Astronomy Reference Libraries

Page 12 of about 169 Articles
Cosmic Rays
2004-10-19 04:45:41

Cosmic Rays -- Cosmic Rays. Cosmic rays are energetic particles that are found in space and filter through our atmosphere. Cosmic rays have interested scientists for many different reasons. They come from all directions in space, and the origination of many of these cosmic rays is unknown. Cosmic rays were originally discovered because of the ionozation they produce in our atmosphere....

Cosmic Background Radiation
2004-10-19 04:45:41

Cosmic Background Radiation -- The Big Bang theory predicts that the early universe was a very hot place and that as it expands, the gas within it cools. Thus the universe should be filled with radiation that is literally the remnant heat left over from the Big Bang, called the cosmic microwave background radiation, or CMB. When any patch of the sky is observed where no individual sources...

2004-10-19 04:45:41

Corona -- The corona is the luminous "atmosphere" of the Sun extending millions of kilometers into space, most easily seen during a total solar eclipse. An interesting feature of the corona is the fact that it is much hotter than the visible "surface" of the Sun; the photosphere is approximately 6000°C compared to the corona at over one million °C. The corona is much less dense than...

Circumpolar Star
2004-10-19 04:45:41

Circumpolar Star -- Circumpolar stars are those stars which are located near the poles of the celestial sphere. As the Earth rotates, the sky appears to rotate; and most stars will be hidden below the horizon at some point in their circular paths. A circumpolar star is near enough to the celestial pole that it will never go under the horizon. It will therefore be visibile for all the night,...

2004-10-19 04:45:41

Chromosphere -- The chromosphere (literally, "color sphere") is a thin layer of the Sun's atmosphere just above the photosphere, roughly 10,000 kilometers deep. The chromosphere is more visually transparent than the photosphere. The most common solar feature within the chromosphere are spicules, long thin fingers of luminous gas which appear like the blades of a huge field of fiery grass...

Cataclysmic Variable Star
2004-10-19 04:45:41

Cataclysmic Variable Star -- Cataclysmic variables are a class of binary stars containing a white dwarf and a companion star. The companion star is usually a red dwarf, although in some cases it is another white dwarf or a slightly evolved star (subgiant). Several hundreds of cataclysmic variables are known. From the observational viewpoint, cataclysmic variables are relatively easy to...

Binary Star
2004-10-19 04:45:41

Binary Star -- A binary star system consists of two stars both orbiting around a gravitational point between them. The term "binary star" was apparently first coined by Sir William Herschel in 1802 to designate "a real double star - the union of two stars that are formed together in one system by the laws of attraction." At present, binary stars are classified into three types according...

Big Bang
2004-10-19 04:45:41

Big Bang -- The Big Bang theory is the dominant theory in cosmology about the early development and current shape of the universe. According to this theory, the universe expanded rapidly starting 13.7 0.2 billion years ago. Extrapolating the history of the universe backwards using current physical models leads to a gravitational singularity, at which all distances become zero and...

2004-10-19 04:45:41

Aurora -- The Polar Aurora are natural displays of light in the sky that can be seen with the unaided eye only at night. An auroral display in the Northern Hemisphere is called the aurora borealis, or the northern lights; in the Southern Hemisphere it is called the aurora australis. Auroras are the most visible effect of the sun's activity on the earth's atmosphere. The beautiful and often...

2004-10-19 04:45:41

Asteroid -- An asteroid, also called a minor planet or planetoid, is a member of a group of small, planet-like bodies that are part of our solar system. They are believed to be remnants of the interstellar clouds, nebula, that were not incorporated into planets during the formation of the solar system. The largest asteroid in the inner solar system is Ceres with a diameter of 1003 km. It...

Word of the Day
  • A pivoted catch designed to fall into a notch on a ratchet wheel so as to allow movement in only one direction (e.g. on a windlass or in a clock mechanism), or alternatively to move the wheel in one direction.
The word 'pawl' probably comes from a Latin word meaning 'stake'.