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.

One of two stars orbiting a common center of gravity: Binary stars are a pair of stars revolving around a common center of gravity, held together by their mutual gravitational interaction.

Binary stars, or a double star, is a system containing two or more stars.

In an "eclipsing binary", one star goes behind the other periodically, changing the total amount of light that we see.

A gaseous body or object smaller in mass than a star, but larger than a planet and heavier than a star..
2. An object less massive than a star, but heavier than a planet: A brown dwarf star is a theoretical "star" and does 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 dwarf stars exist throughout the galaxy, but because of the difficulty in detecting them, none of them were discovered until 1995, when U.S. astronomers discovered a brown dwarf, in the constellation Lepus (Hare).

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: Circumpolar stars are those that are within a circumpolar circle in which the size is determined by the viewer's latitude.

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 older star that has converted most or all of its store of hydrogen into helium: An evolved star is a star that is nearing the end of its existence when most of its fuel has been used up.

This period of the star's duration 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; meteor burst: Jack and Jill decided to watch the stars during the clear, cloudless night, and suddenly saw a falling star, or shooting star, which was a bright streak of light in the sky.

A star whose brightness can increase by as much as two to 100 times in a matter of minutes, then return to normal: The sudden brightness of a flare star, as a faint red dwarf, fades away quickly after amounting to many magnitudes of bright intensity.

agency:
start-up fund:
inventors:

"The U.S. government agency that helped invent the Internet now wants to do the same for travel to the stars."