An Etymological Dictionary of Astronomy and Astrophysics
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A rotating charged black hole. Compare with the → Kerr black hole and the → Reissner-Nordstrom black hole.

Named after Roy P. Kerr and Ezra T. Newman (1929-) who in 1963 independently found this solution to Einstein's → field equations; → black; → hole.

The largest → impact cratrer on → Ceres, which has a diameter of about 280 km. It is distinctly shallow for its size.

Named for The crater is named after the Hopi spirit of sprouting maize, Kerwan. The name was approved by the IAU on July 3, 2015.[1]

In Dirac's notation, a vector which describes the state of a quantum system, whether it is in a space of finite or infinite dimensions. A ket vector, written as | A >, is the dual of the → bra. Like the bra, it appears as an incomplete → bracket expression.

From -ket the second syllable in → bracket.

Kilo (thousand) → electron volt. A unit of → energy used to describe the total energy carried by a → particle or → photon.

→ kilo- + → electron volt.

A usually metal instrument used to operate a lock's mechanism.

M.E. key(e), kay(e), O.E. cæg "key," of unknown origin,

Kelid, variants (Tabari) kali, (Lori) kelil, (Laki) kalil "key; lock," (Kurd) kilil, kolun "latch, bolt;" Mid.Pers. kilêl "key." See also → include.

1) The hole in which a key of a lock is inserted.
2) → Keyhole Nebula.
3) A small, about 600 m wide, region of space close to the Earth where the Earth's gravity would perturb the trajectory of a passing → Near-Earth Object. The object will receive a gravitational push that will bring it back for a collision in the future. Also called resonance keyhole.

→ key; → hole.

A relatively small and dark cloud of molecules and dust seen silhouetted against the much brighter → Carina Nebula. It contains bright filaments of emitting hot gas and is roughly 7 → light-years in size.

→ keyhole; → nebula. The name was given by the English astronomer Sir John Herschel in the 19th century, because of the appearance of the nebula in low-resolution telescopes of that epoch.

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

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.

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

A prefix meaning 10³.

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.

→ 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.

→ kilogram; → force.

A unit of → frequency, equal to 10³ Hz.

→ kilo-; → hertz.

A unit of length, equal to 1000 meters.,

→ 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.

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.

→ 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.

→ kilo-; → watt-hour.

Of or relating to → kinematics. Same as kinematical.

→ kinematics.

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

→ 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).

→ kinematic; → viscosity.