But few of these images can better one taken in 1995 of the so-called “Pillars of Creation,” massive, billowing towers of interstellar gas and dust in the Eagle Nebula, roughly 7,000 light years distant.
That first photo showed the Pillars of Creation in spectacular glory: three giant columns of gas glowing in scorching ultraviolet light emanating from a cluster of young, massive stars in a small region of the Eagle Nebula, otherwise known as M16. Such was the popularity of the 1995 image that it carved out its very own media career, subsequently appearing in movies, TV shows, T-shirts, even a postage stamp.
And now, just as Earth-bound media since 1995 has moved on from videotape to blu-ray, from 35mm film to digicams, so Hubble, a joint NASA/European Space Agency project, as part of celebrations marking the telescope’s 25th anniversary, has moved up to high definition as well as taking another peek at the Pillars of Creation in near-infrared and the visible light spectrum.
Astronomers combined several Hubble exposures to assemble the wider view. The towering pillars are about 5 light-years tall. The dark, finger-like feature at bottom right may be a smaller version of the giant pillars.
The results, revealed this week at the 225th meeting of the American Astronomical Society being held in Seattle, are a significantly sharper and wider view of this iconic cosmic feature and, when photographed in infrared, the Pillars are transformed into spooky, diaphanous silhouettes against a background of thousands upon thousands of stars.
The different imagery occurs since infrared light penetrates much of the pillars’ gas and dust, except for their densest regions. New stars in the course of formation can just be picked out concealed inside the pillars.
Pillars of Destruction
It turns out that ‘Pillars of Creation’ may be something of a misnomer since the new images suggest these gas columns are somewhat ephemeral and in the course of evaporating into the interstellar ether by reason of the ionizing winds from the central star cluster located above the pillars. What’s happening is that the pillars are being heat-blasted by radiation from nearby massive stars, then buffeted by a barrage of charged particles, that tears into the pillars, stripping electrons off their constituent atoms leaving ionized columns of gas.
Paul Scowen of Arizona State University, who, along with astronomer Jeff Hester, formerly of Arizona State University, led the original Hubble observations of the Eagle Nebula, commented, “I’m impressed by how transitory these structures are. They are actively being ablated away before our very eyes. The ghostly bluish haze around the dense edges of the pillars is material getting heated up and evaporating away into space. We have caught these pillars at a very unique and short-lived moment in their evolution.”
Astronomers have gleaned from the infrared image that the reason the pillars exist is because their extremities are dense. They cast a shadow over the gas beneath them, so creating the long, pillar-like structures.
Looking at the top edge of the left-hand pillar, a gaseous fragment can be seen to be flying away from the structure, having been heated up, emphasizing the violent environment of these star-forming regions of space.
“These pillars,” said Scowen, “represent a very dynamic, active process.”
“The gas is not being passively heated up and gently wafting away into space”, he explained, adding, “The gaseous pillars are actually getting ionized and heated up by radiation from the massive stars. And then they are being eroded by the stars’ strong winds, which are sandblasting away the tops of these pillars.”
Streamers of gas appearing to float away from the columns, when Hubble’s first images of the Pillars of Creation were returned back in 1995, were the first thing that struck Scowen and Hester. The eagle Nebula was by no means unique when it came to star formation but contributing to making the images of M16 so striking was its relative proximity to Earth at just 6,500 light years.
Until Scowen and Hester saw the images with their own eyes, astronomers had previously debated what might be the effect of nearby massive stars on the surrounding gas in stellar nurseries. What Hubble produced left Scowen in no doubt.
“There’s only one thing that can light up a neighborhood like this: massive stars kicking out enough horsepower in ultraviolet light to ionize the gas clouds and make them glow,” Scowen explained, adding “Nebulous star-forming regions like M16 are the interstellar neon signs that say, ‘We just made a bunch of massive stars here.’ This was the first time we had directly seen observational evidence that the erosionary process, not only the radiation but the mechanical stripping away of the gas from the columns, was actually being seen.”
Taking recent images of the Pillars of Creation has allowed astronomers to look at changes that have occurred since 1995. They’d originally noted a narrow jet-like feature, reminiscent of a stream of water spurting from a garden hose, which may have been ejected from a newly forming star. Over the intervening 19 years since the first images, this feature has lengthened, stretching further out into space by an estimated 60 billion miles. That would put the speed of expansion at an impressive 450,000 miles per hour.
In comparison with the Pillars of Creation, our own region of space is relatively calm, despite the odd buffeting from meteorites. But it wasn’t always so. Our Sun probably formed in a turbulent star-forming region similar to the Eagle Nebula, while some evidence points to what’s now the solar system receiving shrapnel wounds from a nearby supernova in its distant past. Our Sun could well have formed as part of a cluster that included stars massive enough to produce powerful ionizing radiation, the results of which Hubble has captured in the Eagle Nebula.
As Scowen put it, “That’s the only way the nebula from which the Sun was born could have been exposed to a supernova that quickly, in the short period of time that represents, because supernovae only come from massive stars, and those stars only live a few tens of millions of years,” adding, “What that means is when you look at the environment of the Eagle Nebula or other star-forming regions, you’re looking at exactly the kind of nascent environment that our Sun formed in.”
