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Infrared Astronomy

Beyond Visible Light

The rainbow of light that the human eye can see is a small portion of the total range of light, known in science as the electromagnetic spectrum. Telescopes can be engineered to detect light outside the visible range to show us otherwise hidden regions of space. The James Webb Space Telescope detects near- and mid-infrared wavelengths, the light beyond the red end of the visible spectrum.

Infographic titled “Electromagnetic Spectrum” comparing light detected by the Hubble, Webb, and Spitzer space telescopes. Diagram includes a horizontal bar representing the electromagnetic spectrum. From left to right: Gamma, X-ray, Ultraviolet, Visible, Infrared, Microwave, and Radio. Above each band is a sine wave pattern, with wavelengths increasing from Gamma at the left to Radio at the right. Below the wavelength bar, from left to right: Hubble Space Telescope has a wavelength range of 90 to 2,500 nanometers, corresponding to the right-most portion of Ultraviolet, all of the Visible, and the left-most sliver of Infrared. James Webb Space Telescope has a wavelength range of 600 to 28,500 nanometers, corresponding to a sliver of red visible light and the left half of Infrared. Spitzer Space Telescope has a wavelength range of 3,000 to 160,000 nanometers, corresponding to the right half of Infrared. Click View Description for more details.
This infographic illustrates the spectrum of electromagnetic energy, specifically highlighting the portions detected by NASA’s Hubble, Spitzer, and Webb space telescopes. The portion of the spectrum labeled “visible,” with the colors of the rainbow, is what humans detect as...
Image: NASA, ESA, CSA, Joseph Olmsted (STScI)

Infrared light reveals new details in images, deepening our understanding of celestial objects. To explore what we can learn from other wavelengths of light, click through some of NASA's Universe of Learning ViewSpace Interactives.

Frame is split down the middle: Webb’s near-infrared image at left, and Hubble’s visible light image at right. Both show the Egg at left and the Penguin at right. Webb’s near-infrared image shows the Penguin’s beak, head, and back in shades of pink. Its tail-like region is more diffuse, and a mix of lighter pinks and blues. The Egg appears slightly larger in blue layers. A semi-transparent blue forms an upside down U over top of both galaxies. At top right, an edge-on galaxy has many more pinpricks of light, which are stars. In Hubble’s view, the Penguin is highly detailed, with a bright blue beak, body, and tail that is covered in an arc of bright brown dust. The Egg, to its left, appears bright, gleaming yellowish white. At top right is another galaxy seen from the side, about as long as the Egg’s height. Dozens of galaxies and stars appear in the background. Thousands of galaxies and stars appear in the background. Some galaxies are shades of orange, while others are white.
ArticBoth of these images show the interacting galaxies nicknamed the Penguin and the Egg. At left is Webb’s view in near-infrared light. At right is the Hubble image’s view in visible light. In Webb’s near-infrared view, this dust lane is significantly fainter. Webb’s observations also highlight a faint upside-down U shape that joins the pair of galaxies. This is a combination of stars, gas, and dust that continues to mix as the galaxies mingle. In Hubble’s visible light image, a dark brown dust lane begins across the Penguin’s “beak” and extends through its body and along its back. Learn more about the differences.le content image
 Credit: NASA, ESA, CSA, STScI
A two-part image, with Webb’s observation at left and Hubble’s at right. Webb’s image of the face-on spiral galaxy NGC 1566 shows a densely populated face-on spiral galaxy anchored by its slightly oval central region, which has a light blue haze of stars that covers about a quarter of the view. Two prominent spiny spiral arms made of stars, gas, and dust also start at the center, within the blue haze, and extend to the edges, rotating counterclockwise. The spiral arms of the galaxy are largely orange, ranging from dark to bright orange. Hubble’s image of NGC 1566 shows a central region that has a light yellow haze of stars that takes up about a quarter of the view. Two prominent, delicate spiral arms start near the center and extend to the edges, rotating counterclockwise. There is brown dust beginning at the center, but as the arms extend outward, brown dust lanes alternate with diffuse lines of bright pink stars. Triangles at the corners are black, where there is no data.
The face-on spiral galaxy NGC 1566 is shown twice. At left, Webb’s observations combine near- and mid-infrared light. At right, Hubble’s observations feature visible and ultraviolet light. Dust absorbs ultraviolet and visible light, and then re-emits it in the infrared. In Webb's images, we see dust glowing in infrared light. In Hubble’s images, dark regions are where starlight is absorbed by dust. Compare and contrast these images. 
Credit: NASA, ESA, CSA, STScI, Janice Lee (STScI), Thomas Williams (Oxford), Rupali Chandar (UToledo), Daniela Calzetti (UMass), PHANGS Team.

Infrared Light Is Important to Astronomy in Three Major Ways

First, some objects are better observed in infrared wavelengths. Some bodies of matter that are cool and do not emit much energy or visible brightness, like people or a young planet, still emit infrared light. Humans perceive this as heat, while some other animals, like snakes, are able to “see” infrared energy. 
Visible light’s short, tight wavelengths are prone to bouncing off dust particles, making it hard for visible light to escape from a dense nebula. Longer wavelengths of infrared light slip past dust more easily, which means that instruments that detect infrared light — like those on Webb — are able to observe objects that emit light inside dusty clouds. Low-energy brown dwarfs and young protostars forming in the midst of a nebula are among the difficult-to-observe cosmic objects that Webb can study. In this way, Webb works to reveal a “hidden” universe of star and planet formation that is literally not visible otherwise.
Finally, infrared light holds clues to many mysteries from the beginning of everything, including some of the first generations of stars and galaxies in the early universe. Through a process called cosmological redshift, light is stretched as the universe expands, so light from stars that is emitted in shorter ultraviolet and visible wavelengths is stretched to longer wavelengths of infrared light.
Observations of these early days in the universe’s history shed light on perplexing questions of dark matter and dark energy, black holes, galaxy evolution over time, what the first generations of stars were like, and how we arrived at the universe we experience today.

Video: Reading the Rainbow - Distance

Transcript
How do astronomers learn about something in space that is very far away? In addition to images, they study the light from cosmic objects like planets, stars, and galaxies. Astronomers spread light out to look at the detailed rainbow spectrum (plural: spectra). Light carries a lot of information, if you learn to “read” its rainbow! In this video, discover how astronomers read spectra to measure the vast distances of space
NASA, ESA, Dani Player (STScI).
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