Astronomers were able to observe for the first time the properties of a giant binary system consisting of the most massive and luminous types of stars in the Universe. Called LH54-425, the pair of stars orbiting each other is located in the Large Magellanic Cloud, a satellite galaxy of our Milky Way.
The Large Magellanic Cloud (LMC) is a dwarf galaxy that orbits our own galaxy, the Milky Way. It is at a distance of about fifty kiloparsecs (160,000 light-years). It has about 1/20 the diameter of our galaxy and 10 billion stars, around 1/10 the number of stars found in the Milky Way.
The observations were made by Georgia State University astronomer Stephen Williams at the 1.5-meter (4.9 foot) telescope at the Cerro Tololo Inter-American Observatory in Chile and by a team led by George Sonneborn of NASA Goddard Space Flight Center, Greenbelt, Md., that used NASA`s Far Ultraviolet Spectroscopic Explorer (FUSE) satellite.
Made up of two giant stars, containing about 62 and 37 times the mass of our Sun and being not more than 3 million years old, the system is one the most extreme binaries known.
"The stars are so close to each other -- about one-sixth the average Earth-Sun distance -- that they orbit around a common center of mass every 2.25 days," says Williams' colleague Douglas Gies of Georgia State University, Atlanta.
The two stars are so energetic that they blow off huge amounts of stellar wind that collide, and details of what happens in this collision were captured by the FUSE satellite. When the winds collide, the entire area of the collision wraps around the smaller star and produces a curved surface of superheated gases that emit X-rays and far-ultraviolet radiation.
The most massive star is hurling 500 trillion tons of material into space every second, at a speed of 5.4 million miles per hour, a loss rate almost 400 times greater than that released by our Sun in the form of solar wind. The smaller one is generating only one-tenth of that quantity in the same amount of time.
"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 Sonneborn. "Finding stars this massive so early in their life is very rare. 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."
This will happen after a period of time in the old age of the two stars, after they have exchanged impressive quantities of matter, at which time they will most probably merge into one supersized star, much like the bigger star in the Eta Carinae binary system.