Download Introduction to pulsars - Pulsar Search Collaboratory

Introduction to exploding
stars and pulsars
Harsha Blumer
Department of Physics & Astronomy
West Virginia University
Winnipeg, Canada
About me
WV, USA
Kerala, India
Carl Sagan (1934-1996)
Neil deGrasse Tyson
What are we made of?
Composition of human body
•
18%
Carbon
•
10%
Hydrogen
•
3%
Nitrogen
•
1.4%
Calcium
•
65% Oxygen
Carbohydrates 1%
Minerals 5%
Fat 10%
Proteins 20%
Biological composition
Water 64%
Chemical composition
About 99% of human body made
of six major elements: Oxygen,
Carbon, Hydrogen, Nitrogen,
Calcium, and Phosphorus
Remaining 1%: Potassium,
sulphur, sodium, chlorine,
and Magnesium, and some
trace elements (eg.,
Chromium, Copper, fluorine,
iodine, zinc etc.)
The Planet Earth
What about Sun?
Where did these elements come from?
Big Bang
(temp > trillions of degree F)
Today (temp ~ -270 C)
In the beginning..
In the beginning
Once the universe was created by the Big Bang,
the only abundant elements present were
hydrogen (H) and helium (He).
But we know that elements heavier than
Hydrogen or Helium exists. How did all
other elements come into existence?
All elements heavier than Hydrogen and Helium
came from the stars and supernova explosions.
Life cycle of a star
Stars are born out of gas and dust, live their lives, and die! Just
like us, they also go through different stages in their lives.
Final fate of a star depends on how big the star was to start with.
The story of STAR WARS!
Two forces work inside a star:
Pressure and Gravity.
Gravity balances inward
pressure Star in hydrostatic
equilibrium.
Burning
Nuclear fusion powers
most active stars!
of Fuel
Releases
Increases
Energy
Pressure
Life cycle of a star
Low mass stars - Stars with
mass less than that of Sun
High mass stars - Stars with
mass much greater than that of
Sun
SUN
Mass of Sun = 2 x 1030 (2,000,000,000,000,000,000,000,000,000,000) kg (solar mass)
How elements form inside the star?
High temperature
Fusion
> 10 million degrees
H + H + H + H —> Helium (He)
> 100 million
He + He + He —> Carbon (C)
He + C —> Oxygen (O)
Low mass
stars
White Dwarf (ends
with C+O core)
What happens to our Sun?
What about very massive stars?
High temperature
Fusion
> 10 million degrees
H + H + H + H —> Helium (He)
> 100 million
He + He + He —> Carbon (C)
He + C —> Oxygen (O)
He + O —> Neon (Ne)
> 500 million
C + C —> Magnesium (Mg)
> 1 billion
O + O —> Silicon (Si)
> 3 billion degrees
Si + Si —> Iron (Fe), Cobalt (Co), Nickel (Ni)
Iron (Fe) is special!!
It takes more energy to burn
Fe than it actually gives off.
So, FUSION STOPS.
Gravity pulls matter in
BOOM!!
SUPERNOVA
EXPLOSION
Elements formed inside the star spread all over!
Supernova explosions: death of massive stars
Nature’s spectacular fireworks
Host galaxy before the supernova exploded
A supernova explosion releases so much energy that can outshine the
entire galaxy. The initial power released in one second is enough to
power our entire planet for trillions of years!!
Credit: B.J. Fulton/SDSS/FTN
Pinwheel Galaxy
NGC 4526
SN 1994D
SN PTF 11Kly
Examples of
Supernova explosions
in the galaxies.
http://www.skyandtelescope.com
Naked eye observations of Supernova
-
Observed on 1054AD Jul 4
Crab Nebula (SN 1054)
Chinese records
Visible for 23 days & 653 nights
Historical Supernovae
SN 1006
Tycho’s SN
Kepler’s SN
• 1006AD May 1
• brightest SN observed
• visible for ~18months
• 1572AD November
• as bright as Venus
• visible until 1574
• 1604AD October 9
• visible in day time
for 3 weeks
A glimpse of elements inside a remnant
G292.0+1.8
Oxygen
Neon
Magnesium
Silicon +
Sulphur
Age ~ 1500 yrs
Image: Chandra X-ray observatory
What about elements Beyond Iron (Fe)
The energy is so huge that
elements higher than iron are
made in the debris.
Even Gold & Silver
came from space!
Without supernovae to
disperse elements made in
stars, no planets, no life!!
What happens during a supernova explosion?
Debris of supernova explosion - Supernova remnants
Credit: Chandra X-ray observatory
Why study Supernova
They are cool - most powerful explosions in the universe,
equivalent to 1027 (10,000,000,000,000,000,000,000,000,000)
nuclear bombs!!
Producing all elements heavier than Iron, e.g. Gold, Silver, ..
Recycle materials into space to give rise to new stellar births.
Some supernova leave behind exotic stars - neutron stars or
the pulsars!
A glimpse of the exotic objects in the highenergy universe - the leftovers of violent
supernova explosions.
A neutron star
Supernova remnant RCW 103
Image: Chandra X-ray observatory
Neutron stars: exotic stars of the universe
Neutron stars are
believed to be formed
in supernova explosions.
I’m positive
I’m negative
I don’t care
Neutron stars: why are they exotic?
Very compact: Radius of ~ 10 km, compact enough to fit
inside the borders of Washington DC! Small mass ~ 1.4 times that of Sun.
Washington DC Vs Neutron star
Neutron star
Rapidly rotating:
even up to
600-700 times per
second!
Neutron stars: why are they exotic?
Very dense: A teaspoonful of neutron star material would weigh
~10 million tons or the weight of 20 million elephants!
Room for more!??
Or imagine squeezing all the
people on earth into a small
raindrop!!
Extremely high gravitational fields: ~ 200 billion times that of the
Earth!!
Extremely high magnetic fields: ~ 100 trillion times stronger than
that of the Earth!!
There are different types of neutron stars
showing multiple personality disorders!
Pulsars - Pulsating Source of Radio
- Rotating neutron stars emitting beams of
radiation along the earth’s line of sight.
Crab pulsar
Image credits: NASA/CXC/ASU/J. Hester et al. (X-ray); NASA/HST/ASU/J. Hester et al. (optical).
http://relativity.livingreviews.org/open?pubNo=lrr-2005-7&page=articlesu1.html
Discovery of Pulsars
Jocelyn Bell (1943): A PhD student
of Antony Hewish in Cambridge.
Radio telescope to detect quasars
Periodic signal @ 1.3373011 sec
(1967)
Little green men!
Nobel Prize (1974)
Antony Hewish
Examples of different pulsars
We are born in the heart of exploding
stars! So is a pulsar.
We are all connected!
Image credits: CXC