Solar System Origin - APEC Schools PDF

WIKI: THE ORIGIN OF THE SOLAR SYSTEM There are many planetary systems like ours in the universe, with planets orbiting a host star. Our planetary system is named the "solar system" because our Sun is named Sol, after the Latin word for Sun, "solis," and anything related to the Sun we call "solar...

WIKI: THE ORIGIN OF THE SOLAR SYSTEM There are many planetary systems like ours in the universe, with planets orbiting a host star. Our planetary system is named the "solar system" because our Sun is named Sol, after the Latin word for Sun, "solis," and anything related to the Sun we call "solar." Our planetary system is located in an outer spiral arm of the Milky Way galaxy. Our solar system consists of our star, the Sun, and everything bound to it by gravity – the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune; dwarf planets such as Pluto; dozens of moons; and millions of asteroids, comets, and meteoroids. (Image Source: How Big Is the Solar System?. (2022). Science-Sparks. https://www.science-sparks.com/how-big-is-the-solar-system/) How did the Sun, planets, and moons in the Solar System form? There is a surprising amount of debate and several strong and competing theories, but do scientists have an answer? Any theory about how the Solar System came to be has to account for certain rather tricky facts. We know that the Sun sits at the center of the Solar System with the planets in orbit around it, but this throws up five major problems: 1. The Sun spins slowly and only has 1 percent of the angular momentum of the Solar System - but 99.9 percent of its mass. Why is this? 2. Terrestrial planets have solid cores. How did they form? 3. What about the gas giant planets like Jupiter. Were they formed differently? 4. How did planetary satellites like the Moon come into being? 5. Bode's law states that the distances of the planets from the Sun follow a simple ______________________________________________________________________________________________ This document contains proprietary and confidential information. Reproduction, redistribution, or forwarding to any third party, in whole or in part, is strictly prohibited unless made with prior written consent from APEC Schools. Violation or noncompliance shall be dealt with according to law. Page 1 of 9  arithmetic progression. Why should this be? Taking all these issues into account, science has suggested four key theories considered to be 'reasonable' in that they explain many, but not all, of the phenomena exhibited by the Solar System. These hypotheses are: Nebular Theory Protoplanet Theory Encounter Theory Accretion Theory Let us discuss each theory. A. NEBULAR THEORY According to this theory, the Sun and all the planets of our Solar System began as a giant cloud of molecular gas and dust. Then, about 4.57 billion years ago, something happened that caused the cloud to collapse. This could have been the result of a passing star or shock waves from a supernova, but the end result was a gravitational collapse at the center of the cloud. From this collapse, pockets of dust and gas began to collect into denser regions. As the denser regions pulled in more and more matter, conservation of momentum caused it to begin rotating, while increasing pressure caused it to heat up. Most of the material ended up in a ball at the center, while the rest of the matter flattened out into a disk that circled around it. While the ball at the center formed the Sun, the rest of the material would form into the protoplanetary disc. The planets formed by accretion from this disc, in which dust and gas gravitated together and coalesced to form ever larger bodies. (Image Source: Williams, M. (2016, July 19). How Was the Solar System Formed? - The Nebular Hypothesis. Universe Today. https://www.universetoday.com/38118/how-was-the-solar-system-formed/) Artist’s impression of the early Solar System, where collision between particles in an accretion disc led to the formation of planetesimals and eventually planets. ______________________________________________________________________________________________ This document contains proprietary and confidential information. Reproduction, redistribution, or forwarding to any third party, in whole or in part, is strictly prohibited unless made with prior written consent from APEC Schools. Violation or noncompliance shall be dealt with according to law. Page 2 of 9  (Image Source: Origin of the Solar System. (N.D). Abyss Oregon Education.http://abyss.uoregon.edu/~js/ast121/lectures/lec23.html) Conservation of angular momentum requires that a rotating disk form with a large concentration at the center (the proto-Sun). Within the disk, planets form. While this theory incorporates more basic physics, there are several unsolved problems. For example, a majority of the angular momentum in the Solar System is held by the outer planets. For comparison, 99% of the Solar System's mass is in the Sun, but 99% of its angular momentum is in the planets. Another flaw is the mechanism from which the disk turns into individual planets. You may watch Nebular Hypothesis - Origin of the Earth Solar system to further learn about this theory. ______________________________________________________________________________________________ This document contains proprietary and confidential information. Reproduction, redistribution, or forwarding to any third party, in whole or in part, is strictly prohibited unless made with prior written consent from APEC Schools. Violation or noncompliance shall be dealt with according to law. Page 3 of 9  B. PROTOPLANET THEORY The current working model for the formation of the Solar System is called the protoplanet hypothesis. It incorporates many of the components of the nebular hypothesis, but adds some new aspects from modern knowledge of fluids and states of matter. Just like the nebular theory, protoplanetary theorists Carl von Weizsäcker and Gerard Kuiper believed that the solar system started from a nebula. A dense interstellar cloud produces a cluster of stars. Dense regions in the cloud form and coalesce; as the small blobs have random spins the resulting stars will have low rotation rates. The planets are smaller blobs captured by the star. (Image Source: Williams, M. (2016, July 19). How Was the Solar System Formed? - The Nebular Hypothesis. Universe Today. https://www.universetoday.com/38118/how-was-the-solar-system-formed/) Artist’s impression of the early Solar System through Protoplanet Theory. An unidentified instability resulted in the pulling of dust particles toward each other. This led to the formation of the “planetesimals” – objects made up of dust and rock particles, which is believed to be the origin of planets. Planetesimals combined with other planetesimals and formed protoplanets – larger planetesimals. As the protoplanets formed, like the Sun, they became larger as other