How Scientists Colorize Those Beautiful Space Photos Taken By the Hubble Space Telescope

When you pic­ture the giant for­ma­tions of gasses and space dust that make up a neb­u­la, maybe you see the deli­cious­ly gar­ish CGI of Guardians of the Galaxy. The look of the Mar­vel uni­verse is, of course, inspired by eye-pop­ping images of neb­u­lae tak­en by the Hub­ble tele­scope, images that have appeared rou­tine­ly for the past three decades in the pages of Nation­al Geo­graph­ic, Dis­cov­er, and your favorite screen savers.

Whether you’re into sci-fi super­hero flicks or not, you’ve sure­ly stared in awe and dis­be­lief at these pho­tographs: ghost­ly, glow­ing, resem­bling the illus­tra­tions of out­er space by cer­tain pulp sci-fi illus­tra­tors twen­ty years before the Hub­ble was launched into orbit in 1990. If these images seem too painter­ly to be real, it’s because they are, as the Vox video above explains, to a great degree, prod­ucts of pho­to­graph­ic art and imag­i­na­tion.

The Hub­ble tele­scope only takes images in black and white. The images are then col­orized by sci­en­tists. Their work is not pure fan­ta­sy. A process called “broad­band fil­ter­ing” allows them to rea­son­ably esti­mate a range of col­ors in the black and white pho­to. Some imag­i­na­tive license must be tak­en “to show us por­tions of the image that would nev­er have been vis­i­ble to our eyes in the first place,” notes PetaPix­el. “For exam­ple: turn­ing cer­tain gasses into vis­i­ble col­or in a pho­to­graph.”

In an impres­sive few min­utes, the Vox explain­er digs deep into the sci­ence of optics to explain how and why we see col­or as com­bi­na­tions of three wave­lengths. The sci­ence has been “the guid­ing prin­ci­ple in col­or­ing black and white images” since the turn of the 20th cen­tu­ry. We learn above how broad­band filtering—the pho­to­graph­ic tech­nique bring­ing us full-col­or galac­tic fever dreams—originated in the ear­li­est exper­i­ments in col­or pho­tog­ra­phy.

In fact, the very first col­or pho­to­graph ever tak­en, by physi­cist James Clerk Maxwell in 1861, used a very ear­ly ver­sion of the tech­nique Hub­ble sci­en­tists now use to col­orize images of space, com­bin­ing three black and white pho­tos of the same object, tak­en through three dif­fer­ent-col­ored fil­ters. Giv­en the advances in imag­ing tech­nol­o­gy over the past 100+ years, why doesn’t the pow­er­ful space tele­scope just take col­or pic­tures?

It would com­pro­mise the Hubble’s pri­ma­ry pur­pose, to mea­sure the inten­si­ty of light reflect­ing off objects in space, a mea­sure­ment best tak­en in black and white. But the sci­en­tif­ic instru­ment can still be used as cos­mic paint­brush, cre­at­ing jaw-drop­ping images that them­selves serve a sci­en­tif­ic pur­pose. If you were dis­ap­point­ed to learn that the pho­tog­ra­phy fuel­ing our our space imag­i­na­tion has been doc­tored, watch this video and see if a sense of won­der isn’t restored.

Relat­ed Con­tent:

The Beau­ty of Space Pho­tog­ra­phy

NASA Releas­es a Mas­sive Online Archive: 140,000 Pho­tos, Videos & Audio Files Free to Search and Down­load

NASA Dig­i­tizes 20,000 Hours of Audio from the His­toric Apol­lo 11 Mis­sion: Stream Them Free Online

Josh Jones is a writer and musi­cian based in Durham, NC. Fol­low him at @jdmagness

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