Solar System Formation Solar System Formation Begin with
Solar System Formation
Solar System Formation Begin with Comparative Planetology
Solar System Formation Comparative Planetology • Look at the differences and similarities among the planets, moons, asteroids, and comets of our solar system
Solar System Formation Comparative Planetology • Look at the differences and similarities among the planets, moons, asteroids, and comets of our solar system • Figure out what physical processes could have led to them
Solar System Formation Comparative Planetology • Look at the differences and similarities among the planets, moons, asteroids, and comets of our solar system • Figure out what physical processes could have led to them • Thereby understand the origin of our solar system and others, and come up with a theoretical model of how they form
Solar System Formation Comparative Planetology • Look at the differences and similarities among the planets, moons, asteroids, and comets of our solar system • Figure out what physical processes could have led to them • Thereby understand the origin of our solar system and others, and come up with a theoretical model of how they form • Our solar system has a number of characteristics that any theoretical model must explain
Solar System Formation -- Characteristics of Our Solar System • Large bodies in the solar system have orderly motions and are isolated from each other : – All planets and most moons have nearly circular orbits going in the same direction in nearly the same plane – The Sun and most of the planets rotate in this same direction as well – Most moons orbit their planet in the direction it rotates
Solar System Formation -- Characteristics of Our Solar System • Large bodies in the solar system have orderly motions and are isolated from each other : – All planets and most moons have nearly circular orbits going in the same direction in nearly the same plane – The Sun and most of the planets rotate in this same direction as well – Most moons orbit their planet in the direction it rotates
Solar System Formation -- Characteristics of Our Solar System • Large bodies in the solar system have orderly motions and are isolated from each other : – All planets and most moons have nearly circular orbits going in the same direction in nearly the same plane – The Sun and most of the planets rotate in this same direction as well – Most moons orbit their planet in the direction it rotates
Solar System Formation -- Characteristics of Our Solar System • • Large bodies in the solar system have orderly motions and are isolated from each other : – All planets and most moons have nearly circular orbits going in the same direction in nearly the same plane – The Sun and most of the planets rotate in this same direction as well – Most moons orbit their planet in the direction it rotates Planets fall into two main categories: – Small, rocky terrestrial planets near the Sun – Large, hydrogen-rich jovian planets farther out • The jovian planets have many moons and rings of rock and ice
Solar System Formation -- Characteristics of Our Solar System • Planets fall into two main categories: – Small, rocky terrestrial planets near the Sun
Solar System Formation -- Characteristics of Our Solar System • Planets fall into two main categories: – Small, rocky terrestrial planets near the Sun – Large, hydrogen-rich jovian planets farther out • The jovian planets have many moons and rings of rock and ice
Solar System Formation -- Characteristics of Our Solar System • Planets fall into two main categories: – Small, rocky terrestrial planets near the Sun – Large, hydrogen-rich jovian planets farther out • The jovian planets have many moons and rings of rock and ice
Solar System Formation -- Characteristics of Our Solar System • • • Large bodies in the solar system have orderly motions and are isolated from each other : – All planets and most moons have nearly circular orbits going in the same direction in nearly the same plane – The Sun and most of the planets rotate in this same direction as well – Most moons orbit their planet in the direction it rotates Planets fall into two main categories: – Small, rocky terrestrial planets near the Sun – Large, hydrogen-rich jovian planets farther out • The jovian planets have many moons and rings of rock and ice Swarms of asteroids and comets populate the solar system: – Asteroids are concentrated in the asteroid belt – Comets populate the regions known as the Kuiper belt and the Oort cloud
Solar System Formation -- Characteristics of Our Solar System • Swarms of asteroids and comets populate the solar system: – Asteroids are concentrated in the asteroid belt
Solar System Formation -- Characteristics of Our Solar System • Swarms of asteroids and comets populate the solar system: – Asteroids are concentrated in the asteroid belt – Comets populate the regions known as the Kuiper belt and the Oort cloud
