Astronomers have discovered for the first time an accretion disk around a giant star forming outside the Milky Way. HH 1177 is located in the Large Magellanic Cloud galaxy and is also the first massive young star to be optically visible. This paper was published in the journal Nature.
In gas- and dust-filled regions, massive stars form relatively quickly, making it extremely difficult to track the stages of material accumulation from Keplerian disks to massive (more than 8 solar masses) young stars. is difficult. What can be seen optically can be seen. Several such systems have been discovered in the Milky Way, including systems that generate jets embedded in clouds of gas and dust, but until recently they had not been observed in other galaxies.
A team of astronomers led by Anna McLeod from Durham University has reported the first observation of an accretion disk around a massive young star in the outer reaches of the Milky Way. Observations of the object HH 1177 in the Large Magellanic Cloud, a satellite galaxy of the Milky Way, were carried out using the ALMA system and the VLT telescope complex. HH 1177 is located in star-forming region N180, where the gas is ionized by radiation from the OB union star LH 117. The object produces a highly parallel bipolar jet about 36 light-years long and is characterized as a forming B-type star with a mass of about 12 solar masses.
Observational data suggest that this young star is surrounded by a disk-like structure with a Keplerian rotation and a maximum size of about 6,000 AU. The mass of gas in the disk ranges from 1.8 to 3.9 solar masses, but estimates of the star’s mass vary using different estimation methods, ranging from 9.6 to 19.5 solar masses. The disc is fed with material by a radial flow from the outer ring core.
The system’s properties are similar to the giant young stars in the Milky Way, but it is the only young, high-mass star detected optically. This can be explained by the low metallicity and low dust content of the environment in which HH 1177 formed, as well as the stability of the disk (although instability of the external components cannot be ruled out).