Census Finds Unknown Young Stars of Orion

Amateur stargazers may spot the Orion Nebula as a fuzzy patch in the constellation Orion, but they cannot see an interstellar birthing ground that spans the region of sky from above Orion's head to below his feet.

Now astronomers have completed the most wide-ranging census of baby stars in and around the Orion nebula, and found a stellar nursery that's both chaotic and crowded. The work represents the first complete study of young stars, their gaseous clouds of dust and supersonic jets of hydrogen molecules shooting out from the poles of each star.

Jets arise as young stars are born from a rotating cloud of gas and dust, but usually die out once a star has fully ignited and stopped consuming the surrounding material. In this case, the jets became signals that pinpointed the location of baby stars hidden within the stellar birthing grounds.

"With such a large number of young stars, we can study the 'demographics' of star birth," said Tom Megeath, an astronomer at the University of Toledo in Ohio. "This study will give us an idea of how long it takes baby stars to bulk up by pulling in gas from the surrounding cloud, what ultimately stops a star from growing bigger, and how a star's birth is influenced by other stars in the stellar nursery."

The Orion nebula represents just a blister on the surface of the much larger cloud. Astronomers turned to the United Kingdom Infra-Red Telescope (UKIRT) and the Spitzer Space Telescope to peer through the cloud using infrared vision, and also used the Institut de Radio Astronomie Millimetrique radio telescope in France to see beyond infrared at short radio wavelengths.

Such international collaboration allowed astronomers to match up powerful gas jets with their young star origins, and find the cradles within the clouds where stars were created.

"Each jet is travelling at tens or even hundreds of miles per second; the jets extend across many trillions of miles of interstellar space," said Chris Davis, an astronomer for UKIRT in Hawaii.

UKIRT's wide field camera alone found more than 110 individual jets from the one region of the Milky Way. The results were presented on April 20 at the European Week of Astronomy and Space Science at the University of Hertfordshire, UK.

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