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----------------------------- 1916 - How big is our Solar System?
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- The night sky seems tranquil. Peaceful and quiet. The stars are consistent in the sky throughout our lifetime of observation. Our Solar System seems to be in a similar state. But, evidence shows that tranquility was not the case a few billion years ago.
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- Planets form around their star in a disk. Gravity collects the gas and dust in a rotating wash machine of material. The gas is escaping the disk rapidly, so, planets must form in a short period, 4 to 5 million years. Although the rocky inner planets can form over a longer period, maybe up to 100 million years. The Solar System itself is 4,800 million years since formation.
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- During these phases of planet formation the planets and the planet hopefuls, called planetesimals, often collided. Such a collision is how the Earth-Moon first formed. The Moon is a splash of Earth’s crust. Such collisions also caused Venus to rotate backward compared to the other planets. Uranus got tilted 90 degrees in its rotation. Mercury lost its outer shell. Other planetesimals were knocked out of the Solar System all together.
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- Studying our Solar System is difficult. Evidence for what happened for the first few million years is mostly wiped out. But, thanks to Kepler’s Space Telescope we can begin to collect evident from other solar systems in various stages of formation. We call these planets, “ exoplanets”.
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- Studying Mercury gives us another clue. Mercury is mostly an iron core. Its crust and mantle are missing, or far reduced. Mercury’s orbit is far less circular than the other terrestrial planets. The best explanation ( computer modeling ) suggests that Mercury shared its orbit with other planetesimals. Many collisions occurred. Mercury’s natal shell was vaporized in these collisions.
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- Planetesimals were constantly colliding with in the confined space closer to the Sun. Some were smashed to bits. Some were ejected out of the Solar System all together. Some went crashing into the Sun.
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- Venus and Earth have nearly circular orbits. But, the larger gas planets have elliptical orbits and their orbits dip far above and below the plane. Between 3.8 and 4.1 billion years ago the gas planet’s immense gravity sent rocks and ices hurtling into the inner solar system creating collisions with the smaller rocky planets.
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- All these same computer models are suggesting the likelihood of an undiscovered ‘Planet 9”. Adding another gravitation influence would help explain much of the Solar System structure, particularly with the new discoveries beyond Neptune. The models want to create a Planet 9 with 10 times Earth-mass and orbiting at 250 AU in the outer Kuiper Belt. ( AU is Astronomical Units, Earth-Sun distance, or 93 million miles)
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- Supporting evidence came with other “dwarf planets” found beyond 40 AU, 30% further out than the dwarf planet Pluto. These new dwarf planet orbits are disturbed by an object gravity far outside the effects of Neptune. These objects could take 20,000 years to orbit the Sun. Neptune takes 165 years to orbit.
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- These models tell us that the early Solar System needed twice as much mass as what would up as the 8 planets. All these theories lead us to thinking that the early Solar System started out far more complicated than originally thought. My high school science book is outdated?
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- Studying exoplanets is another source in the search for answers The most intriguing answer would come from the discovery of the mysterious Planet 9. Over 4,000 likely exoplanets have been discovered. Continued study is trying to understand each of their solar systems.
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- Interesting stuff. Stay tuned, an announcement will be made shortly. Maybe it will be “ We have discovered a ninth planet, what should we name it?
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- See Reviews #1872 , #1826, and six other reviews to learn more about our Solar System.
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----- 707-536-3272 ---------------- Tuesday, January 10, 2017 -----
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