General astronomy

General astronomy

Industry: Astronomy

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General astronomy

ephemeris time (ET)

Astronomy; General astronomy

Determined in principle from the sun's apparent annual motion, ET is the numerical measure of uniform time, which is the independent variable in the gravitational theory of the earth's orbital ...

acceleration unit

Astronomy; General astronomy

A unit for measuring acceleration, which is metre per second squared.

achromatic objective

Astronomy; General astronomy

A lens of two or more components with different refraction indices (e.g., crown glass and flint glass), used to correct for chromatic aberration.

actinide

Astronomy; General astronomy

Element with atomic number between 89 (Actinium) and 103

achromatic lens

Astronomy; General astronomy

Lens (or combination of lenses) that brings different wavelenghts within a ray of light to a single focus, thus overcoming chromatic aberration. It was first successfully made by Joseph von ...

1) A process by which a star accumulates matter as it moves through a dense cloud of interstellar gas; or, more generally, whereby matter surrounding a star flows toward it (as in close binaries.) 2) ...