A team of astronomers has determined how the gas flow from a massive infant star is launched. The researchers used the Atacama Large Millimeter\/submillimeter Array (ALMA) to observe the 10-solar-mass protostar Orion KL Source I in the Kleinmann-Low Nebula and obtained clear evidence of rotation in the outflow. <\/p>\n
Artists impression of Orion KL Source I. The massive protostar is surrounded by a disk of gas and dust. The outflow is launched from the surface of the outer disk. Image credit: ALMA \/ ESO \/ NAOJ \/ NRAO. <\/p>\n
Stars form from gas and dust floating in interstellar space. But, astronomers do not yet fully understand how it is possible to form the massive stars seen in space. <\/p>\n
One key issue is gas rotation. The parent cloud rotates slowly in the initial stage and the rotation becomes faster as the cloud shrinks due to self-gravity. <\/p>\n
Stars formed in such a process should have very rapid rotation, but this is not the case. The stars observed in the Universe rotate more slowly. <\/p>\n
How is the rotational momentum dissipated? One possible scenario involves that the gas emanating from protostars. <\/p>\n
If the gas outflow rotates, it can carry rotational momentum away from the system. <\/p>\n
Astronomers have tried to detect the rotation of the outflow to test this scenario and understand its launching mechanism. <\/p>\n
In a few cases signatures of rotation have been found, but it has been difficult to resolve clearly, especially around massive protostars. <\/p>\n
Orion KL Source I observed with ALMA. The massive protostar is located in the center and surrounded by a gas disk (red). A bipolar gas outflow is ejected from the protostar (blue). Image credit: ALMA \/ ESO \/ NAOJ \/ NRAO \/ Hirota et al. <\/p>\n
Dr. Tomoya Hirota, an astronomer at the National Astronomical Observatory of Japan (NAOJ) and SOKENDAI, and colleagues observed a protostar called Orion KL Source I in the Kleinmann-Low Nebula, the most active part of the Orion Nebula complex. <\/p>\n
Thanks to its close vicinity and ALMAs advanced capabilities, Dr. Hirota and co-authors were able to reveal the nature of the outflow from Orion KL Source I. <\/p>\n
We have clearly imaged the rotation of the outflow. In addition, the result gives us important insight into the launching mechanism of the outflow, Dr. Hirota said. <\/p>\n
The new ALMA observations beautifully illustrate the rotation of the outflow: it rotates in the same direction as the gas disk surrounding the star; this strongly supports the idea that the outflow plays an important role in dissipating the rotational energy. <\/p>\n
Furthermore, ALMA clearly shows that the outflow is launched not from the vicinity of Orion KL Source I itself, but rather from the outer edge of the disk. This morphology agrees well with the magnetocentrifugal disk wind model. <\/p>\n
The findings appear today in the journal Nature Astronomy. <\/p>\n
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Hirota et al. Disk-Driven Rotating Bipolar Outflow in Orion Source I. Nature Astronomy, published online June 12, 2017 <\/p>\n
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ALMA Observes Massive Protostar in Kleinmann-Low Nebula - Sci-News.com<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" A team of astronomers has determined how the gas flow from a massive infant star is launched. The researchers used the Atacama Large Millimeter\/submillimeter Array (ALMA) to observe the 10-solar-mass protostar Orion KL Source I in the Kleinmann-Low Nebula and obtained clear evidence of rotation in the outflow. Artists impression of Orion KL Source I Continue reading