P7 Mapping the Universe

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  • P7.3 Mapping the Universe
    • Parralax
      • Distance in parsecs = 1/ Parallax angles in seconds
    • Cepheid Variables
      • The obsevered brightness of Cepheid variables changes regularly. The variation in its luminosity is caused by its expansion and contraction.
    • Shapley VS Curtis
      • A few years later, Edwin Hubble recorded observations of Cepheid variable stars in one nebula and realised that they were much further away than any star in the Milky Way. This evidence supported Curtis’s proposal that there were many galaxies in the universe.
      • Curtis argued that there were many galaxies in the universe and that these nebulae were distant galaxies. Shapley believed that the universe contained only one galaxy and that the nebulae were gas clouds within the Milky Way.
      • Observations with telescopes had identified that the Sun was one of many stars in our galaxy (the Milky Way). Astronomers had also seen lots of fuzzy objects in the sky at night. Astronomers called these objects nebulae.
      • In 1920, two leading astronomers - Heber Curtis and Harlow Shapley - disagreed on whether there was one galaxy or many galaxies in the universe.
    • Hubble's Law
      • Using "redshift" Hubble observed a correlation between the distance "space objects" were from Earth and the speed with which they were moving away.
      • Galaxies FURTHER away are traveling away FASTER.
      • Speed = Hubble's constant X Distance reccesion(v=Ho X A)
        • Ho= 75 km/s


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