Solar System Formation -- Characteristics of Our Solar System • • Large bodies in the solar system have orderly motions and are isolated from each other : – All planets and most moons have nearly circular orbits going in the same direction in nearly the same plane – The Sun and most of the planets rotate in this same direction as well – Most moons orbit their planet in the direction it rotates Planets fall into two main categories: – Small, rocky terrestrial planets near the Sun – Large, hydrogen-rich jovian planets farther out • The jovian planets have many moons and rings of rock and ice Swarms of asteroids and comets populate the solar system: – Asteroids are concentrated in the asteroid belt – Comets populate the regions known as the Kuiper belt and the Oort cloud Several notable exceptions to these general trends stand out: – Planets with unusual axis tilts – Surprisingly large moons – Moons with unusual orbits
Solar System Formation -- Characteristics of Our Solar System • Several notable exceptions to these general trends stand out: – Planets with unusual axis tilts – Surprisingly large moons – Moons with unusual orbits
Solar System Formation -- Characteristics of Our Solar System • Large bodies in the solar system have orderly motions and are isolated from each other : – All planets and most moons have nearly circular orbits going in the same direction in nearly the same plane – The Sun and most of the planets rotate in this same direction as well – Most moons orbit their planet in the direction it rotates • Planets fall into two main categories: – Small, rocky terrestrial planets near the Sun Large, hydrogen-rich jovian planets farther out Any– successful theory account for all and of these • The jovian planets have must many moons and rings of rock ice • Swarms of asteroids and comets populate the solar system: – Asteroids are concentrated in the asteroid belt – Comets populate the regions known as the Kuiper belt and the Oort cloud • Several notable exceptions to these general trends stand out: – Planets with unusual axis tilts – Surprisingly large moons – Moons with unusual orbits
Solar System Formation – The Nebular Theory • It all starts with interstellar clouds of gas and dust. . .
Solar System Formation – The Nebular Theory • It all starts with interstellar clouds of gas and dust. . . • These clouds are mostly hydrogen and helium from the Big Bang
Solar System Formation – The Nebular Theory • It all starts with interstellar clouds of gas and dust. . . • These clouds are mostly hydrogen and helium from the Big Bang • But they contain heavier elements that were not formed in the Big Bang
Solar System Formation – The Nebular Theory • • It all starts with interstellar clouds of gas and dust. . . These clouds are mostly hydrogen and helium from the Big Bang But they contain heavier elements that were not formed in the Big Bang Where did these come from?
Solar System Formation – The Nebular Theory • • It all starts with interstellar clouds of gas and dust. . . These clouds are mostly hydrogen and helium from the Big Bang But they contain heavier elements that were not formed in the Big Bang They came from stars
Solar System Formation – The Nebular Theory • Stars make heavier elements from lighter ones through nuclear fusion
Solar System Formation – The Nebular Theory • Stars make heavier elements from lighter ones through nuclear fusion • The heavy elements mix into the interstellar medium when the stars die
Solar System Formation – The Nebular Theory • Stars make heavier elements from lighter ones through nuclear fusion • The heavy elements mix into the interstellar medium when the stars die • New stars form from the enriched gas and dust
Solar System Formation – The Nebular Theory • • Stars make heavier elements from lighter ones through nuclear fusion The heavy elements mix into the interstellar medium when the stars die New stars form from the enriched gas and dust And at the same time stars are forming
Solar System Formation – The Nebular Theory • • Stars make heavier elements from lighter ones through nuclear fusion The heavy elements mix into the interstellar medium when the stars die New stars form from the enriched gas and dust And at the same time stars are forming…planetary systems can form
Solar System Formation – The Nebular Theory • A large cloud -- a nebula perhaps 1 light year across -- floats in space
Solar System Formation – The Nebular Theory • A large cloud -- a nebula perhaps 1 light year across -- floats in space • The cloud begins to collapse …WHY? . . .
Solar System Formation – The Nebular Theory • A large cloud -- a nebula perhaps 1 light year across -- floats in space • The cloud begins to collapse • As it collapses it begins to spin faster …WHY? . . .
