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Origin of the Solar System Astronomy 311 Professor Lee Carkner Lecture 8 What would be the easiest way to increase the magnification of your telescope? a) b) c) d) e) Increase the size of the primary mirror Increase the size of the secondary mirror Use an eyepiece with a longer focal length Use an eyepiece with a shorter focal length There is no way, the magnification of a given telescope is fixed Which of the following types of electromagnetic radiation are best studied from space? a) b) c) d) e) Ultraviolet Radio X-ray a and c only a, b, and c 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 Inner Region Mercury, Venus, Earth, Mars, Asteroids Outer region Jupiter, Saturn, Uranus, Neptune and Moons Trans-Neptunian region Kuiper Belt and Oort Cloud 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 Rapid rotation causes the outer layers to form a disk Circumstellar Disks We also can see them silhouetted against a bright background in Hubble images Disks are common around young stars From Disks to Planets Many stars between 1-50 million years old have disks, but stars slightly older generally do not 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 1 2 grains stick together to form planetesimals 3 4 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 Dust grains are very small (< 1 mm), how do they form planets? If dust grains are fractal they may stick together more easily At the end of this stage the solar system is populated by a few thousand planetesimals, such a system is invisible to telescopes Disk Star High Density Low Density Larger Grains move to center Accretion in a Protoplanetary Disk 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 Near the Sun the volatiles boiled off leaving only the refractory material behind Outer solar system -- icy planetesimals Rocky Icy Gas Temperature Regions of Formation 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 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
