Turbulence May Promote the Birth of Massive StarsFebruary 24, 2009Cambridge, MA - On long, dark winter nights, the constellation of Orion the Hunter dominates the sky. Within the Hunter's sword, the Orion Nebula swaddles a cluster of newborn stars called the Trapezium. These stars are young but powerful, each one shining with the brilliance of 100,000 Suns. They are also massive, containing 15 to 30 times as much material as the Sun. Where did the Trapezium stars come from? The question is not as simple as it seems. When it comes to the theory of how massive stars form, the devil is in the details. We know the basics: a cloud of cosmic gas draws itself together, growing denser and hotter until nuclear fusion ignites. But how does massive star formation begin? What determines how many stars form from a single cloud? New data from the Submillimeter Array (SMA), a joint project of the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics, is helping to answer these questions. The SMA allows astronomers to examine the earliest stages of star formation, which are hidden within cocoons of dust and gas that block visible light. In a study just accepted for publication in The Astrophysical Journal, a team of astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) studied two cosmic cocoons located 15,000 light-years away in the constellation Serpens Cauda. One region shows significant heating, indicating that massive new stars must have already formed. The other region has ample material to form massive stars, but shows little signs of star formation. It is at one of the earliest stages yet identified in the birth of stars. "The SMA enables us to see the dust and gas in the cocoon with amazing details, and to probe the initial stages of massive star formation," said Smithsonian astronomer Qizhou Zhang, who is lead author on the report. By comparing the SMA data to theoretical predictions, astronomers can test their understanding of how stars more massive than the Sun form. In star formation, gravity pulls material inward and condenses it. Gravity also tends to fragment the contracting cloud into smaller and smaller pieces, which leads to a star cluster. Such fragmentation may also inhibit the formation of massive stars. As a result, some theorists propose that massive stars must form from collisions of smaller protostars. Two forces counteract gravity and suppress fragmentation of the cloud: thermal pressure from the heat of protostars, and turbulence. This may allow massive stars to form directly from accretion. Previous work suggested that thermal pressure was the stronger influence, but the new SMA study finds that turbulence is more important, at least at the spatial scales examined. "What's unique about these SMA observations is that we can check some of the hypotheses for massive star formation against the observations for the first time," said Zhang. "Unlike what has been assumed in theoretical models, we found that fragmentation is suppressed in these clouds, not by stellar heating but rather by turbulence." The team already has planned future studies. "We have just started to understand the initial conditions in distant, massive star-forming regions. A large survey that we have launched with the SMA will, in the near future, reveal the nature of more of such objects," said Thushara Pillai of CfA, a co-author of the report. Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe. Harvard-Smithsonian Center for Astrophysics |
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| Related Star Formation Current Events and Star Formation News Articles The Stars behind the Curtain ESO is releasing a magnificent VLT image of the giant stellar nursery surrounding NGC 3603, in which stars are continuously being born. MSU contributes to new research on star formation "Crazy" and "cool" are two of the words Michigan State University astronomer Megan Donahue uses to describe the two distinct "tails" found on a long tail of gas that is believed to be forming stars where few stars have been formed before. Scientists reveal Milky Way's magnetic attraction An international research project involving the University of Adelaide has revealed that the magnetic field in the centre of the Milky Way is at least 10 times stronger than the rest of the Galaxy. UBC astronomers unveil images of 12-billion-year-old space nursery A University of British Columbia astronomer has produced the most detailed images of deep space from 12 billion years ago, using data from the European Space Agency's Herschel Space Observatory. Hubble finds most distant primeval galaxies The NASA/ESA Hubble Space Telescope has broken the distance limit for galaxies and uncovered a primordial population of compact and ultra-blue galaxies that have never been seen before. Astronomers detect earliest galaxies Astronomers, using NASA's Hubble Space Telescope, have broken the distance limit for galaxies by uncovering a primordial population of compact and ultra-blue galaxies that have never been seen before. They are from 13 billion years ago, just 600 to 800 million years after the Big Bang. New panchromatic capabilities of Hubble reveal an unprecedented view of the universe Shown in an extremely broad range of color and showcasing more than twelve billion years of cosmic history, Hubble's recent image is a full-glory cosmic renaissance of the history of the Universe. Giant Intergalactic Gas Stream Longer than Thought A giant stream of gas flowing from neighbor galaxies around our own Milky Way is much longer and older than previously thought, astronomers have discovered. The new revelations provide a fresh insight on what started the gaseous intergalactic streamer. ESA space telescope with CU-Boulder connection looks back to early galaxies An instrument package developed in part by the University of Colorado at Boulder for the $2.2 billion orbiting Herschel Space Observatory launched in May by the European Space Agency has provided one of the most detailed views yet of space up to 12 billion years back in time. Brown dwarf pair mystifies astronomers Two brown dwarf-sized objects orbiting a giant old star show that planets may assemble around stars more quickly and efficiently than anyone thought possible, according to an international team of astronomers. More Star Formation Current Events and Star Formation News Articles |
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