Space Physics: Big Bang

Space Physics: Big Bang

Life Cycles of Stars

  • Stars are formed from massive clouds of dust and gas, known as nebulae, in a process triggered by disturbances such as a nearby supernova.
  • Dense pockets within the nebula begin to collapse under the force of gravity, forming a protostar.
  • As the gravitational energy increases, it heats the protostar, leading to nuclear fusion of hydrogen atoms. This is the point at which a protostar becomes a main sequence star.
  • How a star develops further depends on its mass: average-sized stars like our Sun become red giants, while larger stars become supergiants.
  • Red giants eventually eject their outer layer of dust and gas, leaving behind a white dwarf star and a surrounding planetary nebula.
  • Over billions of years, white dwarfs cool to become black dwarfs.
  • Large supergiants can explode, after fusion ends, in a supernova, forming neutron stars or black holes.
  • Elements heavier than iron, such as gold or uranium, are made during such explosions.

The Universe: Structure and Evolution

  • The universe is a vast, expanding space filled with everything that exists — galaxies, stars, planets, dark matter, etc.
  • The structure of the universe on the largest scale is the cosmic web; a network of interconnected filaments of galaxies interspersed with enormous voids.
  • Galaxies are huge collections of stars, typically containing billions of stars, as well as dust, gas, and dark matter, held together by gravity.
  • Our Milky Way galaxy is one among billions in the universe, and it is part of a collection of local galaxies known as the Local Group.
  • Evidence for the expansion of the universe comes from the observed redshift of light from distant galaxies.

The Big Bang and the Age of the Universe

  • The Big Bang Theory proposes that the universe started from a hot, dense point around 13.8 billion years ago, and has been expanding ever since.
  • The observed red-shift of distant galaxies and the detection of *Cosmic Microwave Background Radiation (CMBR)** supports this theory.
  • CMBR is the leftover heat from the Big Bang and it fills the universe, further evidence of the universe’s origin.
  • The age of the universe may be estimated from observing distant galaxies and calculating how long the light has taken to reach us.
  • Current scientific understanding estimates the universe to be approximately 13.8 billion years old.