With 2012 just around the corner, doomsday is all the rage today. However, when it comes to how the world may end, the Maya calendar running out probably will have nothing to do with it. Instead, a 3-year study by scientists from Ohio State University were focusing on a much more though very unlikely way in the immediate future) way the world could end: a nearby star going supernova.
Like people, stars are born, mature into 'adulthood,' grow old, and die. The glowing clouds of nebular gasses that so enchant modern astronomers and astrophotographers are, in reality, stellar corpses, the remains of stars that have died after using up all of the fuel that kept them shining brightly for millions, perhaps billions of years, somber reminders that nothing, not even the stars, are forever. When a star is in the prime of life, it fuses hydrogen atoms into helium, releasing untold amounts of energy the equivalent of billions of thermonuclear explosions a second. Why does the star then not blow itself up? Gravity. While the force of the nuclear fusion seeks to push out a star and make it expand, the star's own gigantic mass produces a gravitational force that keeps the star in a state of equilibrium between these two, competing forces.
A star begins to die when it uses up all of its hydrogen fuel. The nuclear fusion stopped but gravity still going strong, the star contracts into itself thanks to gravity. However, as the star contracts, it heats up to the point where it can start fusing helium nuclei together, releasing far more energy than it would with hydrogen fusion. Result: the extreme amount of energy released by the helium fusion somewhat overcomes the force of gravity, thus causing the star to swell to several times its original size, its outer atmosphere cooling as it expands. So, despite its growth in size to the red giant phase, the star is living on borrowed time as it will continue the cycle of burning an element, contracting, fusing an even heavier element, expanding, and so-on until iron is the next material in line for fusion. Unfortunately, iron fusion cannot occur because it takes more energy to fuse the nuclei than the fusion itself will generate. Result: fusion stops and the star dies. In the case of stars larger than the Sun, the expanded star will collapse onto itself, triggering a massive explosion: a supernova.
For any inhabited world within orbiting a nearby star, this would mean a bath of incoming radiation that would strip away any protective atmosphere, leaving the planet and everything, and everyone on it, exposed to deadly cosmic rays from its parent star.
Back to the OSU research. For the past 3 years, researchers at OSU have been observing stars, specifically unstable, large stars that seemed capable of going supernova. The goal: find any telltale sigh that a star was about to explode.
One of the stars under observation by OSU researchers was one in the Whirlpool Galaxy, M51, a spiral galaxy located very near the unmistakable Big Dipper. In fact, the star being observed was not a single star, but a pair. When observing this particular star, one of the signs of instability was a sudden dimming amounting to about a 10% loss in brightness over a 3-year period. Then, in April, the astronomical world went alight as this particular star exploded as a supernova,the brightest in a quarter century.
Now the big question: was that change in brightness just a coincidence or was it the elusive supernova indicator the researchers were looking for?
Unfortunately, the only way to answer that question is with more observations, with the hope being that similar dimming patterns could be found at a rate of one per year. However, only in time and after many observations and supernovae will it be possible to say with certainty whether there is any visible stellar death sign to be seen at all.
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