* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download The Solar Nebula Theory
Advanced Composition Explorer wikipedia , lookup
Planets beyond Neptune wikipedia , lookup
Astrobiology wikipedia , lookup
Rare Earth hypothesis wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
Definition of planet wikipedia , lookup
IAU definition of planet wikipedia , lookup
Satellite system (astronomy) wikipedia , lookup
Accretion disk wikipedia , lookup
Extraterrestrial life wikipedia , lookup
H II region wikipedia , lookup
Planetary system wikipedia , lookup
Directed panspermia wikipedia , lookup
Solar System wikipedia , lookup
Late Heavy Bombardment wikipedia , lookup
Planetary habitability wikipedia , lookup
Timeline of astronomy wikipedia , lookup
Star formation wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
History of Solar System formation and evolution hypotheses wikipedia , lookup
Reading: Chap. 6, Sect.1,2; Chap. 12 Final Exam: Monday, May 2; 9:45-11:45 Homework 10: Due this Thursday, April 21 Astro 120 Spring 2016: Lecture 25 page 1 The Solar Nebula Theory Astro 120 Spring 2016: Lecture 25 page 2 Brief review of last time: Our Sun SUN: a star, up close and personal • Thevital statistics • • photosphere, chromosphere, corona • the solar cycle of the Sun’s energy: • Source combustion fails - 10,000 years of fuel • • contraction fails - 100,000,000 years of “fuel” Fusion: the p-p chain • Hydrogen 1 4 • 4 H → He + photons + neutrinos • 0.7% of mass of H converted to energy via E=mc2 • energy source for 10 billion years Astro 120 Spring 2016: Lecture 25 page 3 Formation of Planetary Systems • Where to begin? • Evidence from our current Solar System • Evidence from the Stars • First phases: collapse to star plus disk • interstellar cloud – gravity takes over • angular momentum – disk formation • The Solar Nebula • mass and composition • temperature distribution • Planet formation • condensation • accretion into planetessimals • accretion into planets and satellites http://www.jach.hawaii.edu/JCMT/publications/newsletter/n16/fom_ann.jpg The planets formed in a dust-filled disk of gas surrounding the very young Sun Where to begin? Astro 120 Spring 2016: Lecture 25 page 4 • Evidence from our current Solar System • all planetary orbits are • counterclockwise • nearly circular • in the same plane } Planets formed out of a disk • inner planets are rocky • outer planets are gas balls • Evidence from the Stars • there are many other solar systems • there are many multiple star systems • youngest stars are embedded in dust and gas Astro 120 Spring 2016: Lecture 25 page 5 Astro 120 Spring 2016: Lecture 25 page 7 First phase: collapse of interstellar cloud • Molecular Clouds: clumps of interstellar medium • mass: up to 106 Msun • radius ~ 10 - 30 pc • To make stars, a cloud must undergo Gravitational Collapse • Collapse –> Spin-up –> formation of Disk • HST observations of Orion disks • HST observations of “Eggs” in M16 • β Pictoris Astro 120 Spring 2016: Lecture 25 page 6 Formation of protoplanetary disk Astro 120 Spring 2016: Lecture 25 page 8 Astro 120 Spring 2016: Lecture 25 page 9 Astro 120 Spring 2016: Lecture 25 page 11 Astro 120 Spring 2016: Lecture 25 page 10 The Solar Nebula (the SS 4.6 Gyr ago) Astro 120 Spring 2016: Lecture 25 page 12 - same as the Sun • Composition 74% Hydrogen • • 24 % Helium • 2% “heavies” (C, O, Si, Fe) • Mass: need enough heavies for Earth, cores of Jovians • • total mass ~ 0.1 x Msun • Temperature hot in inner parts (2000K) • • cooler with distance out (700K at Earth...) • Size1 a.u. thick NGC7822 with WISE • • extent well beyond Pluto’s current orbit Astro 120 Spring 2016: Lecture 25 page 13 Astro 120 Spring 2016: Lecture 25 page 14 Planet Formation - Condensation Planet Formation - Condensation • • nebula cools, compounds “freeze out” nebula • inner • • • nebula cools, compounds “freeze out” nebula • inner • • Condensation 2000K is hot enough to melt all “heavies” heavies condense into microscopic grains • Condensation 2000K is hot enough to melt all “heavies” heavies condense into microscopic grains • iron, silicates (minerals and rocks) • but “ices” still gaseous nebula - outside the FROST LINE • outer • ices condense into grains Astro 120 Spring 2016: Lecture 25 page 15 • iron, silicates (minerals and rocks) • but “ices” still gaseous nebula - outside the FROST LINE • outer • ices condense into grains Final Formation Stages Astro 120 Spring 2016: Lecture 25 page 16 • Sun “Turns On” • solar wind blows remaining gas away • planet growth largely ceases Planet Formation - Accretion • Accretion • grains collide and stick —> planetessimals grow by further collisions • planetesimals gravity holds them together when big enough • • some planetesimals eventually become very large • final sweeping up into present planets All this took a VERY SHORT time ••• less than 100 million years after initial collapse • End of Planetary Formation Phase • final large-scale collisions • Earth–Moon system • Mercury core formation • internal melting, differentiation • satellite formation/capture • large-scale sweeping/bombardment All this took a VERY SHORT time ••• less than 100 million years after initial collapse Astro 120 Spring 2016: Lecture 25 page 17 Astro 120 Spring 2016: Lecture 25 page 18 Planet formation simulation 200 A.U. Astro 120 Spring 2016: Lecture 25 page 19 Observations - explained by the solar nebula theory • Orderly motions of planets • arise naturally for objects formed within a spinning, flattened disk • Two types of planets • within frost line - most abundant stuff is gaseous • form only small, rocky planets beyond frost line - ices more readily accrete more stuff to make big planets • Oddball exceptions • final accretion stages - collisions, migration, and other ‘accidents’ Cha & Takashin 2011 Astro 120 Spring 2016: Lecture 25 page 20 Astro 120 Spring 2016: Lecture 25 page 21 Astro 120 Spring 2016: Lecture 25 page 22 Astro 120 Spring 2016: Lecture 25 page 23 Astro 120 Spring 2016: Lecture 25 page 24 Simulation of HL Tau HL Tau - a planetary system in formation imaged in sub-mm by ALMA