Astronomy and related astronomical terms

The stream of particles "blown" into space.by the radiative pressure of a star: Stellar winds are winds that are emitted from the surface of a star into the space.around it.

The nearest star to earth and the brightest object in the sky which emits electromagnetic radiation of various wavelengths, and 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.

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.

As 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.

1. A dark patch on the surface of the sun, actually an area of cooler gas: A sunspot is thought to be caused by strong magnetic fields that block the outward flow of heat to the Sun's surface. 2. A dark path on the sun's surface (photosphere): A sunspot marks the position of a region of an intense magnetic field.

• 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.

A large massive star (between 10 and 70 solar masses)of low density and very high luminosity: A supergiant is a largest and brightest type of all stars, of which Antares in Scorpius is an example.

Any planet that lies farther from the Sun than the Earth: The superior planets are Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.

The alignment of two celestial bodies when they lie or pass behind the sun: A superior planet conjunction takes place when planets, like Jupiter, have orbits larger or greater than the Earth's orbit, and are on the other side of the Sun from the Earth in which all objects are arranged in a straight line.

Referring to an object whose apparent speed exceeds the speed of light: In the fantasy story, Jane read about a superluminal being that could travel with such a speed that it could be anywhere in space in less than a second.

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: A supernova refers to a stellar explosion which increases the luminosity of the star to many thousands of times brighter than a nova.

The sudden, temporary and enormous increase in brightness of a star, results 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.

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

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

A geostationary 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.

The axial rotation of a planetary satellite is said to be synchronous: A synchronous rotation occurs when the satellite's period of rotation is exactly the same as that for the satellite to orbit once around the central body.

A form of electromagnetic radiation emitted by an electric charge moving relativistically through a magnetic field: Synchrotron radiation is characterized by being polarized.

The length of time during which a body in the solar system makes one orbit of the Sun relative to the Earth, that means that it returns to the same elongation: Because the Earth moves in its own orbit, the synodic period differs from the sidereal period, which is measured relative to the stars.

The synodic period of the Moon, which is called the lunar month, or lunation, is 29 1/2 days long which is longer than the sidereal month.

The synodic period is the time required for a body in the solar system to return to the same or about the same position relative to the Sun as seen from the Earth.

The Moon's synodic period is the time between successive recurrences of the same phase, that means the period between one full moon and the next full moon.

1. One of a group of stars that have irregular light curves, and which are believed to represent the stage in a star's evolution shortly before it appears on the main sequence.

The stars characteristically have rapid rotation and throw off much material in stellar winds.

2. Any of a class of very young stars having a mass of the same order as that of the sun.

So called after a prototype identified in a bright region of gas and dust known as the Hind’s variable nebula, the T Tauri stars are characterized by erratic changes in brightness.

They represent an early stage in stellar evolution, having only recently been formed by the rapid gravitational condensation of interstellar gas and dust.

These young stars are relatively unstable, though contracting more slowly than before, and will remain in that condition until their interior temperatures become high enough to support thermonuclear reactions for energy generation.

More than 500 T Tauri stars have so far been observed. The sun is thought to have gone through the T Tauri stage in its beginning.

A zodiacal constellation in the northern hemisphere near Orion, represented as a bull. The sun passes through Taurus from mid-May to late June.