Blazing winds tear through gigantic binary system

Eta Carinae in a previous life?

NASA astronomers think they have identified one of the most extreme binary systems ever, containing two extremely massive stars in very tight orbit.

The boffins estimate that the larger of the two tips the cosmic scales at 62 solar masses, while its smaller companion can boast 37 solar masses.

Located in the Large Magellanic Cloud, a satellite galaxy of our Milky Way, the system consists of two extremely massive stars orbiting each other at less than one sixth of the distance from the Earth to the Sun.

The two stars are so close to one another they circle their common centre of mass in just 2.25 days. Astronomers predict they will eventually merge into a single ultra-massive star as they age and swell, containing around 80 times the sun's mass.

"The merger of two massive stars to make a single super star of over 80 suns could lead to an object like Eta Carinae, which might have looked like LH54-425 one million years ago," says NASA's George Sonneborn.

Eta Carinae is one of the most massive and luminous stars in the Milky Way Galaxy, with perhaps 100 solar masses.

"Finding stars this massive so early in their life is very rare," he continues. "These results expand our understanding of the nature of very massive binaries, which was not well understood. The system will eventually produce a very energetic supernova."

In such a tight system, the stellar winds crash into each other with astonishing results. Using NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) satellite and ground-based telescopes, the star gazers have watched the collision of the stellar winds emanating from each star.

The larger of the two stars is losing mass at the astonishing rate of 500 trillion tons per second, which it is flinging into space at around 5.4 million miles per hour. The smaller star is losing material at about a tenth of this rate.

The astronomers determined that the matter spewing out of the larger of the two stars smashes into that from the smaller star, creating a collision zone, a curved surface of superheated gases that emit far ultraviolet radiation and x-rays easily detectable with the FUSE kit. This superheated zone then envelopes the smaller star.

"These stars are evolving in the blink of an eye compared to the sun, which has looked pretty much the same for over four billion years," said Rosina Iping of the Catholic University, Washington, leader of the team that observed LH54-425 with FUSE.

"But this binary looks totally different from Eta Carinae even though there is maybe only one million years difference in age. These massive stars zoom through their life cycle really fast. Will this binary system produce something like Eta Carinae? We don't know." ®