The Herschel Space Observatory has made an unexpected discovery: a gaping hole in the clouds surrounding a batch of young stars. The hole has provided astronomers with a surprising glimpse into the end of the star-forming process.
Stars are born hidden in dense clouds of dust and gas, which can now be studied in remarkable detail with Herschel, a European Space Agency mission with important NASA participation. Although jets and winds of gas have been seen streaming from young stars in the past, it has always been a mystery exactly how a star uses the jets to blow away its surroundings and emerge from its birth cloud. For the first time, Herschel may be seeing an unexpected step in this process.
A cloud of bright reflective gas known to astronomers as NGC 1999 sits next to a black patch of sky. For most of the 20th century, such black patches were known to be dense clouds of dust and gas that block light from passing through.
When Herschel looked in its direction to study nearby young stars, astronomers were surprised to see the cloud continued to look black, which shouldn't have been the case. Herschel's infrared eyes are designed to see into such clouds. Either the cloud was immensely dense or something was wrong.
Investigating further using ground-based telescopes, astronomers found the same story no matter how they looked: this patch looks black not because it is a dense pocket of gas but because it is truly empty. Something has blown a hole right through the cloud.
"No one has ever seen a hole like this," says Tom Megeath of the University of Toledo, Ohio, the principal investigator of the research. "It's as surprising as knowing you have worms tunneling under your lawn, but finding one morning that they have created a huge, yawning pit."
The astronomers think that the hole must have been opened when the narrow jets of gas from some of the young stars in the region punctured the sheet of dust and gas that forms NGC 1999. The powerful radiation from a nearby adolescent star may also have helped to clear the hole. Whatever the precise chain of events, it could be an important glimpse into the way newborn stars rip apart their birth clouds.
Other members of the research team include Thomas Stanke of the European Southern Observatory, Germany; Amy Stutz of the Max-Planck Institute for Astronomy, Germany, and the Steward Observatory, Tucson; John Tobin of the University of Michigan, Ann Arbor; Lori Allen of the National Optical Astronomy Observatory, Tucson; Ali Babar of the NASA Herschel Science Center at the California Institute of Technology, Pasadena; and Will Fischer and Erin Kryukova, University of Toledo, Ohio.
Herschel is a European Space Agency cornerstone mission, with science instruments provided by consortia of European institutes and with important participation by NASA. NASA's Herschel Project Office is based at NASA's Jet Propulsion Laboratory, Pasadena, Calif. JPL contributed mission-enabling technology for two of Herschel's three science instruments. The NASA Herschel Science Center, part of the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, supports the United States astronomical community. Caltech manages JPL for NASA.