Astronomers have unveiled the enigmatic origins of two different gas
streams from a baby star. Using ALMA, they found that the slow outflow
and the high speed jet from a protostar
have misaligned axes and that the former started to be ejected earlier
than the latter. The origins of these two flows have been a mystery, but
these observations provide telltale signs that these two streams were
launched from different parts of the disk around the protostar.
Stars in the Universe have a wide range of masses, ranging from
hundreds of times the mass of the Sun to less than a tenth of that of
the Sun. To understand the origin of this variety, astronomers study the
formation process of the stars, that is the aggregation of cosmic gas
and dust.
Baby stars collect the gas with their gravitational pull, however,
some of the material is ejected by the protostars. This ejected material
forms a stellar birth cry which provides clues to understand the
process of mass accumulation.
Yuko Matsushita, a graduate student at Kyushu University and her team
used ALMA to observe the detailed structure of the birth cry from the
baby star MMS5/OMC-3 and found two different gaseous flows: a slow
outflow and a fast jet. There have been a handful of examples with two
flows seen in radio waves, but MMS5/OMC-3 is exceptional.
“Measuring the Doppler shift
of the radio waves, we can estimate the speed and lifetime of the gas
flows,” said Matsushita, the lead author of the research paper that
appeared in the Astrophysical Journal. “We found that the jet and
outflow were launched 500 years and 1300 years ago, respectively. These
gas streams are quite young.”
More interestingly, the team found that the axes of the two flows are
misaligned by 17 degrees. The axis of the flows can be changed over
long time periods due to the precession of the central star. But in this
case, considering the extreme youth of the gas streams, researchers
concluded that the misalignment is not due to precession but is related
to the launching process.
There are two competing models for the formation mechanism of the
protostellar outflows and jets. Some researchers assume that the two
streams are formed independently in different parts of the gas disk
around the central baby star, while others propose that the collocated
jet is formed first, then it entrains the surrounding material to form
the slower outflows. Despite extensive research, astronomers had not yet
reached a conclusive answer.
A misalignment in the two flows could occur in the ‘independent
model,’ but is difficult in the ‘entrainment model.’ Moreover, the team
found that the outflow was ejected considerably earlier than the jet.
This clearly backs the ‘independent model.’
“The observation well matches the result of my simulation,” said
Masahiro Machida, a professor at Kyushu University. A decade ago, he
performed pioneering simulation studies using a supercomputer operated
by the National Astronomical Observatory of Japan. In the simulation,
the wide-angle outflow is ejected from the outer area of the gaseous
disk around a prototar, while the collimated jet is launched
independently from the inner area of the disk. Machida continues, “An
observed misalignment between the two gas streams may indicate that the
disk around the protostar is warped.”
“ALMA’s high sensitivity and high angular resolution will enable us
to find more and more young, energetic outflow-and-jet-systems like MMS
5/OMC-3,” said Satoko Takahashi, an astronomer at the National
Astronomical Observatory of Japan and the Joint ALMA Observatory and
co-author of the paper. “They will provide clues to understand the
driving mechanisms of outflows and jets. Moreover studying such objects
will also tell us how the mass accretion and ejection processes work at
the earliest stage of star formation.”
Additional Information
These observation results were published as Matsushita et al. “Very Compact Extremely High Velocity Flow toward MMS 5 / OMC-3 Revealed with ALMA” in the Astrophysical Journal issued in February 2019.
The research team members are:
Yuko Matsushita (Kyushu University), Satoko Takahashi (Joint ALMA
Observatory/National Astronomical Observatory of Japan/SOKENDAI),
Masahiro Machida (Kyushu University), and Koji Tomisaka (National
Astronomical Observatory of Japan/SOKENDAI)
This research was supported by JSPS KAKENHI (No. 17K05387, 17H06360, 17H02869, 15K05032) and the Science Visitor Program of the Joint ALMA Observatory.
The Atacama Large Millimeter/submillimeter Array (ALMA), an
international astronomy facility, is a partnership of the European
Organisation for Astronomical Research in the Southern Hemisphere (ESO),
the U.S. National Science Foundation (NSF) and the National Institutes
of Natural Sciences (NINS) of Japan in cooperation with the Republic of
Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in
cooperation with the National Research Council of Canada (NRC) and the
Ministry of Science and Technology (MOST) and by NINS in cooperation
with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and
Space Science Institute (KASI). ALMA construction and operations are led
by ESO on behalf of its Member States; by the National Radio Astronomy
Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on
behalf of North America; and by the National Astronomical Observatory of
Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO)
provides the unified leadership and management of the construction,
commissioning and operation of ALMA.
Contacts
Valeria Foncea
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Phone: +56 2 2467 6258
Cell phone: +56 9 7587 1963
Email: valeria.foncea@alma.cl
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Education and Public Outreach Officer, NAOJ Chile
Observatory , Tokyo - Japan
Phone: +81 422 34 3630
Email: hiramatsu.masaaki@nao.ac.jp
Charles E. Blue
Public Information Officer
National Radio Astronomy Observatory Charlottesville, Virginia - USAv
Phone: +1 434 296 0314
Cell phone: +1 202 236 6324
Email: cblue@nrao.edu
Calum Turner
ESO Assistant Public Information Officer
Garching bei München, Germany
Phone: +49 89 3200 6670
Email: calum.turner@eso.org
Contacts
Valeria Foncea
Education and Public Outreach Officer
Joint ALMA Observatory Santiago - Chile
Phone: +56 2 2467 6258
Cell phone: +56 9 7587 1963
Email: valeria.foncea@alma.cl
Masaaki Hiramatsu
Education and Public Outreach Officer, NAOJ Chile
Observatory , Tokyo - Japan
Phone: +81 422 34 3630
Email: hiramatsu.masaaki@nao.ac.jp
Charles E. Blue
Public Information Officer
National Radio Astronomy Observatory Charlottesville, Virginia - USAv
Phone: +1 434 296 0314
Cell phone: +1 202 236 6324
Email: cblue@nrao.edu
Calum Turner
ESO Assistant Public Information Officer
Garching bei München, Germany
Phone: +49 89 3200 6670
Email: calum.turner@eso.org
