Week 8: Origins and the Universe

 WEEK 8: ORIGINS IN THE UNIVERSE

  • The Big Bang

    • The best-supported scientific theory for how the universe was created

    • The Big Bang was an expansion or an inflation rather than an explosion 

    • The universe is still expanding today 

  • Nebulae: clouds of gas and dust 

  • Nuclear fusion: occurs when there are enough particles under intense heat and pressure in the center core, the star ignites and becomes a fully functioning star 

  • An average star (like the Sun) or a supermassive star is then formed

    • As the star burns through its fuel, it loses mass; and has less gravity and its size increases

  • An average star turns into a red giant 

    • As it continues burning fuel, the red giant becomes very large 

    • The outer layers are blown off creating a planetary nebula and the inner core of the star remains (called a white dwarf star) 

  • A supermassive star turns into a super red giant

    • These stars have more mass = burn through fuel quicker 

    • Losing gravity and becoming extremely large 

    • The super red giant will lose its fuel 

    • Collapse in on itself

    • Creates a giant explosion called a supernova 

    • The star can now either form a black hole or an extremely compacted neutron star

  • Galaxies 

    • Galaxy: a collection of billions of stars, gas, and dust held together by gravity in space

    • Hubble Space Telescope: can take pictures of space

    • There are probably 100 billion galaxies in the entire universe

    • There are 3 shapes of galaxies

      • Spiral

      • Elliptical 

      • Irregular

    • Our galaxy is the Milky Way = spiral galaxy 

    • Most galaxies have a supermassive black hole at the center which has an extremely strong gravitational pull that holds the entire galaxy together 

  • Black Holes

    • Black hole: an area with space with extremely strong gravity from which no light can escape 

      • This is why the area appears black 

      • At the end of its life cycle, a supermassive star collapses in on itself which causes a huge explosion called a supernova = results in a black hole 

  • Origins of the Sun, Earth, and Moon

    • Our solar system was most likely formed from a giant rotating nebula after a former star underwent a supernova.

    • 4.65 billion years ago, this rotation and intense gravity caused the nebula to collapse on itself.

    • This caused it to spin faster and flatten into a disk shape, the Plane of the Ecliptic.

    • Plane of the Ecliptic = The disk-shaped plane in which everything in our solar system orbits around the Sun.

    • Much of this material was pulled toward the center of the disk and a star was formed: the Sun.

    • The Sun contains 99.8% of the mass in our solar system.

    • The Sun is an average-sized star. It is mostly made of hydrogen and helium.

    • After the Plane of the Ecliptic was formed, the planets formed from the leftover gas and dust orbiting around the Sun

  • Earth was NOT formed during the Big Bang. 

    • The Big Bang occurred 13.7 billion years ago. 

    • This means there is a lapse of 9 billion years between the Big Bang and the formation of Earth.

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