Question

Astronomical sources emit electromagnetic radiation at various wavelengths. Some sources might emit just visible and infrared radiation. Other sources might emit gamma, UV, visible, and infrared radiation. Some of that radiation travels in the direction of Earth and can be detected with the right telescopes placed in the right locations. Some wavelengths can be read in the atmosphere. However, the majority of wavelengths are either read from space or Earth’s surface. Which observations would require you to launch a telescope above the Earth’s atmosphere? Please drag each observing mode below into either the ground-based (Surface) zone or space-borne (Space) zone, depending on the respective observing requirements. Drag the appropriate items to their respective bins.

Answer 1

Space Zone:
- Far-infrared observations
- Gamma-ray observations
- X-ray observations
- Far-ultraviolet observations

Surface Zone:
- Visible observations
- Radio observations

You may be most familiar with the light that your eyes can perceive. This corresponds to the visible, or optical, part of the electromagnetic spectrum. As shown in the figure, the visible part of the EM spectrum is but a small part of the overall spectrum of wavelengths that is emitted by astronomical sources. To understand the nature of many astronomical sources, astronomers endeavor to obtain observations at multiple wavelengths throughout the EM spectrum. A fair bit of the radio and infrared parts make it through Earth’s atmosphere to be collected and detected by ground-based observing facilities.
However, Earth’s atmosphere is essentially opaque to the cosmic radiation at ultraviolet, X-ray, and gamma-ray wavelengths. To perceive astronomical sources at these wavelengths, it is necessary to loft telescopes above the bulk of Earth’s light-absorbing atmosphere. Collectively, observations of celestial sources at different wavelengths help astronomers to understand the universe, similar to how we use all of our five senses to help us to understand our immediate environment.