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Astronomers Unveiling Life's Cosmic Origins

The Cosmic Chemistry Cycle. (Credit: Bill Saxton, NRAO/AUI/NSF)

ScienceDaily (Feb. 13, 2009) — Processes that laid the foundation for life on 
Earth -- star and planet formation and the production of complex organic 
molecules in interstellar space -- are yielding their secrets to astronomers 
armed with powerful new research tools, and even better tools soon will be 

Astronomers described three important developments at a symposium on the 
"Cosmic Cradle of Life" at the annual meeting of the American Association for 
the Advancement of Science in Chicago, IL.

In one development, a team of astrochemists released a major new resource for 
seeking complex interstellar molecules that are the precursors to life. The 
chemical data released by Anthony Remijan of the National Radio Astronomy 
Observatory (NRAO) and his university colleagues is part of the Prebiotic 
Interstellar Molecule Survey, or PRIMOS, a project studying a star-forming 
region near the center of our Milky Way Galaxy.

PRIMOS is an effort of the National Science Foundation's Center for Chemistry 
of the Universe, started at the University of Virginia (UVa) in October 2008, 
and led by UVa Professor Brooks H. Pate. The data, produced by the NSF's Robert 
C. Byrd Green Bank Telescope (GBT) in West Virginia, came from more than 45 
individual observations totalling more than nine GigaBytes of data and over 1.4 
million individual frequency channels.

Scientists can search the GBT data for specific radio frequencies, called 
spectral lines -- telltale "fingerprints" -- naturally emitted by molecules in 
interstellar space. "We've identified more than 720 spectral lines in this 
collection, and about 240 of those are from unknown molecules," Remijan said. 
He added, "We're making available to all scientists the best collection of data 
below 50 GHz ever produced for the study of interstellar chemistry," Remijan 

Astronomers have already identified more than 150 molecules in interstellar 
space in the past 40 years, including complex organic compounds such as sugars 
and alcohols. "This is a major change in how we search for molecules in space," 
Remijan explained. "Before, people decided beforehand which molecules they were 
looking for, then searched in a very narrow band of radio frequencies emitted 
by those molecules. In this GBT survey, we've observed a wide range of 
frequencies, collected the data and immediately made it publicly available. 
Scientists anywhere can 'mine' this resource to find new molecules," he said.

Another key development, presented by Crystal Brogan of the NRAO, showed that 
highly-detailed images of "protoclusters" of massive young stars reveal a 
complex mix of stars in different stages of formation, complicated gas motions, 
and numerous chemical clues to the physical conditions in such stellar 
nurseries. "We saw a much more complex picture than we had expected and now 
have new questions to answer," she said.

Using the Smithsonian Astrophysical Observatory's Submillimeter Array (SMA) in 
Hawaii, Brogan and her colleagues studied a nebula 5,500 light-years from Earth 
in the constellation Scorpius where stars significantly more massive than our 
Sun are forming. "It's essential to understand what's going on in systems like 
this because most stars, Sun-like stars included, form in clusters," Brogan 

"The most massive stars in the cluster have a tremendous impact on the 
formation and environment of the rest of the cluster, including the 
less-massive stars and their planets," Brogan said, adding that "if we want to 
understand how solar systems that could support life form and evolve, we need 
to know how these giant stars affect their environment."

Also, Brogan said, the massive young stars are surrounded by "hot cores" that 
include copious organic material that later may be spewed into interstellar 
space by stellar winds and other processes. This can help "seed" star-forming 
regions with some of the chemicals found by the GBT and other telescopes.

Narrowing in on the problem of how planets form around young stars, David 
Wilner of the Harvard-Smithsonian Center for Astrophysics presented 
observations with the SMA that revealed new details of solar systems in the 
earliest stages of their formation. Wilner and his colleagues studied nine 
dusty disks surrounding young stars in a region in the constellation Ophiuchus.

"These are the most detailed images of such disks made at these wavelengths," 
Wilner said. The images show the distribution of material on the same size 
scale as our own Solar System, and indicate that these disks are capable of 
producing planetary systems. Two of the disks show large central cavities where 
young planets may already have swept out the material from their neighborhoods.

"Before, we knew that such disks have enough material to form solar systems. 
These new images tell us that material is in the right places to form solar 
systems. We're getting a tantalizing peek at the very earliest stages of planet 
formation," said Sean Andrews, a Hubble Fellow at the CfA.

All three areas of study are poised for major advances with the impending 
arrival of powerful new radio-telescope facilities such as the Atacama Large 
Millimeter/submillimeter Array (ALMA) and the Expanded Very Large Array (EVLA), 
and new capabilities for the GBT.

Studies of protoplanetary disks and young solar systems will benefit greatly 
from the groundbreaking new capabilities of ALMA, Wilner said. "While we've 
been able to study a few of these objects so far, ALMA will be able to give us 
highly-detailed images of many more that we can't study today," he said. Wilner 
added that ALMA also will likely provide new information on the chemicals in 
those still-forming planetary systems.

The complex motions and chemistry of Brogan's protoclusters of young, massive 
stars, also will become much clearer with ALMA. "Both the detail of the images 
and the ability to find molecular spectral lines will improve by a factor of at 
least 25 with ALMA," she said. In addition, the increased power of the EVLA 
will give astronomers a far better look into the inner regions of the disks 
around young stars -- regions obscured to telescopes operating at shorter 

"We know that complex chemicals exist in interstellar space before stars and 
planets form. With the new research tools coming in the next few years, we're 
on the verge of learning how the chemistry of the interstellar clouds, the 
young stars and their environments, and the disks from which planets are formed 
is all linked together to provide the chemical basis for life on those 
planets," Remijan explained.

Astrophysicist Neil deGrasse Tyson of the American Museum of Natural History 
noted, "Like no other science, astrophysics cross-pollinates the expertise of 
chemists, biologists, geologists and physicists, all to discover the past, 
present, and future of the cosmos -- and our humble place within it."
Adapted from materials provided by National Radio Astronomy Observatory.
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