Astronomy and related astronomical terms

Greek, ; Latin, A, a.

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A red super giant star in the constellation of Orion.

It is the tenth brightest star in the night sky, although its brightness varies. It is over 10,000 times as luminous as the sun, and lies 650 light-years from earth.

Light takes 60 minutes to travel across the giant star.

A way of arranging a telescope mount so that the telescope can move parallel to the horizon (azimuth) and at right angles to the horizon (altitude).

Very easy to mechanize, it is becoming more popular in combination with computer control systems, which can alter the altitude and azimuth angles to follow the path of a star as it rises and sets.

1. The measurement of height, usually given in meters above sea level.
2. The angular distance; usually measured in degrees, above the horizon, from zero degrees at the horizon to 90 degrees at the zenith.

One of the two co-ordinates (the other being azimuth) that define a celestial object's position, used with an altazimuth mount.

The figure-8 representing the equation of time and the variation of the sun's altitude in the sky during the course of a year.

A unit of wavelength or distance, equivalent to 1/10,000 micrometer or 1/10,000,000,000 meter.

The product of the moment of inertia of a body and the angular velocity.

Its importance lies in the fact that a body with a large angular momentum needs a considerable force (torque) to slow or to stop its rotation.

The annual solar savings of a solar building is the energy savings attributable to a solar feature relative to the energy requirements of a non-solar building.

1. A solar eclipse in which a ring (an annulus or the figure bounded by and containing the area between two concentric circles) of solar photosphere remains visible.
2. The type of eclipse seen when the moon is too far from the earth at the time of a solar eclipse to completely cover the sun's disk.

The result is a bright ring, or annulus, of light encircling the moon.

Material made of atomic particles having certain properties opposite to those of ordinary matter.

If combined, matter and antimatter would explode.

The point that is directly on the opposite side of a planet; such as, the earth's north pole is antipodal to its south pole.

The clear diameter of the light-gathering surface of a telescope.

For a refractor telescope, it is the diameter of the objective lens, and for a reflecting telescope, it is the diameter of the primary mirror.

1. The point in the orbit of a planet, comet, or other celestial body's point of orbit, at which it is farthest from the sun.
2. A point on the earth's elliptical orbit at which the sun is farthest from the earth.

Point of the moon's orbit farthest from the earth.

1. Magnitude as seen by an observer.
2. The brightness of a star as seen from the earth.
3. A measure of the brightness of stars as they appear on the celestial sphere.