Where do all those colors in space telescope images come from?
By Briley Lewis | Published Apr 18, 2024 10:28 AM EDT
We’ve all seen beautiful images of outer space, with vivid swirls and bright stars resting on a black abyss. With how quick it is to snap a color photo on an iPhone, you might think that sophisticated space telescopes churn out color photos automatically, too.
However, all digital cameras—from your phone to the James Webb Space Telescope—can’t actually see in color. Digital cameras record images as a bunch of ones and zeros, counting the amount of light hitting their sensors. Each pixel has a colored filter over it (either red, green, or blue), which only allows specific wavelengths of light to go through. The filters are arranged in a specific pattern (typically a four-pixel repeating square known as the Bayer pattern), which allows the camera’s computing hardware to combine the captured data into a full-colored image. Some digital cameras spread the colored filters out across three individual sensors, the data from which can similarly combine into a full-color image. Telescope cameras, however, have to take images with one filter at a time, such that they have to be combined by experts later into a composite image.
In our smartphones, the combination of layers happens incredibly fast—but telescopes are complicated scientific behemoths, and it takes a bit more effort to get the stunning results we know and love. Plus, when we’re looking at the cosmos, astronomers use wavelengths of light that our eyes can’t even see (e.g. infrared and X-rays), so those also need to be represented with colors in the rainbow. There are lots of decisions to be made about how to colorize space images, which begs the question: who is making these images, and how do they make them?
