Effects of Earth's Atmosphere on Astronomical Observations
Effects of Earth’s Atmosphere on Astronomical Observations
Atmospheric Extinction
- Atmospheric extinction is the scattering and absorption of electromagnetic radiation by the atmosphere which diminishes the intensity of celestial objects.
- Objects at different altitudes are affected by extinction in varying degrees - those near the horizon more so than those at the zenith, due to the increased length of the atmospheric path.
Refraction
- As light from celestial objects enters the Earth’s atmosphere, it bends due to a phenomenon known as refraction.
- Refraction makes the object appear higher in the sky than it actually is.
- This effect is more pronounced when the object is closer to the horizon, since light travels through more atmosphere.
Scintillation (or Twinkling)
- Scintillation is the fluctuation in star brightness caused by the Earth’s atmosphere.
- Caused by pockets of air at slightly different temperatures, it results in stars appearing to “twinkle”.
Skyglow
- Skyglow refers to the brightening of the night sky caused by artificial light pollution.
- This significantly hampers visibility of faint celestial objects.
Astronomical Seeing
- The term astronomical seeing refers to the blurring and twinkling of astronomical objects, which is caused by the turbulence in Earth’s atmosphere.
- Rapid changes in air density create an effect like viewing objects through a rippling pool of water.
Atmospheric Windows
- Atmospheric windows are specific wavelengths or ranges of electromagnetic radiation that can penetrate the Earth’s atmosphere.
- Visible light, some ultraviolet (UV) light, and some infrared (IR) light can reach the ground, whereas most other forms of electromagnetic radiation are absorbed.
Weather and Observations
- Weather significantly impacts astronomy. Clouds can obscure objects, winds can cause telescopes to vibrate, and humidity can form droplets on equipment.
Radiowaves and Atmosphere
- The Earth’s atmosphere is largely transparent to radiowaves, which means data at these wavelengths can be received at ground-based observatories.