James Webb Space Telescope - Blog Posts

How Do Space Telescopes Break Down Light?

Space telescopes like Hubble and our upcoming James Webb Space Telescope use light not only to create images, but can also break light down into individual colors (or wavelengths). Studying light this way can give us a lot of detail about the object that emitted that light.  For example, studying the components of the light from exoplanets can tell us about its atmosphere’s color, chemical makeup, and temperature. How does this work?

Remember the primary colors you learned about in elementary school?

Those colors are known as the pigment or subtractive colors. Every other color is some combination of the primary colors: red, yellow, and blue.

Light also has its own primary colors, and they work in a similar way. These colors are known as additive or light colors.          

TVs make use of light’s colors to create the pictures we see. Each pixel of a TV screen contains some amount of red, green and blue light. The amount of each light determines the overall color of the pixel. So, each color on the TV comes from a combination of the primary colors of light: red, green and blue.

Space telescope images of celestial objects are also a combination of the colors of light.

Every pixel that is collected can be broken down into its base colors. To learn even more, astronomers break the red, green and blue light down into even smaller sections called wavelengths.

This breakdown is called a spectrum.

With the right technology, every pixel of light can also be measured as a spectrum.

Images show us the big picture, while a spectrum reveals finer details.  Astronomers use spectra to learn things like what molecules are in planet atmospheres and distant galaxies.

An Integral Field Unit, or IFU, is a special tool on the James Webb Space Telescope that captures images and spectra at the same time.

The IFU creates a unique spectrum for each pixel of the image the telescope is capturing, providing scientists with an enormous amount of valuable, detailed data. So, with an IFU we can get an image, many spectra and a better understanding of our universe.

Watch the full video where this method of learning about planetary atmospheres is explained:

The James Webb Space Telescope is our upcoming infrared space observatory, which will launch in 2021. It will spy the first galaxies that formed in the universe and shed light on how galaxies evolve, how stars and planetary systems are born and tell us about potentially habitable planets around other stars.

To learn more about NASA’s James Webb Space Telescope, visit the website, or follow the mission on Facebook, Twitter and Instagram.

Text and graphics credit: Space Telescope Science Institute

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