Extragalactic Astronomy

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Extragalactic Astronomy Cosmology Review
of Building Blocks of the Universe
4097 Physics 316

• Jane Turner
• Joint Center for Astrophysics
• UMBC NASA/GSFC
• 2003 Spring

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The Quantum Revolution

In 1905 particle/wave duality of light
known Rutherford had discovered the nature of the
atom Bohr discovered electron orbits are
quantized The realm of very small scales is
called the quantum realm and the science of that
is quantum mechanics
From there ideas about atoms and subatomic
particles took off in a quantum revolution
Protons and neutrons found not to be truly
fundamental Building blocks of matter are quarks
leptons
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Fundamental Particles

Quarks leptons belong to category called
fermions Photons belong to category called
bosons
Antimatter is real - when particle antiparticle
meet they annihilate and produce energy Four
forces govern all interactions
Gravity Electromagnetism Strong nuclear
force Weak nuclear force
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Fundamental Forces

These four are manifestations of a smaller number
of forces -perhaps a single force rules all of
nature Quantum laws show us that all tiny
particles exhibit the wave-particle duality known
for light Quantum Laws important for
astronomy Degeneracy Pressure prevents a star
from collapsing Quantum tunneling makes nuclear
fusion possible Virtual particles affect the fate
of black holes
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Particles

By early 1960s hundreds of different particles
were discovered (e.g. from particle accelerators
where electrons and photons accelerated using
magnets - collisions produce great energy , some
turns to mass ) Murray Gell-Mann suggested these
could all be combinations of just a few
fundamental components with different mass,
charge, spin
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Quarks Leptons
Particles are classed as fermions or bosons
depending on spin Fermions are sometimes made of
quarks - protons neutrons sometimes not -
electrons

In general particles can be made of 2 or 3 quarks
quarks can be up, down, strange, charmed, top,
bottom leptons can be electron, electron
neutrino, muon, mu neutrino, tauon, tau
neutrino 12 of each type when we consider the
antimatter counterparts
Electrons are fundamental Protons neutrons
made of quarks Up quark - charge 2/3 down
quark - charge -1/3 (relative to -1 of
electrons) proton2 up plus 1 down 1 neutron
1 up plus 2 down 0
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BARYONIC MATTER
Protons neutrons belong to a category of
particles called baryons, so ordinary matter is
sometimes called baryonic matter (Technically,
a baryon is a particle made from three
quarks) By extension, extraordinary matter is
called non-baryonic matter
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Anti-matter

Quarks electrons have antiquarks
positrons -opposite charges, annihilation when a
pair meet
Universe predominantly matter, -so antimatter
does not last long before annihilation!
Reverse process occurs- pair production, high
energy photons meet and produce e- e pair
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Forces
Forces are the way particles communicate and
exchange momentum etc Electromagnetism groups
electrons,protons into atoms, atoms into
molecules, molecules into cells - EXCHANGE
PARTICLEPHOTON Gravity holds people on planets,
planets in orbits, stars in galaxies EXCHANGE
PARTICLEGRAVITON Strong weak nuclear forces
only effective over short distances -within
atoms while EM force pushes protons within
nuclei apart, strong nuclear force opposes this
holds nuclei together EXCHANGE
PARTICLEGLUON weak nuclear force similar,
acting on neutrinos EXCHANGE PARTICLEWEAK BOSON

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Summary

• Relative Strength
• Within Nuc /Beyond
• / 0
• 1 / 1
• 10-5 / 0
• 10-43 / 10-43

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Unification ?

EM and weak nuclear forces are different aspects
of the electroweak force Further Unification
possible?