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 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 Any successful theory must account for all of these

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 "gravitational-instability 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 don't last long enough for jovians to form by core-accretion

Solar System Formation – The Nebular Theory

Solar System Formation – The Nebular Theory An alternative to the core accretion model -- the "gravitational-instability 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 "gravitational-instability 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 "gravitational-instability 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 don't last long enough for jovians to form by core-accretion

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