Astronomical Dictionary
Letter: P


Dictionary of Astronomical Definitions and Terms.
Astronomical | P

 

Definition


info

Pahoehoe
A basaltic lava with a smooth, undulating surface.
Category: Astronomical
Leave comment here
Parallax
The angular difference in apparent direction of an object seen from two different viewpoints. This occurs as the observer moves from location to location.
Category: Astronomical
Leave comment here
Parsec
The distance at which a star (or other object) would have a parallax of 1" (one second of arc). It is the distance at which a star would have a parallax of one arc second with a baseline of 1AU (the mean Sun-Earth distance). A Parsec isequal to 3.2616 light years, 206,265 astronomical units (AU) or 30.857 * 10E12 km.
Category: Astronomical
Leave comment here
Penumbra
The partial shadow or darkness of an eclipse. Means, literally, "dim light". It most often refers to the outer shadow cast during eclipses, and defines the region of shadow which gives rise to a partial eclipse. It is also the lighter area surrounding the central region of a sunspot.
Category: Astronomical
Leave comment here
Periapsis
A genericterm. The point in an orbit closest to a body other than the Sun or the Earth. For bodies which orbit about the Sun, this point is called perihelion; about the Moon, perilune; about the Earth: perigee; about Mars, perimartian; about Jupiter: perijove; about a star: periastron.

Category: Astronomical
Leave comment here
Perigee
From the Greek "near the Earth." The point in its orbit where the Moon, or planet is closest to the Earth.
Opposite of apogee.
Category: Astronomical
Leave comment here
Perihelion
From the Greek "near the Sun." The point in its orbit when an object is closest to the Sun. Opposite of Aphelion.
Category: Astronomical
Leave comment here
Perturb
To cause a celestial body, to deviate from its predicted orbit, usually under the gravitational influence of another celestial object. Example: The effect of Jupiter on the orbit of a comet.
Category: Astronomical
Leave comment here
Photosphere
The visible surface of the Sun;
Category: Astronomical
Leave comment here
Plage
Bright regions in the Sun's chromosphere.
Category: Astronomical
Leave comment here
Planisphere
An aid to locatiing stars and constellations in the night sky. It consists of two discs. One with the entire night sky, and the other, which covers the first, having a window through which a portion of the sky can be seen. The second disc is set according to the date and time.
Category: Astronomical
Leave comment here
Precession
Also called Precession of the Equinoxes. Circular motion about the axis of rotation of a body; fixed with respect to the stars. The Earth is a giant gyroscope whose axis passes through the North and South Poles and this axis precesses with a period of 27,700 years.
Category: Astronomical
Leave comment here
Prominence
A cloud, or plume, of hot, luminous gas in the Sun's corona. It appears bright when seen against the cool blackness of space. When they are in silhouette against the disc they are known as filaments. They are mainly composed of hydrogen, helium and calcium
Category: Astronomical
Leave comment here
Phobos
In Greek mythology, a son of Ares (Mars) who, with brother Deimos, was a constant companion to his father.
Category: Astronomical
Leave comment here
Plateau
Any comparatively flat area of great extent or elevation.
Category: Astronomical
Leave comment here
Plume
A buoyant mass of hot, partially molten mantle material that rises to the base of the lithosphere.
Category: Astronomical
Leave comment here
Pluto
Planet ninth in order, and farthest, from the sun. In Greek mythology, god of the dead and the underworld.
Category: Astronomical
Leave comment here
Prometheus
A Greek mythological hero who gave humankind fire.
Category: Astronomical
Leave comment here
   
Astronomical

Horoscope | Daily | Weekly | Monthly | News | Zodiac | Compatibility | Natal |
Proverbs | Chinese Astrology | Links | Glossary | Contact |