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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