ASTRO-110 Lecture Notes - Lecture 3: Supercluster, Cosmic Microwave Background, Usable Fuel
22 Sep 2020
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Document Summary
Planet, solar system, local group (or galaxy cluster if large enough), supercluster then universe. Distance in space is measured by light years (distance light can travel in one year) The universe is largely empty space between objects. Light travels at 3 x 10^8 m/s or 300,000 km/s. The closest star is alpha centauri (at 4. 4 light years away) Our solar system is about 27,000 light years from the centre of the milky way. Most of the mass in the universe is made out of dark matter (we can"t see it but we can. The milky way is composed of more than 100 billion stars feel the effect of its gravity) It also comprises the majority of the mass of our galaxy. A form of energy called dark energy is pushing galaxies apart even though their gravitational pull is trying to keep them together. The universe is expanding (the average distance between galaxies is growing.
