by the orbital motion of the galaxies around each other, before the merger.

While this is a plausible scenario, it can only explain some of the counter-rotating cores.

Recently A. Tsatsi et al. (2015, ApJ 802, L3) have shown that although the two → progenitor galaxies are initially following a → prograde orbit, strong reactive forces during the merger can cause a short-lived change of their orbital spin; the two progenitors follow a → retrograde orbit right before their final coalescence. This results in a central kinematic decoupling and the formation of a large-scale (~2 kpc radius) counter-rotating core at the center of the final elliptical-like merger remnant, while its outer parts keep the rotation direction of the initial orbital spin.

See also: → kinematical; → decouple; → core.

The branch of mechanics dealing with the description of the motion of bodies or fluids without reference to the forces producing the motion.

Etymology (EN): From Gk. kinetikos “moving, putting in motion,” from kinetos “moved,” verbal adj. of kinein “to move;”
PIE base *kei- “to move to and fro” (cf. Mod.Pers. šodan, šow- “to go; to become;” Av. šiyav-, š(ii)auu- “to move, go,” šiyavati “goes,” šyaoθna- “activity; action; doing, working;” O.Pers. šiyav- “to go forth, set,” ašiyavam “I set forth;” Skt. cyu- “to move to and fro, shake about; to stir,” cyávate “stirs himself, goes;” Goth. haitan “call, be called;” O.E. hatan “command, call”).

Etymology (PE): Jonbešik, from jonbeš “motion” + -ik→ -ics. The first element from Mid.Pers. jumbidan, jumb- “to move,” Lori, Laki jem “motion,” related to gâm “step, pace;”
O.Pers. gam- “to come; to go,” Av. gam- “to come; to go,” jamaiti “goes,” gāman- “step, pace”
(Mod.Pers. âmadan “to come”); Skt. gamati “goes;” Gk. bainein “to go, walk, step,” L. venire “to come;” Tocharian A käm- “to come;” O.H.G. queman “to come;” E. come; PIE root *gwem- “to go, come.”

The branch of mechanics dealing with the description of the motion of bodies or fluids without reference to the forces producing the motion.

Etymology (EN): From Gk. kinetikos “moving, putting in motion,” from kinetos “moved,” verbal adj. of kinein “to move;”
PIE base *kei- “to move to and fro” (cf. Mod.Pers. šodan, šow- “to go; to become;” Av. šiyav-, š(ii)auu- “to move, go,” šiyavati “goes,” šyaoθna- “activity; action; doing, working;” O.Pers. šiyav- “to go forth, set,” ašiyavam “I set forth;” Skt. cyu- “to move to and fro, shake about; to stir,” cyávate “stirs himself, goes;” Goth. haitan “call, be called;” O.E. hatan “command, call”).

Etymology (PE): Jonbešik, from jonbeš “motion” + -ik→ -ics. The first element from Mid.Pers. jumbidan, jumb- “to move,” Lori, Laki jem “motion,” related to gâm “step, pace;”
O.Pers. gam- “to come; to go,” Av. gam- “to come; to go,” jamaiti “goes,” gāman- “step, pace”
(Mod.Pers. âmadan “to come”); Skt. gamati “goes;” Gk. bainein “to go, walk, step,” L. venire “to come;” Tocharian A käm- “to come;” O.H.G. queman “to come;” E. come; PIE root *gwem- “to go, come.”

Of or relating to motion; caused by motion; characterized by movement.

Etymology (EN): From Gk. kinetikos “moving, putting in motion,” from kinein “to move,” → kinematics.

Etymology (PE): Jonbeši, adj. of jonbeš, verbal noun of jonbidan, → move.

Of or relating to motion; caused by motion; characterized by movement.

Etymology (EN): From Gk. kinetikos “moving, putting in motion,” from kinein “to move,” → kinematics.

Etymology (PE): Jonbeši, adj. of jonbeš, verbal noun of jonbidan, → move.

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.

See also: → kinetic; → 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.

See also: → kinetic; → energy.

In fluid mechanics, a quantity that describes helical flow. It is defined by the integrated scalar product of the velocity field and the → vorticity: K_K = ∫ dVu . (∇ x u). In the absence of magnetic field, this quantity is conserved by the → Euler equation. See also → magnetic helicity.

See also: → kinetic; → helicity.

In fluid mechanics, a quantity that describes helical flow. It is defined by the integrated scalar product of the velocity field and the → vorticity: K_K = ∫ dVu . (∇ x u). In the absence of magnetic field, this quantity is conserved by the → Euler equation. See also → magnetic helicity.

See also: → kinetic; → helicity.

Same as → Lagrangian function.

See also: → kinetic; → potential.

Same as → Lagrangian function.

See also: → kinetic; → potential.

The temperature of a gas defined in terms of the average kinetic energy of its atoms or molecules.

See also: → kinetic; → temperature.

The temperature of a gas defined in terms of the average kinetic energy of its atoms or molecules.

See also: → kinetic; → temperature.

A theory that explains macroscopic properties of gases, such as pressure, temperature, or volume, by considering their molecular composition and motion.

See also: → kinetic; → theory;
→ gas.

A theory that explains macroscopic properties of gases, such as pressure, temperature, or volume, by considering their molecular composition and motion.

See also: → kinetic; → theory;
→ gas.

A plot representing the evolution of the internal structure of a star as a function of time. The x-axis indicates the time, the y-axis the mass, and a color or
shading specifies convective regions. A vertical line through the graph corresponds to a model at a particular time.

