Astronomy 1021 Chapter Notes - Chapter 1: Cosmic Calendar, Millisecond Pulsar, Usable Fuel
28 May 2018
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Astronomy 1021
Chapter 1: A Modern View of the Universe
History of the Universe
Big Bang, Expansion, and Age of Universe
•Big Bang: galaxies are moving apart meaning they must have had an expansion point called the
BB (nearly 14 billion years ago)
•While the universe continues to expand, galaxies and galaxy clusters don’t b/c gravity keep them
tog.
•Star is born when gravity compresses a cloud to the point at which the center become dense and
hot to generate energy by nuclear fusion; star lives as long as it can generate energy, dies when it
exhausts it usable fuel
•During death stars eject material into space; the large stars die in explosions called supernovae;
the matter mixes w/ floating matter to form new stars; therefore galaxies are cosmic recycling
plants
•Cloud that gave birth to our Solar system made of 98% hydrogen and helium and 2% other
elements- which made Earth
•Elements of Earth like carbon, nitrogen, oxygen, and iron came from nuclear fusion of stars and
nuclear explosions during stars’ death
Cosmic Calendar
•Compresses local history of the Universe into a single Earth year
•Milky Way starts forming in February; shape of today in May; our solar system forms in
September, around the same time as Earth; after planets life on Earth appears; in December- 29th
dinosaurs reach the top of the food chain, 30th they become extinct
•1 second is about 400 years
•Last day, new years eve 11:54 pm- modern humans evolve; last 30 seconds we have all of our
recorded history
How do we measure longer timescales?
•Universe’s oldest objects- must be at least as old as anything that is in it
•We can determine universe’s expansion time- see how long it took for everything to expand
•Determine the expansion of universe by looking at when a star is becoming a supernova it
becomes relatively bright as the galaxy
•Abundances of elements- ratio of one element to another element- hydrogen being converted to
helium; compare starting ratio to how much we have now and how long it would have taken
•Use observations (spectra) and simulations/models- looking at the breakdown of light from
different objects
Document Summary
Chapter 1: a modern view of the universe. Big bang, expansion, and age of universe: big bang: galaxies are moving apart meaning they must have had an expansion point called the. Bb (nearly 14 billion years ago: while the universe continues to expand, galaxies and galaxy clusters don"t b/c gravity keep them tog. Cosmic calendar: compresses local history of the universe into a single earth year, milky way starts forming in february; shape of today in may; our solar system forms in. September, around the same time as earth; after planets life on earth appears; in december- 29th dinosaurs reach the top of the food chain, 30th they become extinct. 1 second is about 400 years: last day, new years eve 11:54 pm- modern humans evolve; last 30 seconds we have all of our recorded history.