materials condensed with them until the fusion of hydrogen and helium happened. This fusion led to the production of the heat of the Sun and resulted to the blasting off of the protoplanets made up of gases. The smaller protoplanets were attracted by the gravity of the larger protoplanets and made them larger until they became the planets as we know it. ______________________________________________________________________________________________ This document contains proprietary and confidential information. Reproduction, redistribution, or forwarding to any third party, in whole or in part, is strictly prohibited unless made with prior written consent from APEC Schools. Violation or noncompliance shall be dealt with according to law. Page 4 of 9  (Image Source: Origin of the Solar System. (N.D). Abyss Oregon Education.http://abyss.uoregon.edu/~js/ast121/lectures/lec23.html) Meanwhile in the inner Solar System: ______________________________________________________________________________________________ This document contains proprietary and confidential information. Reproduction, redistribution, or forwarding to any third party, in whole or in part, is strictly prohibited unless made with prior written consent from APEC Schools. Violation or noncompliance shall be dealt with according to law. Page 5 of 9  (Image Source: Origin of the Solar System. (N.D). Abyss Oregon Education.http://abyss.uoregon.edu/~js/ast121/lectures/lec23.html) Note that as the planet's began to form they grew in mass by accreting planetesimals. Since force of gravity is proportional to mass, the largest planetesimals are accreted first. The early proto-planets are able to sweep the early Solar System clean of large bodies. Notice also that the lighter compounds are vaporized in the inner Solar System. So where did all the outgassing material come from? The answer is comets that fall from the outer Solar System after the planets form. ______________________________________________________________________________________________ This document contains proprietary and confidential information. Reproduction, redistribution, or forwarding to any third party, in whole or in part, is strictly prohibited unless made with prior written consent from APEC Schools. Violation or noncompliance shall be dealt with according to law. Page 6 of 9  This theory led to successful predictions when astronomers went looking for evidence of a nearby supernova that could have caused all of the turbulence 4.6 billion years ago. They located two supernovas that were the right age and distance from Earth. As a result, the Protoplanet Hypothesis is currently the most popular hypothesis explaining how the solar system formed. You may watch Astronomy - Ch. 8: Origin of the Solar System (12 of 19) The Protoplanets to further learn about this theory. C. ENCOUNTER THEORY One of the earliest theories for the formation of the planets was called the encounter hypothesis. The Encounter Theory proposed by Georges Leclerc and Comte de Buffon. As the star passes near the Sun, the materials of both the Sun and the star were drawn out. The interaction from the gravity of the passing star and the Sun led to the formation of the planets in the solar system. ______________________________________________________________________________________________ This document contains proprietary and confidential information. Reproduction, redistribution, or forwarding to any third party, in whole or in part, is strictly prohibited unless made with prior written consent from APEC Schools. Violation or noncompliance shall be dealt with according to law. Page 7 of 9  (Image Source: Origin of the Solar System. (N.D). Abyss Oregon Education.http://abyss.uoregon.edu/~js/ast121/lectures/lec23.html) In this scenario, a rogue star passes close to the Sun about 5 billion years ago. Material, in the form of hot gas, is tidally stripped from the Sun and the rogue star. This material fragments into smaller lumps which form the planets. This hypothesis has the advantage of explaining why the planets all revolve in the same direction (from the encounter geometry) and also provides an explanation for why the inner worlds are denser than the outer worlds. However, there are two major problems for a theory of this type. One is that hot gas expands, not contracts. So lumps of hot gas would not form planets. The second is that encounters between stars are extremely rare, so rare as to be improbable in the ______________________________________________________________________________________________ This document contains proprietary and confidential information. Reproduction, redistribution, or forwarding to any third party, in whole or in part, is strictly prohibited unless made with prior written consent from APEC Schools. Violation or noncompliance shall be dealt with according to law. Page 8 of 9  lifetime of the Universe (15 billion years). You may watch Cosmology, Critical Density, Big Crunch, Oscillating Universe, Accelerating Expansion, Dark Energy to further learn about this theory. D. ACCRETION THEORY Accretion Theory states that the particles that formed after the big bang slowly clustered together to form asteroids, planets, and even stars. This happens as a cloud of gaseous material & dust compresses to form an Accretion disc, which serves as a catalyst for the formation of a sun and the rest of a galaxy. The problem is that of getting the cloud to form the planets. The terrestrial planets can form in a reasonable time, but the gaseous planets take far too long to form. The theory does not explain satellites or Bode's law and is therefore considered the weakest of those described here. References: Astronomy - Ch. 8: Origin of the Solar System (12 of 19) The Protoplanets - 2. (2015, March 20). [Video]. YouTube. https://www.youtube.com/watch?v=OoqihBXXjVQ How did Earth form? (2022). Space. https://www.space.com/19175-how-was-earth-formed.html Nebular Hypothesis - Origin of the Earth Solar system. (2016, December 10). [Video]. YouTube. https://www.youtube.com/watch?v=2ESGUAU2Du0 Origin of the Solar System. (n.d.). Abyss Oregon Edu. http://abyss.uoregon.edu/~js/ast121/lectures/lec23.html The Origin of the Solar System. (n.d.). Royal Museums Greenwich. https://www.rmg.co.uk/stories/topics/origin-solar-system Williams, M. (2016, July 19). How Was the Solar System Formed? - The Nebular Hypothesis. Universe Today. https://www.universetoday.com/38118/how-was-the-solar-system-formed/ ______________________________________________________________________________________________ This document contains proprietary and confidential information. Reproduction, redistribution, or forwarding to any third party, in whole or in part, is strictly prohibited unless made with prior written consent from APEC Schools. Violation or noncompliance shall be dealt with according to law. 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