Astronomy and related astronomical terms

Greek,; Latin, A, a.

For more information, go to this alpha link.

You may also see the Greek alphabet with this link.

A red super giant star in the constellation of Orion: Alpha Orionis, 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 system 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, the altazimuth mount 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: The guide told the tourists to take along warm clothes because as the altitude increases, the colder it gets when hiking up the mountains in the Alps.
2. The angular distance: Altitude is 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 that represents the equation of time: An analemma also depicts 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: An angstrom can be used to measure the distances between atoms.

The product of the moment of inertia of a body and the angular velocity: The importance of angular momentum 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 yearly energy savings of a solar building attributable to a solar feature: The annual solar savings are relative to the energy requirements of a non-solar house.

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: When a annular eclipse occurs, the moon is too far from the Earth. to completely cover the sun's disk at the time of the eclipse.

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.

One of two spots or places at opposite ends of a diameter of a sphere: The location that is directly on the opposite side of a planet, like the Earth's north pole being the antipodal point to its south pole.

The clear diameter of the light-gathering surface of a telescope: For a refractor telescope, the aperture 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.