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LECTURE NOTES PHYC10008.docx - PHYC10008 – SOLAR SYSTEM TO...

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PHYC10008 – SOLAR SYSTEM TO COSMOSPlanets and moons:8 planets in our solar system185 moons (of planets) currently (vs. 90 in 2001technologies helped thisdoubling in finding moons/tiny orbiting objects)Classification of a planet: (IAU – 2006 planet debate) international astronomyunionOrbits the sunHas enough mass to be ‘round’ (bigger=gravity pulls body together=roundshape)Has cleared the neighbourhood around its orbitWhat is a moon or satellite?Celestial body orbiting another bodyDwarf planets?Pluto = prototypeEarth = 1, mars = 2, Jupiter = 79, Saturn 62, Uranus = 27, Neptune = 14,Pluto = 5Pluto:1990’s astronomers found new objects outside its’ orbitoSome of which = larger than Pluto (there’s a continuum of objects)Issue for astronomers? Either increase the number of planets to solar systemor exclude PlutoReal issue?What is a planet, scientifically?Pluto’s moon Charon:is of comparable size.The sun: a ‘common’ starHydrogen gasGenerates heat and light by nuclear fusionSun spots = brown spotsHot ball of H and HeNuclear fusion process in the core = hydrogen atoms stick together -> helium+ heat/energy which travels = making it shine brightlyWhat is a galaxy?A collection of starsThe milky way:Spiral galaxy~100 billion starsOrbiting a supermassive black holeSupermassive = mass of at least x106-x109Local group of galaxies:+54 galaxies3 of sensible size: milky way, andromeda (M31) and M32Dwarf galaxies in the local group discovered yearlyoMost dwarf galaxies are satellites of the 2 main galaxiesPart of the Virgo superclusterAndromeda = biggest galaxyGravitationally bound in local neighborhood = local group ofgalaxiesVirgo Cluster:Thousands of galaxies gravitationally bound together with lots of dark matterSuperclusters of clusters
PHYC10008 – SOLAR SYSTEM TO COSMOSHubble space telescope: takes very deep images of small part of the universeBaryonic matter = e/p (small part of universe), usDark matter = has gravitational effectHow do we describe the universe quantitatively?

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Dark Matter, Issue, Pluto s moon Charon

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