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The Pistol Star is an extremely luminous blue
The Pistol Star was discovered using the 
Later studies have reduced its estimated luminosity making it a candidate
NASA Discovery press release, Oct 7, 1997
Further details on the Pistol Star from hubblesite.org
{{DEFAULTSORT:Pistol Star Luminous blue variables Sagittarius (constellation) B-type hypergiants Sagittarii, V4647 ? J17461524-2850035 Stars with proper names
hypergiant
A hypergiant (luminosity class 0 or Ia+) is a very rare type of star that has an extremely high luminosity, mass, size and mass loss because of its extreme stellar winds. The term ''hypergiant'' is defined as luminosity class 0 (zero) in the MK ...
star
A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
, one of the most luminous and massive known in the Milky Way
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...
. It is one of many massive young stars in the Quintuplet cluster
The Quintuplet cluster is a dense cluster
may refer to:
Science and technology Astronomy
* Cluster (spacecraft), constellation of four European Space Agency spacecraft
* Asteroid cluster, a small asteroid family
* Cluster II (spacecraft ...
in the Galactic Center
The Galactic Center or Galactic Centre is the rotational center, the barycenter, of the Milky Way galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a compact rad ...
region. The star owes its name to the shape of the Pistol Nebula
The Pistol Nebula is located in the constellation Sagittarius. It surrounds one of the most luminous stars known, the Pistol Star. Both are located 25,000 light years away from Earth in the Quintuplet cluster, near the center of the Milky Way ga ...
, which it illuminates. It is located approximately 25,000 light-year
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s from Earth in the direction of Sagittarius. The star has a large mass comparable to V4998 Sagittarii
V4998 Sagittarii is a luminous blue variable star (LBV) in the constellation of Sagittarius (constellation), Sagittarius. Located some 100 exametres, 25,000 light years away, the star is positioned about 7 parsec, pc (23 light year, ly) a ...
and a luminosity 3.3 million times that of the Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
(). It would be visible to the naked eye as a 4th-magnitude star if it were not for the interstellar dust near the Center of the Milky Way that absorbs almost all of its visible light.
Properties
The Pistol Star was discovered using the Hubble Space Telescope
The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...
in the early 1990s by Don Figer, an astronomer at UCLA
The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California. UCLA's academic roots were established in 1881 as a teachers college then known as the southern branch of the California St ...
.
The star is thought to have ejected almost 10 solar mass
The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...
es of material in giant outbursts perhaps 4,000 to 6,000 years ago (as observed from Earth). Its stellar wind
A stellar wind is a flow of gas ejected from the upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spherically symmetric.
D ...
is over 10 billion times stronger than the Sun's. Its exact age and future are not known, but it is expected to end in a brilliant supernova
A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...
or hypernova
A hypernova (sometimes called a collapsar) is a very energetic supernova thought to result from an extreme core-collapse scenario. In this case, a massive star (>30 solar masses) collapses to form a rotating black hole emitting twin energetic je ...
in 1 to 3 million years. The mass is equally uncertain, thought to have been up to 200 times the Sun when initially formed but now considerably less due to extreme mass loss although likely still over 100 times the Sun. Modelling the star itself to match its spectrum gives a mass of , while matching its current properties to an evolutionary model gives a much higher mass (). Earlier studies once claimed the Pistol Star as the most massive star known at around .
Later studies have reduced its estimated luminosity making it a candidate luminous blue variable
Luminous blue variables (LBVs) are massive evolved stars that show unpredictable and sometimes dramatic variations in their spectra and brightness. They are also known as S Doradus variables after S Doradus, one of the brightest stars of the Larg ...
about (one third as luminous as the binary star
A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...
system Eta Carinae
Eta Carinae (η Carinae, abbreviated to η Car), formerly known as Eta Argus, is a stellar system containing at least two stars with a combined luminosity greater than five million times that of the Sun, located around distant in t ...
), hence a radius of based on an effective temperature
The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...
around , or as high as , hence a correspondingly larger radius of anywhere from to . Even so, it radiates about as much energy in 10 seconds as the Sun does in a year.
A close point source has been discovered hidden in the surrounding nebulosity
A nebula ('cloud' or 'fog' in Latin; pl. nebulae, nebulæ or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regio ...
, but there has been no confirmation of this being a star or whether it is physically associated.
See also
* LBV 1806−20 *List of largest known stars
Below are lists of the largest stars currently known, ordered by radius and separated into categories by galaxy. The unit of measurement used is the radius of the Sun (approximately ).
The angular diameters of stars can be measured directly us ...
* Wolf–Rayet star
Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of ionised helium and highly ionised nitrogen or carbon. The spectra indicate very high surface ...
Notes
References
External links
NASA Discovery press release, Oct 7, 1997
Further details on the Pistol Star from hubblesite.org
{{DEFAULTSORT:Pistol Star Luminous blue variables Sagittarius (constellation) B-type hypergiants Sagittarii, V4647 ? J17461524-2850035 Stars with proper names