Using Light to Learn About the Universe, Part 2
Because light interacts with matter in different ways, telescopes designed to detect specific wavelengths of light can capture different types of information about distant objects. Telescopes on Earth and in space have been engineered to detect the entire spectral range. For example, X-ray telescopes capture and show radiation from very hot regions in stars and from violent events like explosions or collisions.
Infrared Telescopes
Watch this video, which explains what scientists can learn by studying light in the universe in the infrared portion of the spectrum. As you watch, note the explanation given for what happens to infrared light when it strikes silver- and gold-coated surfaces.
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Video: Treasures of the Earth | Golden Telescope Mirrors
After watching the video, read the following passage. As you read, highlight statements that help clarify ideas about light given off by astronomical objects.
Instructions for highlighting: Using your cursor, select the phrases and sentences in the text you want to highlight. Next, click on the pen icon. You may add a comment or question in the text box that appears. Be sure to click Save before continuing.
With many scientists interested in understanding the early universe, engineers are developing a telescope that observes light in the part of the spectrum where the oldest astronomical objects are visible—ones that date back not just millions of years, but several billions of years, when the first galaxies formed. Enter the James Webb Space Telescope (JWST), named after the NASA administrator who oversaw the Apollo space program.
Whereas the Hubble Space Telescope (HST) makes its observations primarily in the visible light spectrum, the JWST will be optimized to observe some of the oldest galaxies' earliest stars in infrared wavelengths. Infrared light allows astronomers to see objects that are hidden from view by stellar gas and dust or that are otherwise too cool to be visible in other wavelengths. Infrared also allows astronomers to look back in time because short wavelengths emitted by distant objects are stretched into the infrared range as the universe expands. Astronomers are able to use infrared light to study in greater detail the formation and evolution of planets, stars, and galaxies as well as the distribution of matter throughout the universe.
A telescope's sensitivity, or how much detail it can see, is directly related to the size of its mirror area. A telescope’s mirror collects the light from objects being observed, and a larger mirror area can collect more light. The JWST design features a primary mirror with a diameter of 6.5 meters (21.4 feet). This will give it a light-collecting area about seven times larger than the HST’s mirror, which has a diameter of 2.4 meters (8 feet). The ability of the JWST to collect more light means that it will see deeper into space than the HST can.
Take Notes
- Based on what you learned from the video and in the reading, briefly describe how properties of light influence telescope design, especially with respect to mirror size and coating.
