Stellar cocoon with organic molecules at the edge of our galaxy

Date:
December 2, 2021
Source:
Niigata University
Summary:
Astronomers have detected a newborn star and the surrounding
cocoon of complex organic molecules at the edge of our Galaxy,
which is known as the extreme outer Galaxy. The observations with
the Atacama Large Millimeter/submillimeter Array reveal the hidden
chemical complexity of our Universe.



FULL STORY ==========================================================================
For the first time, astronomers have detected a newborn star and the surrounding cocoon of complex organic molecules at the edge of our Galaxy, which is known as the extreme outer Galaxy. The discovery, which revealed
the hidden chemical complexity of our Universe, appears in a paper in
The Astrophysical Journal.


==========================================================================
The scientists from Niigata University (Japan), Academia Sinica Institute
of Astronomy and Astrophysics (Taiwan), and the National Astronomical Observatory of Japan, used the Atacama Large Millimeter/submillimeter
Array (ALMA) in Chile to observe a newborn star (protostar) in the
WB89-789 region, located in the extreme outer Galaxy. A variety of
carbon-, oxygen-, nitrogen-, sulfur-, and silicon-bearing molecules,
including complex organic molecules containing up to nine atoms,
were detected. Such a protostar, as well as the associated cocoon of chemically-rich molecular gas, were for the first time detected at the
edge of our Galaxy.

The ALMA observations reveal that various kinds of complex organic
molecules, such as methanol (CH3OH), ethanol (C2H5OH), methyl formate (HCOOCH3), dimethyl ether (CH3OCH3), formamide (NH2CHO), propanenitrile (C2H5CN), etc., are present even in the primordial environment of the
extreme outer Galaxy. Such complex organic molecules potentially act as
the feedstock for larger prebiotic molecules.

Interestingly, the relative abundances of complex organic molecules
in this newly discovered object resemble remarkably well what is found
in similar objects in the inner Galaxy. The observations suggest that
complex organic molecules are formed with similar efficiency even at
the edge of our Galaxy, where the environment is very different from
the solar neighborhood.

It is believed that the outer part of our Galaxy still harbors a
primordial environment that existed in the early epoch of galaxy
formation. The environmental characteristics of the extreme outer
Galaxy, e.g., low abundance of heavy elements, small or no perturbation
from Galactic spiral arms, are very different from those seen in the present-day solar neighborhood. Because of its unique characteristics,
the extreme outer Galaxy is an excellent laboratory to study star
formation and the interstellar medium in the past Galactic environment.

"With ALMA we were able to see a forming star and the surrounding
molecular cocoon at the edge of our Galaxy," says Takashi Shimonishi, an astronomer at Niigata University, Japan, and the paper's lead author. "To
our surprise, a variety of abundant complex organic molecules exists in
the primordial environment of the extreme outer Galaxy. The interstellar conditions to form the chemical complexity might have persisted since
the early history of the Universe," Shimonishi adds.

"These observations have revealed that complex organic molecules can be efficiently formed even in low-metallicity environments like the outermost regions of our Galaxy. This finding provides an important piece of the
puzzle to understand how complex organic molecules are formed in the
Universe," says Kenji Furuya, an astronomer at the National Astronomical Observatory of Japan, and the paper's co-author.

It is not yet clear, however, if such a chemical complexity is common in
the outer part of the Galaxy. Complex organic molecules are of special interest, because some of them are connected to prebiotic molecules
formed in space. The team is planning to observe a larger number
of star-forming regions in the future, and hopes to clarify whether chemically-rich systems, as seen in our Solar System, are ubiquitous
through the history of the Universe.

*This work is supported by a Grant-in-Aid from the Japan Society for
the Promotion of Science (19H05067, 21H00037, 21H01145).

========================================================================== Story Source: Materials provided by Niigata_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Takashi Shimonishi, Natsuko Izumi, Kenji Furuya, Chikako Yasui. The
Detection of a Hot Molecular Core in the Extreme Outer
Galaxy. The Astrophysical Journal, 2021; 922 (2): 206 DOI:
10.3847/1538-4357/ac289b ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211202141600.htm

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