Lecture Notes: Understanding Radio and Infrared Waves in Astronomy

Introduction to Radio Waves

• Historical Milestones

  • Guglielmo Marconi's first radio transmissions in 1894.
  • Radio waves have traveled into space for over 100 years, passing significant stars such as Sirius (1903), Vega (1919), and Regulus (1971).
  • Heinrich Hertz discovered radio waves in 1888.
  • First commercial radio station aired in Pittsburgh, Pennsylvania, on November 2, 1920.

• Properties of Radio Waves

  • Longest electromagnetic waves, contain the least energy.
  • Wavelengths range from 19 centimeters to longer than the Earth’s diameter.

Radio Astronomy

• Key Discovery

  • Karl Jansky discovered that stars and space objects radiate radio waves in 1932.
  • Birth of radio astronomy.

• Detection of Radio Waves

  • Requires giant antennas due to weak, long wavelengths.
  • Arecibo radio dish: 305 meters in diameter.
  • Arrays of separate antennas act as single collectors (e.g., New Mexico array with 27 antennas).
  • Global linked antennas can mimic powerful telephoto lenses.

• Significant Discoveries Using Radio Waves

  • Pulsars.
  • Giant clouds of superheated plasma.
  • Quasars over 10 billion light-years away.

Local and Cosmic Information from Radio Waves

• Astronomical and Planetary Observation
  • Magnetic fields produce radio waves (e.g., the Sun).
  • NASA's STEREO satellite monitors solar radio bursts.
  • WIND spacecraft records radio waves from planetary ionospheres (e.g., Jupiter).

Radio Waves in Daily Life

• Applications
  • Entertainment and communication.
  • Sound waves created by vibrating radio receivers.
  • Cannot hear cosmic radio transmissions but provide vital astronomical insights.

Introduction to Infrared Waves

• Understanding Near-Infrared

  • Solar radiation beyond the visible spectrum.
  • Reflection from Earth's surface used to study land cover changes.

• Vegetation and Land Cover Studies

  • Near-infrared reflection reveals insights into vegetation health and types.
  • Monitoring of forests for infestations or drought impacts.
  • Helps in studying snow, ice, urbanization, and agriculture changes.

• Cooler Objects and Infrared Waves

  • Used to study cooler objects in the Universe such as planets, cool stars, and nebulae.

Conclusion

• Radio and infrared waves have revolutionized our understanding of the Universe.
• They provide essential data for both local and distant cosmic phenomena.