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Astronomers have found some of the youngest
stars ever seen thanks to the Herschel space observatory, a European
Space Agency mission with important NASA contributions. Dense envelopes
of gas and dust surround the fledging stars known as protostars, making
their detection difficult until now. The discovery gives scientists a
window into the earliest and least understood phases of star formation.
Image credit: NASA/ESA/ESO/JPL-Caltech/Max-Planck Institute for
Astronomy.› Full image and caption
PASADENA, Calif. - Astronomers have found some of the youngest stars
ever seen, thanks to the Herschel space observatory, a European Space
Agency mission with important NASA contributions.
Observations from NASA's Spitzer Space Telescope and the Atacama
Pathfinder Experiment (APEX) telescope in Chile, a collaboration
involving the Max Planck Institute for Radio Astronomy in Germany, the
Onsala Space Observatory in Sweden, and the European Southern
Observatory in Germany, contributed to the findings.
Dense envelopes of gas and dust surround the fledging stars known as
protostars, making their detection difficult. The 15 newly observed
protostars turned up by surprise in a survey of the biggest site of star
formation near our solar system, located in the constellation Orion.
The discovery gives scientists a peek into one of the earliest and least
understood phases of star formation.
"Herschel has revealed the largest ensemble of such young stars in a
single star-forming region," said Amelia Stutz, lead author of a paper
to be published in The Astrophysical Journal and a postdoctoral
researcher at the Max Planck Institute for Astronomy in Heidelberg,
Germany. "With these results, we are getting closer to witnessing the
moment when a star begins to form."
Stars spring to life from the gravitational collapse of massive clouds
of gas and dust. This changeover from stray, cool gas to the ball of
super-hot plasma we call a star is relatively quick by cosmic standards,
lasting only a few hundred thousand years. Finding protostars in their
earliest, most short-lived and dimmest stages poses a challenge.
Astronomers long had investigated the stellar nursery in the Orion
Molecular Cloud Complex, a vast collection of star-forming clouds, but
had not seen the newly identified protostars until Herschel observed the
"Previous studies have missed the densest, youngest and potentially most
extreme and cold protostars in Orion," Stutz said. "These sources may
be able to help us better understand how the process of star formation
proceeds at the very earliest stages, when most of the stellar mass is
built up and physical conditions are hardest to observe."
Herschel spied the protostars in far-infrared, or long-wavelength,
light, which can shine through the dense clouds around burgeoning stars
that block out higher-energy, shorter wavelengths, including the light
our eyes see.
The Herschel Photodetector Array Camera and Spectrometer (PACS)
instrument collected infrared light at 70 and 160 micrometers in
wavelength, comparable to the width of a human hair. Researchers
compared these observations to previous scans of the star-forming
regions in Orion taken by Spitzer. Extremely young protostars identified
in the Herschel views but too cold to be picked up in most of the
Spitzer data were further verified with radio wave observations from the
APEX ground telescope.
"Our observations provide a first glimpse at protostars that have just
begun to 'glow' at far-infrared wavelengths," said paper coauthor Elise
Furlan, a postdoctoral research associate at the National Optical
Astronomy Observatory in Tucson, Ariz.
Of the 15 newly discovered protostars, 11 possess very red colors,
meaning their light output trends toward the low-energy end of the
electromagnetic spectrum. This output indicates the stars are still
embedded deeply in a gaseous envelope, meaning they are very young. An
additional seven protostars previously seen by Spitzer share this
characteristic. Together, these 18 budding stars comprise only five
percent of the protostars and candidate protostars observed in Orion.
That figure implies the very youngest stars spend perhaps 25,000 years
in this phase of their development, a mere blink of an eye considering a
star like our sun lives for about 10 billion years.
Researchers hope to document chronologically each stage of a star's
development rather like a family album, from before birth to early
infancy, when planets also take shape.
"With these recent findings, we add an important missing photo to the
family album of stellar development," said Glenn Wahlgren, Herschel
Program Scientist at NASA Headquarters in Washington. "Herschel has
allowed us to study stars in their infancy."
Herschel is a European Space Agency mission, with science instruments
provided by a consortia of European institutes with important
participation by NASA. NASA's Herschel Project Office is based at the
agency's Jet Propulsion Laboratory in Pasadena, Calif. JPL is a division
of the California Institute of Technology, Pasadena.