hining Bright The Sun is currently stable, about halfway through its lifecycle. Its estimated it will live for about another five billion years before consuming all the hydrogen in its core and transforming into a red giant. he Birth of the Sun A New Day Begins It was five billion years ago. A giant cloud of matter in our own galaxy, the Milky Way, condensed under its gravity, exploding in nuclear fusion. This fusion released what we call sunshine. Very, very, very hot sunshine. And the newly formed star was our Sun. It drew in most of the surrounding matter, but some escaped. And some of this material clumped together, settling into a protoplanetary orbit. Tasty morsels of gas and rock Those chemically rich leftovers orbiting our young Sun were stewing with all the ingredients to form the planets in our Solar System. The intense heat of the young Sun drove away most of the lighter hydrogen and helium elements — 99% of the leftovers — the furthest. These eventually condensed to form the gassy outer giants — Jupiter, Saturn, Uranus, and Neptune. The tiny bit of heavier elements that remained made up the rockier Mercury, Venus, Earth, and Mars. Through a combination of gentle collisions and gravity these atoms and molecules began attracting other like-sized material. Over millions of years, they gradually shaped themselves into solid planetesimals, and later protoplanets with their own unique orbits. Astronomers call all this smashing and joining together accretion. After 10 to 100 million years of this banging, eight spherical, stable planets remained. Our Solar System spun into place. Ptolemy (about 85—165) Claudius Ptolemys theory extended the cosmological theories of Aristotle. Earth was at a center of a series of concentric spheres containing the Moon, the planets, the Sun, and a final sphere of fixed stars. Copernicus (1473—1543) A Catholic, Polish astronomer, Nicolaus Copernicus, synthesized observational data to formulate a Sun-centered cosmology, launching modern astronomy and setting off a scientific revolution. Galileo (1564—1642) Galileo Galilei, an Italian Renaissance man, used a telescope of his own invention to collect evidence that supported the Sun-centered model of the Solar System. Sir Isaac Newton (1643—1727) By combining physics, mathematics, and astronomy, Newton developed the three basic laws of motion and the theory of universal gravity. Henrietta Leavitt (1868—1921) By measuring the amount of time between the fluctuating brightness levels of variable stars, Leavitt discovered that it would be possible to estimate their distance away from the Earth, and possible to map the Universe. Edwin Hubble (1889—1953) Hubble drew upon existing ideas and evidence to demonstrate that the Universe was much larger than previously thought and proved that it is expanding — laying the foundations for the Big Bang theory.
Posted on: Sat, 13 Dec 2014 09:05:41 +0000
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