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jetA long thin linear feature of bright emission extending from a compact object, such as a galaxy. Jets are very common at radio wavelengths, but have also been seen in optical and X-ray emission. They are sometimes broken up into a number of bright knots. In extragalactic sources a jet is usually associated with the presence of an active galactic nucleus. An example is that found in the giant elliptical galaxy M87 (see Virgo A). See also radio-source structure.
a variety of pit coal; it is tough and has a deep black color, a strong, dull luster, and a flinty fracture. Its hardness on the mineralogical scale is 3-3.5; its density is approximately 1,300-1,400 kg/m3.
The formation of jet is associated with the metamorphism of wood buried in marine silts of Mesozoic and Cenozoic deposits. It is found in the form of separate aggregates or pieces in sandstones and marls, as well as in layers of weakly metamorphosed bituminous coal and lignite. Jet is easily worked and takes on a handsome luster when polished; because of this quality it is widely used (especially in the countries of the East) for small articles of jewelry, beads, and rosary beads.
a calibrated opening used to meter the supply of liquid fuel or air. In the technical literature the term “jet” is used to designate carburetor parts with calibrated openings (plugs or injectors). According to their operational functions and the type of carburetor in which they are installed, jets may be classified as fuel jets, air jets, main jets, compensating jets, or idling jets. Jets are rated by their transmissive capacity—that is, the quantity of a liquid (usually water) that can pass through the calibrated opening per unit time. The transmissive capacity of jets is measured in cm3/min.
ii. A gas turbine engine may be referred to as a jet engine.
iii. A strong, well-defined stream of fluid either issuing from an orifice or moving in a contracted duct, such as the jet of combustion gases issuing from a reaction engine or the jet in the test section of a wind tunnel. A jet is also a forceful stream of fuel discharged from a small nozzle. Normally referred to as a jet-stream.
iv. A calibrated, restricted orifice, tube, nozzle, or the like through which metered fluid passes, or from which it issues, in a jet—such as a jet in a carburetor. The size of the jet and the pressure across the nozzle determine the quantum of fuel flow.
v. A narrow band of high-velocity wind in the upper troposphere normally referred to as a jet stream.