April 16, 2013
J.D. Harrington
Headquarters, Washington
202-358-5241
j.d.harrington@nasa.gov
Nicholas A. Veronico
SOFIA Science Center
Ames Research Center, Moffett Field, Calif.
650-604-4589 / 650-483-6902
nveronico@sofia.usra.edu
RELEASE: 13-099
SOFIA OBSERVATIONS REVEAL A SURPRISE IN MASSIVE STAR FORMATION
WASHINGTON -- Researchers using the airborne Stratospheric Observatory
for Infrared Astronomy (SOFIA) have captured the most detailed
mid-infrared images yet of a massive star condensing within a dense
cocoon of dust and gas.
The star is G35.20-0.74, commonly known as G35. It is one of the most
massive known protostars and is located relatively close to Earth at
a distance of 8,000 light-years.
Until now, scientists expected the formation process of massive stars
would be complicated by the turbulent, chaotic environments in the
centers of new star clusters where they form. But observations of G35
suggest this giant star, more than 20 times the mass of our sun, is
forming by the same orderly process as do stars with the same mass as
the sun. Stars most like the sun are understood to form by simple,
symmetric collapse of interstellar clouds.
"The focus of our study has been to determine how massive stars
actually form," said Yichen Zhang of the University of Florida. Zhang
is lead author of a paper about the discovery published April 10 in
the Astrophysical Journal. "We thought the G35 protostar's structure
would be quite complicated, but instead we found it is simple, like
the cocoons of protostars with the sun's mass."
The observations of G35 were made in 2011 with a special camera aboard
SOFIA, a modified Boeing 747SP aircraft that can carry a telescope
with an effective diameter of 100 inches (2.5 meters) to altitudes as
high as 45,000 feet (13,700 meters).
G35 was an ideal target for investigations because it is in an early
stage of development. But infrared light coming from G35 is so strong
it prevented infrared space telescopes from making detailed images.
Also, the protostar is embedded so deeply in its natal cloud that it
cannot be detected by optical telescopes observing from the ground at
visible wavelengths.
Flying high above the light-blocking water vapor in Earth's
atmosphere, the airplane-mounted Faint Object Infrared Camera for the
SOFIA Telescope (FORCAST) enabled astronomers to see G35 where it
hides -- inside a dark, dense, interstellar dust cloud -- by
collecting infrared light escaping the cloud. Uniquely suited for
this work, FORCAST detected faint details next to bright structures
at wavelengths inaccessible to any other telescope on the ground or
in space.
"Massive stars, although rare, are important because there is evidence
they foster the formation of smaller stars like our sun, and because
at the ends of their lives they create and distribute chemical
elements that are the basic building blocks of Earth-like planets,"
said co-author James De Buizer, a SOFIA staff scientist with the
Universities Space Research Association (USRA) at NASA's Ames
Research Center in Moffett Field, Calif.
Images of G35 may be viewed on NASA's SOFIA site:
http://www.nasa.gov/sofia
Figures 1a and 1b show FORCAST images of G35 at wavelengths of 31 and
37 microns. Figures 2a and 2b respectively present G35 images
obtained by NASA's Spitzer Space Telescope and the Gemini-North
telescope at Mauna Kea, Hawaii, also used in this study. Figure 3
shows computer model images intended to match characteristics of the
central regions of the images in figures 1a and 1b.
The model images show greatly simplified versions of what is revealed
especially in the SOFIA images: a luminous protostar heating a dense
interstellar cloud from the inside while simultaneously expelling
cone-shaped jets of gas toward the tops and bottoms of the frames.
The top outflow cone appears brighter because it is directed toward
us and there is less obscuring material along the line of sight.
The high resolution of the images showcases the capability of modern
infrared detector arrays when used on an airborne platform and gives
scientists hope that data gathered in this way substantially will
advance their understanding of the Milky Way galaxy.
FORCAST was built by a team led by Terry Herter of Cornell University
in Ithica, N.Y. Co-authors of the Astrophysics Journal paper include
scientists from the University of Florida in Gainesville; University
of Wisconsin in Madison; University of California at Berkeley;
Louisiana State University in Baton Rouge; the Arcetri Observatory in
Florence, Italy; and the USRA SOFIA science staff at Ames.
SOFIA is a joint project of NASA and the German Aerospace Center.
SOFIA is based and managed at NASA's Dryden Aircraft Operations
Facility in Palmdale, Calif. NASA's Ames Research Center in Moffett
Field, Calif., manages the SOFIA science and mission operations in
cooperation with the Universities Space Research Association (USRA)
headquartered in Columbia, Md., and the German SOFIA Institute at the
University of Stuttgart.
For links to USRA and the German SOFIA Institute, visit NASA's SOFIA
site and click on "SOFIA Science Center."
-end-
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