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The point at which a body in orbit around the Earth reaches its farthest distance from the Earth.
Industry:Astronomy
1) A measure of how bright a star looks in the sky. The brighter the star, the smaller the apparent magnitude. A star that is one magnitude brighter than another (e.g., +1 versus +2) looks 2.5 times brighter. The brightest star of all, of course, is the Sun, whose apparent magnitude is -26.74, followed by Sirius, whose apparent magnitude is -1.46, Canopus (-0.72), Alpha Centauri (-0.27), Arcturus (-0.04), and Vega (+0.03). Stars of the Big Dipper are fainter, most of them around magnitude +2. On a clear, dark night, the unaided eye can see stars as faint as apparent magnitude +6, and the largest telescopes penetrate to apparent magnitude +30.
2) Measure of the observed brightness of a celestial object as seen from the Earth. It is a function of the star's intrinsic brightness, its distance from the observer, and the amount of absorption by interstellar matter between the star and the observer. The mv, of Sun, -26.5 mag. A sixth-magnitude star is just barely visible to the naked eye.
Industry:Astronomy
colourless, odourless gas comprising 1% of the atmosphere
Industry:Astronomy
a metalloid element with two main forms, grey α arsenic and β arsenic
Industry:Astronomy
a satellite made by humans which is gravitationaly bound and in orbit of a larger physical object
Industry:Astronomy
An optical surface with departures in shape from a perfect sphere in order to cancel optical imperfections or aberrations.
Industry:Astronomy
A sparsely populated grouping (mass range 102-103 Msun) of very young, massive stars lying along a spiral arm of the Milky Way, whose spectral types or motions in the sky indicate a common origin. The star density is insufficient for gravitation to hold the group together against shear by differential galactic rotation, but the stars have not yet had time to disperse completely. OB associations are composed of stars of spectral types O-B2; T associations have many young T Tauri stars. The internationally approved designation for associations is the name of the constellation followed by an arabic numeral - e.g., Perseus OB2.
Industry:Astronomy
a group of bright stars which form a conspicuous pattern on the celestial sphere
Industry:Astronomy
