2. What separates these disciplines?
Scale - http://htwins.net/scale2/ (zoom in to ~1fm, or ~10-15m)
Simplicity - very small objects have very simple structure (particle physics)
Energy - high energies probe smaller/simpler structure small &
simple
energetic per
unit mass
large &
complicated
not so energetic
per unit mass
Trevor Picard ‘16
4. Keep Zooming in: String Theory
https://www.youtube.com/watch?v=kYAdwS5MFjQ
Trevor Picard ‘16
5. What separates these disciplines?
Scale - http://htwins.net/scale2/ (zoom in to ~1fm, or ~10-15m)
Simplicity - very small objects have very simple structure (particle physics)
Energy - high energies probe smaller/simpler structure small &
simple
energetic per
unit mass
large &
complicated
not so energetic
per unit mass
Trevor Picard ‘16
6. High Energy Astrophysics: Simple!
We typically deal with protons, neutrons, electrons, neutrinos, etc.
The most complicated objects (e.g., stars) are still very simple compared to
living organisms.
Trevor Picard ‘16
7. When the Sun Runs out of Fuel...
Nuclear fusion in the core exerts an outward pressure that balances the
inward pull of gravity for most of a star’s life.
When a star runs out of fuel gravity starts to win: star begins collapsing
Trevor Picard ‘16
8. High Energy Astrophysics: Stellar Evolution
Central
Density
Central
Temperature
Degeneracy
Particles are
at relativistic
speeds
Trevor Picard ‘16
9. What is Degeneracy?
State - how electrons are assigned to orbitals (1s2, 2s2, 2p6, etc.)
Fermions (electrons) - particles cannot occupy the same state (Pauli
Exclusion Principle, 2 electron spins)
Trevor Picard ‘16
10. What is Degeneracy? Particle Properties
Temperature - random motions of particles
Density - how squished together the particles are
Keeping the temperature constant, as you squish the particles together
(increase the density) they eventually run out of states to occupy. A
degenerate gas then forms, which exerts an outward degeneracy pressure.
This degeneracy pressure is just like the resistance you feel if you try to shove
2 bullets in the same slot, only you are trying to shove too many electrons into
the same energy state. Something must give.
Trevor Picard ‘16
11. When the Sun Runs out of Fuel...
Electron degeneracy now exerts an outward pressure to again balance the
inward pull of gravity: white dwarf becomes stable.
This happens in the case of low mass stars.
Trevor Picard ‘16
13. High Energy Astrophysics: Stellar Evolution
Central
Density
Central
Temperature
White Dwarfs
Trevor Picard ‘16
14. When Massive Stars Run out of Fuel...
For high mass stars electron degeneracy pressure is not enough. Protons
and electrons smash together to form neutrons!
Neutron degeneracy pressure >> electron degeneracy pressure
Trevor Picard ‘16
15. When Massive Stars Run out of Fuel...
Neutron degeneracy now exerts an outward pressure to again balance the
inward pull of gravity: neutron star becomes stable.
What if neutron degeneracy pressure cannot stop gravity?
Trevor Picard ‘16
17. Scale - http://htwins.net/scale2/ (zoom in to ~1Å, or ~10-10m)
Simplicity - very small objects have very simple structure (particle physics)
Energy - high energies probe smaller/simpler structure
small &
simple
energetic per
unit mass
large &
complicated
not so energetic
per unit mass
Trevor Picard ‘16
24. Excited Molecular States: CO
Energy States: J-state (rotation), v-state (vibration), KE (translation)
Rotational/vibrational states are quantized (quantum mechanics), while
kinetic energy is continuous (it can take on any values).
Spacing between J-states is much smaller than spacing between v-states.
According to QM: ΔJ = ±1 when Δv = +1
Trevor Picard ‘16
30. Scale - http://htwins.net/scale2/ (zoom in to ~10nm, or ~10-8m)
Simplicity - very small objects have very simple structure (particle physics)
Energy - high energies probe smaller/simpler structure
small &
simple
energetic per
unit mass
large &
complicated
not so energetic
per unit mass
Trevor Picard ‘16
