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astronomical unit

(Encyclopedia)astronomical unit (AU), mean distance between the earth and sun; one AU is c.92,960,000 mi (149,604,970 km). The astronomical unit is the principal unit of measurement within the solar system, e.g., M...

Astronomical Ephemeris

(Encyclopedia)Astronomical Ephemeris: see ephemeris. ...

thermal unit

(Encyclopedia)thermal unit: see British thermal unit. ...

Infrared Astronomical Satellite

(Encyclopedia)Infrared Astronomical Satellite: see infrared astronomy. ...

Orbiting Astronomical Observatory

(Encyclopedia)Orbiting Astronomical Observatory (OAO), series of four orbiting observatories (see observatory, orbiting) launched between 1966 and 1972 by the National Aeronautics and Space Administration (NASA) to...

astronomical coordinate systems

(Encyclopedia)astronomical coordinate systems. A coordinate system is a method of indicating positions. Each coordinate is a quantity measured from some starting point along some line or curve, called a coordinate ...

atomic mass unit

(Encyclopedia)atomic mass unit or amu, in chemistry and physics, unit defined as exactly 1⁄12 the mass of an atom of carbon-12, the isotope of carbon with six protons and six neutrons in its nucleus. One amu is e...

British thermal unit

(Encyclopedia)British thermal unit, abbr. Btu, unit for measuring heat quantity in the customary system of English units of measurement, equal to the amount of heat required to raise the temperature of one pound of...

European Currency Unit

(Encyclopedia)European Currency Unit: see European Monetary System. ...

newton, unit of measure

(Encyclopedia)newton, abbr. N, unit of force in the mks system of units, which is based on the metric system; it is the force that produces an acceleration of 1 meter per second per second when exerted on a mass of...