6.5 Observations outside Earth’s Atmosphere

Airborne and Space Infrared Telescopes

• Telescopes positioned in space to avoid disturbances due to atmospheric interferences

• Allows telescopes for infrared radiation to be cooled without condensation 

  • Helps observe cool cosmic objects of dust clouds, star nurseries and stellar remnants

Hubble Space Telescope: Launched in 1990

• 2.4 meter mirror

• Installed corrective optics

• No more servicing missions

James Webb Space Telescope: Launched 2021

• Orbits on earths orbit 1.5 million km away 

  • Cold location for peak infrared radiation capture 

• Made of 18 segments of 6.5 meter mirror with a large sunshield

• Observed

  • Southern Ring Nebula: Two stars at the center and expanding dusty shells from a dying star.

  • Stephan’s Quintet: Interacting galaxies with stellar tails shaped by gravity

HIgh-Energy Observatories

• UV, X-ray, Gamma Ray → only observed from space since earth's atmosphere blocks these high energy waves out 

• Components of OBservatories remain the same → Designing the mirrors is difficult 

  • Hard to reflect such penetrating radiation, normally pass through the material 

• Some gamma rays can also be detected from Earth using atmospheric cascades

Atmospheric cascades

processes where energy or other properties are transferred across multiple scales