Look familiar? Popularly known as the “Pillars of Creation,” these ghostly fingers—part of a stellar nursery called the Eagle Nebula—awed Earthlings 20 years ago in an image taken by the Hubble Space Telescope. The picture above, released earlier this year, revisits the iconic scene to commemorate Hubble’s 25th anniversary this month.
The resolution of the new photo is crisper—about double that of the first version—thanks to new cameras installed on Hubble during its latest service mission in 2009. And “it’s a wider field [of view], so we see more of the area around the pillars,” says Zolt Levay, imaging group lead at the Space Telescope Science Institute and a member of the team that created the new picture.
Suspended in space 7,000 light years away, the Eagle Nebula (also known as M16) is composed of thousands of stars, including dozens of massive ones 20-30 times the size of our sun. They thread through a molecular cloud of gas and dust that, in some places, is collapsing to form a subsequent generation of stars. But at the same time, ionizing wind and radiation from the existing massive stars are eroding the surrounding cloud, creating ephemeral sculptures—like the three pillars—in the process.
“It’s a competition between how quickly can those [new] stars collapse, versus how quickly can the nearby guys blow all of that stuff away so they can’t collapse anymore,” says Paul Scowen, a research scientist at Arizona State University, who was involved in making the original “Pillars of Creation” image. “So there’s a tension there.”
The pillars first piqued Scowen and his team’s interest because they’re a dramatic example of that interstellar strife. “These pillars have been left behind because there were three dense clumps of gas that refused to be beaten up by these massive stars and are still trying to form stars themselves,” he says. As a result, the researchers could look at the edge of the nebula in unprecedented detail.
A discerning comparison between the new Hubble image and the original suggests where some of those budding stars might be (see image above). “There’s a few places where we actually see some changes in the structure,” says Levay. “We think that’s caused by material that’s coming off newly formed stars that are obscured by the passing dust.”
A near-infrared version of the pillars—also recently released—offers a more penetrative look at those baby stars, as well as older studs (see image below). “By taking a picture in the infrared, you actually get to lift the veil [of the molecular cloud],” says Scowen, and in so doing, we “see a lot better how many second generation stars are being formed.” For example, in the middle pillar, a little spangle appears in the center, towards the top.
The pillars probably have a few hundred-thousand years until they bite the dust, as it were. In astronomical time, that’s the blink of an eye. “We really are catching these things at a very unique time,” says Scowen. “They’re very transitory features.”
Along with pictures such as “Earth Rise,” taken during the Apollo 8 mission, Hubble’s original “Pillars of Creation” has become a wildly popular astronomical scene. “Part of [the reason] is how sharp and clear an image it is. Part of it is the color distribution that you see. Part of it was the composition,” says Scowen. (He’s not sure where the evocative name came from.)
To create both the original picture and its sequel, researchers added color to black and white snapshots taken by Hubble and assembled them into a composite image. While the hues don’t exactly reflect what the eye would see, they’re representative of the physical processes they depict—the wavelength of light emitted by various chemical elements guided the color choices. For instance, ionized sulfur is represented by red, while ionized hydrogen—which has a similar, but shorter wavelength—appears green, and ionized oxygen is blue.
“A lot of people have the impression that we just make up these colors and paint these pictures,” says Levay, but “it’s not made up at all—it’s from the science.”
Indeed, over the past 25 years, Hubble has shed copious light on the blackness beyond, making more than 1.2 million observations of more than 38,000 different celestial objects, according to Levay. “We’ll never be able to travel to these places,” he says. But with space observatories, “we can visualize this stuff that our feeble human senses and experiences just can’t do on their own.”
*This article was updated on April 22nd, 2015, to reflect the following change: An earlier version stated that “Pillars of Creation” might be one of history's most popular astronomical scenes. The article has been changed to state that the scene is wildly popular.
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