ALMA distinguishes two birth cries from a single star – obvious evidence of the independent origin of two gas streams

The stars of the universe have a wide range of masses, ranging from hundreds of times the mass of the sun to less than one tenth of that of the sun. To understand the origin of this variety, astronomers study the process of star formation, that is, the aggregation of cosmic gas and dust.

Small stars collect gas with their gravitational pulling force. However, some of the material is ejected by the protostars. This ejected material forms a stellar birth cry that provides clues to understand the process of mass accumulation.

Yuko Matsushita, a graduate student from Kyushu University and her team used ALMA to observe the detailed structure of baby star MMS5 / OMC-3's birth cry and found two different gaseous streams: a slow flow and a fast jet. There have been a handful of examples with two streams seen in radio waves, but MMS5 / OMC-3 is exceptional.

"By measuring the Doppler shift of radio waves, we can estimate the speed and life span of the gas streams," said Matsushita, lead author of the research paper in the Astrophysical Journal. "We found that the jet and the outflow were launched 500 years ago and 1300 years ago, respectively, these gas flows are quite young."

More interestingly, the team found that the axes of the two streams are misaligned by 17 degrees. The axis of flux can be changed over long periods of time due to the precession of the central star. But in this case, given the extremely young gas flows, the researchers concluded that the misalignment was not due to a precession, but was related to the launch process.

There are two competing models for the formation mechanism of protostellar streams and jets. Some researchers assume that the two streams are independently formed in different parts of the gas disk around the central star, while others suggest that the colloidal stream first forms and then causes surrounding materials to form more flows. slow. Despite extensive research, astronomers have not yet found a conclusive answer.

A "misalignment" between the two flows could occur in the "independent model", but is difficult in the "model of training". In addition, the team found that the exit was ejected much earlier than the jet. This clearly supports the "independent model".

"The observation corresponds well to the result of my simulation," said Masahiro Machida, a professor at Kyushu University. Ten years ago, he conducted pioneering simulation studies with the aid of a supercomputer operated by Japan's National Observatory of Astronomy. In the simulation, the wide-angle output stream is ejected from the outer area of ​​the gas disk around a protostar, while the collimated jet is launched regardless of the internal area of ​​the disk. Machida continues: "A misalignment observed between the two gas streams may indicate that the disk around the protostar is deformed."

"ALMA's high sensitivity and high angular resolution will allow us to find more and more outgoing and energetic jet systems like the MMS 5 / OMC-3," said astronomer Satoko Takahashi. National Astronomical Observatory of Japan. Joint ALMA Observatory and co-author of the document. "They will provide clues to understand the flow control mechanisms and jets. Moreover, the study of such objects will also tell us how the processes of accretion and mass ejection work at all. start of star training. "

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More information:
Yuko Matsushita et al. Extremely compact, very high speed flow to MMS 5 / OMC-3 revealed with ALMA, The astrophysical journal (2019). DOI: 10.3847 / 1538-4357 / aaf1b6