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What is a Luminous Blue Variable Star?

Luminous Blue Variable name came about in 1984 by a talk by Paul Conti. He describes them as being non-Wolf-Rayet stars. In his talk, he united the other known types of S Doradus, Hubble Sandage Variable and P Cygni.

LBV for short, were thought to be between Main Sequence and Wolf-Rayet stages. Latter research from 2017 seems to disprove this theory and that they cannot be the next step in massive star evolution. Royal Society

Only twelve have been spotted in our galaxy. In addition to our galaxy, the milky way, LBVs can also be found in Messier spiral galaxies of Andromeda Galaxy (M31) and Triangulum Galaxy. Other local group spiral galaxies do not have these. E.S.A.

The word Variable gives their style away, these star's sizes can change. LBVs are massive blue stars that flare up by ejecting a large amount of mass and then die back down again. They will stay calm for a short period of time before flaring up again then repeat. LBVs extremely hot stars and the hotter and bigger a star is, the shorter the life of the star. U.C.S.B.

Of the four LBV covered by this site, three are too far and dim to be able to be located without a visual aid. The fourth, AF Andromedae, the apparent magnitude is not known by us.

These stars when they eventually die will leave behind a black hole. The eruptions are caused when extreme luminosity wins over from gravity which is pulling in matter. Cosmos

LBV stars are post-Main Sequence where the star has finished converting hydrogen into helium. Whilst some stars will then progress to red supergiant stage such as Betelgeuse, there is no evidence that Classic LBV (Mag -9) stars have been in supergiant phase nor will they actually get to that phase. The other type of LBVs are cooler (mag -8 -> -9) and have lower temperatures, these could have been red supergiants. I.O.P

Pistol Star

The Pistol Star is one of the most luminous stars, pumping out more energy than our Star. It is the largest in terms of mass and brightness, the star that has the largest radius in currently is UY Scuti which is a massive red star.

The star has an apparent magnitude of 11.83 which means you would need a 4-6 " telescope to see it. It is amongst the Pistol nebula, an area of space near the centre of the Milky Way, known as Sagittarius A*. It gets its name from the Pistol Nebula. If the nebula of dust and cloud was not there, the star would have an apparent magnitude of about 4 which would mean it would easily be seen by the naked eye. The star would be as bright as the star Jabbah.

The star has more than 200 times the mass of the Sun. As mentioned before, the bigger and hotter does not result in a longer lifetime. Whereas our Sun can expect to live for about ten billion years, this star would only live say millions of years.

The star has a radius of around 306 times that of our Sun. If the star was in the place of the Sun, Earth would be orbiting within the star and no-one would be alive. N.A.S.A.

The following picture is a false colour image of the Pistol Nebula with the Pistol Star in the middle. The outer magneta blur is the shell being blown off and is as large as four light years. It is equivalent to the distance from the sun to Proxima Centauri. Hubble

False colour image of Pistol Star taken by the <a href=/fact/hubblespacetelescope>hubble space telescope</a>.


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