The origin of the majestic "pillars of creation," one of the most familiar and colorful scenes in space, is a bit of a mystery. Now researchers say it might have started from gaseous clumps pushed into shadowed areas by radiation from nearby stars.
Such clumps of gas creep toward darker regions of gas and dust and create dense knots, according to new simulations. The shadows around the knots then screen out the intense ultraviolet radiation that might interfere with further gas formation, the model indicates.
The research might help astronomers better understand the pillars and similar gas environments that act as stellar wombs, giving birth to new stars.
"There is, as yet, no clear consensus in the literature regarding the formation of the pillars, except that it is most likely related to photo-ionization processes due to nearby massive stars," said Andrew Lim, an astrophysics researcher at the Dublin Institute for Advanced Studies in Ireland.
Photo-ionization or photo-evaporation occurs when intense radiation from stars energizes neutral gas clouds to create a hot outer layer of ionized gas. The hot gas then expands rapidly like an explosion and sends shockwaves outward into any nearby clumps, Lim explained.
The process could explain how the pillars of creation piled up in the iconic images of the Eagle Nebula, located about 7,000 light-years away and first spotted by NASA's Hubble Space Telescope in 1995. A light-year is the distance light travels in a year, or roughly 6 trillion miles (10 trillion kilometers).
"We have been able to produce [virtual] pillars which are roughly consistent with the sizes and lifetimes which are inferred from observations," Lim told SPACE.com.
Earlier research looked only at how lone gas clumps might lead to pillar creation. The shadow effect represents one of the prime suspects behind the creation process, although gas instability from the radiation bombardment might also contribute.
Perhaps the most surprising result from the new simulations is that the largest clumps don't necessarily serve as foundations for the pillar-like structures, Lim noted.
But another interesting effect came from modeling a "point source" of radiation, such as a star the photo-ionization effect of the radiation bombardment had a stronger influence on gaseous knobs that could potentially grow into pillars, because of knobs having a larger surface area than just a flat surface.
"In this way the radiation field tends to 'hammer the nail that sticks out,' making it more difficult to form a pillar," Lim said. That again suggests the importance of the shadow effect shielding the newborn pillars.
Lim and his colleagues used 2-D and 3-D computer models to test different scenarios with many different sizes and configurations of gas clumps. They next plan to study the effects of magnetic fields and gravitational effects on the pillars of creation.
In the real universe, the Eagle Nebula's pillars may have already been knocked down by a giant supernova explosion, according to a previous study. But the pillars will appear intact to Earth observers for another 1,000 years and perhaps permit further study, because the light we see now left the scene long ago.
The current simulation results were to be presented this week at the European Week of Astronomy and Space Science at the University of Hertfordshire, UK.
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