Astronomers are reporting that they have glimpsed what could be the youngest known star at the moment of its birth.
Not yet developed into a true star, the object has just begun pulling in matter from a surrounding envelope of gas and dust, according to a new study that appears in the current issue of The Astrophysical Journal.
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A star-forming region similar to the one where astronomers say they have found a star in its earliest stages of formation. The region pictured above is known as the Orion-KL region. (Photo: NASA, ESA)
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The authors found the object using the Spitzer Space Telescope and the Submillimeter Array telescope in Hawaii. It lies in the Perseus star-forming region, about 800 light years away within our Milky Way galaxy. (A light-year is the distance light travels in a year).
Stars form out of large, cold, dense regions of gas and dust called molecular clouds, which pepper the galaxy.
Astronomers think the newfound object is in between its prestellar phase, when a particularly dense region of a molecular cloud first begins to clump together, and the protostar phase, when gravity has pulled enough material together to form a dense, hot core out of the surrounding envelope.
“It’s very difficult to detect objects in this phase of star formation, because they are very short-lived and they emit very little light,” said Xuepeng Chen, a postdoctoral associate at Yale University and lead author of the paper. The team detected the faint light emitted by the dust surrounding the object.
Most protostars are between one to 10 times as luminous as the Sun, with large dust envelopes that glow in infrared light, a low-energy form of light not visible to the unaided eye.
Because the new object, dubbed L1448-IRS2E, is less than one tenth as luminous as the Sun, the astronomers believe it’s too dim to be a true protostar. Yet they also found it’s ejecting streams of high-speed gas from its center, confirming, they said, that some sort of preliminary mass has formed and the object is beyond its prestellar phase. This kind of outflow is seen in protostars as a result of the magnetic field surrounding the forming star, but has not been seen at such an early stage until now.
The team hopes to use the new Herschel space telescope, launched last May, to look for more of these objects caught between the earliest stages of star formation so they can better understand how stars grow and evolve. “Stars are defined by their mass, but we still don’t know at what stage of the formation process a star acquires most of its mass,” said Yale’s Héctor Arce, another author of the paper. “This is one of the big questions driving our work.”
The research group also includes astronomers from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. and the Max Planck Institute for Astronomy in Heidelberg, Germany.
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