Scanning Electron Microscope image of a large
(approximately 1.5 micrometer diameter) aggregate of nanograins produced in the
Cosmic Simulation Chamber at NASA's Ames Research Center, using a 95 percent Ar
– 5% C2H2 gas mixture. The nanograins and aggregates are deposited onto
ultra-high vacuum aluminum foil.
Image Credit: NASA/Ames/Farid Salama
A team of scientists at NASA's Ames Research Center in Moffett Field, Calif.,
has successfully reproduced, right here on Earth, the processes that occur in
the atmosphere of a red giant star and lead to the formation of planet-forming
interstellar dust.
Using a specialized facility, called the Cosmic Simulation Chamber (COSmIC)
designed and built at Ames, scientists now are able to recreate and study in the
laboratory dust grains similar to the grains that form in the outer layers of
dying stars. Scientists plan to use the dust to gather clues to better
understand the composition and the evolution of the universe.
Dust grains that form around dying stars and are ejected into the
interstellar medium lead, after a life cycle spanning millions of years, to the
formation of planets and are a key component of the universe's evolution.
Scientists have found the materials that make up the building blocks of the
universe are much more complicated than originally anticipated.
"The harsh conditions of space are extremely difficult to reproduce in the
laboratory, and have long hindered efforts to interpret and analyze observations
from space," said Farid Salama, project leader and a space science researcher at
Ames. "Using the COSmIC simulator we can now discover clues to questions about
the composition and the evolution of the universe, both major objectives of
NASA's space research program."
In the past, the inability to simulate space conditions in the gaseous state
prevented scientists from identifying unknown matter. Because conditions in
space are vastly different from conditions on Earth, it is challenging to
identify extraterrestrial materials. Thanks to COSmIC, researchers can
successfully simulate gas-phase environments similar to interstellar clouds,
stellar envelopes or planetary atmospheres environments by expanding gases using
a cold jet spray of argon gas seeded with hydrocarbons that cools down the
molecules to temperatures representative of these environments.
COSmIC integrates a variety of state-of-the-art instruments to allow
scientists to recreate space conditions in the laboratory to form, process and
monitor simulated planetary and interstellar materials. The chamber is the heart
of the system. It recreates the extreme conditions that reign in space where
interstellar molecules and ions float in a vacuum at densities that are
billionths of Earth's atmosphere, average temperatures can be less than -270
degrees Fahrenheit (about 100 degrees Kelvin), and the environment is bathed in
ultraviolet and visible radiation emanating from nearby stars.
"By using COSmIC and building up on the work we recently published in the
Astrophysical Journal August 29, 2013, we now can for the first time truly
recreate and visualize in the laboratory the formation of carbon grains in the
envelope of stars and learn about the formation, structure and size distribution
of stellar dust grains," said Cesar Contreras of the Bay Area Environmental
Research (BAER) Institute and a research fellow at Ames. "This type of new
research truly pushes the frontiers of science toward new horizons, and
illustrates NASA's important contribution to science."
The team started with small hydrocarbon molecules that it expanded in the
cold jet spray in COSmIC and exposed to high energy in an electric discharge.
They detected and characterized the large molecules that are formed in the gas
phase from these precursor molecules with highly sensitive detectors, then
collected the individual solid grains formed from these complex molecules and
imaged them using Ames' Scanning Electron Microscope (SEM).
"During COSmIC experiments, we are able to form and detect nanoparticles on
the order of 10 nm size, grains ranging from 100-500 nanometers and aggregates
of grains up to 1.5 micrometers in diameter, about a tenth the width of a human
hair, and observe their structure with SEM, thus sampling a large size
distribution of the grains produced," said Ella Sciamma-O'Brien, of the BAER
Institute and a research fellow at Ames.
These results have important implications and ramifications not only for
interstellar astrophysics, but also for planetary science. For example, they can
provide new clues on the type of grains present in the dust around stars. That
in turn, will help us understand the formation of planets, including Earth-like
planets. They also will help interpret astronomical data from the Herschel Space
Observatory, the Stratospheric Observatory for Infrared Astronomy (SOFIA) and
the ground-based Atacama Large Millimeter/submillimeter Array observatory in
Chile.
"Today we are celebrating a major milestone in our understanding of the
formation and the nature of cosmic dust grains that bears important implications
in this new era of exoplanets discoveries," concluded Salama.
This work is funded through the Laboratory Astrophysics Carbon-in-the-Galaxy
consortium program, an element of the Astrophysics Division's Astrophysics
Research and Analysis program in NASA's Science Mission Directorate at NASA
Headquarters in Washington and is supported by Ames' Advanced Studies
Laboratories, a partnership between Ames and the University of California in
Santa Cruz.
For more information about COSmIC, visit:
For more information about Ames, visit:
NASA
Guillermo Gonzalo Sánchez Achutegui
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