Astronomers Find a Newly-Forming Quadruple-Star System

Surprising discovery of a young quadruple Star System

A recent discovery by the international ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP) team has unveiled a remarkable breakthrough—a young quadruple star system nestled within a star-forming region within the Orion constellation. This revelation was the result of an intricate study involving the examination of 72 dense cores within the Orion Giant Molecular Clouds (GMCs), conducted using the powerful Atacama Large Millimeter/submillimeter Array (ALMA) located in Chile. This unforeseen finding not only sheds light on the origin and formation mechanisms of binary and multiple-star systems but also advances our comprehension of galactic evolution, planetary birth, and the emergence of life.


Multiple Star System formation for galactic evolution

Led by Prof. Liu Tie from the Shanghai Astronomical Observatory (CAS-SHAO), the ALMASOP team embarked on a comprehensive investigation that engaged researchers from distinguished institutions worldwide, including CAS-SHAO, CAS-SASS, NRC Herzberg Astronomy and Astrophysics, NAOJ, MPIA, KASI, ASIAA, NSF NOIRLab’s International Gemini Observatory, Armagh Observatory and Planetarium, NASA’s Jet Propulsion Laboratory, and several universities and institutes.

ALMASOP Research and Observations

Astronomers Find a Newly-Forming Quadruple-Star System
ALMA observations of the star-forming region G206.93-16.61E2, showing the 1.3mm emissions (blue) and the CO molecular outflow (orange).

The backdrop to this breakthrough lies in the well-established knowledge that a substantial portion of Milky Way stars resides within binary systems. However, comprehending the intricacies of how multiple star systems form is a pivotal enigma essential to unraveling galactic processes, planetary formation dynamics, and the potential emergence of life. While the Nebular Hypothesis has effectively explained the genesis of individual star systems, the mechanisms governing the formation of multi-star systems have remained elusive.

A prevailing notion proposes that multi-star systems arise from the fragmentation of cloud cores in their initial stages. Nonetheless, such a notion has lacked robust observational evidence. To decipher this cosmic puzzle, the ALMASOP team meticulously scrutinized 72 youthful and cold cores within the Orion GMCs. Their focus centered on thermal emissions with a wavelength of 1.3 mm, an exceptionally high frequency range.

Quadruple Star System Discovery

Intriguingly, during their meticulous observations, the team pinpointed a dense cold core within Orion B GMC, situated approximately 1,500 light-years from Earth. This specific core, designated G206.93-16.61E2, revealed a quartet of stellar entities within its confines. This quartet comprised two protostars and two gas concentrations teetering on the brink of imminent gravitational collapse. Remarkably, the distance between these entities was profoundly compact, with the largest separation spanning over 1,000 Astronomical Units (AUs), over 33 times the expanse between the Sun and Neptune (30 AUs).

This finding contrasts with a prior discovery made in 2015 by another international team utilizing ALMA. In that instance, a young protostar was accompanied by three gravitationally-bound dense gas clouds, set to evolve into new stars within approximately 40,000 years. Notably, the observed quadruple system exhibited a significantly wider separation exceeding 1,000 AUs. Additionally, distinct elongated ribbon-like structures intertwining the four objects were discernible from the dust emission spectra.

Unique Characteristics of the System

Astronomers Find a Newly-Forming Quadruple-Star System
G205.46-14.56 clump located in Orion molecular cloud complex. The yellow contours represent the dense cores discovered by the JCMT, and the zoomed-in pictures show the 1.3mm continuum emission of ALMA observation. Credit: Qiuyi Luo et al. (2022).

To elucidate the role of these structures, the team embarked on a numerical simulation, juxtaposing a similar quadruple system to the one observed. The simulation outcomes have led to the proposition that these elongated ribbons could serve as conduits transporting gas from the core’s outer envelope to the protostars while concurrently connecting nascent stars. Prof. Liu added that these ribbons could potentially serve as extensive accretion streamers, nurturing the formation of stars by facilitating gas flow. Furthermore, these streamers could fragment, birthing additional stars in the process.

Theoretical Implications

Intricate gas outflows, induced by the protostars’ stellar winds, were also unveiled through the observations. These winds led to the loss of certain accreting gas and dust, akin to the phenomena observed around Active Galactic Nuclei (AGNs), where supermassive black hole-generated winds expel material from galactic centers. This intriguing revelation possesses implications for the system’s evolutionary trajectory.

Future Observations and Conclusions

The road ahead promises further revelations. Subsequent observations leveraging ALMA and other advanced millimeter/submillimeter observatories are poised to uncover deeper insights into the intricate processes underlying the formation of multi-star systems. This latest discovery underscores the complexity inherent in the interactions within nascent higher-order star systems and underscores the indispensable role that cutting-edge observational technologies play in advancing our cosmic comprehension.

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