Bow shocks thought to mark the paths of massive, speeding stars are
highlighted in these images from NASA's Spitzer Space Telescope and
Wide-field Infrared Survey Explorer, or WISE. Image Credit:
NASA/JPL-Caltech/University of Wyoming. › Full image and caption
Astronomers are finding dozens of the fastest stars in our galaxy
with the help of images from NASA's Spitzer Space Telescope and
Wide-field Infrared Survey Explorer, or WISE.
When some speedy, massive stars plow through space, they can cause
material to stack up in front of them in the same way that water piles
up ahead of a ship. Called bow shocks, these dramatic, arc-shaped
features in space are leading researchers to uncover massive, so-called
runaway stars.
"Some stars get the boot when their companion star explodes in a
supernova, and others can get kicked out of crowded star clusters," said
astronomer William Chick from the University of Wyoming in Laramie, who
presented his team's new results at the American Astronomical Society
meeting in Kissimmee, Florida. "The gravitational boost increases a
star's speed relative to other stars."
Our own sun is strolling through our Milky Way galaxy at a moderate
pace. It is not clear whether our sun creates a bow shock. By
comparison, a massive star with a stunning bow shock, called Zeta
Ophiuchi (or Zeta Oph), is traveling around the galaxy faster than our
sun, at 54,000 mph (24 kilometers per second) relative to its
surroundings. Zeta Oph's giant bow shock can be seen in this image from
the WISE mission: http://www.nasa.gov/mission_pages/WISE/multimedia/gallery/pia13455.html
Both the speed of stars moving through space and their mass
contribute to the size and shapes of bow shocks. The more massive a
star, the more material it sheds in high-speed winds. Zeta Oph, which is
about 20 times as massive as our sun, has supersonic winds that slam
into the material in front of it.
The result is a pile-up of material that glows. The arc-shaped
material heats up and shines with infrared light. That infrared light is
assigned the color red in the many pictures of bow shocks captured by
Spitzer and WISE.
Chick and his team turned to archival infrared data from Spitzer and
WISE to identify new bow shocks, including more distant ones that are
harder to find. Their initial search turned up more than 200 images of
fuzzy red arcs. They then used the Wyoming Infrared Observatory, near
Laramie, to follow up on 80 of these candidates and identify the sources
behind the suspected bow shocks. Most turned out to be massive stars.
The findings suggest that many of the bow shocks are the result of
speedy runaways that were given a gravitational kick by other stars.
However, in a few cases, the arc-shaped features could turn out to be
something else, such as dust from stars and birth clouds of newborn
stars. The team plans more observations to confirm the presence of bow
shocks.
"We are using the bow shocks to find massive and/or runaway stars,"
said astronomer Henry "Chip" Kobulnicky, also from the University of
Wyoming. "The bow shocks are new laboratories for studying massive stars
and answering questions about the fate and evolution of these stars."
Another group of researchers, led by Cintia Peri of the Argentine
Institute of Radio Astronomy, is also using Spitzer and WISE data to
find new bow shocks in space. Only instead of searching for the arcs at
the onset, they start by hunting down known speedy stars, and then they
scan them for bow shocks.
"WISE and Spitzer have given us the best images of bow shocks so
far," said Peri. "In many cases, bow shocks that looked very diffuse
before, can now be resolved, and, moreover, we can see some new details
of the structures."
Some of the first bow shocks from runaway stars were identified in
the 1980s by David Van Buren of NASA's Jet Propulsion Laboratory in
Pasadena, California. He and his colleagues found them using infrared
data from the Infrared Astronomical Satellite (IRAS), a predecessor to
WISE that scanned the whole infrared sky in 1983.
Kobulnicky and Chick belong to a larger team of researchers and
students studying bow shocks and massive stars, including Matt Povich
from the California State Polytechnic University, Pomona. The National
Science Foundation funds their research.
Images from Spitzer, WISE and IRAS are archived at the NASA Infrared
Science Archive housed at the Infrared Processing and Analysis Center at
the California Institute of Technology in Pasadena. Caltech manages JPL
for NASA.
More information about Spitzer is online at: http://www.nasa.gov/spitzer - http://spitzer.caltech.edu
More information about WISE is at: http://www.nasa.gov/wise
Media Contact
Whitney Clavin
Jet Propulsion Laboratory, Pasadena, California
818-354-4673
whitney.clavin@jpl.nasa.gov
