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Chapter 1

AS101 Chapter Notes - Chapter 1: Big Bang, Cosmic Calendar


Department
Astronomy
Course Code
AS101
Professor
Ioannis John Haranas
Chapter
1

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1.1 From Solar System to Galaxy to Universe
Earths Motion
Diameter= 13 000 km
Earth rotates W to E and crosses the sunset line which means the sun has set
Moon is 1/4 the size of Earth and orbits around the Earth
Earth orbits the sun once a year
Light reaches in 8 mins from sun to earth
Not possible to see any distance larger than 13.8 billion light years
The Universe:
The start nearest to the sun is Centuari (Proxima)
Light takes 4.5 years form Centauri to get to Earth
Space between stars are filled with gas
Clouds give birth to stars (galaxy has billions of them)
Ex: A cloud gave birth to the Sun billions of years ago
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Gases of stars generates energy by nuclear fusion
Spiral arms extend from the centre to the edge
Galaxies:
Local group: clusters of galaxies with ours included
Clusters of clusters= superclusters, they link together to form filaments that outline voids
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Filaments are the largest structure in the universe
Super voids: huge voids that have no galaxies
Voids in higher dense areas are smaller than voids in low dense areas
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Scientific notation: recording very positive or
negative numbers with the power of 10
Field of view: area visible in a photo
Astronomical Unit: the average distance of
the sun to Earth (150,000,000 km)
Light year: unit= distance light travels in a
year (10^13 km/ 63 000 AU)
Galaxy: a large system that consists of star
clusters, gas, dust that orbit around a
common centre mass
Milky Way: hazy band of light that’s
produced by our galaxy's glow and it
circles our sky
Milky Way Galaxy: spiral galaxy with our
sun and can be seen at night
Spiral arms: long spiral pattern of bright
stars, clusters + dust
Star: a ball of gas that’s held
together by gravity and pressure of
its hot gasses
Planet: round, non-luminous body
that orbits around a star
Filaments: walls/boundaries
between galaxies
Cosmic voids: empty spaces
between filaments that barely have
any galaxies
1.2 The Cosmic Calendar: Concepts and Time
Cosmic calendar is the way our yearly calendar fits the time and scale of universe
13 billion years since the big bang
Gravity +atoms work together to create everything in our universe
11:52 AM
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