In 1995, the Hubble Space Telescope’s “Pillars of Creation” image of the Eagle Nebula became one of the most-viewed stellar pictures of the 20th century. Now, two of the European Space Agency’s orbiting observatories have shed new light on this enigmatic star-forming region of our galaxy.
The Eagle Nebula is 6,500 light-years away in the constellation of Serpens. It contains a young hot star cluster, called NGC 6611, which is sculpting and illuminating the surrounding gas and dust, resulting in a huge hollowed-out cavity and pillars, each several light-years long.
The 1995 Hubble image hinted at new stars being born within the pillars, deeply inside small clumps known as “evaporating gaseous globules” or EGGs. Owing to obscuring dust, with Hubble’s visible-light picture it was impossible to see inside the pillars and prove that young stars were indeed forming.
A new image of this nebula taken by ESA’s Herschel Space Observatory provides a different view of the pillars and the wide field of gas and dust around them. Captured in far-infrared wavelengths of light, the image allows astronomers to see inside the pillars and structures in the region.
In parallel, a new multi-energy X-ray image from ESA’s XMM-Newton telescope shows those hot young stars responsible for carving the pillars.
Combining the new space data with near-infrared images from the European Southern Observatory’s Very Large Telescope at Paranal, Chile, and with visible-light data from ESO’s Max Planck Gesellschaft 2.2-meter-diameter telescope at La Silla, Chile, we see this iconic region of the sky in a uniquely beautiful and revealing way.
In visible wavelengths, the nebula shines mainly due to reflected starlight and hot gas filling the giant cavity, covering the surfaces of the pillars and other dusty structures. At near-infrared wavelengths, the dust becomes almost transparent and the pillars practically vanish. And in far-infrared light, the Herschel Space Observatory detects this cold dust and the pillars reappear, this time glowing in their own light. Intricate tendrils of dust and gas are seen to shine, giving astronomers clues about how they interact with strong ultraviolet light from the hot stars seen by XMM-Newton.
In 2001, near-infrared images from the Very Large Telescope at Paranal had hinted that only a small minority of the EGGs were likely to contain stars being born. However, the new Herschel Space Observatory image shows it to be possible to search for young stars over a much wider region and thus come to a much fuller understanding of the creative and destructive forces inside the Eagle Nebula.
Earlier mid-infrared images from ESA’s Infrared Space Observatory and NASA’s Spitzer Space Telescope, together with the new XMM-Newton data, have led astronomers to suspect that one of the massive hot stars in NGC 6611 may have exploded in a supernova some 6,000 years ago, emitting a shockwave that would have destroyed the pillars. However, because of the distance to the Eagle Nebula, we won’t see this happen for several hundred years yet.
Powerful ground-based telescopes continue to provide astonishing views of our Universe, but images in far-infrared, mid-infrared and X-ray wavelengths are impossible to obtain from the ground because of the absorbing effects of Earth’s atmosphere. Space-based observatories such as ESA’s Herschel and XMM-Newton help to peel back that veil and show the full beauty of the Universe across the electromagnetic spectrum.
In regions like the Eagle Nebula, combining all of these observations helps astronomers to understand the complex life cycle of stars.
You can contact Bob Eklund at firstname.lastname@example.org, or visit his website at www.bobeklund.com.