An Etymological Dictionary of Astronomy and Astrophysics
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The premature termination of star formation process in some galaxies. The ultimate quenching of star formation is caused by stripping of the gas reservoir which will finally turn into stars. A wide variety of mechanisms have been proposed to provide quenching. For example, → major mergers can transform spiral galaxies into ellipticals, and may also quench future star formation by ejecting the → interstellar medium from the galaxy via starburst, → active galactic nucleus, or shock-driven winds. In rich clusters, where merging is less efficient because of the large relative velocities of galaxies, rapid encounters or fly-bys may cause the formation of a bar and growth of a spheroidal component instead of larger scale star formation. Also, cold gas can be stripped out of the galaxy both by tidal forces and ram pressure in the intracluster medium. Similarly, the hot halo that provides future fuel for cooling and star formation may be efficiently stripped in dense environments, thus quenching further star formation (see, e.g., Kimm et al., 2009, MNRAS 394, 1131, arXiv:0810.2794).

→ star; → formation; → quench.

The rate at which a molecular cloud or a galaxy is currently converting gas into stars. It is given by the ratio of the number of stars to the star formation time-scale.

→ star formation; → rate.

A region in the → interstellar medium where processes of → star formation are going on or have occurred in the past.

→ star; → formation; → region.

The time necessary for a star to form. It depends inversely on the stellar mass.

→ star formation; → time scale.

A → main sequence→ B-type star that orbits the → supermassive black hole candidate → Sgr A* in the → Galactic center. The star S2, which is bright enough for making detailed measurements, has a highly elliptical, 16-year-period orbit around Sgr A*. Near → pericenter at 120 → astronomical units, ~ 1400 → Schwarzschild radii, the star has an orbital speed of ~ 7650 km s^-1, such that the first-order effects of → special relativity and → general relativity have become detectable with current capabilities (Auber et al., 2018, A&A 615, L15).

→ star.

Same as → stellar system.

→ stellar; → system.

A curved → path left by a star on an → imaging detector attached to a → telescope when the telescope does not keep up with the → rotation of the → Earth.

→ star; → trail.

A galaxy that is located on the → galaxy main sequence in the plane relating → star formation rates to total stellar masses.

→ star; → formation; → galaxy.

A region in which → star formation is going on.

→ star; → formation; → region.

Simultaneous formation of a large number of stars in a region of a galaxy at an exceptionally high rate, compared to the usual star formation rates seen in most galaxies.

→ star; → burst.

A galaxy showing a short-lived intense period of star formation that is unsustainable over the → Hubble time due to the limited supply of gas within a galaxy. Starburst galaxies were first classified by Searle & Sargent (1972) and Searle et al. (1973), based on the blue colors produced by the → massive stars formed during the burst. In the local Universe, starbursts create approximately 10% of the radiant energy and 20% of the massive stars. At z = 1, starburst characteristics are found in 15% of galaxies, presumably attributable to the greater amounts of gas typically present in young galaxies and increased galactic interactions. The starburst's impact on a galaxy and the surrounding → intergalactic medium is primarily due to the consumption of gas that fuels the burst and the feedback from massive stars formed in the burst (McQuinn et al. 2010, astro-ph/1008.1589).

→ starburst; → galaxy.

The → splitting of spectral lines of atoms and molecules due to the presence of an external electric field, which slightly changes the → energy levels of the atom. → Zeeman effect.

Named after Johannes Stark (1874-1957), a German physicist, and Physics Nobel Prize laureate (1919); → effect.

An astrophysical phenomenon that occurs when the → crust of a → neutron star undergoes a sudden adjustment, analogous to an → earthquake on Earth. Starquakes are thought to be caused by huge → stresses exerted on the surface of the neutron star produced by twists in the ultra-strong interior → magnetic fields. They are thought to be the source of the intense → gamma-ray bursts that come from → soft gamma repeaters.

→ star; → quake.

A phenomenon similar to a → sunspot but occurring on the surface of a star other than Sun. Due to spatial resolution constraints, starspots so far observed are in general much larger than those on the Sun, up to about 30% of the stellar surface may be covered, corresponding to sizes 100 times greater than those on the Sun.

→ star; → spot.

A prefix attached to the name of a practical electrical unit indicating that it is part of the → CGS electrostatic system, e.g. statcoulomb, statvolt. These units are also indicated by the notation → esu (as in "volt esu").

Combining form representing → electrostatic, → -stat

A unit of → electric charge in the electrostatic → cgs system of units; equal to the charge that exerts a force of 1 → dyne on an equal charge at a distance of 1 cm under vacuum; equal to 3.3356 x 10^-10 → coulombs. Same as → electrostatic unit (esu).

→ stat-; → coulomb.

1a) The → condition of a → system characterized by a particular set of values for its properties.
1b) The → phase of matter; → solid, → liquid, or → gas.
See also:
→ eigenstate, → energy state, → equation of state, → equation of state parameter, → equilibrium state, → excited state, → ground state, → Hartle-Hawking initial state, → Hoyle state, → macroscopic state, → macrostate, → metastable state, → microscopic state, → microstate, → normal state, → quantum state, → singlet state, → solid state, → solid state physics, → steady state theory, → triplet state, → virial equation of state.
2a) To declare definitely or specifically.
2b) To set forth formally in speech or writing (to state a hypothesis).
2c) To set forth in proper or definite form (Dictionary.com).

M.E. stat, partly from M.Fr. estat, partly from L. status "manner of standing, position, condition," noun of action from p.p. stem of stare "to stand;" cognate with Pers. istâdan "to stand," as below.
The sense of "declare in words" (1640s) comes from the notion of "placing (something on the record), setting in a position."

Estât, from istâdan "to stand;" Mid.Pers. êstâtan; O.Pers./Av. sta- "to stand, stand still; to set" (Sogd. ôštât "to stand"); Av. hištaiti; cf. Skt. sthâ- "to stand;" Gk. histemi "put, place, weigh," stasis "a standing still;" L. stare "to stand;" Lith. statau "place;" Goth. standan; PIE base *sta- "to stand"); hâlat, from Ar. Hâlat "state, quality."

1) Something stated.
2) A communication or declaration in speech or writing, setting forth facts, particulars, etc.
3) A single sentence or assertion (Dictionary.com).

Verbal noun of → state (v.)

A person who is experienced in the art of government or versed in the administration of government affairs (Dictionary.com).

From state's man, translation of Fr. homme d'Etat; → state; → man.

1) Pertaining to bodies, forces, charges, etc. that act in equilibrium; at rest; stationary.
2) Pertaining to → statistics.

From Mod.L. statica, from Gk. statikos "causing to stand," from stem of histanai "to cause to stand," cognate with Pers. istâdan "to stand," as below.

Istâ "standing, static," from istâdan "to stand" (Mid.Pers. êstâtan; O.Pers./Av. sta- "to stand, stand still; set;" Av. hištaiti; cf. Skt. sthâ- "to stand;" Gk. histemi "put, place, weigh," stasis "a standing still;" L. stare "to stand;" Lith. statau "place;" Goth. standan; PIE base *sta- "to stand").