Lecture Ten - Review lecture Flashcards
Describe the timeline of the growth of the universe.
Inflation occured at the very beginning of the universe.
First atoms at 3 minutes and 45 seconds.
Present day, dark energy accelerating expansion.
What is the universe made of?
70% dark energy.
26% dark matter.
4% everything else (stars, planets, us).
What is the age of the universe?
Best estimate from March 2013:
67.15 +/- 1.2 km/s/mPc
Age of the universe = 13.82 billion years.
How will the universe end?
Big Rip:
If dark energy increases, acceleration increases so quickly that everything will eventually be town apart (including atoms). This is known as the Big Rip.
Big Crunch:
If dark energy decreases, acceleration decreases and everything collapses back into one spot in space and time. This is known as the Big Crunch.
Constant dark energy:
If dark energy remains constant, it will keep accelerating and expanding forever.
How are stars formed?
Formation:
Shockwave from supernova (dying star) passes thorugh a nebula (creates clumps).
Gravity pulls on particles in the nebula.
Gas and dust accumulate.
Accumulating matter spins as it becomes more dense.
If it passes critival mass, fusion begins.
Birth:
Solar winds blows away the unnacumulated gas and dust, revealing a solar system.
Rates of star formation was higher when the universe was younger.
Out sun is at least a second generation star, as Earth has Fe and other elements which could only exist due to the supernova of a very very large star.
What are the equations for nuclear fusion?
This produces energy, neutrinos and photons (light).
Enough hydrogen in the sun to power it for 10 billion years, already 4.6 billion years old.
What is the origin of the elements?
At the Big Bang, H and some He and some Li formed early.
H transformed into He inside stars by nuclear fusion reactions, triggered by gravitational squashing within stars - lasts about 7 billion years.
heat given off fuels more H –> He reactions.
In stars 8* ours:
He forms C after H is burned.
C forms O, Mg and Ne.
O forms Si, S and Mg.
In massive stars, Si forms Fe.
Fe forms heavier elements.
Other elements up to Fe are formed, but are unstable.
What happens during the death of a large star?
Go to Nova or Super Nova.
Collapse into a Neuron Star - pulsars (radio emitters).
Or form black holes - X ray emmiters (gravitational lenses).
What are the things that must be expained in a Theory of Solar System formation?
All planets orbit approximatly in the same plane (ecliptic plane) which is the same plne as the suns rotational equator.
Planets all orbit the sun int he same direction as the suns rotation.
Planetary orbits are nearly circular.
Planets contain most of the angular momentum in the solar system.
The sun contains most of the mass of the solar system (99.8%).
Distance of a planet from the sun follows a simple mathematical rule.
Planets differ in composition as you move out form the sun in a consistent manner - moons of gas giants do the same.
Difference in density between inner (rocky) planets and outer (gas giant) planets.
What are the solar system theories?
1) Vortex theory
Solar system form in vortecies in space.
2) Leplace’s Nebular hypothesis
Formed from nebula that threw off gas rings.
3) Protoplanet theory
Sun captures planets forming from nebula.
4) Encounter hypothesis
Filament dragged out of star and captured by the sun.
5) Nebula (condensation) theory
Condenses out of disk shaped nebula.
6) Modern Laplacian Theory
Planets condense out of gas rings cause by supersonic turbulence in the Sun.
What are the ways to find an exoplanet?
Doppler shift: Light spectrum shift as star moves towards or away from us.
Astrometric movement: Movement of star against background stars.
Gravitational microlensing: Brightening or dimming of background star.
Transit method: Dimming of light from star as planet crosses its face.
Direct detection: Actual images of exoplanets.
How many exoplanets might be habitable by humans?
15-20% of stars int he mily way are sunlike and have Earth sized planets in habitable zones.
There are 8 billion potentially habitable planets in out galexy.
there are between 10 billion and 50 billion galexies in the universe.
So thats between 8 * 10^22 and 4 * 10^23 potentially habitable planets in the universe.
Compare the characteristics of the Terrestrial planets.
What are the characteristics of asteroids?
Most asteroids are found in the asteroid belt between Mars and Jupiter = Main belt asteroids = over one million found so far.
Some have orbits that bring them close to Earth = Near Earth Asteroids or Near Earth Objects (NEOs) = oer 10,000.
Leftovers from a planet that never quite formed.
Different compositions and types and sizes.
Largest is planet like, as it is rounded = Dwarf planet Ceres.
Others somtimes called minor planets.
Widely spaced - on average one asteroid every 3,000km^2.
Compare the characteristics of the Gas Giants.
What is the IAU definition of a planet?
