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Question 3:
The electromagnetic spectrum is composed of many different types of light. The following types of light are ordered from the lowest-energy waves to those of the highest energy: radio, microwave, infrared, visible, ultraviolet, X-ray, and gamma ray. If you could observe the Horsehead Nebula in any of these types of light, which would you choose and why?

A student's answer will depend on which part of the electromagnetic spectrum is chosen:

  • Radio waves can be detected from celestial objects in any kind of weather. Sunlight, clouds, and rain do not affect a radio telescope. Many astronomical objects give off radio waves, which give the astronomer clues about the object's makeup, structure, and motion.
  • Microwaves can be used by satellites to study Earth's geological features, such as sea ice or rivers. Astronomers uncovered clues to the beginning of the universe when the cosmic microwave background radiation was discovered.
  • Infrared light allows astronomers to peer into clouds of gas and dust to reveal objects hidden inside.
  • Visible light is the only portion of the spectrum that our eyes detect. It has been used by astronomers since ancient times.
  • Astronomers use ultraviolet light to study stars and galaxies. Massive, hot stars give off lots of ultraviolet light, but smaller, cooler stars do not. Astronomers can learn about the evolution of stars and galaxies by studying the ultraviolet light they give off.
  • Many objects in space give off X-rays. They include black holes, neutron stars, supernova remnants, and the Sun.
  • Gamma rays, the highest-energy waves, are given off by solar flares, supernovae, neutron stars, black holes, and active galaxies.

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