The Cosmic Crucible

THE COSMIC
CRUCIBLE
ELENA VAN ALEBEEK ALONSO AND MAUREEN LORHO
WHO IS THE COSMIC CRUCIBLE?
THE SUN: It acts similarly to a crucible in a way

that it fuses elements together under high
temperatures.
2
Gravitational equilibrium regulates the Sun’s core temperature.
Everything is in balance if the amount of energy leaving the core
THE SOLAR equals the amount of energy produced by fusion.
THERMOSTAT A rise in core temperature triggers a chain of events that causes the
core to expand, lowering its temperature to its normal value. A
decrease in core temperature triggers the opposite chain of events,
also restoring the normal core temperature.
3
NUCLEAR FUSION
The high temperatures and pressures within the sun allow the
hydrogen atoms to come together and therefore overcome the
electromagnetic force that would initially cause them to repel.
Most of the time the pair break apart and go their own way because
two protons cant stick together without a neutron.
2nd Scenario: Weak nuclear force causes some of the hydrogen atoms
within the sun to go through beta decay, turning them into neutrons.
Strong nuclear force follows once the two molecules make contact to
keep them together forming helium molecules:
THE PROTON-PROTON CHAIN
6
THE SOLAR INTERIOR
How can we know if we can’t see it?
1. Mathematical Models
2. Sun Quakes
3. Solar Neutrinos
7
→ Primary way we learn about the inside of the
sun
→ Use the laws of physics to predict the internal

conditions
→ Basic model = gravitational equilibrium, the

solar thermostat, the speed of solar energy
MATHEMATICAL → Computer = sun’s temperature, pressure, and
MODELS density
→ Rate of nuclear fusion (using labs on Earth)
→ Correctly “predict” the radius, surface

temperature, luminosity, age, and many other
properties of the Sun
→ Not everything
→ Scientist working to discover what’s missing
8
→ Secondary way we learn about the inside of the sun
→ Earth’s crust suddenly shifts releasing seismic waves
→ Recording seismic waves on Earth’s surface with

seismographs
→ Waves of pressure (sound waves) propagate deep

within the Sun at all times
SUN → Solar surface to vibrate when they reach it
QUAKES → Detect the vibrations of the surface by measuring

Doppler shifts
→ Rising toward us is blueshifted
→ Falling away from us is redshifted
→ Deduce and analyse these vibrations
→ Helioseismology — helios means “sun”
→ Prove our mathematical models and helps us develop

them further 9
→ Tertiary way we learn about the inside of the sun
→ Observe the neutrinos coming from fusion reactions in the core
→ As you read this sentence about a thousand trillion solar

neutrinos will zip through your body
→ Neutrinos created by fusion in the solar core fly quickly through

the Sun as if passing through empty space
→ Neutrinos do occasionally interact with matter, and it is possible

SOLAR to capture a few solar neutrinos with a large enough detector
NEUTRINOS → Neutrino detectors are usually placed deep inside mines
→ Homestake gold mine in South Dakota
→ Consisted of a 400,000-liter vat of chlorine-containing

dry-cleaning fluid
→ One neutrino captured per day
→ Proves nuclear fusion
→ Two decades later, one every three days
→ Disagreement between model predictions and actual

observations is called the solar neutrino problem 11
→ Captured only high-energy neutrinos that are produced in step 3
→ Recent experiments detect lower-energy neutrinos from step 1
→ all experiments have found fewer neutrinos than predicted by

current models
→ Either something wrong with the models
→ Or something is missing in our understanding of neutrinos
SOLAR → Neutrinos come in three types: electron neutrinos, muon

neutrinos, and tau neutrinos
NEUTRINOS → Fusion reactions in the Sun produce only electron neutrinos, and
most solar neutrino detectors can detect only electron neutrinos
→ Recent experiments show that some of the electron neutrinos

might change into muon and tau neutrinos as they fly out through
the solar plasma
→ Take at least a few more years before confirmed
→ Nobel Prize for Physics - shared by Masatshi Koshiba, leader of

Super-Komiokande, and Raymond Davis, leader of the Homestake
experiment
12
THANKS!
Any questions?
13

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THE COSMIC

THE SUN: It acts similarly to a crucible in a way

→ Use the laws of physics to predict the internal

→ Basic model = gravitational equilibrium, the

→ Rate of nuclear fusion (using labs on Earth)

→ Correctly “predict” the radius, surface

→ Scientist working to discover what’s missing

→ Earth’s crust suddenly shifts releasing seismic waves

→ Recording seismic waves on Earth’s surface with

→ Waves of pressure (sound waves) propagate deep

SUN → Solar surface to vibrate when they reach it

QUAKES → Detect the vibrations of the surface by measuring

→ Rising toward us is blueshifted

→ Falling away from us is redshifted

→ Deduce and analyse these vibrations

→ Helioseismology — helios means “sun”

→ Prove our mathematical models and helps us develop

→ Observe the neutrinos coming from fusion reactions in the core

→ As you read this sentence about a thousand trillion solar

→ Neutrinos created by fusion in the solar core ﬂy quickly through

→ Neutrinos do occasionally interact with matter, and it is possible

NEUTRINOS → Neutrino detectors are usually placed deep inside mines

→ Homestake gold mine in South Dakota

→ Consisted of a 400,000-liter vat of chlorine-containing

→ One neutrino captured per day

→ Proves nuclear fusion

→ Two decades later, one every three days

→ Disagreement between model predictions and actual

→ Recent experiments detect lower-energy neutrinos from step 1

→ all experiments have found fewer neutrinos than predicted by

→ Either something wrong with the models

→ Or something is missing in our understanding of neutrinos

SOLAR → Neutrinos come in three types: electron neutrinos, muon

→ Recent experiments show that some of the electron neutrinos

→ Take at least a few more years before conﬁrmed

→ Nobel Prize for Physics - shared by Masatshi Koshiba, leader of

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