Our Sun is quite a ‘regular’ star, and quite a small one, so we can enjoy our smooth lives on the planet Earth. However, there is a number of significantly larger stars out there in the vast depths of the galaxy. Sometimes these stars are more than 100 times heavier than our home star, or even bigger. Until now astronomers had no exact facts about the origins of such gigantic celestial bodies. It was unknown if these stars can originate only from star clusters, under the abundance of interstellar matter, or they can also form separately from their other shining counterparts.

Anyway, the hypothesis about the isolated formation of super-massive stars has existed for more than ten years. German scientists from the Institute for Physics and Astronomy at Potsdam and the Leibniz Institute for Astrophysics, made some observations of the central region of our Milky Way galaxy to check this theory. According to them, this region is ideal to look for the very massive stars and, at least, to try to find one in relative isolation from the neighboring star clusters, where other massive bodies could impact their formation.

Not all ‘isolated’ massive stars have no relations to star clusters. The authors explain in the paper published at arXiv.org, that some of those stars may have actually born in the star clusters residing near the center of the galaxy, but later, due to some disturbance or action of interfering cosmic force, they were ejected into an open space outside the native cluster. In any case, it is possible to detect these “runaway” stars by analyzing their characteristic – the so-called bow shock.

The authors have made a logical assumption, that if the star doesn’t display a bow shock, it means that they were not forced to move out from some other region of the galaxy sometime in the distant past.

The team was able to locate a candidate – a massive star, WR 102ka (Peony nebula star), without a bow shock detected around it. This star is also one of the most massive and luminous stars in our galaxy, and is also located in its own circumstellar nebula of the space dust.

The astronomers have performed additional measurement-based verifications of the stellar spectra and radial velocity using the integral field spectrograph SINFONI, which is a part of ESO’s Very Large Telescope (VLT) system. The observations confirmed that WR 102ka has really formed in isolation from other stars.

Certainly, this formation requires two important factors. First of all, it must have happened at the galactic location with a large amount of high-density molecular gas. Also, the place should be near the center of our galaxy, where the proximity to the super-massive black hole plays an important role.

The research proves the fact that the star formation processes in this central galactic region are more sophisticated compared to the outskirts of the galaxy, and it is possible to test unique theories of star and star cluster formation there.

By Alius Noreika, Source: Technology.org