Astronomy and related astronomical terms

Saturn's inner ring, also known as the C-ring; ring C: The crepe ring, extends inward to the planet from the brightest ring or the B-ring.

One of the phases of the moon or the inner planets (Venus and Mercury) as seen from Earth: The crescents of the moon fir example, are caused by the relative angles of sunlight and the observer's viewpoint.

From a spacecraft, crescents of the Earth, Mars, Jupiter, and Saturn have also been seen.

The thin, outermost rocky layer of a moon or terrestrial planet: The crust is the topmost stratum of the solid body of a planet, extending down to the mantle.

The point when a celestial object reaches its greatest possible height above the planet Earth's horizon: A culmination is the highest or the lowest altitude reached by a heavenly body when it crosses the meridian.

Massive objects in space, such as stars, cause space to curve and light to bend: The curvature of space relates to Einstein's theory of gravitation.

Matter or substances that are not able to be revealed by its radiation: Dark matter comprises a large portion of the universe. It cannot be seen but can be perceived through its gravitational effects.

The position of a star as located through the combination of two coordinates, east-west (right ascension) and north-south of the celestial equator: The declination is the angular distance between a celestial object, such as a star, and the celestial equator.

The declination is the celestial coordinate analogous to latitude that is usually measured in degrees, minutes, and seconds of arc north (+) or south (-) of the celestial equator. 3.

The symbol for this term is the Greek letter δ or delta.

The large circular orbit around which a planet was thought to orbit, in one or many epicycles: A deferentin the time of the Ptolemaic astronomy, was an imaginary circle that surrounded the planet Earth, around which the heavenly bodies orbited.

An "epicycle" is a circular orbit of a body around a point that is itself in a circular orbit round a parent body.

Such a system was formulated to explain some planetary orbits in the solar system before they were known to be elliptical.

Mass per unit of volume: In astronomy, the mean relative density compares a planet's density with the density of water, 62.4 pounds per cubic foot or one gram per cubic centimeter.

Density is also the thickness of consistency or is impenetrable.

Density can be the complexity of structure or content.

In addition,density is a measure of how tightly mass is packed into a given space.

A theory to account for the spiral structure of galaxies: Supposing that such a density wave could be set up in the first place, the theory suggests that the spiral arms mark the positions of regions of higher than average density, which rotate around the galaxy.

Stars orbiting the center of the galaxy spend a considerable amount of time in the higher density regions before moving out, with the higher density also favoring the formation of young stars by fragmentation within it.

A phenomenon seen as a flash of sunlight shineing down a lunar valley during a total solar eclipse: A diamond-ring effect is created as the total phase of a solar eclipse is about to begin, when the last Baily's bead, a remaining bit of phosphere, glows so intensely by contrast with the sun's faint corona that it looks like the jewel on a ring.

The diamond-ring effect also refers to the equivalent phase at the end of totality.

The change in an astronomical object's apparent position caused by the change in the observer's position: A diurnal parallax is due to the motion or rotation of the planet Earth during the day:

1. Change in frequency of sound or light waves caused by the relative motion of the source and the viewer: The Doppler effect refers to the perceived alteration in the frequency as a wave changes, like the distance between the source and the observer. For example, the sound of a siren on a moving vehicle appears to change as it approaches and passes a listener.

The Doppler effect is also the shift of spectral lines due to a body's motion toward or away from an observer.

Astronomers can tell by the Doppler effect if a distant star is moving toward or away from us.
2. Etymology: named after Christian J. Doppler (1803-1853), an Austrian physicist and mathematician who first described the principle known as the Doppler effect in 1842.

Doppler observed that the frequency of light and sound waves is affected by the relative motion of the source and the detector.

Another example is that of a train which approaches an observer, and a lower pitch after it passes by. The Doppler effect applies to all types of waves, including light.

1. A pair of stars that appear close together in the sky only because they lie in the same direction from the planet Earth:, Double stars are not physically associated binary stars.
2. A system containing two or more stars: In a true double,star the stars are physically close to each other in an "optical double". They lie in approximately the same direction from the planet Earth and so appear close to each other, but are actually far apart.

An advanced type of photovoltaic cell that uses a dye-impregnated layer of titanium dioxcide: The dye-sensitized solar cells generate a voltage, rather than the semiconducting materials used in most solar cells.