--------------------- #1507 - Geological History of the Solar System
- See Review # 1506 for the geological history of the Earth. To carry our lineage back further this review is about the geological history of our Solar System. We do not have many rocks to work with, a few meteorites, so the history lesson takes more imagination.
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- By studying the rocks, gas , and stars within 6,500 lightyears of Earth with detailed observations astronomers believe:
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--------------The Sun formed in a nebula of 1,000 to 10,000 other stars. An example can be seen today in the Orion Nebula ( M42 ) in the Constellation Orion the Warrior.
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------------- One very large star, 25 Solar Mass, exploded in a supernova within the nebula. It was only 1 lightyear from our cluster of dense gas and clouds that became a nursery for stars to be born. An example today is the Star Cluster Pleiades ( M45 ).
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- The cloud of dust and gas has a temperature of 10 to 20 Kelvin. That is cool, only 18 to 26 F above Absolute Zero temperature. The surrounding interstellar medium has a density of one atom per cubic centimeter but an average temperature of 100 Kelvin. Atoms and particles in the colder cloud pack together to densities of million of atoms per cubic centimeter.
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- Atoms began to join together to form molecules. the molecular cloud was dozens of lightyears across. Gravity begins to have its effects the cloud begins contracting as it is brought together by the shockwave of the close exploding supernova.
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- The cloud does not contract evenly. It fragments into smaller pieces. Over a million years the cloud separates into individual clumps. Each clump is likely to become an individual star looking like the Star Cluster Pleiades.
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- Our Sun evolved without a binary star. Only 30% of the stars form without a binary. Our star has a higher percentage of the elements heavier that helium. Astronomers call all these elements metals.
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- Of the 50 closest stars only Sirius and Procyon are more massive than our Sun. Using the wider survey only 12% of the stars are more massive than our Sun. Only 25% of the stars have a higher percentage of metals.
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- Our Sun has a solar system with 4 giant gas planets and 4 smaller rocky planets. astronomers have discovered over 1,000 planets around other stars, but, they have to learned enough to define how common our type of solar system is. Some put the probability at 0.2%. However, this small probability would still mean that amongst the 200 billion stars in the Milky Way Galaxy there would be 400 million Solar Systems like ours.
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- Evidence for the supernova blast that started the evolution of our Sun and its Solar System comes form meteorites (geology), dating the radioactive isotopes of Nickel-6 and iron-60. Iron-60 has a half-life of 1.5 million years. Therefore, these meteorites had to be delivered form a nearby source during the Solar System’s earliest days.
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- It takes a massive star to have the gravity and explosive power to create the element iron-60. Other radioactive elements, aluminum-26 and calcium-41 were also found. All this implies that the supernova star was a massive 25 Solar Mass. Such a massive star has a lifetime of 7.5 million years.
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- The distance away from the supernova could not be too close or too far away. It needed to occur about 1 lightyear away.
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- A few million years later our Sun began fusing hydrogen and helium. the accretion disk surrounding the Sun began to form planets. This all started 4,600 million years ago.
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- To help your imagination turn your binoculars on the Orion Nebula tonight. Search out the Pleiades Star Cluster. Our Sun was like one of these bright stars born in the nursery of the nebula. To see an animation of this event see www.astronomy.com/toc.-
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- To learn what happened starting 4,600 million years ago see Review #1506 The Geology of the Earth
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- #1157 Mysteries of Our Solar System
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- #15 The Sun and the Planets in Six Easy Pieces.
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- #1150 What is New and Extreme in Our Solar System?
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707-536-3272, Wednesday, October 31, 2012
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