The Discovery of the Neutron
Star
The Neutron
Predicted by Ernest
Rutherford in 1920
Experimentally discovered
by James Chadwick in
1932
The Neutron Star
Fritz Zwicky and Walter Baade
mathematically predicted the
existence of a neutron star in 1934.
Massive Star Life Cycle
The Discovery of the Pulsar
Jocelyn Bell discovers the first
pulsating star (pulsar for short) using a
radio telescope in 1967. The star
pulsed once every 1.3 seconds.
Pulsars and Their Relation to Neutron Stars
Crab Pulsar in the
Crab nebula
By 1968, with the discovery of the
Crab and Vela pulsars in Supernova
Remnants, MOST scientists believed
that pulsars were in fact neutron stars.
How do Neutron Stars Form
What is a pulsar?
A pulsar is a rapidly rotating neutron star
that beam radio waves towards Earth.
This brings up some new questions...
What
is a neutron star?
Why
is it rotating?
Why
is it beaming radio waves?
Life of a Massive Star
Stars spend most of
their lives fusing
hydrogen into helium
•
The star is literally
blowing itself apart
while gravity tries to
crush it
When a star runs out
of hydrogen it tries to
fuse heavier elements
Death of a Massive Star
No energy can be extracted by fusing iron
Without a source of energy, what do you
think will happen to the star?
Watch and see:
http://www.youtube.com/watch?v=p8Hc
DnhkM3I
Supernovae
1. Gravity causes the outer layers to
collapse at super-sonic speeds
2. When outer layers hit the Iron core, they
pile up and “bounce back”
3. Most of the star explodes
A Neutron Star is Born
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The star's core is left
behind and goes
through a wild
transformation
What was once a core
of Iron is now a superdense neutron star
Write and equation to
represent what is happening here.
Electron Capture (inverse Beta decay)
Beta Decay Process
Neutron Star Facts –
Diameter, Mass, Temperature and Rotation
•
•
•
•
•
1.4 times as massive as
our Sun (500,000 Earth
masses – 40% more
massive than our Sun)
About 12 miles across
1 teaspoon would weigh
5.5 billion tons
10 million ºF at birth
Some spin several times
a second or faster
Why do neutron stars spin?
Stellar Remnant – Size Comparisons
The more massive the Progenitor Star
– the smaller the Remnant
Neutron Star: Mass and Diameter
•
1.4 times as massive as our Sun
(500,000 Earth masses – 40% more massive than our Sun)
•
About 12 miles across
Calculate the density of a neutron star
Density = Mass/Volume
Density
• Extremely dense objects
– 100,000,000,000,000,000 kg m-3
– Next thing down from a black hole
Your weight
You can calculate your
weight on Earth and any
other planet or object
using this formula.
G is the universal
gravitational constant
𝐺 = 6.674 × 10−11
Calculate your weight on a neutron star
applet
• http://www.exploratorium.edu/ronh/weight/
Neutron star properties
• Extremely rapid spin
– Rotation rates in excess of 700 Hz
– Speed at surface ~ significant fraction of c
Neutron Star Facts
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•
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Neutron stars can also highly magnetized
Fields thousands – billions times stronger than
the strongest man made magnets
This has an amazing effect
Neutron stars can emit beams of radio waves
Do You See a Pulsar?
•
•
Pulsars are like
interstellar
lighthouses
If the beam points
towards Earth, we
see a pulse of radio
waves
Sounds of Pulsars
What did you notice?
Pulsar Recycling
•
–
•
Some pulsars spin faster than others
When the pulsar period is a few milliseconds,
we call it a millisecond pulsar
MSPs are actually recycled pulsars and
are the most exciting kinds
Pulsar Recycling
•
–
•
Some pulsars spin faster than others
When the pulsar period is a few milliseconds,
we call it a millisecond pulsar
MSPs are actually recycled pulsars and
are the most exciting kinds
Millisecond Pulsars