* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download The structure and formation of the Solar System
Advanced Composition Explorer wikipedia , lookup
Geocentric model wikipedia , lookup
Observational astronomy wikipedia , lookup
Tropical year wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
Circumstellar habitable zone wikipedia , lookup
Astronomical unit wikipedia , lookup
Rare Earth hypothesis wikipedia , lookup
Astrobiology wikipedia , lookup
History of astronomy wikipedia , lookup
Astronomical naming conventions wikipedia , lookup
Planets beyond Neptune wikipedia , lookup
Star formation wikipedia , lookup
Comparative planetary science wikipedia , lookup
Extraterrestrial life wikipedia , lookup
Planets in astrology wikipedia , lookup
Exoplanetology wikipedia , lookup
Planetary system wikipedia , lookup
Directed panspermia wikipedia , lookup
Satellite system (astronomy) wikipedia , lookup
Definition of planet wikipedia , lookup
Planetary habitability wikipedia , lookup
IAU definition of planet wikipedia , lookup
Nebular hypothesis wikipedia , lookup
Solar System wikipedia , lookup
Timeline of astronomy wikipedia , lookup
History of Solar System formation and evolution hypotheses wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
The structure and formation of the Solar System By Mark Richardson The structure of a solar system • • • • • • Star(s): the gravitational centre(s) of the system. Undergoing nuclear fusion. Planets: Bodies of adequate size orbiting a sun Dwarf Planets: Small versions of planets – perhaps captured, not formed. Moons: Bodies orbiting planets and dwarf planets Asteroids: Smallest bodies in the system made mostly of rock (refractory material) Comets: Smallest bodies in the system made of significant ice (volatiles) Origin of the solar system • In the galaxy there are gas clouds. • Inside the cloud there is: – Pressure – Gravity • These forces are typically in balance. The beginning of the beginning • ~5-6 Billion years ago this balance got disturbed! – Possibly a nearby supernova etc. • Gravity won! • The gas cloud then collapses – most towards the centre. Why a disk? • Some gas on the edge of the cloud feels a gravitational pull towards the centre • Assume the cloud has some initial spin Why a disk? • Written with components Why a disk? • Now as things get closer to the spin axis, they speed up: – Conservation of Angular Momentum – Figure Skater • The faster you do a turn in a car – the stronger the force you feel Why a disk? • How is that important? • The component of gravity acting towards the spin axis is serving the purpose of your door in a turning car – it’s what’s making you turn – It is NOT making you move towards the axis • Only the other component will actually move you! The planetary disk • More complicated view: • Link: Formation Movie • Eventually most material cannot move closer to the forming sun. The layout of things • The original cloud had some inhomogeneities. • These have accumulated more mass than the average bit of the cloud (the largest of these is typically at the centre) • These form the first planetesimals! What’s next … and the controversy • At this point it is believed that the planetesimals collide with one another, due to gravity. • These eventually become the foundation for our planets • Some theories show this process to take almost the age of the solar system itself (see the Origin and Evolution of the Solar Sytem – Woolfson) for planets to form, and that the sun should be rotating much faster. Possible Solutions • The sun may rotate slowly because it lost angular momentum through magnetic fields and jets – research is still ongoing. • Interesting solutions to the planet growth problem have been suggested, although both the nature of the problem and these solutions need to be studied further. Inner System: Planetismals • As the protosun heats up it emits a wind of photons that push the lightest compounds in the disk to the outer region. • This leaves the inner system almost free of gas – this is why the inner planets are rocky planets. • Atmospheres subsequently form by a combination of outgassing and comet impacts. Inner System: Planetismals Constitution of the planets • The planets form through the continuous accretion of planetoids. • The impacts of large planetoids can completely liquefy the material. • This allows denser materials, such as iron, to sink to the centre, explaining the constitution of material. Outer System • The same general process takes place in the outer system, only there are more gases and ice. • This allows for significant atmospheres, and larger planets. • These larger planets are more able to capture smaller objects in a stable orbit – moons and rings The Sun • During this process the protosun has continued to accrete more material • This increases the pressure on material in the core of the protosun which in turn increases the temperature. • At ~1 million K the protosun can begin Hydrogen burning – it is now a sun The big picture • We have seen a theory explaining the creation of a star and planets and other materials from an initially disturbed gas cloud. • It is the most accepted theory – but not without its inconsistencies. • Some last minute problems and most likely explanations: Last minute problems • Venus and Uranus don’t rotate the same direction as everything else. • Venus is flipped 180o while Uranus is flipped roughly 90o. • Everything should be rotating the same if they came out of the same cloud. • Only explanation is a large impact made the whole planet rotate. • This would only be possible if very early objects of comparable mass hit each planet. Leftovers • All the material in the early solar system is not used up when planets are formed. • Left over stuff is still flying around out there – these asteroids, meteoroids and comets still make impacts. • The asteroid belt is a large collection of asteroids. A theory, which is most favoured, is that the proximity to Jupiter tore apart a planet that was forming there. • Starting at about Pluto’s orbit, the Kuiper belt extends much farther out and houses most of the comets in the solar system. • Beyond this is a cloud called the Oort cloud. This is the farthest extent of the solar system. This has very small objects in it, as well as some larger ones. Sources and Acknowledgments • • • • • Solar Views: www.solarviews.com, 1997-2007, Copyright Calvin J. Hamilton. Wikipedia Astronomy.org: http://www.astronomy.org/astronomy-survival/solform.html, 19962008, Copyright GGary A. Becker Astronomy Online: http://astronomyonline.org/SolarSystem/SolarSystemFormation.asp, Copyright 2004-2009 Mad Star: http://www.astro.wisc.edu/~townsend/static.php?ref=diploma-1, 2009 Copyright Rich Townsend • A special thanks to Ian Short, Mary Lou Whitehorne, And You!