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The formation of stars and planets Day 5, Topic 3: Migration of planets and Outlook... Lecture by: C.P. Dullemond Three types of migration • Type I: low mass planets • Type II: high mass planets • Type III: rare type II variant Type I migration • • Planet’s gravity launches spiral waves in disk These spiral waves exert torque on planet: – Inner spiral wave pushes planet outward – Outer spiral wave pushes planet inward • Outer spiral wave wins: inward migration QuickTime™ and a YUV420 codec decompressor are needed to see this picture. Type I migration Zur Anzeige wird der QuickTime™ Dekompressor „YUV420 codec“ benötigt. by Frederic Masset www-star.qmul.ac.uk/~masset/ Type I migration Time scale of inward type I migration (1 solar mass star): 1 1 1/ 2 2 M r h /r gas tType I 10 4 ...10 5 years 2 10M 100g/cm AU 0.07 Review Thommes & Duncan in “The Formation of Planets” 2005 3-D estimates: 105...106 (Tanaka et al. 2002) Gap opening Hill sphere: sphere of gravitational influence of planet: M rHill r 3M* 1/ 3 If Hill radius larger than h of disk: disk can be regarded as thin compared to potential. This happens for massive enough planets. Planet will affect structure of the disk. P. Ciecielag Effective potential, Lagrange points r1 r1 M 2 r2 M1 r2 L4 Effective potential in the co-rotating frame: eff GM1 GM2 1 2 2 K r r r1 r r2 2 centrifugal kinetic energy L3 L1 L5 Example: M2/M1=0.1 L2 Effective potential, Lagrange points r1 r1 M 2 r2 M1 r2 L4 Effective potential in the co-rotating frame: eff GM1 GM2 1 2 2 K r r r1 r r2 2 centrifugal kinetic energy L3 L1 L5 Example: M2/M1=0.01 L2 Trojans of Jupiter Motion of gas / particles in horseshoe Gap opening Zur Anzeige wird der QuickTime™ Dekompressor „YUV420 codec“ benötigt. by Frederic Masset www-star.qmul.ac.uk/~masset/ Type II migration • Massive planet opens a gap • Accretion in the disk is stopped by the gap – If the disk is massive enough: accretion continues, simply by pushing the planet inward. Planet is locked to the disk accretion. Type II migration – If the disk is not massive enough: planet will not migrate. Inner disk will deplete. • Three-dimensional models: accretion can still proceed somewhat by flowing in 3-D past the planet. Transition from I to II and gap opening Zur Anzeige wird der QuickTime™ Dekompressor „YUV420 codec“ benötigt. by Frederic Masset www-star.qmul.ac.uk/~masset/ Type III migration (run-away migration) Masset & Papaoloizou Type III migration (run-away migration) Masset & Papaoloizou Type III migration (run-away migration) • If planet initially moves inward: – Some inner disk material enters horseshoe, gets flung to outer orbit of horseshoe by planet. Planet loses angular momentum. – Some horseshoe material enters outer disk, does not get flung back to inner orbit of horseshoe. – Netto: one-sided asymmetric angular momentum transport from planet to disk: inward push! Run-away! • If planet initially moves outward: Same thing, but the other way: planet is pushed outward. Also runaway! Type III migration (run-away migration) Zur Anzeige wird der QuickTime™ Dekompressor „YUV420 codec“ benötigt. by Frederic Masset www-star.qmul.ac.uk/~masset/ Note: this movie has opposite rotation as discussion above. Why do planets exist everywhere? • Migration should have depleted all planets • What about bandwagon approach (form planets all the time, lose most of them via migration, but when disk dissipates some are left)? – Problem: Need plenty of solid disk material to form a planet – Problem: First make rocky core, then accrete gas. This process takes longer than migration time scale. • Problem of migration is one of main open questions of planet formation! How to planets get in resonance? G. Bryden Stopping migration with a resonance Masset & Snellgrove Outlook Outlook • Field of star- and planet formation more lively than ever! • New telescopes give us unprecedented view of disks: – – – – Spitzer Space Telescope (infrared) Very Large Telescope interferometer (infrared) ALMA (submillimeter) >= 2010 Herschel (far-infrared) >= 2007 • Theory/lab: – Computers are now powerful enough to model the growth from dust to planets – Laboratory experiments measure sticking and collision properties of particles Outlook Very Large Telescope: Infrared Interferometry Resolving the earth forming regions of disks (in operation) Outlook Herschel Space Observatory (far-infrared/submillimeter) Looking for water in extrasolar (pre-)planetary systems Outlook Atacama Large Millimeter Array (ALMA) Chemistry, small scale disk structure, large grain dust population Outlook • Planet-hunting is hot! – Space missions will even be able to detect Earth-like planets! DARWIN / TPF – We may even analyze their atmospheres!!! (life??) Outlook Darwin/TPF: hunting for other ‘Earths’ Outlook Detection of possible life on extrasolar Earth-like planets