Now, this is a question that almost all of us have thought about or asked someone. Isn't it?
Well, for me it was one of the most important and interesting questions when I first stumbled upon it? I got a clear and convincing answer much later when I read Michio Kaku's fantastic book, Parallel Worlds.
A typical star like our Sun begins its life as a large ball of diffuse hydrogen gas called a protostar and gradually contracts under the force of gravity. As it begins to collapse, it begins to spin rapidly (which often leads to the formation of a double-star system, where two stars chase each other in elliptical orbits, or the formation of planets in the plane of rotation of the star). The core of the star also heats up tremendously until it hits approximately 10 million degrees or more, when the fusion of hydrogen to helium takes place.
After the star ignites, it is called a main sequence star and it may burn for about 10 billion years, slowly turning its core from hydrogen to waste helium. Our Sun is currently midway through the process. After the era of hydrogen burning ends, the star begins to burn helium, whereupon it expands enormously to the size of the orbit of Mars and becomes a "red-giant". After the Helium fuel in the core is exhausted, the outer layers of the star dissipate, leaving the core itself, a "white-dwarf" star about the size of Earth. Smaller stars like our Sun will die in space as hunks of dead nuclear material in white dwarf stars.
But in stars, perhaps ten to forty times the mass of our Sun, the fusion process proceeds much more rapidly. When the star become a red supergiant, its core rapidly fuses the lighter elements, so it resembles a Hybrid Star, a white-dwarf inside a red-giant. In this white-dwarf star, the lighter elements up to iron on the periodic table of elements may be created. When the fusion process reaches the stage where the element iron is created, no more energy can be extracted from the fusion process, so the nuclear furnace, after billions of years, finally shuts down. At this point, the star abruptly collapses, creating huge pressures that actually push the electrons into the nuclei. (The density can exceed 400 billion times the density of water.) This causes temperatures to soar to trillions of degrees. The gravitational energy compressed into this tiny object explodes outward into a Supernova. (about which I have discussed in the next post.) The intense heat of this process causes fusion to start once again, and the elements beyond iron on the periodic table are synthesized.
The red supergiant Betelgeuse, for example, which can be easily seen in the constellation Orion, is unstable; it can explode at any time as a supernova, spewing large quantities of gamma ray and X-Rays into the surrounding neighborhood. When that happens, this supernova will be visible in daytime and might outshine the moon at night.
It was once thought that the titanic energy released by a supernova destroyed the dinosaurs 65 million years ago. A supernova about 10 Light-years away could, in fact, end all life on Earth. Fortunately, the giant stars Spica and Betelgeuse are 260 and 430 light-years away, respectively, too far to cause much serious damage to Earth when they finally explode. But some scientists believe that a minor extinction of sea creatures 2 million years ago was caused by a supernova explosion of a star 120 light-years away.
Hence, we are safe for the time being, so no worries but, beware as any big cosmological event can indeed end Life on Earth!! :-)
Well, for me it was one of the most important and interesting questions when I first stumbled upon it? I got a clear and convincing answer much later when I read Michio Kaku's fantastic book, Parallel Worlds.
A typical star like our Sun begins its life as a large ball of diffuse hydrogen gas called a protostar and gradually contracts under the force of gravity. As it begins to collapse, it begins to spin rapidly (which often leads to the formation of a double-star system, where two stars chase each other in elliptical orbits, or the formation of planets in the plane of rotation of the star). The core of the star also heats up tremendously until it hits approximately 10 million degrees or more, when the fusion of hydrogen to helium takes place.
After the star ignites, it is called a main sequence star and it may burn for about 10 billion years, slowly turning its core from hydrogen to waste helium. Our Sun is currently midway through the process. After the era of hydrogen burning ends, the star begins to burn helium, whereupon it expands enormously to the size of the orbit of Mars and becomes a "red-giant". After the Helium fuel in the core is exhausted, the outer layers of the star dissipate, leaving the core itself, a "white-dwarf" star about the size of Earth. Smaller stars like our Sun will die in space as hunks of dead nuclear material in white dwarf stars.
But in stars, perhaps ten to forty times the mass of our Sun, the fusion process proceeds much more rapidly. When the star become a red supergiant, its core rapidly fuses the lighter elements, so it resembles a Hybrid Star, a white-dwarf inside a red-giant. In this white-dwarf star, the lighter elements up to iron on the periodic table of elements may be created. When the fusion process reaches the stage where the element iron is created, no more energy can be extracted from the fusion process, so the nuclear furnace, after billions of years, finally shuts down. At this point, the star abruptly collapses, creating huge pressures that actually push the electrons into the nuclei. (The density can exceed 400 billion times the density of water.) This causes temperatures to soar to trillions of degrees. The gravitational energy compressed into this tiny object explodes outward into a Supernova. (about which I have discussed in the next post.) The intense heat of this process causes fusion to start once again, and the elements beyond iron on the periodic table are synthesized.
The red supergiant Betelgeuse, for example, which can be easily seen in the constellation Orion, is unstable; it can explode at any time as a supernova, spewing large quantities of gamma ray and X-Rays into the surrounding neighborhood. When that happens, this supernova will be visible in daytime and might outshine the moon at night.
It was once thought that the titanic energy released by a supernova destroyed the dinosaurs 65 million years ago. A supernova about 10 Light-years away could, in fact, end all life on Earth. Fortunately, the giant stars Spica and Betelgeuse are 260 and 430 light-years away, respectively, too far to cause much serious damage to Earth when they finally explode. But some scientists believe that a minor extinction of sea creatures 2 million years ago was caused by a supernova explosion of a star 120 light-years away.
Hence, we are safe for the time being, so no worries but, beware as any big cosmological event can indeed end Life on Earth!! :-)
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