Just watched a brilliant BBC programme called Seven Ages of Starlight on BBC Four. All about the life of stars. I made notes for my own purposes as I watched it. These are below. Purely for my own purposes. So if it don’t make sense then tough. I didn’t write it as a blog post for anybody else. (this is the problem with putting a blog somewhere public perhaps.)
1 Birth of a star
Pleiades as a star forming region. apparently mentioned by Homer in Odessey
Plasma – soup of unattached particles. Proton and electron of Hydrogen particles in atom become separated. Fusion is where the proton that are repelling occasionally collide. 4 protons make Helium atom.E=mc^2 comes into play. Mass becomes energy. C is big so small mass gives lot of energy.
Copernicus – heliocentric model.
Planets forming – blank out star in Pegasus and you see the white spots of planets forming.
2 Adulthood
Sunspot sketching by projection. Galileo showed that over days they moved and showed rotation of sun.
Solar wind – causes aurora where planets have magnetic field. Runs out of momentum at the outer limit of the solar system – the Heliosphere. Provides protection against galactic radiation and cosmic rays.
Talked of the sun running out of fuel. We didn’t know when it would come. I remember being at infant school and being told that. Only young but genuinely scared. Remember going home at lunchtime being very worried about it. It’s ok. We’re about 1/2 way through. 5 billion years left.
Sun is balanced – fusion balances gravity.
Lifecycle of stars – colour and luminosity. – the Hertzsprung Russell diagram
Main sequence. Central diagonal line.
2 outcrops. Fate of sun is to head off main sequence to red giant.
3 Red Giant
Eg Betelgeuse, Arcturus
Stars fuse H to He. When hydrogen runs out, core collapses, heats up and starts hydrogen fusion to helium in a shell around core. This overcomes gravity. Expands further. Expansion leads to cooling.
Next stage is helium fusion – carbon and oxygen created.
4 White Dwarf
come next.
Sirius in Canis Major has a faint companion, Sirius B, a white dwarf.
Very dense.
Burnt out remains of star where fusion has stopped-fuel run out. Why does it even shine?
Gravity wins over fusion – collapses under it’s own weight. Very small.
Quantum mechanics comes into play – don’t collapse completely – pressure of electrons trying not to be in same place is what keeps it from collapsing. Still shines because of this – cools and fades over time.
Slow and quiet death.
5 Supernova
This is the alternative to Red Giant-White Dwarf for larger stars. Is what happens to large star when it dies. Huge explosion. Leave behind remnants.
Alex Filipenko – supernovae hunter.
Different elements give off different colours. We can tell what a star is by the colour.
Colours of elements in the supernova remnants.
Look at supernova with spectrograph.
Where did elements come from? Fred Hoyle had answer.
Red giants not hot enough to create all elements. Supernovas were.
All about final stage in fight against gravity. Fusion occurs time and time again with heavier and heavier elements forming each time in similar way to the Hydrogen to Helium to Oxygen and Carbon cycles until we get to iron. When ball of iron reaches critical mass size of earth, collapses to size of city, rebounds and goes supernova explosion. That creates even heavier elements and throws them out. This would be where the famous Sagan quote from Cosmos arises “We are made of star stuff” – we are stardust.
And so it starts again. This dust collides under gravity, clouds collapse, stars are born. Next generation.
6. Neutron Stars
Calculations of Zwicky predicted neutron stars. Solidity is an illusion. Lot of empty space in atom.
Zwicky predicted that implosion of iron core squeezes protons and electrons together so closely to form neutrons. Intense Magnetic field generated.
Supernova leaves behind dense kernel.
Dismissed as until radio astronomy when in 1967 picked up strange signal – exact and predictable. – Pulsar.
Then found Crab Pulsar within Crab Nebula in Taurus.
Pulses come from the intense magnetic field. As it spins these are thrown out from n and s poles.
7 Black Holes
Also predicted by taking relativity to it’s logical conclusion.
Event horizon – literally that.
Happens when super massive star goes nova.
Infinite density, zero volume.
Language and imagery of big bang is always misleading – fireball – well not really.
Get’s into the whole , where did the first H atoms come from?
Epilogue – Nebulae
NASA have made one in the Ames lab. Have seen organic molecules in nebulae. This is where life comes from? Ties into podcast I listened to on abiogenesis the other day?
And how did the amino acids get here? They’ve found meteorites containing them.
One of those what if? epilogues you get in documentaries.
Tags: abiogenesis, Arcturus, BBC, betelgeuse, black hole, cab nebula, fusion, gravity, heliosphere, Hertzsprung-Russell, homer, Hoyle, nebulae, neutron star, plasma, Pleiades, pulsar, radio astronomy, red giant, sagan, supernova, white dwarf, Zwickau