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PUBLIC LECTURE - SEDS Celestia
Neutron Stars -Extraordinary
Cosmic Laboratories Dr. Vanessa Graber
Institute of Space Sciences (IEC), Spain
JULY 5TH, 3:30pm (CEST)
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LABORATORIES
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THE UNIVERSE AS A LABORATORY
Image credit: NASAImage credit: NASA
Combine observations, mathematical calcula-
tions and computer simulations to learn about the Universe.
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Neutron stars unite many extremes of physics that cannot be recreated
on Earth.
WHAT are these extremes?
HOW do we know these
extremes exist?
WHAT is going on in theirinteriors?
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Neutron stars unite many extremes of physics that cannot be recreated
on Earth.
WHAT are these extremes?
HOW do we know these
extremes exist?
WHAT is going on in theirinteriors?
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NEUTRON STAR EXTREMES
Image credit: NASA, ESA, J. Hester, A. Loll (ASU)
Neutron stars are born in supernova explosions.
Image credit: NASA, JPL-Caltech, STScI, CXC, SAO
Crab Nebula, 1054 Cassiopeia A, ~1670
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Image credit: Google, ESO, L. Calçada
Neutron stars have a mass comparable to the Sun but the
size of a city.
Image credit: NASA, SDO
NEUTRON STAR EXTREMES
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Image credit: Arthimedes/Shutterstock.com
Neutron stars mainly consist of neutrons and are
the densest object we know of.
Densities up to 1015 g/cm3 =
1,000,000,000,000,000 g/cm3
NEUTRON STAR EXTREMES
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Neutron stars are very fast and stable rotators.
They can rotate up to ~700 times per second.
NEUTRON STAR EXTREMES
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Neutron stars are the strongest
magnets in the Universe.
Image credit: ESO, L. Calçada
Magnetic axis
Field strengths of~1012 Gauss =
2,000,000,000,000x Earth’s
magnetic field
NEUTRON STAR EXTREMES
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Neutron stars unite many extremes of physics that cannot be recreated
on Earth.
WHAT are these extremes?
HOW do we know these
extremes exist?
WHAT is going on in theirinteriors?
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OBSERVING NEUTRON STARS
Neutron stars emit light in different parts of the electromagnetic spectrum.
Image credit: NASA
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OBSERVING NEUTRON STARS
They were first observed in the radio band in 1967 by Jocelyn Bell Burnell.
Neutron stars emit radiation like a lighthouse - they pulse.
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OBSERVING NEUTRON STARS
The first source had a period of ~1.3 seconds and was nicknamed LGM-1, which stands
for ‘Little Green Man’.
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OBSERVING NEUTRON STARS
Image credit: J. Christiansen
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OBSERVING NEUTRON STARS
~2,700 neutron stars have been observed as radio pulsars.
We time pulsars to measure
the period and its derivative.
Obtain age and magnetic field
strength estimate.
Image credit: Arecibo Obs., NSF
Period
Per
iod
der
ivat
ive
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OBSERVING NEUTRON STARS
If the pulsar is in a binary, the arrivaltime of the pulses is altered as thetwo stars orbit around each other.
High precision measurements
allow us to extract the neutron star mass.
Image credit: B. Saxton, NRAO, AUI, NSF
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OBSERVING NEUTRON STARS
Neutron stars emit light in different parts of the electromagnetic spectrum.
Image credit: NASA
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OBSERVING NEUTRON STARS
Using X-ray observatories, we can learn about their temperatures and radii.
Image credit: NASA
Image credit: D. Bice
Wave length
En
erg
y em
itte
d
Temperatureincreases
With temperatures of ~107 °C = 10,000,000 °C, they emit thermal black-body radiation in the X-rays.
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Neutron stars unite many extremes of physics that cannot be recreated
on Earth.
WHAT are these extremes?
HOW do we know these
extremes exist?
WHAT is going on in theirinteriors?
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EQUATION OF STATE
Neutron star conditions are so extreme that the equation of state of matter is unknown.
Image credit: N. Wex
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EQUATION OF STATE
Neutron star conditions are so extreme that the equation of state of matter is unknown.
How squishy are neutron stars?
Image credit: N. Wex
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NEUTRON STAR STRUCTURE
Atmosphere
Like the Earth, neutron stars are composed of distinct layers.
Image credit: NASA GSFC, Conceptual Image Lab
Outer crust
Inner crust
Outer core
Inner core
(hydrogen, helium, carbon)
(ions, electrons)
(neutrons, ions, electrons)
(neutrons, protons, electrons)
(?????)
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NEUTRON STAR STRUCTURE
Like the Earth, neutron stars are composed of distinct layers.
Image credit: NASA GSFC, Conceptual Image Lab
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FERMIONIC PARTICLES
Neutrons, protons and electrons are fermions - elementary particles with spin 1/2.
Fermions have to obey the Pauli
exclusion principle.
fermions bosons bosons
spin 1/2, 3/2, 5/2, ... spin 0 spin 1, 2, 3, ...
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FERMIONIC PARTICLES
Neutrons, protons and electrons are fermions - elementary particles with spin 1/2.
Fermions have to obey the Pauli
exclusion principle.
fermions bosons bosons
spin 1/2, 3/2, 5/2, ... spin 0 spin 1, 2, 3, ...
Neutrons resist compression, which
prevents neutron stars from collapsing.
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PHASE TRANSITIONS
Neutron stars are cold enough to containnew quantum phases of matter.
Neutrons (protons) can form pairs and undergo phase transitions into
superfluid (superconducting) states.
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SUPERFLUIDITY/SUPERCONDUCTIVITY
Superfluid are fluids that flow without viscosity.
Superconductors have zero electrical resistivity and try
to expel their magnetic field.
Their existence is a direct resultof quantum mechanics.
Neutron stars are the largest superfluids and superconductors
in the Universe.
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SUPERFLUID VORTICES
Superfluids cannot rotate like classical fluids.
They have to form vortices, which can be envisaged as tiny,
rapidly rotating tornadoes. Image credit: NOAA Photo Library
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SUPERFLUID VORTICES
Each vortex carries a unit of circulation,adding up to mimic classical rotation.
Image credit: Peter Engels, JILA
Neutron star interiors contain ~105 = 100,000 vortices per square centimetre.
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SUPERFLUID VORTICES
Each vortex carries a unit of circulation,adding up to mimic classical rotation.
Neutron star interiors contain ~105 = 100,000 vortices per square centimetre.
The more vortices are present,
the faster the superfluid rotates.
Image credit: Peter Engels, JILA
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PULSAR GLITCHES
Sudden glitches interrupt the regular spin-down of pulsars.
Over a long time, the neutron star loses energy and will rotate slower and slower.
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PULSAR GLITCHES
Sudden glitches interrupt the regular spin-down of pulsars.
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PULSAR GLITCHES
To illustrate the concept: what happens when a rotating cooked / raw egg is stopped?
Transfer of angular momentum!
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PULSAR GLITCHES
Sudden spin-ups (glitches) interrupt the regular spin-down of pulsars.
Glitches are a manifestation of quantum mechanics.
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PULSAR GLITCHES
Sudden spin-ups (glitches) interrupt the regular spin-down of pulsars.
Glitches are a manifestation of quantum mechanics.
Studying glitches is one way to learn
about the properties of matter.
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Because neutron stars unite many extremes of physics that cannotbe recreated on Earth, they are ...
GREAT COSMIC LABORATORIES!!
THANKS FOR LISTENING.