Topic 7 - Astronomy Flashcards
(25 cards)
Describe the steady state theory
The universe has always existed but is expanding and creating matter to counteract the loss in density
Describe the Big Bang theory
The universe expanded from a very small dense point about 14 billion years ago
What is red shift?
A perceived increase in the wavelength of light due to the source moving away from the observer
What does red shift provide evidence for?
Universe is expanding
Supports big bang theory
What does the Big Bang theory suggest?
The entire universe started from a very small hot and dense region in space
Compare the observed red shift of 2 galaxies, one further away than the other
Galaxy further away is travelling faster
Observed red shift is greater the further away it is
What did scientists observe to provide evidence that the universe is expanding at an ever faster rate?
Observed supernovae - suggested galaxies are moving away at ever faster rate
Prior to observations of supernovae, what was believed about the rate of expansion of the universe and why?
Rate of expansion was expected to occur more slowly
Thought that gravitational forces would cause this slowing down
What does CMBR stand for?
Cosmic microwave background radiation
What does CMBR provide further evidence for?
Big Bang theory
Believed that CMBR originates from radiation produced in the big bang
How does the existence of CMBR support the expansion of the universe?
Thought that gamma radiation was released in Big Bang
Expansion of universe has stretched radiation = microwave radiation.
What factor determines the type of lifecycle a star goes through?
The size of the star
Which 2 phases do all stars the same size or bigger than the sun go through?
- Protostar phase
2. Main sequence phase
What do stars like the sun become at the end of their life cycle?
A black dwarf
What 2 things can stars much bigger than the sun become at the end of their lifecycle?
- Neutron star
2. Black hole
What 2 phases do stars of similar size to the sun go through between being a main sequence star and black dwarf?
- Red giant
2. White dwarf
What 2 phases do stars bigger than the sun go through between being a main sequence star and a neutron star/black hole?
- Red supergiant
2. Supernova
Describe the transition of the star from the nebula stage to the main sequence
Nebula increases until pulled in by gravity
GPE turns to KE
Collisions between particles turn KE to thermal
Nebula becomes dense and hot enough for fusion
What occurs in the stage when a star is a main sequence star?
Fusion in star releases energy
Energy balances out w GPE leaving star
Star in equilibrium so won’t collapse due to gravity or expand due to radioactive behaviour. Is stable
What happens when a star transitions to red giant stage?
Once all hydrogen fuel used up, star begins to fuse helium and other large nuclei
Causes star to expand and become a red giant
How does a red dwarf become a white dwarf?
Once all reactions have taken place, stars gravity pulls in all mass = make white dwarf
Why are telescopes located outside the earths atmosphere?
Earths atmosphere absorbs many EM waves, hard to detect certain ones.
Light pollution = less clear.
Can operate night and day.
What’s disadvantage of telescopes located outside atmosphere?
Hard to maintain - have to be repaired in space or brought down = very expensive
Disadvantages of optical telescopes?
Only used at night w clear sky
