Data Bases • Custom Term Papers • Free Term Papers • Free Research Papers • Free Essays • Free Book Reports • Plagiarism? Links • Top 100 Term Paper Sites • Top 25 Essay Sites • Top 50 Essay Sites • Search 97,000 Papers @ DirectEssays.com • Search 101,000 Papers @ ExampleEssays.com • Search 90,000 Papers @ MegaEssays.com Free Essays • Term Paper Sites • Chuck III's Free Essays • Free College Essays • TermPaperSites.com • My Term Papers • Get Free Essays • Essay World • Planet Papers	Search Lots of Essays Back to Subjects - Astronomy Future of Our Galaxy Galactic Millenium Future of Our Galaxy Galactic Millenium (adopted from an article by Greg Laughlin and Fred Adams, "Celebrating the Galactic Millennium", Astronomy November 2001) Not too long ago, we were looking forward to the New Millennium. To many of us, this was an important event of our lives. On a larger scale, however, the New Millennium looks insignificant. "If we adopt an astronomical perspective, however, a much larger and more distant celebration remains on the schedule-the Galactic Millennium," write Greg Laughlin and Fred Adam in their article Celebrating the Galactic Millennium. Laughlin and Adam speculate about the proposed changes to the Universe in the future and the coming of the Galactic Millennium. According to the authors, the present day galaxy is relentlessly empty and spans a tremendous scope. In a scale model of the galaxy where stars are the size of sand grains, the nearest stellar system (Alpha and Proxima Centauris) is six miles away. Our Galaxy contains approximately 100 Billion stars. In this model, the stars move through their orbits at a pace of only a few feet per terrestrial year. The sun takes nearly 100 million terrestrial years to make a full circuit of the galaxy. The last time the sun passed through our current galactic longitude was in the middle of the Cretaceous period, when the giant continent Gondwanaland was beginning to break up into African and South America and the giant Carnotaurus enjoyed its place at the top of the food chain (before the reign of T.Rex). The authors' prospected views on the future of our galaxy are rather harsh. The authors argue that a billion terrestrial years from now-in 10 galactic years-the galaxy will look much like it does now. Certain details, however, will be different. As the sun executes its next ten circuits around our galaxy's central hub, our today-familiar constellations will be scrambled one hundred times over. Many of the night stars in the sky will no longer exist. Deneb and Rigel, for example, will explode as supernovae. Sirious will swell into a red giant and puff out a planetary nebula. Alpha Centauri, currently the sun's closest neighbor, will recede from the sun, and its apparent brightness will fade below the threshold of naked-eye visibility. As the next billion years unfold, Earth will face pressing problems because of sun's activity. So far, the sun has fused approximately half of its central store of hydrogen into helium. As inert helium ash accumulates in the solar core, the efficiency of nuclear processes steadily decreases, and gravity impels the center of the sun to contract and heat up. Contraction and heating in the solar center raise the overall power output at the surface. As a result, in ten galactic years sun will be 10 percent brighter than it is today. As a result of this increase in sun's luminosity will induce "unwelcome" weather on Earth (the authors do not give the details about the kind of weather). Today's global climate models indicate that Earth may experience a "moist greenhouse effect". Earth will lose its water and presumably its entire life forms and will wind up as a twin of the planet Venus. According to computer models of stellar evolution, the hydrogen fuel in the sun's central core will be exhausted in 6.2 billion years. At that time, the sun will be 2.2 times brighter than it is now, and Mars will be receiving roughly the same ray of illumination that Earth currently enjoys. The exhaustion of its central hydrogen will mark the end of our sun's 11-billion-year role as a main sequence star. As the hydrogen level becomes exhausted, energy will leak out of the sun, and pure helium core remaining at the center of the sun will be unable to support the crushing weight of the layers above. Thus, the core will be forced to contract and heat up. This extra heat will cause the thinner outer layers of the sun to swell, and the sun will be launched into 700 million year career as a red giant. "The red giant sun will wreak havoc on the solar system". Mercury, and possibly Venus, will be engulfed and vaporized by the sun's outer layers. The rocky surface of the Earth will melt. Even Pluto and other objects in the Kuiper Berlt will eventually warm above the freezing point. At its brightest, the sun's radius will swell to 1 astronomical unit (AU), as wide as the present Earth-sun distance. During its red giant phases, the sun will lose 45 percent of its mass to a strong outflowing wind. This mass will cause the orbits of the surviving planets to expand. Eventually, the sun will eject its outer layers as a planetary nebular and a white dwarf remnant will be exposed. This remaining white dwarf will exert less of a gravitational pull of the remaining planets. Earth's final orbit will expand to 1.7 AU, and every terrestrial year will drag on for 1,100 days. Many asteroids, especially those near the inner edge of the main asteroid belt, will end up in unstable orbits and will either crash into a planet or be ejected into the interstellar space. According to the authors, Earth is now in its 46th galactic year, and the galaxy is between 100 and 150 galactic years old. The celebration of the Galactic Millennium, when the universe is 100 billion years old, will involve a very different kind of a universe. The human race will most likely not exist by then. The spiral structure of the galaxy will be gone. Earth will be a frozen cinder. The sun will become a frigid sphere of degenerate carbon. This is how the authors imagine the scene on Earth on the eve of the Galactic Millennium: "The white dwarf sun is several thousand miles across and subtends only a pinpoint in Earth's sky. The sun has long since crystallized and its surface has cooled to a frigid 63 K, roughly the temperature of liquid nitrogen. This steady temperature is maintained with energy supplied by dark matter particles annihilating in the degenerate interior. The sun glows faintly in the infrared… On the hard surface of Earth, the temperature is about 1 degree above absolute zero. The atmosphere is gone. Every trace of the once-flourishing biosphere has vanished. Here and there, the surface has been cratered by increasingly infrequent asteroid and comet impact… Beyond the solar system, the sky contains a surprising number of bright red stars, which merge into an impressive glow in the direction of the gas free and unobscured center of the galaxy". Such is the current view on the future of our galaxy, pieced together, as the authors note, from our present understanding of physics and astronomy. However, it is important to realize that our knowledge of science changes over time. Fifty years ago, for example, the theory of the future of our galaxy might have looked very different from this one. To quote the authors: "Who knows what… processes might alter the course of our distant future…." Bibliography: Word Count: 1179
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