Astronomy and related astronomical terms

(the science of the celestial bodies: the sun, the moon, and the planets; the stars and galaxies; and all of the other objects in the universe)

The astronomer said,
As he raised his cup,
"Thank heavens my business
Is looking up."
—Ennis Rees, Pun Fun;
Scholastic Book Services; New York; 1965; page 13.
Spörer's law, Sporer's law
1. A relationship to indicate the frequency of the occurrene of sunspots and their progressive movements to lower latitudes on the sun.
2. This "law" predicts the variation of sunspot latitudes during a solar cycle and refers to changes in the amount of total solar radiation and its spectral distribution.
3. The tendency of sunspots to appear at the start of the sun's eleven-year sunspot cycle at high solar latitudes, and for later sunspots to appear at successively lower solar latitudes, before starting the next cycle at the higher latitudes again.
star, stars
1. A hot, glowing sphere of gas, usually one that emits energy from nuclear reactions in its core.
2. A luminous globe of gas, mainly hydrogen and helium, which produces its own heat and light by nuclear reactions.

Although some stars may shine for a very long time; even, many billions of years, they are not eternal, and have been found to change in appearance at different stages in their appearances.

3. A body; such as, the sun, that produces energy by means of nuclear reactions taking place within it.

The star is held in a stable state by balancing the outward radiation pressure by the inward gravitational force.

steady-state theory
1. A theory of the evolution of the universe that states that the universe has always been in the state it is now, which leads to the implication that the universe has no origin, but has always existed.
2. A rival theory to that of the Big Bang which claims that the universe has no origin but is expanding because new matter is being created continuously throughout the universe.

The theory was proposed in 1948 by Austrian-born British cosmologist Hermann Bondi, Austrian-born U.S. astronomer and physicist Thomas Gold, and English astronomer Fred Hoyle, but this concept was challenged in 1965 by the discovery of cosmic background radiation and is now largely rejected by scientists.

stellar wind
The stream of particles "blown" by the radiative pressure of a star away into space.
The nearest star to earth and the brightest object in the sky which emits electromagnetic radiation of various wavelengths; some of them harmful to life.

The earth's atmosphere absorbs most of these injurious radiations and life on earth would be impossible with out the heat and light from the sun.

So, it is understandable that as far as life on earth is concerned, people realize that the sun is the most important star in the sky.

The sun's distance from Earth has been calculated as

  • Farthest distance: 94,500,000 miles or 152,100,000 kilometers.
  • Nearest distance: 91,400,000 miles or 147,100,000 kilometers.
  • Average distance: 92,960,000 or 149,600,000 kilometers.
—Based on information presented in
Astronomy, The World Book Encyclopedia of Science;
World Book, Inc.; Chicago; 2000; page 62.

The sun is about 4.6 billion years old and is the dominant body of the solar system, with more than 99% of its mass.

It converts about 4.5 million tons of matter into energy every second by nuclear fusion reactions in its core, producing neutrinos and solar radiation.

The small amount of this energy that penetrates Earth’s atmosphere provides the light and heat that support life.

A sphere of luminous gas 1,392,000 kilometers, or 864,950 miles, in diameter, the Sun has about 330,000 times the mass of Earth.

Its core temperature is close to 15,000,000 Kelvins, 27,000,000 °Fahrenheit, and its surface temperature is about 6,000 Kelvins, 10,000 °Fahrenheit.

—Encyclopædia Britannica,
Encyclopædia Britannica Online;
retrieved May 11, 2010.
1. A dark patch on the surface of the sun, actually an area of cooler gas, thought to be caused by strong magnetic fields that block the outward flow of heat to the sun's surface.

Sunspots consist of a dark central umbra and a lighter surrounding penumbra. They last from several days to over a month.

2. A dark path on the sun's surface (photosphere) marking the position of a region of intense magnetic field.

A sunspot can be divided into two regions:

  • The central umbra which has a typical temperature of about 4000 degrees Fahrenheit or 2200 degrees Centigrade.
  • The outer penumbra, at about 5500 degrees Fahrenheit or 3000 degrees Centigrade.

The relative coolness of these regions compared to their surroundings produces the dark contrast. Sunspots usually occur in groups, with typical lifetimes of about two weeks.

1. A large massive star of low density and very high luminosity.
2. The largest and brightest type of all stars, of which Antares in Scorpius is an example.
superior planet
Any planet that lies farther from the sun than the earth.

The superior planets are Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.

superior planet conjunction
In conjunction or the alignment of two celestial bodies when they lie or pass behind the sun.
Any object whose apparent speed exceeds the speed of light.
supernova (s), supernovae (pl)
1. The explosive death of a star, which temporarily attains a brightness of 100 million suns or more, so that it can shine as brilliantly as a small galaxy for a few days or weeks.
2. A stellar explosion which increases the luminosity of the star to many thousands of times brighter than a nova.
3. The sudden, temporary and enormous increase in brightness of a star, resulting from the blowing off of most of its constituent material during its destructive process.

Such an event occurs for stars only about six times more massive than the sun, the result being a white dwarf.

supernova remnants
The gas cloud ejected by the explosion of a supernova that spreads out into space, perhaps for millions of years.

During this time, the stellar remnants radiate huge amounts o energy, not only as visible radiation, or light, but also as X-rays and radio waves.

synchronous orbit
A satellite whose orbital period around the central body is the same as the rotation period that the central body has a synchronous orbit.
synchronous rotation
The axial rotation of a planetary satellite is said to be synchronous when its period of rotation is exactly the same as that for the satellite to orbit once around the central body.
synchrotron radiation
A form of electromagnetic radiation emitted by an electric charge moving relativistically through a magnetic field.

It is characterized by being polarized.

Also check out the Index of other Scientific and Technological Topics.