Presentation on theme: "The structure and formation of the Solar System By Mark Richardson."— Presentation transcript:
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 SkaterFigure 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 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 planetsplanets 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 180 o while Uranus is flipped roughly 90 o.Uranus 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: , Copyright Calvin J. Hamilton.www.solarviews.com Wikipedia Astronomy.org: , Copyright GGary A. Beckerhttp://www.astronomy.org/astronomy-survival/solform.html Astronomy Online: Copyright Mad Star: Copyright Rich Townsendhttp://www.astro.wisc.edu/~townsend/static.php?ref=diploma-1 A special thanks to Ian Short, Mary Lou Whitehorne, And You!