High density and turbulent state of the gas contribute to the formation of multiple stellar systems

(ORDO NEWS) — Astronomers studying “stellar cradles”, which are the place of formation of new stars, inside the Milky Way, have found that about half of the number of stars in the Galaxy are formed in binary or multiple (for example, triple or quadruple) star systems.

Despite the fact that such a large number of stars are formed in binary or multiple systems, previous studies of “stellar cradles” have mainly studied the mechanisms of formation of single stars. As a result, the origin of binary/multiple systems remained insufficiently studied for a long time.

In a new study, a team of astronomers led by Luo Qiuyi of the Shanghai Astronomical Observatory, China, found that higher material density and increased turbulence contribute to the formation of multiple star systems.

The birth of any new star occurs as a result of the gravitational collapse of cold “pockets” of gas and dust (known as cores) within structures known as molecular clouds.

However, in previous studies, almost no study was made of the influence of the properties of these dense cores on the multiplicity of forming stellar systems.

In this new work, the researchers observed the Orion Cloud, the closest region of active star formation to Earth, using the James Clerk Maxwell Telescope (JCMT, Hawaii) and Atacama Large Millimeter/submillimeter Array (ALMA, Chile) observatories.

Located about 1500 light-years away in the direction of the constellation Orion, this molecular cloud is the perfect laboratory for testing various models of star formation.

Using the JCMT telescope, scientists have identified 49 cold, dense cores in the Orion Cloud where young stars are forming.

Then, using the ALMA telescope, Chiu Yi, together with his colleagues, was able to examine the internal structure of the nuclei.

Based on high-resolution observations made with the ALMA observatory, the authors found that about 13 dense cores will give rise to binary or multiple systems, while the remaining cores will form single stars.

The authors then estimated the physical characteristics (eg, size, gas density, and mass) of these dense nuclei based on observations made with the JCMT telescope.

An analysis of the data obtained showed that the cores that would give rise to binary/multiple stars were characterized by a higher hydrogen density and mass compared to the cores that would form single stars, although these cores were almost the same in size.

“Dense nuclei fragment more easily due to perturbations caused by gravitational instability within the nuclei,” said Chiu Yi.

In addition, using the turbulence characterization based on the N2H+ spectral linewidth (J=1-0) that the authors observed with the 45-meter Nobeyama telescope, they found that multiple systems preferentially form in more turbulent conditions.

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