Stellar Nucleosynthesis Formation of heavier elements inside stars

How old are your atoms?

Almost as old as the universe

92 Natural Elements The periodic chart contains 92 naturally-occurring elements in the universe Elements 1 (H) to 26 (FE, iron) are synthesized in the core of normal stars like the Sun

Most Abundant Element in the Universe Hydrogen, H, comprises 99% of the visible universe Hydrogen is the lightest element H has one proton

Elements Heavier than 26 The heavier elements are much less abundant than H Elements heavier than 26 are formed in supernova explosions

Supernovae are vast explosions in which a whole star is blown up Supernovae are vast explosions in which a whole star is blown up. They are mostly seen in distant galaxies as `new' stars appearing close to the galaxy of which they are members. They are extremely bright, rivaling, for a few days, the combined light output of all the rest of the stars in the galaxy.

A supernova is one of the most energetic explosive events known to man A supernova is one of the most energetic explosive events known to man. Supernovas occur when a stars nuclear fuel is exhausted and thus no longer being supported by the pressure from the release of nuclear energy.

If the star is really massive, then its middle will collapse and release a lot of energy. Many supernovae have been seen in galaxies close by. They are considered rare occurrences in our own galaxy.

If the star is particularly massive, then its core will collapse and in so doing will release a huge amount of energy. This will cause a blast wave that ejects the star's envelope into interstellar space.

The result of the collapse may be, in some cases, a rapidly rotating neutron star that can be observed many years later as a radio pulsar.

Supernovae emit huge amounts of various types of radiation: X-rays, ultraviolet, infrared, gamma rays, neutrinos, cosmic rays and radio waves.

Type II Supernova Explosions A progenitor star that will explode must have 8 or more solar masses Sun can never go supernova because it has only 1 solar mass and is thus not massive enough

Frequency of Supernovae About once per second in the universe Last one visible to the naked eye was in 1987 in the LMC (Large Magellanic Cloud) No supernova has been seen in our Galaxy since Kepler's (1604).

Force of a Supernova The tremendous force of the explosion when a star goes supernova forces protons together and also neutron capture Protons have a like charge (+)(+) and do not want to be next to one another Once the protons are forced together, the strong nuclear force (SNF) takes over and glues the protons together with gluons.

Balance of Gravity and Nuclear Pressure A star like the sun assumes a natural spherical shape due to the 2 main forces that act upon it. The gravitational force due to the 8 solar masses tries to collapse the star while: The tremendous pressure from the nuclear reaction occurring at the core of the star tries to expand the star

Start of a Supernova Fuel in the core becomes Iron. Iron cannot produce fusion energy Fusion stops (Proton-proton chain) Nuclear pressure fails Gravity wins and star collapses Mass falls into the core crushing the electrons into the protons forming neutrons

Iron Core Collapse It takes about 1 second for the iron core to collapse

Rebound When the mass reaches the center and after it forms the neutron star, the mass rebounds and the supernova explosion ensues A nebula forms around the neutron star Crab nebula from the 1054 supernova A teaspoon of neutron star weighs a billion tons!

If the Star is a Super Massive Star Then a black hole forms instead of the neutron star

Elements in your Body Of the elements in your body, the only one not formed by stellar nucleosynthesis is H

Don’t really want a supernova to occur too close to earth Radiation equivalent to 1 billion suns

Type I Supernova Mass transfer to a white dwarf from a giant primary

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