Back in 1995, NASA’s Hubble Space Telescope snapped a truly awe-inspiring image of the Eagle nebula, a cluster of stars located some 6,500 light-years away in the Serpens constellation. Coined the “Pillars of Creation,” the image is thought to show areas of new star formation within finger-like towers of interstellar gas and dust, sculpted by intense radiation and winds from neighboring massive stars . But how did these iconic columns come about? Cardiff University astronomer Scott Balfour may have some answers.
By running computer simulations, Balfour has managed to recreate remarkably similar structures to the infamous pillars, suggesting their likely origins. Furthermore, he thinks that the stars that forged these structures are less likely to assist in the formation of new stars than once believed.
The kind of star responsible for the pillars is an O-type star- an incredibly hot star around 16 times more massive than our Sun. These stars emit a vast amount of UV radiation and stellar material within fierce winds, both of which mold the surroundings. They also heat up any neighboring interstellar gas, forming bubbles that plow through cooler material. Astronomers have observed that star formation is commonplace in these regions, leading them to assume that these massive stars fuel the birth of new stars.
In order to understand how these massive stars affect their surroundings, Balfour ran a simulation of the birth of such a star within a collapsing gas cloud. He then observed what happened to the gas over a period of 1.6 million years.
As expected, the radiation drove the formation of a huge bubble within the cloud, but he discovered that the bubble had three possible outcomes which were dependent on the intensities of the UV radiation emitted. He found if the UV emission was too weak, the bubble first expanded and then collapsed. If the star emitted extremely strong UV radiation the bubble continued to expand, forming the familiar pillar structures. However, the pillars weren’t dense enough to support the birth of new stars.
Balfour discovered that if the UV output was “just right,” the bubble would expand, contract a little and then remain stationary. The edges of the bubble would then crumble, resulting in towers of gas with sufficient density to act as a stellar nursery.
“If I’m right, it means that O-type and other massive stars play a much more complex role than we previously thought in nursing a new generation of stellar siblings to life,” Balfour said in a news-release. “The model neatly produces exactly the same kind of structures seen by astronomers in the classic 1995 image, vindicating the idea that giant O-type stars have a major effect in sculpting their surroundings.”
Balfour presented his findings today (June 26) at the National Astronomy Meeting in Portsmouth.