Light and the Spectrum

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 shown above 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 we can see, but they also emit energy or radiation in other forms. In fact, the majority of the radiation emitted is “invisible,” and include radio, infrared, microwaves, ultraviolet, X-rays, and gamma rays. These other forms of energy give us a better understanding of the universe. The light that we see with our 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.

Download a printable version of the interactivity above.

The Visible Spectrum

Even though stars, planets, and other celestial bodies stand miles upon miles away from Earth, astronomers still study their chemical composition, even from afar. Astronomers make observations on faraway objects in space using the visible portion of the electromagnetic spectrum. The visible spectrum is just a small part of radiation presented in the electromagnetic spectrum, yet astronomers can use the visible spectrum to analyze the light emitted in the night sky. In this interactivity, use the arrows in the lower right corner or click on each of the numbers to explore the visible spectrum and its use in astronomy.

Download a printable version of the interactivity above.

 

Light and the Spectrum Review

Check your knowledge of how astronomers use light and the spectrum to study space by answering the questions in this non-graded activity. Then, click SUBMIT to check your response(s). Click the interactivity thumbnail, and then click NEXT to begin.