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• Cosmic ray spallation is a form of naturally occurring nuclear fission and nucleosynthesis. It refers to the formation of chemical elements from impact of cosmic rays on an object.
• Fusion - combining of nuclei to form a bigger and heavier nucleus.
• Stellar nucleosynthesis is the process involving nuclear reactions through which fresh atomic nuclei are synthesized from pre-existing nuclei or nucleons. 
• STELLAR EVOLUTION- the process by which a star changes over the course of time
• Stars come in a variety of masses and the mass determines how radiantly the star will shine and how it dies. All stars, irrespective of their size, follow the same 7 stage cycle, they start as a gas cloud and end as a star remnant.
• Massive stars transform into supernovae, neutron stars and black holes while average stars like the sun, end life as a white dwarf surrounded by a disappearing planetary nebula.
• THE ORION GAS COMPLEX

  That glow is a giant molecular cloud, the Orion Nebulae, a member of the largest objects in the galaxy, and the birthplace of stars. If you have a telescope, the small group of stars in the middle of the nebulae are stars emerging from the cloud as the star cluster
• Seven Main Stages of a Star

  1. Giant Gas Cloud
  2. Protostar
  3. T-Tauri Phase
  4. Main Sequence
  5. Red Giant
  6. The Fusion of Heavier Elements
  7. Supernovae and Planetary Nebulae
• Giant Gas Cloud

  • A star originates from a large cloud of gas. The temperature in the cloud is low enough for the synthesis of molecules. The Orion cloud complex in the Orion system is an example of a star in this stage of life.
• Protostar

  When the gas particles in the molecular cloud run into each other, heat energy is produced. This results in the formation of a warm clump of molecules referred to as the Protostar. The creation of Protostars can be seen through infrared vision as the Protostars are warmer than other materials in the molecular cloud. Several Protostars can be formed in one cloud, depending on the size of the molecular cloud.
• A protostar looks like a star but its core is not yet hot enough for fusion to take place. The luminosity comes exclusively from the heating of the protostar as it contracts. Protostars are usually surrounded by dust, which blocks the light that they emit, so they are difficult to observe in the visible spectrum.
• 3. T-Tauri Phase

  • begins when materials stop falling into the Protostar and release tremendous amounts of energy. The mean temperature of the Tauri star isn’t enough to support nuclear fusion at its core. The TTauri star lasts for about 100 million years, following which it enters the most extended phase of development – the Main sequence phase.
• 4. Main Sequence

  • The main sequence phase is the stage in development where the core temperature reaches the point for the fusion to commence. In this process, the protons of hydrogen are converted into atoms of helium. This reaction is exothermic; it gives off more heat than it requires and so the core of a mainsequence star releases a tremendous amount of energy.
• 5. Red Giant

  • A star converts hydrogen atoms into helium over its course of life at its core. Eventually, the hydrogen fuel runs out, and the internal reaction stops. Without the reactions occurring at the core, a star contracts inward through gravity causing it to expand. As it expands, the star first becomes a subgiant star and then a red giant. Red giants have cooler surfaces than the main-sequence star, and because of this, they appear red than yellow.
• Once a star becomes a red giant, it might stay that way for up to a billion years. Then the star will slowly contract and cool to become a white dwarf. The opposite of red giants, white dwarfs are Earth-sized, ultra-dense corpses of stars radiating a tiny fraction of their original energy.
• • A red giant forms after a star has run out of hydrogen fuel for nuclear fusion, and has begun the process of dying. A star maintains its stability through a fine balance between its own gravity, which holds it together, and the outwards pressure from ongoing thermonuclear fusion processes taking place at its core.
• 6. The Fusion of Heavier Elements

  • Helium molecules fuse at the core, as the star expands. The energy of this reaction prevents the core from collapsing. The core shrinks and begins fusing carbon, once the helium fusion ends. This process repeats until iron appears at the core. The iron fusion reaction absorbs energy, which causes the core to collapse. This implosion transforms massive stars into a supernova while smaller stars like the sun contract into white dwarfs.
• 7. Supernovae and Planetary Nebulae

  • Most of the star material is blasted away into space, but the core implodes into a neutron star or a singularity known as the black hole. Less massive stars don’t explode, their cores contract instead into a tiny, hot star known as the white dwarf while the outer material drifts away. Stars tinier than the sun, don’t have enough mass to burn with anything but a red glow during their main sequence. These red dwarves are difficult to spot. But, these may be the most common stars that can burn for trillions of years.
• Heavy elements are produced by nucleosysthesis - the fusion of nuclei deep within the cores of stars. At some point in time, the first stars were formed, and within their cores the fusion process created heavier and heavier elements; the most massive stars produced nuclei as heavy as iron.
• Life Cycle of our Sun

