Origin of the Solar System Astronomy 311 Professor Lee Carkner Lecture 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? Bring pencil and calculator! No sharing!
The Solar System The solar system is not just a random collection of planets The solar system has a structure
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 Stars are formed in clouds of gas and dust when a clump of material starts to contract The mutual gravity of the particles in the clump causes the contraction to continue Conservation of angular momentum makes the clump spin faster
Star Formation in Action
Star Formation in Orion
Protoplanetary Disks in Orion
Protostellar Jet
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? A disk has more surface area than a group of planets with the same mass, so it radiates more light
How Do Planets Form? There are 4 stages to planet formation 11 22 33 4 gas and leftover planetesimals are cleared from solar system
What Was the Solar Nebula Made of? Solar Nebula -- Initial disk of material that the solar system formed from Two basic components Gas -- Dust --
Solar System Dust Grain
Accretion of Grains Dust grains are very small (< 1 mm), how do they form planets? 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
Accretion in a Protoplanetary Disk Star Disk High Density Low Density Larger Grains move to center
Temperature and the Solar Nebula Two basic types of material in solar nebula: Volatiles -- Refractory Material -- Temperatures were higher in the inner solar system and lower in the outer solar system Near the Sun the volatiles boiled off leaving only the refractory material behind Inner solar system -- Outer solar system --
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 Thus, in the outer system where the temperatures are lower you have gas giants
Formation of Terrestrial Planets In the inner solar system planets grew more slowly out of less material, most of it refractory
Accretion of the Inner Planets
Beyond the Gas Giants Beyond Neptune the densities are so low and the orbital timescales are so long no planets form at all Other icy planetesimals are ejected by a close encounter with Jupiter or another gas giant
Cleaning Up Some of the material in the solar nebula does not end up in the final solar system The solar wind will eventually blow most of the unaccreted gas and small particles out of the system
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 We have also found other types of planetary systems different from our own
Regions of Formation Temperature Rocky Icy Gas
Building the Solar System By looking at stars with protoplanetary disks and the structure of our own solar system and we can develop a theory of how planetary systems form Our current picture of planet formation explains the 3 regions of the solar system
Step by Step 1Inner solar system -- 2Outer solar system -- large planet cores form rapidly from refractory and icy material, acquire large gas envelopes 3Edge of solar system --