LBV 1806-20 is a
luminous blue variableLuminous blue variables, also known as S Doradus variables, are very bright, blue, hypergiant variable stars named after S Doradus, the brightest star of the Large Magellanic Cloud. They exhibit long, slow changes in brightness, punctuated by occasional outbursts in brightness during substantial...
or possible
binary starA binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...
located 30,000–49,000
light-yearA light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s from the
SunThe Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, towards the center of the
galaxyThe Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
. It has a total system mass of 130–200
solar massThe solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
es and an estimated variable luminosity of up to 40 million times that of the Sun, making it comparably luminous to
Eta Carinae or the
Pistol StarThe Pistol Star is a blue hypergiant and is one of the most luminous known stars in the Milky Way Galaxy.It is one of many massive young stars in the Quintuplet cluster in the Galactic Center region....
, contenders for the
most luminous known star (all of which are
luminous blue variableLuminous blue variables, also known as S Doradus variables, are very bright, blue, hypergiant variable stars named after S Doradus, the brightest star of the Large Magellanic Cloud. They exhibit long, slow changes in brightness, punctuated by occasional outbursts in brightness during substantial...
s).
Despite its high luminosity, it is virtually invisible from the
Solar SystemThe Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
, because less than one billionth of its visible light reaches us, the rest being absorbed by intervening interstellar gas and dust. Although the star is 8th
magnitudeThe apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
at the near infrared wavelength of 2
micrometersA micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
, it is calculated to be about 35th
magnitudeThe apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
at visible wavelengths, which is undetectable.
Formation theory
Current star formation theories suggest that a star can have at most about 120 solar masses, but LBV 1806-20 has been measured to have at least 130 solar masses. Some measurements even give the star 150 to 200 solar masses.
There has been some dispute as to whether LBV 1806-20 is a single star or a cluster. Its luminosity has been estimated through very high-resolution
speckle imagingSpeckle imaging describes a range of high-resolution astronomical imaging techniques based either on the shift-and-add method or on speckle interferometry methods...
, the results of which suggest that LBV 1806-20 may be a single star. However, more recent high-resolution spectroscopy reveals that there may be a companion and that the mass of each star in the system could be considerably less than 130 solar masses.
Location
LBV 1806-20 lies at the core of radio
nebulaA nebula is an interstellar cloud of dust, hydrogen gas, helium gas and other ionized gases...
G10.0-0.3 and is a component of the
star clusterStar clusters or star clouds are groups of stars. Two types of star clusters can be distinguished: globular clusters are tight groups of hundreds of thousands of very old stars which are gravitationally bound, while open clusters, more loosely clustered groups of stars, generally contain less than...
Cl* 1806-20, itself a component of W31, one of the largest
H II regionAn H II region is a large, low-density cloud of partially ionized gas in which star formation has recently taken place. The short-lived, blue stars forged in these regions emit copious amounts of ultraviolet light, ionizing the surrounding gas...
s in the Milky Way. Cluster 1806-20 is made up of some highly unusual stars, including at least two carbon-rich Wolf–Rayet stars (WC9d and WCL), two blue
hypergiantA hypergiant is a star with a tremendous mass and luminosity, showing signs of a very high rate of mass loss.-Characteristics:...
s, and a
magnetarA magnetar is a type of neutron star with an extremely powerful magnetic field, the decay of which powers the emission of copious high-energy electromagnetic radiation, particularly X-rays and gamma rays...
, (
SGR 1806-20|- style="vertical-align: top;"| Distance | 50,000 light-years SGR 1806-20 is a magnetar, a particular type of neutron star. It has been identified as a soft gamma repeater. SGR 1806-20 is located about 14.5 kiloparsecs from Earth on the far side of our Milky Way galaxy in the constellation of...
).
See also
- Cl* 1806-20 -- star cluster
Star clusters or star clouds are groups of stars. Two types of star clusters can be distinguished: globular clusters are tight groups of hundreds of thousands of very old stars which are gravitationally bound, while open clusters, more loosely clustered groups of stars, generally contain less than...
- SGR 1806-20
|- style="vertical-align: top;"| Distance | 50,000 light-years SGR 1806-20 is a magnetar, a particular type of neutron star. It has been identified as a soft gamma repeater. SGR 1806-20 is located about 14.5 kiloparsecs from Earth on the far side of our Milky Way galaxy in the constellation of...
-- soft gamma-ray repeaterA soft gamma repeater is an astronomical object which emits large bursts of gamma-rays and X-rays at irregular intervals. It is conjectured that they are a type of magnetar or, alternatively, neutron stars with fossil disks around them....
- List of most luminous stars
External links
- SolStation article
- The Double-Lined Spectrum of LBV 1806-20, Donald F. Figer (STScI), Francisco Najarro (CSIC), Rolf P. Kudritzki (UH), 2004
- Massive Stars in the SGR 1806-20 Cluster, Donald F. Figer (STScI), Francisco Najarro (CSIC), T. R. Geballe (Gemini Observatory), R. D. Blum (CTIO), Rolf P. Kudritzki (UH), 2005