Star
A star (or "sun") is a massive energy-producing sphere of plasma and gas located in space. The region around a star that is held by its gravity, including any planets, moons, comets, and asteroids, is called a star system. A set of stars inside a field of view is called a starfield.

Stellar life cycle

Formation
Stars are born out of huge gaseous nebulae. Inside these nebulae, centers of higher density form, slowly accumulating more mass as the center's gravity increases, to form a protostar. Pressure in the interior of the protostar rises, in turn increasing the density and temperature until the gas turns to plasma, where the atomic nuclei and the electrons are dissociated from each other. At a sufficient temperature and pressure, nuclear fusion is initiated at the stellar core, producing light: the star is born.

Star evolution
Stars can be made up of various different elements depending on their age. 

Young stars mainly consist of hydrogen, which is fused to helium thereby increasing the star's helium ratio over time and producing large quantities of energy. This energy, in turn, creates extreme pressure, preventing the star from collapsing under its own gravity. 

Dr. Tolian Soran used a trilithium weapon in 2371 to stop all fusion reactions inside the Amargosa sun, thereby collapsing the star and altering the gravitational conditions in the system. ()

As a sun gets older it begins to fuse heavier elements, like helium, as the lighter elements like hydrogen are depleted. This, however, releases more energy, causing the star to swell, which increases its surface area from which the energy is emitted. This phase marks the beginning of the star's end.

In 2367, Dr. Timicin of the planet Kaelon II tried to save the dying star Kaelon by regulating its ever-increasing temperature with the bombardment of photon torpedoes. However, the experiment failed after testing the procedure with a star in an uninhabited solar system. ()

Because of its larger surface area, the star turns red and is then called a red giant. After the sun runs out of light elements and the number of fusion reactions decreases, its own gravity causes it to collapse and to expel its outer layers of matter, creating beautiful "planetary nebulae". The remnant of the star is called white dwarf. 

Every star has to pass these stages of evolution. However, depending on their masses, some suns experience further changes.

Below 1.5 Sol masses: After one to ten billion years any nuclear reactions inside the white dwarf finally cease and the star turns to a "black dwarf", a very small stellar corpse.

Planets orbiting stars going through this phase would often experience extreme temperature decreases, such as in the case of Psi 2000 and Exo III, which orbited black dwarves. ()
In 2370, the  hosted Dr. Gideon Seyetik's successful attempt to re-ignite the stellar corpse Epsilon 119 by using a protomatter-laden shuttlepod remotely sent into the star. In the case of a failure, the star could have exploded in a supernova instead. ()

Above 1.5 Sol masses: The white dwarf swells again, fusing all elements up to iron. After the last iron is depleted, the star turns into a supernova, where the outer layers of the sun explode, which, in turn, causes a massive shock wave. The remains of this explosion are a vast matter nebula and a tiny neutron star, which is so dense, that all protons and electrons are neutralized to neutrons. A special form of neutron stars are pulsars.

In 2269, the star Beta Niobe turned to a supernova, when crewmembers of the Federation starship  were almost trapped on its planet Sarpeidon. ()

The resulting electromagnetic pulse from the supernova of Beta Magellan in 2364 was so feared by the computer-dependent Bynar in the nearby Beta Magellan system that they commandeered the  as a temporary dump for their planetary computer. ()

In 2373, a series of supernovae witnessed by the  in the Delta Quadrant turned out to be the real-time result of "battles" during a civil war in the Q Continuum. They were actually created by spatial disruptions in the Continuum, which created a negative-density false vacuum that sucked nearby matter into the Continuum. ()

In 2387, the Romulan sun went supernova and destroyed Romulus. Although this was known at least two years in advance, the planet's evacuation could not be completed in time. (; )

If the remnant of a supernova is more massive than 2.5 Sol masses, it collapses to a black hole.

Stellar classification 
Stars are assigned to different spectral classes.

Parts 
 Corona
 Stellar core
 Chromosphere

Types 
Protostar
F-type star
G-type star
Hypergiant
Neutron star
O-type star
Pulsar
Red dwarf
Red giant
Supergiant
T-Tauri type
White dwarf
Yellow dwarf
Black hole
Black star

As a symbol 
According to Roberta Lincoln's official file, she had a star-shaped birthmark on part of her anatomy. ()

Islam might be symbolized by a star within a crescent moon. ()

See also 
 Heat shield
 Metaphasic shield
 Unnamed stars
 Gold star
 Star of David
 Sun of May

External links
 
 

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fr:Étoile
it:Stella
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Celestial objects