Splashy Portrait Helps Explain How Stars Form

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Whitney Clavin 818-354-4673
Jet Propulsion Laboratory
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Image Advisory: 2008-188 Oct. 8, 2008

Splashy Portrait Helps Explain How Stars Form

Different wavelengths of light swirl together like watercolors in a new, ethereal portrait of a
bright, star-forming region.

The multi-wavelength picture combines infrared, visible and X-ray light from NASA's Spitzer
Space Telescope, the European Southern Observatory's New Technology Telescope, and the
European Space Agency's XMM-Newton orbiting X-Ray telescope, respectively.

The colorful image offers a fresh look at the history of the star-studded region, called NGC
346, revealing new information about how stars form in the universe. NGC 346 is the brightest
star-forming region in the Small Magellanic Cloud, a so-called irregular dwarf galaxy that orbits
our Milky Way galaxy, 210,000 light-years away.

"NGC 346 is an astronomical zoo," said Dimitrios Gouliermis of the Max Planck Institute for
Astronomy in Germany, lead author of a new paper describing the observations in an upcoming
issue of the Astrophysical Journal. "When we combined data at various wavelengths, we were
able to tease apart what's going on in different parts of the cloud."

The new picture is available online at:
http://www.nasa.gov/mission_pages/spitzer/multimedia/20081008.html .

Small stars are scattered throughout the NGC 346 region, while massive stars populate its
center. The massive stars and most of the small stars formed at the same time out of one dense
cloud, while other small stars were created later through a process called triggered star
formation. Intense radiation from massive stars ate away at the surrounding dusty cloud,
triggering gas to expand and create shock waves that compressed nearby cold dust and gas into
new stars. The red-orange filaments surrounding the center of the image show where this
process has occurred.

But a set of even younger small stars in the region, seen as a pinkish blob at the top of the
image, couldn't be explained by this mechanism. Scientists were scratching their heads over
what caused this seemingly isolated group of stars to form.

By combining multi-wavelength data of NGC 346, Gouliermis says he and his team were able
to pinpoint the trigger as a very massive star that blasted apart in a supernova explosion about
50,000 years ago. According to the astronomers, this very massive star spurred the isolated
young stars into existence before it died, but through a different type of triggered star formation
than that which occurred near the center of the region. Fierce winds from the massive star, and
not radiation, pushed dust and gas together, compressing it into new stars.

The finding demonstrates that both wind- and radiation-induced triggered star formation are at
play in the same cloud. According to Gouliermis, "The result shows us that star formation is a far
more complicated process than we used to believe, comprising different competitive or
collaborative mechanisms."

The new image also reveals a bubble, seen as a blue halo to the left, caused by the supernova
explosion that happened 50,000 years ago. Further analysis shows that this bubble is located
within a large expanding gaseous shell, possibly powered by the explosion and the winds of
other bright stars in its vicinity.

Infrared light (red) shows cold dust; visible light (green) denotes glowing gas; and X-rays (blue)
represent very warm gas. Ordinary stars appear as blue spots with white centers, while young
stars enshrouded in dust appear as red spots with white centers.

Other authors of this paper include Thomas Henning and Wolfgang Brandner of the Max Planck
Institute for Astronomy, and You-Hua Chu and Robert Gruendl of the University of Illinois at
Urbana-Champaign.

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.

More information about Spitzer is at http://www.spitzer.caltech.edu/spitzer and
http://www.nasa.gov/spitzer .

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