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 Carbohydrates 1% Minerals 5% Fat 10% Water 64% Proteins 20% Biological composition
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) In the beginning.. Today (temp ~ -270 C)
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. Nuclear fusion powers Burning of Fuel Releases Energy Increases Pressure most active stars!
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 10 30 (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 > 1 billion > 3 billion degrees C + C > Magnesium (Mg) O + O > Silicon (Si) 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 PTF 11Kly SN 1994D 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 1006AD May 1 brightest SN observed visible for ~18months Tycho s SN 1572AD November as bright as Venus visible until 1574 Kepler s SN 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 10 27 (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 Rapidly rotating: even up to 600-700 times per second! Neutron star
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