Astronomy

Astronomy

Some useful Astronomy terms (Click on links for more detailed discriptions)

Celestial Coordinates - declination (Dec) and right ascension(R.A.). Two angles that locate a point on the celestial sphere in the equatorial coordinate system.

Declination - the angular distance of a point north or south of the celestial equator

Right ascension - the distance of a point east of the First Point of Aries, measured along the celestial equator and expressed in hours, minutes, and seconds. ( increases to the east )

Conjunction - when two astronomical objects or spacecraft have either the same right ascension or the same ecliptic longitude

Solar Conjunction - When two objects in a Solar system are obscured from each other by their Sun(Star).

Opposition - two astronomical objects are said to be in opposition when they are on opposite sides of the celestial sphere, as observed from a given body.

Precession - change in the orientation of the rotational axis of a rotating body.

equinox - time when an orbiting Solar body equator is at the closest distance to the Sun ( twice a year with Precession ).

Light Year - distance that light travels(in a vacuum) in one year, which is nearly 6 million million miles.

Astronomical Unit (AU) - Average distance between Earth and the Sun, which is about 93 million miles or 150 million kilometers. mainly used to measure distances within Solar Systems.

Parsec - Distance measurement, Parallax of one Arc second. One parsec is approximately 3.26 light-years.

Parallax - displacement or difference in the apparent position of an object viewed along two different lines of sight measured in degrees.

Hill Sphere - the gravitational region around a astronomical body in which it dominates the attraction of satellites.

The distance to the stars is measured using the speed of Light in Years (ly)

The size of the earth among the rest of the planets and suns