Feature: Spitzer's Eyes Perfect for Spotting Diamonds in the Sky

Feature Feb. 26, 2008

Spitzer's Eyes Perfect for Spotting Diamonds in the Sky

Diamonds may be rare on Earth, but surprisingly common in space -- and the
super-sensitive infrared eyes of NASA's Spitzer Space Telescope are perfect for
scouting them, say scientists at the NASA Ames Research Center in Moffett
Field, Calif.

Using computer simulations, researchers have developed a strategy for finding
diamonds in space that are only a nanometer (a billionth of a meter) in size. These
gems are about 25,000 times smaller than a grain of sand, much too small for an
engagement ring. But astronomers believe that these tiny particles could provide
valuable insights into how carbon-rich molecules, the basis of life on Earth,
develop in the cosmos.

Scientists began to seriously ponder the presence of diamonds in space in the
l980s, when studies of meteorites that crashed into Earth revealed lots of tiny
nanometer-sized diamonds. Astronomers determined that 3 percent of all carbon
found in meteorites came in the form of nanodiamonds. If meteorites are a
reflection of the dust content in outer space, calculations show that just a gram of
dust and gas in a cosmic cloud could contain as many as 10,000 trillion
nanodiamonds.

"The question that we always get asked is, if nanodiamonds are abundant in
space, why haven't we seen them more often?" says Charles Bauschlicher of
Ames Research Center. They have only been spotted twice. "The truth is, we just
didn't know enough about their infrared and electronic properties to detect their
fingerprint."

To solve this dilemma, Bauschlicher and his research team used computer
software to simulate conditions of the interstellar medium--the space between
stars--filled with nanodiamonds. They found that these space diamonds shine
brightly at infrared light ranges of 3.4 to 3.5 microns and 6 to 10 microns, where
Spitzer is especially sensitive.

Astronomers should be able to see celestial diamonds by looking for their unique
"infrared fingerprints." When light from a nearby star zaps a molecule, its bonds
stretch, twist and flex, giving off a distinctive color of infrared light. Like a prism
breaking white light into a rainbow, Spitzer's infrared spectrometer instrument
breaks up infrared light into its component parts, allowing scientists to see the
light signature of each individual molecule.

Team members suspect that more diamonds haven't been spotted in space yet
because astronomers have not been looking in the right places with the right
instruments. Diamonds are made of tightly bound carbon atoms, so it takes a lot
of high-energy ultraviolet light to cause the diamond bonds to bend and move,
producing an infrared fingerprint. Thus, the scientists concluded that the best
place to see a space diamond's signature shine is right next to a hot star.

Once astronomers figure out where to look for nanodiamonds, another mystery is
figuring out how they form in the environment of interstellar space.

"Space diamonds are formed under very different conditions than diamonds are
formed on Earth," says Louis Allamandola, also of Ames.

He notes that diamonds on Earth form under immense pressure, deep inside the
planet, where temperatures are also very high. However, space diamonds are
found in cold molecular clouds where pressures are billions of times lower and
temperatures are below minus 240 degrees Celsius (minus 400 degrees
Fahrenheit).

"Now that we know where to look for glowing nanodiamonds, infrared telescopes
like Spitzer can help us learn more about their life in space," says Allamandola.

Bauschlicher's paper on this topic has been accepted for publication in
Astrophysical Journal. Allamandola was a co-author on the paper, along with
Yufei Liu, Alessandra Ricca, and Andrew L. Mattioda, also of Ames.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space
Telescope mission for NASA's Science Mission Directorate, Washington. Science
operations are conducted at the Spitzer Science Center at the California Institute
of Technology, also in Pasadena. Caltech manages JPL for NASA.

For more information about Spitzer, visit http://www.spitzer.caltech.edu/spitzer

and http://www.nasa.gov/spitzer .

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