Stellar Birth in the Galactic Wilderness
A new image from NASA's Galaxy Evolution Explorer shows baby stars sprouting
in the backwoods of a galaxy -- a relatively desolate region of space more
than 100,000 light-years from the galaxy's bustling center.
The striking image, a composite of ultraviolet data from the Galaxy Evolution
Explorer and radio data from the National Science Foundation's Very Large Array
in New Mexico, shows the Southern Pinwheel galaxy, also known simply as M83.
In the new view, the main spiral, or stellar, disk of M83 looks like a pink and
blue pinwheel, while its outer arms appear to flap away from the galaxy like giant
red streamers. It is within these so-called extended galaxy arms that, to the
surprise of astronomers, new stars are forming.
"It is absolutely stunning that we find such an enormous number of young stars up
to 140,000 light-years away from the center of M83," said Frank Bigiel of the Max
Planck Institute for Astronomy in Germany, lead investigator of the new Galaxy
Evolution Explorer observations. For comparison, the diameter of M83 is only
40,000 light-years across.
The new image is online at http://www.nasa.gov/mission_pages/galex/20080416.html
Some of the "outback" stars in M83's extended arms were first spotted by the Galaxy
Evolution Explorer in 2005. Remote stars were also discovered around other galaxies
by the ultraviolet telescope over subsequent years. This came as a surprise to
astronomers because the outlying regions of a galaxy are assumed to be relatively
barren and lack high concentrations of the ingredients needed for stars to form.
The newest Galaxy Evolution Explorer observations of M83 (colored blue and green)
were taken over a longer period of time and reveal many more young clusters of stars
at the farthest reaches of the galaxy. To better understand how stars could form in
such unexpected territory, Bigiel and his colleagues turned to radio observations
from the Very Large Array (red). Light emitted in the radio portion of the electromagnetic
spectrum can be used to locate gaseous hydrogen atoms, or raw ingredients of stars. When
the astronomers combined the radio and Galaxy Evolution Explorer data, they were
delighted to see they matched up.
"The degree to which the ultraviolet emission and therefore the distribution of young
stars follows the distribution of the atomic hydrogen gas out to the largest distances
is absolutely remarkable," said Fabian Walter, also of the Max Planck Institute for Astronomy,
who led the radio observations of hydrogen in the galaxy.
The astronomers speculate that the young stars seen far out in M83 could have formed under
conditions resembling those of the early universe, a time when space was not yet enriched
with dust and heavier elements.
"Even with today's most powerful telescopes, it is extremely difficult to study the first
generation of star formation. These new observations provide a unique opportunity to
study how early generation stars might have formed," said co-investigator Mark Seibert
of the Observatories of the Carnegie Institution of Washington in Pasadena.
M83 is located 15 million light-years away in the southern constellation Hydra.
Other investigators include: Barry Madore of The Observatories of the Carnegie Institution
of Washington; Armando Gil de Paz of the Complutense University of Madrid, Spain; David
Thilker of Johns Hopkins University, Baltimore; Elias Brinks of the University of
Hertfordshire, England; and Erwin de Blok of the University of Cape Town, South Africa.
The California Institute of Technology in Pasadena leads the Galaxy Evolution Explorer
mission and is responsible for science operations and data analysis. NASA's Jet Propulsion
Laboratory, also in Pasadena, manages the mission and built the science instrument.
Caltech manages JPL for NASA. The mission was developed under NASA's Explorers Program
managed by NASA's Goddard Space Flight Center, Greenbelt, Md. Researchers sponsored by
Yonsei University in South Korea and the Centre National d'Etudes Spatiales (CNES) in
France collaborated on this mission.
The Very Large Array is part of the National Radio Astronomy Observatory, a facility
of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.
Additional information about the Galaxy Evolution Explorer is online at
Media contact: Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.