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Monster Star Cut Down to Size

Monster Star Cut Down to Size
The Pismis 24 star cluster sits within the emission nebula NGC 6357 seen here in an image taken by the Hubble Space Telescope.
(Image: © NASA/ESA/Jesús Maíz Apellániz/Instituto de astrofísica de Andalucía, Spain.)

A monster star thought to be among the mostmassive in our Milky Way galaxy isactually slimmer than expected because it's actually a pair of twins,astronomers announced today.

Researchersonce believed the star--known as Pismis 24-1--loomed large with a mass between200 and 300 times that of the Sun. Butmore accurate measurements by the Hubble Space Telescope foundnot one, but two stars in Pismis 24-1's location, effectively cutting the estimatedweight in half to about 100 solar masses.

The stellarfind is part of a study to determine the upper mass limit for stars.

Pismis 24-1sits in star cluster at the core of the emissionnebula NGC 6357 some 8,000 light-years from Earth towards the constellationSagittarius [image].Young hot stars spew intense ultraviolet radiation into the nebula, heating upthe surrounding interstellar gas to create a sort of local bubble, Hubbleresearchers said in a statement.

Astronomer Jes?s Ma?z Apell?niz, of Spain's Instituto de Astrof?sicade Andaluc?a, led the study to weigh Pismis 24-1. His team also managed togauge the mass of a third nearby star, dubbed Pismis 24-1, and pegged thatobject at about 100 solar masses.

Theresearch, which relied on images taken by Hubble's Advanced Camera forSurveys, was presented this month at the Massive Stars Workshop inArgentina.

The trio ofheavyweight stars within the Pismis 24 system is a rare find for such a smallstellar cluster, Hubble researchers said. For every discovery of a 65-solarmass star, some 18,000 Sun-mass stars are formed, they added.

Thelifecycle of a 65-solar mass star ends after just three million years, though aSun-mass star can burn for more than 3,000 times that. Our own Sun isconsidered middle-aged at 4.6 billion years old.

It's possiblethat Pismis 24-1 may include a third star based on some ground observations,Hubble researchers added. If true, each of the three stars would average about70 stellar masses, but remain on the Top 25 roster of the Milky Way's mostmassive stars.

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