An explanation for the double birth cry of a newborn star

MMS5/OMC-3 (Image ALMA (ESO/NAOJ/NRAO), Matsushita et al.)
MMS5/OMC-3 (Image ALMA (ESO/NAOJ/NRAO), Matsushita et al.)

An article published in the journal “The Astrophysical Journal” reports the analysis that led to unveil the origin of two gas flows from the newborn star MMS5/OMC-3. A team of researchers used the ALMA radio telescope to study this situation which was a mystery because there are two very different flows since one is a slow outflow while the other is a fast jet and they concluded that they were formed independently in different parts of the gas disk surrounding the star.

Astronomers are studying the processes that lead to the formation of stars that can have very different masses, from a minimum of less than one tenth of the Sun’s mass to hundreds of times the Sun’s mass. To understand that huge variety it’s very useful to study protostars, newborn stars that haven’t yet completed the growth that will take them into the main sequence in which they will spend most of their lives. Protostars are not yet stable, so for example while they still attract gas and dust they eject a part of it what were compared to birth cries.

Yuko Matsushita, a student from Kyushu University in Japan, led a team that observed MMS5/OMC-3, a very interesting protostar because two very different birth cries were detected from it: a slow outflow and a fast jet. The ALMA radio telescope (Atacama Large Millimeter/submillimeter Array), inaugurated in March 2013, allowed to study a situation that hadn’t been explained yet, discovering some key features of those two flows.

A help in this study came from the Doppler effect of the radio waves coming from the flows emitted by the star MMS5/OMC-3, which go in different directions so different distortions were detected on the electromagnetic emissions. The result allowed to estimate the speed and duration of the two flows: the fast jet was emitted about 500 years ago while the slow outflow was emitted about 1,300 years ago. The axes of the two flows are misaligned by 17 degrees, a phenomenon that is generally the consequence of the star axis precession but in this case according to the researchers is the consequence of the ejection process.

The previous observations of the flows from the star MMS5/OMC-3 led to two theories to explain their origin: according to one the two flows were formed independently in different parts of the disk surrounding MMS5/OMC-3, according to the other the fast jet was formed first and entrained the materials that surround it generating slower outflows.

This new research indicates that the slow outflow was ejected well before the fast jet, so the independent flow theory seems to be the correct one. Professor Masahiro Machida of Kyushu University, another of the study’s authors, added that the observations well match the results of the simulations he conducted, which indicate that the slow outflow is ejected from the outer area of ​​the gas disk around to a protostar while the fast jet is launched independently of the inner area of ​​the disk. In his opinion the misalignment between the two flows could indicate that the disk is warped.

The authors of the research admit that their conclusions still leave open possibilities regarding the other theory. In these cases it’s more important than ever that the results of a research are discussed and examined by other scientists as well, and new observations can always bring important data to improve certain models. An instrument such as the ALMA radio telescope, with its power and sensitivity, is very useful in the study of star formation processes so each new observation can be a step forward in this type of research.

Artist's concept of MMS5/OMC-3 (Image courtesy NAOJ)
Artist’s concept of MMS5/OMC-3 (Image courtesy NAOJ)

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