  1. Stellar Nebula
  2. Protostar
  3. Main Sequence
  4. Red Giant
  5. Planetary Nebula
  6. White Dwarf
  7. Black Dwarf
• A star's life cycle is determined by its mass. The larger its mass, the shorter its life cycle. A star's mass is determined by the amount of matter that is available in its nebula, the giant cloud of gas and dust from which it was born.
• More massive stars have higher core temperatures and pressures, which allows them to fuse heavier elements and burn through their fuel faster. This results in a shorter lifespan compared to less massive stars. A star's mass also determines its luminosity, or the amount of energy it radiates per unit time.
• There are approximately 200-400 billion stars in our Milky Way Galaxy alone.
• The light from stars take millions of years to reach Earth. Therefore, when you look at the stars, you are literally looking back in time.
• There is a maximum of 2,500 stars visible to the naked eye at any one time in the night sky.
• Did you know that some of the stars we see in the sky may already be dead! Their light travels millions and millions of kilometers, and by the time it reaches us, the star would have died. So the distance between our planet and the stars further away is unimaginable, but measurable still. Watch and learn how these distances can be measured and the secrets hiding among the stars.
• STELLAR NUCLEOSYNTHESIS

  The process by which the natural abundances of the chemical elements within stars vary due to nuclear fusion reactions in the cores and overlying mantles of stars.
• SUPERNOVA NUCLEOSYNTHESIS 


  The theory of the production of many different chemical elements in supernova explosions, first advanced by Fred Hoyle in 1954.
• PROTON-PROTON CHAIN REACTION 


  One of the two known sets of fusion reactions by which stars convert hydrogen to helium. It dominates in stars the size of the Sun or smaller.
• Neutrinos are the most abundant particles that have mass in the universe. Every time atomic nuclei come together (like in the sun) or break apart (like in a nuclear reactor), they produce neutrinos. Even a banana emits neutrinos—they come from the natural radioactivity of the potassium in the fruit
• A positron is the antiparticle of an electron. It has all the properties of an electron except for the polarity of the electrical charge, which is positive. Therefore, a positron can simply be considered an electron having positive unit electrical charge.
• TRIPLE ALPHA PROCESS NUCLEOSYNTHESIS 


  A set of nuclear fusion reactions by which three helium-4 nuclei (alpha particles) are transformed into carbon
• ALPHA LADDER/PROCESS 


  One of two classes of nuclear fusion reactions by which star convert helium into heavier elements, the other being the triple alpha process.
• CNO CYCLE 


  (for carbon-nitrogen-oxygen) Is one of the two known sets of fusion reactions by which stars convert hydrogen into helium. It is a catalytic cycle
• ‘CNO CYCLE’

  REFERS TO THE CARBON-NITROGEN-OXYGEN CYCLE, A PROCESS OF STELLAR NUCLEOSYNTHESIS IN WHICH STARS ON THE MAIN SEQUENCE FUSE HYDROGEN INTO HELIUM VIA A SIX-STAGE SEQUENCE OF REACTIONS.
• THIS SEQUENCE PROCEEDS AS FOLLOWS:

  • A carbon-12 nucleus captures a proton and emits a gamma ray, producing nitrogen-13.

  • Nitrogen-13 is unstable and emits a beta particle, decaying to carbon-13.

  • Carbon-13 captures a proton and becomes nitrogen-14 via emission of a gammaray.

  • Nitrogen-14 captures another proton and becomes oxygen-15 by emitting a gamma-ray.

  • Oxygen-15 becomes nitrogen-15 via beta decay.

  • Nitrogen-15 captures a proton and produces a helium nucleus (alpha particle) and carbon-12, which is where the cycle started.
• MAIN-SEQUENCE STAR 


  Any star that is fusing hydrogen in its core and has a stable balance of outward pressure from core nuclear fusion and gravitational forces pushing inward
• RED GIANT STAR 


  A dying star in the last stages of stellar evolution.
• SUPERNOVA 


  The explosion of the star. The largest explosion that takes place in space
• R-PROCESS


  The r-process, or the rapid neutron-capture process, of stellar nucleosynthesis is called for to explain the production of the stable (and some long-lived radioactive) neutron-rich nuclides heavier than iron that are observed in stars of various metallicities, as well as in the solar system.