Astrophysics Flashcards
Define planet:
an object with sufficient mass for its own gravity to make it spherical and clear the orbit of other objects
Define dwarf planet:
orbit not cleared of other objects
What are planetary satellites?
bodies that orbit a planet
What are asteroids?
objects that are too small and uneven to be planets, near circular orbit to sun
What are comets?
small, irregular sized balls of rock, dust, and ice; have an eccentric elliptical orbit around the sun
What are solar systems?
group of stars and orbiting objects
What are galaxies?
collection of stars (around 100 billion), dust and gas
What is the doppler effect?
apparent shift in wavelength occurring when the source of the wavelength is moving
What happens to the wavelengths according to the doppler effect?
wavelength emitted remains the same, wavelength received changes
What is the formation of a small star?
nebula > protostar > main sequence > red giant > white dwarf > black dwarf
What is the formation of a large star?
nebula > protostar > main sequence> super red giant > supernova > (supermassive) black hole/ neutron star
Which pressures are balanced in main sequence?
gravitational and radiation
How heavy is a star for it to be a large star?
greater than 10 mass units
How heavy is a star for it to be a small star?
between 0.5 to 10 mass units
When can electrons bound to an atom exist?
in certain energy levels
What is needed when moving an electron to a higher energy level?
external energy (heat/ absorbing a photon)
What happens when an electron moves to a lower energy level?
releases a photon with specific wavelength
What is the lowest energy level?
ground state
What is the energy of an electron free of an atom?
0J
Why is energy change between levels negative?
it is the energy required to remove the electron from the atom
What is Wein’s law?
the black body radiation curve for different temperatures peaks at a wavelength inversely proportional to the temperature of the object
What does the peak of Wein’s graph represent?
temperature
What does the x axis of Wein’s graph represent?
wavelength
What is Stephan’s Law?
radiant heat energy emitted from a surface is proportional to temperature^4
List light years, parsecs and astronomical units in smallest to largest:
astronomical units, light years, parsecs
What unit is a parallax angle measured in?
arcsec
What are parallax angles used to find?
unknown distances that stars are away
What is the cosmological principle?
the universe is isotropic and homogenous and the laws of physics are universal
What does isotropic mean?
same in all directions
What does homogenous mean?
matter is universally distributed
What is Hubble’s law?
recessional velocity of a galaxy is proportional to it’s distance from the earth
What does Hubble’s law show?
the universe is expanding and distance from galaxies are redshifted (moving away from earth)
What is the big bang theory?
all objects were initially a singularity
What is the evidence for the big bang?
Hubble’s law (universe expanding) and background microwave radiation
What happened in the evolution of the universe?
- Big Bang: time and space created
- 10^-35s: inflation
- 10^-6s: fundemental particles gain mass
- 10^-3s: mass created via pair production (hadrons and leptons)
- 1s: production of mass halted
- 100s: protons and neutrons fuse
- 380,000 years: first atom
- 30 million: stars formed + fusion for heavier elements
- 200 million: galaxies form and gravitational fields pull hydrogen and stars together
- 9 billion: solar system formed
- 10 billion: sun and earth formed
- 11 billion: life on earth
- 13.7 billion: humans
What is dark matter?
hypothetical form of matter that fills space and accelerates expansion and shows there is no centre to the universe
