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.

1. A gaseous body smaller in mass than a star, but larger than a planet.
2. An object less massive than a star, but heavier than a planet.

Brown dwarfs do not have enough mass to ignite nuclear reactions at their centers, but shine by heat released during their contraction from a gas cloud.

Some astronomers believe that vast numbers of brown dwarfs exist throughout the galaxy, but because of the difficulty in detecting them, none of them were detected until 1995, when U.S. astronomers discovered a brown dwarf, in the constellation Lepus (Hare).

A reference to a star, asterism, or constellation that is close enough to the celestial pole that, depending on the latitude at which a person is observing, it never appears to set.

1. A pair of stars that appear close together in the sky only because they lie in the same direction from the earth, and not because they are physically associated binary stars.
2. A system containing two or more stars.

In a true double, the stars are physically close to each other; in an optical double, they lie in approximately the same direction from the earth and so appear close to each other, but are actually far apart.

1. An older star that has converted most or all of its store of hydrogen into helium.
2. A star near the end of its lifetime when most of its fuel has been used up.

This period of the star's existence is characterized by loss of mass from its surface in the form of a stellar wind or the ejection of gas off the surface of a star.

Many different types of stars, including our sun, have stellar winds; however, a star's wind is strongest near the end of its existence when it has consumed most of its fuel.

A popular term for a meteor.

A star whose brightness can increase by as much as two to 100 times in a matter of minutes, then return to normal.

1. The result of the collapse of the remnant from a supernova explosion if its mass exceeds the chandrasekhar limit, but is less than that required for gravity to continue the collapse down to a black hole. 2. A very small core of a super-dense star composed mostly of neutrons (electrically neutral subatomic particles in the baryon family).

One of a family of pulsating giant stars, with periods of less than one day.

The period of particular examples does show changes, both abrupt and slow. Such stars are commonly found in globular clusters.

A popular name for a meteor.

A listing of the known stars with their names, positions, and movements.

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.

1. A star whose brightness changes over time.
2. A star whose luminous output varies significantly with time.

Such variation may be regular; that is, eclipsing variable stars, or irregular, as with flare stars.

In addition, the variation can be intrinsic, because of changes within the star itself, or extrinsic, as the result of the interaction of one star with another.

A member of a class of stars undergoing rapid mass loss, and having peculiar spectra.

Most Wolf-Rayet stars have companions in binary systems.

"The Sun does not move", wrote Leonardo da Vinci in 1495

Well, everything in the Cosmos moves, including the sun, the earth and the Star Signs of the Zodiac. The Signs of the Zodiac were first mapped by the ancient Babylonians about 3,000 years ago when, indeed, there were 12 Star Signs.

Movement on the Cosmic time-scale is very slow compared with the time-scale of a human life. The Star Signs are slipping by a small amount each year, so that there are now 13 Signs in the Zodiac.

The Sign of Ophiuchus (30 November-17 December) moved into the Zodiac over 1,000 years ago. Most astrologers continued to use the traditional 12 Signs of the Zodiac because they were unaware of star movements. That practice has continued to the present day.

To illustrate just how slowly the Cosmic clock advances: the Age of Pisces replaced the Age of Aries about 1,400 years ago, and the much-heralded Age of Aquarius will not be here for another 600 years!

The New Signs of the Zodiac

1. The New Pisces: First Sign of the Zodiac: 12 March to 18 April.
2. The New Aries: Second Sign of the Zodiac: 19 April to 13 May.
3. The New Taurus: Third Sign of the Zodiac: 14 May to 20 June.
4. The New Gemini: Fourth Sign of the Zodiac: 21 June to 19 July.
5. The New Cancer: Fifth Sign of the Zodiac: 20 July to 19 August.
6. The New Leo: Sixth Sign of the Zodiac: 20 August to 15 September.
7. The New Virgo: Seventh Sign of the Zodiac: 16 September to 30 October.
8. The New Libra: Eighth Sign of the Zodiac: 31 October to 22 November.
9. The New Scorpio: Ninth Sign of the Zodiac: 23 to 29 November.
10. The New Ophiuchus: Tenth Sign of the Zodiac: 30 November to 17 December.
11. The New Sagittarius: Eleventh Sign of the Zodiac: 18 December to 18 January.
12. The New Capricorn: Twelfth Sign of the Zodiac: 19 January to 15 February.
13. The New Aquarius: Thirteenth Sign of the Zodiac: 16 February to 11 March.