The Electromagnetic Spectrum and the Doppler Effect

You might be surprised to learn that all objects emit radiation at all times. Radiation is the emission of energy released from the motion of atomic particles in objects. This energy is released as electromagnetic waves or particles, and does not need any physical connection to transmit from one location to another. Energy is the capacity of an object to perform work in the form of light, heat, potential and kinetic energy, and electricity.

Objects in the Solar System appear as different sizes and colors because of the wavelength of sunlight reflecting off of their surface and their distances away. Planets have their colors because the materials on their surfaces or in their clouds absorbs some of the wavelengths of sunlight and reflect a combination of wavelengths. One example is the rusty red color of Mars or the bluish-green color of Uranus. Outside of the Solar System, light produced by other stars makes them appear as different colors, if they are visible at all. By studying different waves emitted by objects in space, astronomers can learn much more than if they studied just one type of radiation. For example, the images to the left are of the M-51 Whirlpool Galaxy. Notice the differences in the images taken with the various types of waves.

The Electromagnetic Spectrum

Stars not only emit light you can see, but they also emit energy or radiation in other forms. In fact, the majority of the radiation emitted is “invisible,” and includes radio, infrared, microwaves, ultraviolet, X-rays, and gamma rays. These other forms of energy give astronomers a better understanding of the universe. The light that you see with your eyes is made of electromagnetic waves that are actually very tiny. Their average length is only a few billionths of a meter wide. In comparison, they are about as long as bacteria.

There are several types of radiation, with wavelengths varying from the size of buildings to as small as the nucleus of an atom. In this interactivity, click on the buttons on the electromagnetic spectrum to learn more about the various types of radiation emitted by stars and other celestial bodies. As you explore the spectrum, notice the size of the waves for each type of radiation. Click the player button to begin.

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The Doppler Effect

Light from a star can reveal its chemical make-up and its temperature. It can also show if it is moving toward Earth or away from Earth and how fast it is moving. In order to better understand how astronomers can tell so much about a star just from the light it emits, you must first understand the phenomenon called the Doppler effect. This requires that astronomers also utilize the spectrum emitted from a star's elements and determine shifts in it. These shifts can tell a lot about the movement of a star.

View this presentation on the Doppler effect to see just how the wave phenomenon is an important tool of study of the stars and other celestial objects. Take note of what the Doppler effect is, and what shifts in spectrum can reveal. Click the player button to begin.

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The Electromagnetic Spectrum and the Doppler Effect Review

Now that you have examined the electromagnetic spectrum and the Doppler effect, review your knowledge in this non-graded activity. Read the directions associated with each question and select the correct answer(s). Then, click SUBMIT to check your response(s). Click the player button to get started.