The Universe is everything we can touch, feel, sense, measure or detect. It includes living things, planets, stars, galaxies, dust clouds, light, and even time. ... The Universe contains billions of galaxies, each containing millions or even trillio...
Light waves, radio waves, and X-rays are all forms of energy-carrying waves called electromagnetic (EM) radiation. Stars, galaxies, and other objects in space give off the entire range of EM radiation. This range, from low to high energy, is named the EM spectrum (electromagnetic spectrum).
Waves of energy EM waves move at the speed of light-about 300,000 km (186,000 miles) per second- but carry different amounts of energy depending on the length of their waves. Wavelength is the distance from the top of a wave to the next top.
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Radio waves Radio waves have wavelengths several meters long, but less energy than forms of radiation.
Microwaves Wavelengths between radio and infrared.
Infrared Infrared radiation, or heat, from hot gas and dust is seen in red, while that from speeding electrons appears blue.
Visible light Visible light is the radiation that we can see with our eyes. Gas and electrons in the Crab Nebula both produce visible light. Light ranges from long-wavelength red light to short-wavelength violet.
Ultraviolet Ultraviolet rays have shorter wavelengths than visible light. The incredibly hot central region of the nebula gives of these waves.
X-rays X-rays are high energy waves released by very hot material.
Gamma rays Gamma rays have the shortest wavelengths and the most energy. A spinning neutron star (see p.77) at the nebula's centre produces these rays.
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