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Giant star pushes the theoretical limit |
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Written by Derek Kessler on
Thursday, 02 October 2008
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 Weighing in at 116 times the mass of the sun - that’s 254,000,000,000,000,000,000,000,000,000 tons - coming close to the theoretical limit of 150 solar masses (at which point gravity would not be strong enough to keep the hydrogen and helium in close). The next closest star hardly comes close, at just 89 solar masses. And they are brother and sister, gravitationally bound to each other.
The two stars were discovered last year, but it wasn’t until new measurements this year that astronomers realized just how heavy they were. Stars of this size are extremely rare, with tens of thousands of stars around 0.5-5 solar masses for every supermassive star. The measurements were taken by the Very Large Telescope in Chile and the infrared cameras aboard the Hubble Space Telescope.
Similarly to how astronomers measure the gravitational wobble that large extrasolar planets exert on their parent stars, the mass of the two stars was calculated by analyzing how they orbited around each other. There is some variance in the measurements - plus-or-minus 30 solar masses, so the largest star could weigh in at close to 146 solar masses. The binary star system, named A1, is in the star cluster NGC 3603, about 20,000 light-years away in the Carina arm of our galaxy.
They fall into a class of stars called Wolf-Rayet stars. They are large hot stars that are so powerful that their solar wind and radiation actually overcomes the force of the star’s gravity and blows away large amounts of the star’s mass. Over their lifetime, the star can lose up to ten percent of their mass. For these massive stars, the extreme power of their fusion core can burn itself out in 2-3 million years. In comparison, our own sun is estimated to have been around for 4.5 billion years, and to last for at least that much longer.
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