Solar System Formation – The Nebular Theory • • A large cloud -- a nebula perhaps 1 light year across -- floats in space The cloud begins to collapse As it collapses it begins to spin faster And as it spins faster, it flattens out …WHY? . . .
Solar System Formation – The Nebular Theory • • • A large cloud -- a nebula perhaps 1 light year across -- floats in space The cloud begins to collapse As it collapses it begins to spin faster And as it spins faster, it flattens out At the same time, it begins to heat up in the center …WHY? . . .
Solar System Formation – The Nebular Theory • • • A large cloud -- a nebula perhaps 1 light year across -- floats in space The cloud begins to collapse As it collapses it begins to spin faster And as it spins faster, it flattens out At the same time, it begins to heat up in the center When it gets hot enough, a star forms in the center
Solar System Formation – The Nebular Theory • • A large cloud -- a nebula perhaps 1 light year across -- floats in space The cloud begins to collapse As it collapses it begins to spin faster And as it spins faster, it flattens out At the same time, it begins to heat up in the center When it gets hot enough, a star forms in the center And in the disk around the forming star, planets can form
Solar System Formation – The Nebular Theory • • A large cloud -- a nebula perhaps 1 light year across -- floats in space The cloud begins to collapse As it collapses it begins to spin faster And as it spins faster, it flattens out At the same time, it begins to heat up in the center When it gets hot enough, a star forms in the center And in the disk around the forming star, planets can form Whether and what type of planets can form depends on what the cloud is made of
Solar System Formation – The Nebular Theory • This is what our own solar nebula was made out of
Solar System Formation – The Nebular Theory • This is what our own solar nebula was made out of • But how do we know this?
Solar System Formation – The Nebular Theory • We know from the absorption line spectrum of the Sun
Solar System Formation – The Nebular Theory • We know from the absorption line spectrum of the Sun • The absorption lines tell us the composition of the outer layers of the Sun
Solar System Formation – The Nebular Theory • We know from the absorption line spectrum of the Sun • The absorption lines tell us the composition of the outer layers of the Sun • And this is what that is
Solar System Formation – The Nebular Theory • We know from the absorption line spectrum of the Sun • The absorption lines tell us the composition of the outer layers of the Sun • And this is what that is • We think this was also the composition of the solar nebula the Sun and planets formed from
Solar System Formation – The Nebular Theory • But does it make sense that the outer layers of the Sun today should have the same composition as the solar nebula?
Solar System Formation – The Nebular Theory • The nebular theory proposes that the solar nebula collapsed to form the planets and the Sun
Solar System Formation – The Nebular Theory • The nebular theory proposes that the solar nebula collapsed to form the planets and the Sun • But why would the outer layers of the Sun have the same composition today as the solar nebula did 4. 6 billion years ago?
Solar System Formation – The Nebular Theory • The nebular theory proposes that the solar nebula collapsed to form the planets and the Sun • But why would the outer layers of the Sun have the same composition today as the solar nebula did 4. 6 billion years ago? • Here’s the argument…
Solar System Formation – The Nebular Theory • What is the Sun made out of?
Solar System Formation – The Nebular Theory • What is the Sun made out of? – Hydrogen and helium mostly. . . from the solar nebula
Solar System Formation – The Nebular Theory • What is the Sun made out of? – Hydrogen and helium mostly. . . from the solar nebula • What is the Sun doing with that?
Solar System Formation – The Nebular Theory • What is the Sun made out of? – Hydrogen and helium mostly. . . from the solar nebula • What is the Sun doing with that? – Fusing the hydrogen into helium to produce sunlight
Solar System Formation – The Nebular Theory • What is the Sun made out of? – Hydrogen and helium mostly. . . from the solar nebula • What is the Sun doing with that? – Fusing the hydrogen into helium to produce sunlight • Where is it doing that?
