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1) A solar eclipse in which the solar disk is never completely covered but is seen as an annulus or ring at maximum eclipse. An annular eclipse occurs when the apparent disk of the Moon is smaller than that of the Sun.
2) An eclipse of the Sun in which the Moon is too far from Earth to block out the Sun completely, so that a ring of sunlight appears around the Moon.
Industry:Astronomy
1) A period of time based on the revolution of the Earth around the Sun, where a year is defined as the mean interval between successive passages of the Earth through perihelion.
2) The interval between two successive perihelion passages of Earth.
Industry:Astronomy
The antiparticle of a neutron. A neutron and antineutron both have the same mass and zero electric charge, but can be differentiated by their interactions: a neutron and an antineutron can annihilate into gamma rays, while two neutrons cannot.
Industry:Astronomy
The antiparticle of a proton, identical in mass and spin but of opposite (negative) charge.
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
1) Divination using the positions of the planets, the Sun and the Moon as seen against the stars in the constellations of the zodiac - a "science" almost as old as homo sapiens. Although at one stage in history astrology and astronomy were almost synonymous- the latter has advanced so far during the last three centuries that the two now bear little relation to each other.
2) The belief that human affairs and people's personalities and characters are influenced by (or encoded in) the positions of the planets.
Industry:Astronomy
