A “Nasty” Star!


Wolf-Rayet stars represent a final blaze of glory before a doomed massive star finally reaches the end of that long stellar road and explodes in a brilliant and invariably fatal supernova explosion. Massive stars live fast and die young–and Wolf-Rayet stars are very massive, indeed. These stars are at least 20 times more massive than our own relatively small Star, the Sun, and their grand finale is truly a stellar farewell performance when they violently and brilliantly blow themselves to pieces. In May 2015, a team of astronomers using NASA’s Hubble Space Telescope (HST) announced that they have uncovered amazing new clues about a rapidly aging, massive star whose weird behavior has never been observed before in our Milky Way Galaxy. In fact, this elderly, heavy star is so bizarre and unique among the known stellar denizens of the Cosmos that astronomers have nicknamed it Nasty 1, a play on its more dignified catalog name of NaST1–and this nasty star may represent a fleeting transitory stage in the evolution of extremely massive stars.

Nasty 1 was first discovered several decades ago, and was identified as a Wolf-Rayet star–a rapidly evolving star that is considerably more massive than our Sun. Wolf-Rayet stars lose their hydrogen-laden outer gaseous layers rapidly, exposing their extremely hot and brilliantly bright helium-burning hearts.

Stars like our Sun maintain a very precious and delicate balance between two eternally warring forces–gravity and radiation pressure. A main-sequence (hydrogen-burning) “normal” star, like our Sun, keeps itself bouncy and fluffy against its own gravity as a result of pressure derived from nuclear fusion. Gravity tries to pull everything in towards the star, while radiation pressure tries to push everything out and away from the star. When the two opposing rivals are about equal, the star is a stable, glaring, roiling ball of mostly seething-hot hydrogen gas that is blissfully fusing heavier atomic elements out of lighter ones. For planets like our Earth, lucky enough to be the happy child of a stable parent-star, this period can continue on and on for billions and billions of years. Our own Sun is still in active mid-life at about 4.56 billion years of age, and it will not “die” for another 5 billion years, or so. 바카라사이트

Alas, the planetary offspring of massive stars are not so fortunate. Massive stars evolve quickly and perish earlier in their “lives” than small Sun-like stars. In the case of a Wolf-Rayet star, it rapidly (for a star) runs out of lighter atomic elements to fuse inside its hot core. Our own Sun is happily fusing hydrogen into helium in its hot heart, but Wolf-Rayets rampage through elements such as oxygen in order to attempt to maintain precious, delicate equilibrium.

Massive stars, such as red or blue supergiants, shortly before they go supernova, have frequently been likened to familiar onions. By “burning” multiple elements as the result of the process of nuclear fusion, a massive star creates the seething, searing-heat necessary to keep it fluffy against its own gravity. Fusion, however, stops at iron. At this point, with no energy any longer rushing in from the central core to keep the other elements roasting, the massive star collapses and the rebounding shock wave blasts it to smithereens.

The multiple atomic elements that are heavier than helium–called metals by astronomers–are manufactured in the searing-hot, nuclear-fusing furnaces of massive stars, and they possess more atoms per unit than the lightest elements (hydrogen and helium). Because of this, massive stars churn out more energy than their less massive stellar kin–specifically as heat and radiation. The heavy star starts to blast out fierce winds reaching a breathtaking 2.2 million to 5.4 million miles per hour. As time goes by, the violent winds tear away the outer gaseous layers of the doomed Wolf-Rayet. This tosses off most of its former stupendous mass, while simultaneously liberating its elements to be recycled elsewhere in the vastness of the Cosmos.

But the stellar grand finale inevitably approaches as the doomed star runs out of increasingly heavier and heavier atomic elements to fuse in its hot heart. This process can go no further than iron. When fusion ceases, the pressure within the star is no longer there, and nothing can prevent merciless gravity from pulling all of the stellar material in. Massive stars blast themselves to pieces in the fiery tantrum of supernovae explosions–and the most massive of their kind see their gravity warped to such a great extent that nothing, nothing, nothing at all, not even light, can escape to freedom. A black hole is born.

 


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