The Hubble Telescope Uses Real Colors fact

Does the Hubble Space Telescope use Real Colors?

The Hubble Space Telescope images use real colors in the sense that their color palette correlates with the wavelengths of observed light. The images don’t, however, use “exact” colors, as Hubble deals with light that isn’t visible to the human eye. Instead, Hubble images use natural, representative, and enhanced color palettes to bring out details that wouldn’t be possible otherwise.^[1]

How Does Hubble Work?

Hubble works by sensing electromagnetic wavelengths (light) via an array of electromagnetic detectors. Each sensor registers a different wavelength from the ultraviolet to the near infrared. That image is later translated to an RGB color palette that correlates those wavelengths to frequencies of visible light.

If you were to see each detector’s data as an image, you would see it in grayscale (as this allows each image to capture more detail). Each image we see is a composite image of many separate images taken with highly specific filters, which only let in one particular wavelength, or color, of light. When data from several different filters is combined, the resulting images can be expressed in color. The color can be spectrally correct, but it is not necessarily so. Some “artistic license” is taken to present a useful and detailed image.^[2]

“Creating color images out of the original black-and-white exposures is equal parts art and science.” – Truth Behind the Photos: What the Hubble Space Telescope Really Sees.

FACT: Hubble’s cameras take black-and-white images. The only color information is from what filter was used. Each filter senses a certain range of wavelengths. All that information is translated back into the RGB images we see.

How Does the Hubble Space Telescope see Light?

The Hubble Telescope operates much like a digital camera and uses a CCD (share-coupled device) to record photons.^[3]

Photons are massless energy field interactions which produce characteristic wavelengths. Each wavelength relates to the energy content of the photon, which in turn relates to its color. For more about the nature of light and photons, please see the visible electromagnetic spectrum and what is light?

FACT: Most people associate each wavelength of visible light with a color when their eyes and brains process it. Some animals have the ability to see a wider spectrum of light in the infrared range (like the pit viper) or the ultraviolet range (like bees).

FACT: Every color reproduction technology, and even the human eye, breaks light into different colors based on wavelength and then presents a composite image. Hubble is no different in this respect, but Hubble is different in that it is representing wavelengths that our eyes or standard cameras can’t detect.

What Information do Different Wavelengths of Light Carry?

The light from stars and galaxies often has a frequency other than that of visible light; the visible spectrum is only a small range of frequencies in the full spectrum. Astronomers need infrared filters to see the lower frequency portion of the spectrum between microwaves and visible light, and ultraviolet filters to see the higher frequencies between visible light and x-rays.^[4]

The ultraviolet operation of the spectrum provides information such as the chemical composition of celestial bodies, which provides crucial knowledge about the cosmos.^[5]

Hubble’s sensors return information about the invisible spectrum as black-and-white images. It is up to those who work with the photos to translate that back into visible spectrum colors. It is this process where some “natural” color is lost.

This “visible light” corresponds to a wavelength range of 400 – 700 nanometers (nm).

How is Color Used by the Hubble Space Telescope Scientists?

Color can be used in one of three ways given the filtered grayscale images: Natural Color, Representative Color, and Enhanced Color. The most exciting interactive site to visit in order to explore the use of these three types of color is the Hubblesite Gallery’s Meaning of Color’s pages. ^[6].

• Natural Color uses only visible light spectrum. Combinations of images taken with red, green and blue filters can simulate natural light colors. Cameras and televisions use this method.
• Representative Color uses infrared or ultraviolet light to explore detail that would usually be invisible to us. Hubble assigns the color blue to short wavelength infrared light; red to the longest wavelength; and green to intermediate length wavelength.
• Enhanced Color also uses red blue and green to enhance the filtered images to bring out structural detail. For instance, hydrogen might be shown in red, oxygen in blue, and nitrogen in green.

Does Everyone Use the Same Colors?

You can look at Almaden Observatory for an interesting discussion of the use of color palettes to generate information about celestial bodies. Quantum mechanics requires that each energy state directly maps to wavelength. Filters can be encoded three at a time to create an output or palette. Each of the three colors used- red, green, and blue – can correspond to any of the elements found in the filters.^[7]

The Hubble palette uses red for Sulfur, green for Hydrogen alpha, and blue for Oxygen III. Using other palettes such as the one used most often at Almaden Observatory, red might represent Hydrogen, green for Oxygen, and blue for Nitrogen.

Do All the Hubble Pictures Come in Color?

Funding shortages threatened to end NASA’s programs. In 1998 the Hubble Heritage Project was created to increase general public interest and enhance the perceived value of the space program. The raw scientific data from the Hubble does not look impressive, although it provides much information. Gorgeous color images generated from this data were released to excite enough interest to carry the space program forward. Although the grayscale data from the telescope fulfills Hubble’s scientific mission, the project is kept alive by its color images.^[8]

1. Color as a Tool
2. Hubble
3. What the Hubble Space Telescope Really Sees
4. The Electromagnetic Spectrum
5. Exploratorium
6. Hubblesite Gallery’s Meaning of Color’s pages
7. Almaden Observatory
8. Hubble Heritage Project