Solar System Formation – The Nebular Theory • What is the Sun made out of? – Hydrogen and helium mostly. . . from the solar nebula • What is the Sun doing with that? – Fusing the hydrogen into helium to produce sunlight • Where is it doing that? – In its core. . . which is no more than the central 10% of its volume
Solar System Formation – The Nebular Theory • What is the Sun made out of? – Hydrogen and helium mostly. . . from the solar nebula • What is the Sun doing with that? – Fusing the hydrogen into helium to produce sunlight • Where is it doing that? – In its core. . . which is no more than the central 10% of its volume • So the surface layers should be unchanged since the Sun first formed
Solar System Formation – The Nebular Theory • So it is reasonable to conclude that this was the composition of the solar nebula
Solar System Formation – The Nebular Theory • The key to the nebular theory is the condensation temperature of these materials, at which they will condense into solid form
Solar System Formation – The Nebular Theory • The key to the nebular theory is the condensation temperature of these materials, at which they will condense into solid form • This is because once the nebula collapse and heated, the temperature was different at different distances from the center
Solar System Formation – The Nebular Theory • This graph shows a temperature profile of the solar nebula as a function of distance from the center • It also shows where the various components of the nebula would condense
Solar System Formation – The Nebular Theory • Metals, rocks, and hydrogen compounds existed throughout the solar nebula
Solar System Formation – The Nebular Theory • Metals, rocks, and hydrogen compounds existed throughout the solar nebula • They could only be solid where the temperature was below their condensation temperature
Solar System Formation – The Nebular Theory • Metals, rocks, and hydrogen compounds existed throughout the solar nebula • They could only be solid where the temperature was below their condensation temperature • The “frost line” is the boundary beyond which icy compounds can condense
Solar System Formation – The Nebular Theory • Metals, rocks, and hydrogen compounds existed throughout the solar nebula • They could only be solid where the temperature was below their condensation temperature • The “frost line” is the boundary beyond which icy compounds can condense • It was between the present-day orbits of Mars and Jupiter
Solar System Formation – The Nebular Theory • Once materials condense, they can stick together
Solar System Formation – The Nebular Theory • Once materials condense, they can stick together • This process is called “accretion”
Solar System Formation – The Nebular Theory • Once materials condense, they can stick together • This process is called “accretion” • “Core accretion” is the next step in planet formation
Solar System Formation – The Nebular Theory
Solar System Formation – The Nebular Theory • This suffices to explain terrestrial planet formation, but jovian planets require adding an extra layer to the process. . . literally
Solar System Formation – The Nebular Theory • An alternative to the core accretion model -- the "gravitationalinstability model" -involves the direct collapse of the cool gas beyond the frost line into jovian planets • This takes much less time than the "core-accretion model" • And this makes it consistent with (controversial) claims that protoplanetary disks
Solar System Formation – The Nebular Theory
Solar System Formation – The Nebular Theory • An alternative to the core accretion model -- the "gravitationalinstability model" -involves the direct collapse of the cool gas beyond the frost line into jovian planets
Solar System Formation – The Nebular Theory • An alternative to the core accretion model -- the "gravitationalinstability model" -involves the direct collapse of the cool gas beyond the frost line into jovian planets • This takes much less time than the "core-accretion model"
Solar System Formation – The Nebular Theory • An alternative to the core accretion model -- the "gravitationalinstability model" -involves the direct collapse of the cool gas beyond the frost line into jovian planets • This takes much less time than the "core-accretion model" • And this makes it consistent with (controversial) claims that protoplanetary disks
Solar System Formation – The Nebular Theory • Whatever the details of how the jovian planets form, moons would have formed in the disk around the jovian planet just as planets formed in the solar nebula around the Sun
Solar System Formation – The Nebular Theory • Whatever the details of how the jovian planets form, moons would have formed in the disk around the jovian planet just as planets formed in the solar nebula around the Sun • And the whole process of planet formation would be finalized by the infant Sun
Solar System Formation – The Nebular Theory • As the Sun became a star, a strong solar wind blew out from it
Solar System Formation – The Nebular Theory • As the Sun became a star, a strong solar wind blew out from it • This cleared the remaining nebular gas away
Solar System Formation – The Nebular Theory • As the Sun became a star, a strong solar wind blew out from it • This cleared the remaining nebular gas away • And this froze the planets in whatever form they had attained at that time
- Slides: 77