Structure and Composition of the Universe

Structure and Composition of the Universe

• The universe includes all space, time, matter, and energy.
• Composition:
  • 4.6% baryonic matter (ordinary matter: protons, electrons, neutrons, and all atomic structures).
  • 24% cold dark matter (exerts gravitational effects but doesn’t emit light).
  • 71.4% dark energy (provides anti-gravity, contributing to the universe's expansion).

Role of Dark Matter and Dark Energy

• Dark matter helps explain the gravitational binding of galaxies despite low total visible mass.
• Dark energy accounts for the observed acceleration in the universe's expansion.

Abundant Elements and Star Formation

• The most prevalent elements in the universe are hydrogen, helium, and lithium.
• Stars originate from clouds of gas and dust through processes that lead to gravitational collapse and heating, resulting in the formation of proto stars.

Stellar Lifecycle

• Stellar interiors function as stellar furnaces, where element fusion occurs.
• Most stars, including the Sun, are classified as main sequence stars.
• In main sequence stars, hydrogen is fused into helium through thermonuclear reactions.
• Larger main sequence stars exhaust their hydrogen supplies faster than smaller ones, typically within a few million years compared to the Sun's 10 billion years.

Star Evolution and Galactic Structure

• The remnants of star formation may evolve into planets, asteroids, or other celestial bodies within planetary systems.
• A galaxy consists of billions of stars, while groups of galaxies form superclusters.
• Cosmic space between clusters is relatively empty, contributing to the vast structure of the universe.