Pistol Star

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**Pistol Star**
Observation data Epoch J2000
False-color image of the Pistol Star and Pistol Nebula, taken by NICMOS.
Constellation	Sagittarius
Right ascension	17^h 46^m 15.3^s
Declination	-28° 50′ 04″
Apparent magnitude (V)	4
Physical Characteristics
Mass	150 M_☉
Radius	300-340 R_☉
Luminosity	> 10⁶ L_☉
Temperature	14-21,000 K
Metallicity	?
Rotation	?
Age	2 × 10⁶ years

The Pistol Star, is one of the most luminous known stars in the Milky Way Galaxy. ("Luminosity" means radiated power.) Early reports suggested that it might be the most extreme known star, producing almost 10 million times as much power as the Sun. Later studies, however, have reduced this number to roughly 1.7 million, making it one-third as luminous as Eta Carinae, for example^[1]. The Pistol Star radiates about as much energy in 20 seconds as the Sun does in a year. Objects in this class have 80 to 150 times the mass of the Sun and "lifetimes" of about 3 million years. Unlike ordinary stars, they are strongly affected by outward pressure of the light that they emit.

This object owes its name to the shape of the Pistol Nebula which it illuminates. It is located in a remarkable place, near the center of our Galaxy, approximately 25,000 light years from Earth in the direction of Sagittarius. The Pistol Star would be visible to the naked eye as a fourth magnitude star, if it were not for the interstellar dust clouds hiding it from view; instead it was discovered by the Hubble Space Telescope in the early 1990s using infrared wavelengths that penetrate the dust.

The Pistol Star is thought to have ejected almost 10 solar masses of material in giant outbursts perhaps 4000 to 6000 years ago. Its stellar wind is 10 billion times stronger than the Sun's. Its exact age and future cannot be determined for certain, but it is expected to end in a brilliant supernova or hypernova in 1 to 3 million years. Some astronomers conjecture that its large mass may be related to its location near the galactic center, since the star formation process there may favor massive objects.

In addition to the Pistol Star, several other objects have been cited as "most luminous star" in recent years. Almost all of them have been demoted by later, improved studies. The highest confirmed luminosity is about 5 million times that of the Sun in the case of Eta Carinae, which was probably born with between 150 and 200 solar masses. Our Galaxy most likely has 10 to 100 stars that surpass Eta Car, and they are probably detectable in infrared light; but their visible light is hidden by interstellar dust, and practical difficulties obstruct astronomers from identifying them.