Likely impression of a Luminous Blue Variable

A Luminous Blue Variable (or LBV), aka S Doradus variable is a hot blue star that changes its volume, luminosity, and temperature over an uncertain period of time. It is a star that was once a red supergiant (or hypergiant) and a yellow hypergiant, although in the future it may become a Wolf-Rayet star before exploding into a supernova or hypernova.

This article provides a few examples of them.

Eta Carinae

Eta Carinae is a binary star system consisting of two blue stars with a combined luminosity more than 5 million times greater than the Sun located in the constellation Carina.

The Great Eruption


Size comparison of Eta Carinae compared to Betelgeuse, HR 5171, and VY Canis Majoris.

Previously a 4th magnitude star, in 1837 it brightened to become the second brightest star marking the start of the Great Eruption. This astronomical event was observed by people around the world, even by the Aborigines of Australia, who named the star Collowgulloric War (the wife of Canopus). In 1856, Eta Carinae faded to become invisible to the naked eye.[10]

Homunculus Nebula

Following the Great Eruption, the gas expelled formed a small nebula around the star called the Homunculus Nebula. This nebula is around $ 2,750 $ billion kilometers in diameter.[11] The Homunculus Nebula is part of an even larger nebula, the Great Nebula of Carina (aka Carina Nebula).

S Doradus


S Doradus

Eso9931d (circled)

S Doradus is the star circled.

S Doradus is a blue hypergiant located 160,000 light years away from Earth in the Large Magellanic Cloud. It is one of the most luminous stars, with a luminosity between $ 910,000 $ and $ 1,400,000 $ solar luminosities.[12] The star has a temperature of $ 20,000 $ degrees Kelvin that can reach as low as $ 8,000 $ degrees Kelvin during outbursts.[13] The star has a diameter that pulsates between $ 100 $to$ 380 $ R $ (= 139 - 529 $ million km). It is also the prototype of class of Luminous blue variables.

S Doradus is the brightest member of the open cluster NGC 1910 (aka the LH41 stellar association), which is visible in binoculars as a bright condensation within the main spiral bar of the Large Magellanic Cloud. Another Luminous Blue Variable, R85, is just two arcminutes away from S Doradus. The rich star-forming surroundings also host a third Wolf-Rayet star and 20 other supergiants.[14]

Celestia 1.6.1.'s impression of S Doradus

The Pistol Star


Pistol Star


The Pistol Star and the Pistol Nebula are clearly visible.

The Pistol Star is named after the shape of the nebula it resides in, the Pistol Nebula. The Pistol Star has a diameter $ 306 $ times greater than the Sun's, a mass 27.5 times greater, and is $ 1,600,000 $ times brighter.[15] It is $ 25,000 $ light years away in the constellation Sagittarius, and could end its life in a hypernova. The Pistol Nebula obscures what could have been a magnitude 4 star from view.

P Cygni

P Cygni is a luminous blue variable located between $ 5,000 $ and $ 6,000 $ light years away from Earth and is widely considered to be the first LBV discovered. P Cygni has been identified as a possible type IIb supernova candidate in terms of modelling of the death of stars between $ 20 $ and $ 25 $ times the mass of the Sun.

LBV 1806-20


LBV 1806-20


LBV 1806-20 (circled) in its parent cluster, 1806-20.

LBV 1806-20 is a possible binary star located 40,000 light years away from the Sun in the Sagittarius constellation. It is $ 2 $ million[18] times brighter than the Sun but it is invisible from the Solar System at visual wavelengths because less than one billionth of its visible light reaches us. Among other Luminous Blue Variables, LBV 1806-20 is larger than the Sun, but only by $ 75.4 $ times $ (= 105 $ million km).[19]

LBV 1806-20 is located in the star cluster 1806-20, along with many other unidentified luminous blue variables and the magnetar SGR 1806-20.


  8. 8.0 8.1
  18. and
  19. Calculated from the mean temperature and luminosity: $ \sqrt{((5772/25000)^4 * 2,000,000)} = 75.385 $