Download Cosmology

Cosmology
Suggested time: 4 weeks
Outline:
1. Astronomical distances
2. The structure of the Universe
3. Stellar Evolution
4. Supernovae, neutron stars and black holes
5. Comets, meteorites and Binary star systems
6. The Big Bang
7. The Evolution and Fate of the Universe
8. Cosmology test
Book resources:
OCR Physics A2 – Hackett & Hutchings
OCR Cosmology – Cambridge Advanced Sciences
University of Bath Science – Astrophysics – Ingham
Astronomical Distances
Define the light year as the distance that light travels in one year (9.46 x 1015
metres)
Explain that professionals don’t tend to use the light year but instead the
parsec.
Define the arcminute and arcsecond.
Define the parsec carefully. 1 pc = 3.086 x 1016 metres
Define the astronomical unit as the mean distance from the Earth to the Sun.
1 AU = 1.496 x 1015 metres.
The structure of the Universe
Give a brief outline of the Solar System. Explain the 8 planets and briefly
cover the demotion of Pluto.
Discuss the asteroid belt and the fact that Jupiter’s influence prevents a planet
from forming there.
Oort cloud and Kuiper belt.
Discuss and show Earth’s proposed position in the spiral arm of our galaxy
and that the milky way seen from Earth is due to us looking directly at the
galactic centre.
Discuss different types of galaxies. Show images.
Images from the Hubble deep field to show multiple galaxies.
Discuss Olber’s paradox and that although large, the universe cannot be
infinite.
Problem sheet for homework.
Stellar Evolution
State the mean solar power received at the Earth’s upper atmosphere as
1400 Wm-2 across all wavelengths. Show that the radiated power of the Sun
is therefore 4 x 1026 W.
Discuss the source of the power as nuclear fusion and that the Sun is
converting hydrogen to helium.
State that 4x1026/c2 kgs-1 of mass is converted to energy and that when we
cover fusion in detail this will be clear.
Outline the formation of a Sun-like star from its birth in a GMC to red giant.
Describe and discuss the fate of Sun-like stars as a red giant -> planetary
nebulae  white dwarf.
Discuss in reasonable the Hertzsprung-Russell diagram and its significance.
Supernovae, neutron stars and black holes
Describe the fate of large stars to red-super giant, supernova and black holes
or neutron stars.
Describe the Schwarzschild radius and event horizon of a black hole.
Problem sheet for homework.
Comets, Meteorites and Binary stars
Describe and explain the term comet.
Give the structure of a comet and the nature of its orbit.
Describe and explain asteroids and meteorites and that these usually
vaporize on entering the Earth’s atmosphere.
Binary stars- most stars are part of a binary system and rotate around their
common centre of mass.
The Big Bang
Discuss cosmic background radiation and its discovery. Talk about the
significance of how a small, dense, hot early universe may have expanded,
lowered its density and temperature.
Discuss redshift and the Doppler effect
Show and discuss Hubble’s data from 1929. Discuss how the age of the
universe is obtained from it and how Hubble got a value of 2 billion year.
Refined data has now led to an age of c.13.8 billion years.
Give a ‘timeline’ evolution of the universe. Ask students to present this as a
timeline. Page 24 of the OCR a2 Physics text is useful for this.
The Fate of the Universe
Discuss the critical density of the universe and compare this with the
estimated mean density of the universe. Neither of these are known to any
great precision.
Discuss the three fates of the universe based on the critical density – open,
flat and closed.
Discuss dark matter and how its importance relates to the fate of the universe.
The search for finding the ‘missing matter’ is one of the key goals for
cosmology.