The Secrets Behind All Those Gorgeous Photos of Space
In an era when NASA’s vast photographic archive is a click away and even the Curiosity Rover is on Instagram, it’s easy to lose sight of the fact that photographing the cosmos is an amazing achievement and a complex process.
Travis Rector reminds us of this in his excellent book, Coloring the Universe. Rector is an astronomer and an expert on the topic; he’s used everything from the Hubble Space Telescope to the Very Large Array to make more than 250 photos during the past two decades. He and his co-authors, Kim Arcand and Megan Watzke of the Chandra X-Ray Observatory, bring a photographer’s sensibility to the book, explaining just how NASA made some of the stunning photos we too often take for granted.
“People have a lot of questions about [space] images, such as ‘Are the colors real’ or ‘Is this what it really looks like?'” says Rector. “We wanted to write a book to answer these questions, so that people can better understand and appreciate what they’re seeing when they look at pictures of space.”
Astronomers have focused their cameras on the cosmos since the mid-19th century. They started with the moon, of course, and then looked ever further into space to the sun and other stars. Refracting telescopes and highly sophisticated reflecting telescopes designed specifically became more widespread in the early 20th century and grew ever larger through the mid-1900s.
Electronic imaging came to the fore in the 1970s, and by the end of the century NASA and others were using multi-mirror telescopes and space-based telescopes like the Hubble—which brought astrophotography into the Internet era when it launched in 1990. Four years later, Hubble captured fragments of the Shoemaker-Levy 9 comet pummeling Jupiter and people worldwide overloaded NASA’s servers trying to download photographs. “[It] demonstrated how effectively the internet could share new images and science results—something we take for granted today,” Rector says.
Astrophotography is far more difficult than simply pointing a lens at the sky. The best photos come from powerful telescopes like the Hubble or Gemini North hooked up to highly specialized cameras. Using the Hubble as an example, scientists aim the telescope toward the expanse of sky they want to explore, with a pointing accuracy of 0.007 arc seconds—which NASA says is like being able to shine a laser on a dime 200 miles away. Incoming light is reflected off a primary mirror almost 8 feet in diameter onto the secondary mirror, which reflects it into the telescopes optical equipment, which includes half a dozen cameras.
NASA likes to say the Hubble can see objects with an angular size as small as 0.05 arc seconds, which is like being in Washington, DC, and spotting two fireflies in Tokyo. The telescope captures images in monochromatic grayscale. Filters sensitive to specific wavelengths of light recreate color; the final images that amaze us are composites.
The Hubble—which will be succeeded by the James Webb Space Telescope when it launches in 2018—is much more than a telescope; it is in may way a time machine, peering into the distant past at the very origin of the cosmos. The telescope has seen locations 13.8 billion light years away, and has collected more than 100 terabytes of data, according to NASA. “When the data arrive from the telescope it’s like Christmas,” Rector says. “I pretty much can’t get anything else done until I’ve had a chance to take a peek.”
Rector created many of the striking photographs in Coloring the Universe. To make his image of the IC 1396 portion of the Elephant Trunk nebula, Rector used the Mayall 4-meter telescope at the Kitt Peak National Observatory in 2009. He covered the detectors of a Mosaic I camera with two narrowband filters allow only hydrogen alpha and sulphur light to pass and a broadband infrared filter.
The amazing image reveals a dark, gaseous form stirring within a red sky splattered with stars. “Cameras that can see kinds of light other than what our eyes see have vastly improved our ability to study the universe,” Rector says. “Having data in a digital format has also enabled us to analyze astronomical objects in ways never imagined before. As a result we really are in a golden age of astronomy.”
Rectors fell in love with astronomy as a child when he watched the Perseid meteor shower while camping in Colorado. Photography is his way of getting others excited about it too. “I love making these images because it is a way to share with people what our telescopes can see,” Rector says. “It’s a visceral way to connect with the scientific discoveries these amazing machines enable astronomers to make.”
