origin of the solar system astronomy 311 professor lee carkner lecture 8
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Origin of the Solar System
Astronomy 311Professor Lee
CarknerLecture 8
Quiz 1 Monday Covers lectures 1-8 and associated readings About half multiple choice (~20 questions), half
short answer/problems (~4 questions) Study:
Notes Can you write a paragraph explaining each major concept?
Exercises Can you solve all the exercises with no resources?
Readings Can you do all the homework with no book and Quizdom
questions with no notes?
Bring pencil and calculator! No sharing!
The Solar System
Questions When did it form? Why does it have structure?
Structure of the Solar System
The solar system has three distinct regions
Mercury, Venus, Earth, Mars, Asteroids Made of metal and rock
Outer region Jupiter, Saturn, Uranus, Neptune and Moons Made of ice and gas
Kuiper Belt and Oort Cloud Made of ice
Where Did the Solar System Come From?
We can’t look back in time to see how the Sun and planets formed, but we can look at young stars that are forming today
Star Formation
Due to an external stimulus (e.g., supernova shockwave, stellar wind)
Gravity causes the core to contract to a star
Conservation of angular momentum makes the clump spin faster Rapid rotation causes the outer layers to form a disk
Circumstellar Disks
Disks are fairly cool and can be detected with infrared and millimeter telescopes
Disks are common around young stars
From Disks to Planets
Where does the disk go? Formed into planets
Disks you can see, planets you can’t
How Do Planets Form?
There are 4 stages to planet formation grains stick together to form
planetesimals gas and leftover planetesimals are
cleared from solar system
What Was the Solar Nebula Made of?
Solar Nebula --
From studying meteorites and star forming regions we hope to discover what the solar nebula was made of
Two basic components Gas -- Dust -- made of rock (silicates), metal (iron) and
ices (water, methane, ammonia, carbon dioxide)
Solar System Dust Grain
Accretion of Grains
Grains get larger by sticking together and settle to the center of the disk
Eventually the grains form into larger bodies (a few km in size) called planetesimals At the end of this stage the solar system is populated by a few
thousand planetesimals, such a system is invisible to telescopes
Accretion in a Protoplanetary Disk
Star
Disk
High Density LowDensity
Larger Grainsmove to center
Temperature and the Solar Nebula
Two basic types of dust in solar nebula: Volatiles -- Refractory Material --
Temperatures were higher in the inner solar system and lower in the outer solar system
Inner solar system -- rocky planetesimals Outer solar system -- icy planetesimals
Regions of Formation Temperature
Rocky Icy
Gas
Planetesimals to Planets
Due to gravity and intersecting orbits the planetesimals collide with each other
Planet formation happens differently in inner and outer solar system
Formation of Gas Giants In the outer solar system you have more
material (both volatiles and refractory material), so planets are larger
No more hydrogen gas after a few million years Thus, in the outer system where the
temperatures are lower you have gas giants
Formation of Terrestrial Planets
Result is small rocky planets with no large gassy outer layers
Accretion of the Inner Planets
Orbital Evolution
This causes: Shifting of the orbits of the Gas Giants
Icy planetesimals ejected to form the Kuiper Belt and Oort cloud
The Final Solar System Our picture of planet formation is driven
by an attempt to explain our own solar system and its three regions Outer or Gas Giant region Trans-Neptunian or Cometary Region
We have also found other types of planetary systems different from our own
Steps in Solar System Formation
1 Inner solar system -- volatiles boil off, resulting in small rocky planets
2 Outer solar system -- large planet cores form rapidly from refractory and icy material, acquire large gas envelopes
3 Edge of solar system -- leftover and ejected icy planetesimals form Kuiper belt and Oort cloud