See also: Named after Rudolf Kippenhahn (1926-), a German astrophysicist;
→ diagram

A plot representing the evolution of the internal structure of a star as a function of time. The x-axis indicates the time, the y-axis the mass, and a color or
shading specifies convective regions. A vertical line through the graph corresponds to a model at a particular time.

See also: Named after Rudolf Kippenhahn (1926-), a German astrophysicist;
→ diagram

The radiation law which states that at thermal equilibrium the ratio of the energy emitted by a body to the energy absorbed by it depends only on the temperature of the body.

See also: Gustav Robert Kirchhoff (1824-1887), a German physicist who made major contributions to the understanding of electric circuits, spectroscopy, and the emission of black-body radiation from heated objects; → law.

The radiation law which states that at thermal equilibrium the ratio of the energy emitted by a body to the energy absorbed by it depends only on the temperature of the body.

See also: Gustav Robert Kirchhoff (1824-1887), a German physicist who made major contributions to the understanding of electric circuits, spectroscopy, and the emission of black-body radiation from heated objects; → law.

Regions in the asteroid belt within which few asteroids are found. The Kirkwood gaps are due to the perturbing effects of Jupiter through resonances with Jupiter’s orbital period.

See also: Named for the American astronomer Daniel Kirkwood (1814-1895), who Discovered them in 1866; → gap.

Regions in the asteroid belt within which few asteroids are found. The Kirkwood gaps are due to the perturbing effects of Jupiter through resonances with Jupiter’s orbital period.

See also: Named for the American astronomer Daniel Kirkwood (1814-1895), who Discovered them in 1866; → gap.

A → dwarf galaxy with a → kiloparsec size → starburst at one end, giving the system a → tadpole or → cometary shape. Also called LEDA-36252, KUG 1138+327. Its distance is 24.5 → megaparsecs (Mpc). The rotation speed of ~ 35 km s^-1 combined with a radius of 1.2 kpc in the bright part of the disk implies that the corresponding → dynamical mass is 3 × 10⁸/ sin²i Msun. This estimate
is a factor of ~ 6 larger than the → stellar mass of 5 × 10⁷ Msun from the → Sloan Digital Sky Survey photometry, but is comparable to the total → neutral hydrogen (H I) mass of ~ 3 × 10⁸ Msun. The metallicity in the → starburst “head” appears to be less than in the rest of the galaxy (the “tail”). This peculiar pattern of metallicity, seen also in several other comparable galaxies, suggests that the starbursts in these systems were triggered by accreting a gas with lower metallicity than in the rest of the galaxy.

The → Hubble Space Telescope observations of Kiso 5639 in six UV-optical and Hα filters were used to resolve the head and derive the star formation properties. The head contains 14 young → star clusters more massive than 10⁴Msun and an overall clustering fraction for star formation of 25-40%. The Hα luminosity of the core region of the head is 8.8 ± 0.16 × 10³⁹ erg s^-1 inside an area of 3.6 × 3.6 square arcsec. The corresponding → star formation rate is ~ 0.04 Msun yr^-1

(Elmegreen et al., 2018, arxiv/1805.08253, and references).

See also: Kiso Survey of UV Bright Galaxies (Miyauchi-Isobe et al., 2010, Pub.Nat.Astro.Ob.Japan, 13, 9).

A → dwarf galaxy with a → kiloparsec size → starburst at one end, giving the system a → tadpole or → cometary shape. Also called LEDA-36252, KUG 1138+327. Its distance is 24.5 → megaparsecs (Mpc). The rotation speed of ~ 35 km s^-1 combined with a radius of 1.2 kpc in the bright part of the disk implies that the corresponding → dynamical mass is 3 × 10⁸/ sin²i Msun. This estimate
is a factor of ~ 6 larger than the → stellar mass of 5 × 10⁷ Msun from the → Sloan Digital Sky Survey photometry, but is comparable to the total → neutral hydrogen (H I) mass of ~ 3 × 10⁸ Msun. The metallicity in the → starburst “head” appears to be less than in the rest of the galaxy (the “tail”). This peculiar pattern of metallicity, seen also in several other comparable galaxies, suggests that the starbursts in these systems were triggered by accreting a gas with lower metallicity than in the rest of the galaxy.

The → Hubble Space Telescope observations of Kiso 5639 in six UV-optical and Hα filters were used to resolve the head and derive the star formation properties. The head contains 14 young → star clusters more massive than 10⁴Msun and an overall clustering fraction for star formation of 25-40%. The Hα luminosity of the core region of the head is 8.8 ± 0.16 × 10³⁹ erg s^-1 inside an area of 3.6 × 3.6 square arcsec. The corresponding → star formation rate is ~ 0.04 Msun yr^-1

(Elmegreen et al., 2018, arxiv/1805.08253, and references).

See also: Kiso Survey of UV Bright Galaxies (Miyauchi-Isobe et al., 2010, Pub.Nat.Astro.Ob.Japan, 13, 9).

Any of several small birds of the hawk family Accipitridae that have long, pointed wings, feed on insects, carrion, reptiles, rodents, and birds, and are noted for their graceful, gliding flight (Dictionary.com).

Etymology (EN): M.E. kyte, O.E. cyta, cognate with Ger. Kauz “owl.”

Etymology (PE): Zaqan “kite,” of uknown origin.

Any of several small birds of the hawk family Accipitridae that have long, pointed wings, feed on insects, carrion, reptiles, rodents, and birds, and are noted for their graceful, gliding flight (Dictionary.com).

Etymology (EN): M.E. kyte, O.E. cyta, cognate with Ger. Kauz “owl.”

Etymology (PE): Zaqan “kite,” of uknown origin.