March 20, 2013
Europe’s Herschel Space Observatory Has Detected Some Very Young Stars
April Flowers for redOrbit.com - Your Universe Online
Herschel's observations were used in conjunction with contributing 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 (MPIFR) in Germany, the Onsala Space Observatory (OSO) in Sweden, and the European Southern Observatory (ESO) in Germany.
The fledgling stars, known as protostars, are surrounded by dense envelopes of gas and dust. These clouds make detection of the protostars difficult. The scientists were surprised to find the 15 new protostars, discovered during a survey of the biggest site of star formation near our Solar System, located in the constellation Orion. The newly discovered stars give scientists a peek into 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, a postdoctoral researcher at MPIFR, in a statement. "With these results, we are getting closer to witnessing the moment when a star begins to form."
The gravitational collapse of massive clouds of gas and dust bring stars to life. This transition from stray, cool gas to the ball of super-hot plasma known as a star is a relatively quick one by cosmic standards, lasting only a few hundred thousand years. Until now, finding protostars in their earliest, most short-lived and dimmest stages posed a challenge for astronomers.
The stellar nursery in the Orion Molecular Cloud Complex is a vast collection of star-forming clouds. Astronomers investigated this formation for a long time in the past, but until Herschel observed the region they had not yet seen the newly identified protostars.
"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."
The protostars were observed by Herschel in far-infrared, or long-wavelength, light. Far-infrared can shine through the dense clouds around burgeoning stars that block out higher-energy, shorter wavelength light. This includes the light our eyes can process.
The Herschel Photodetector Array Camera and Spectrometer (PACS) collected infrared light at 70 and 160 micrometers in wavelength, comparable to the width of a human hair. The research team compared these observations to scans of the star-forming regions in Orion taken previously by NASA's Spitzer. The protostars were too cold to be picked up in most of the Spitzer data, but 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 Elise Furlan, a postdoctoral research associate at the National Optical Astronomy Observatory (NOAO) in Tucson, Ariz.
Eleven of the new stars possess very red colors, meaning their light output trends toward the low-energy end of the electromagnetic spectrum. This indicates that the stars are still embedded deeply in a gaseous envelope and that they are very young. Spitzer has observed an additional seven protostars that share this characteristic. These 18 "infant" stars, taken together, represent only five percent of the protostars and candidate protostars observed in Orion, implying that the very youngest stars spend perhaps 25,000 years in this phase of their development. This is a mere blink of an eye in cosmic terms, considering that a star such as our own lives for about 10 billion years.
Researchers hope to create a "family album" from before birth to early infancy, chronologically documenting each stage of a star's development.
"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."