A team of astronomers has discovered a massive protostellar disk in the center of the Milky Way. Accretion disks, also known as “protostellar disks,” are key components in star formation. These disks continually feed gas to the protostars from their immediate surroundings. In this sense, they are stellar cradles where stars are born and raised.
The mysterious object is located 26,000 light-years away from Earth and, according to experts, researchers at the Shanghai Astronomical Observatory (SHAO), of the Chinese Academy of Sciences, looks like a mini spiral-shaped galaxy that revolves around from the galactic center.
Scientists used high-definition observations taken with the ALMA telescope in Chile to discover this strange structure that, far from being a small galaxy, is actually a gigantic wandering and “deformed” star, affected by the collision with a body intruder during its formative stage.
a misshapen star
Located near the dense and dusty galactic center, the O-type star is about 32 times more massive than our Sun and lies within a huge disk of swirling gas, known as a “protostellar disk.”
As the authors explain in their research published in the journal Nature Astronomy , the disk appeared to have been literally shaken up by a nearby collision with another body, possibly the mysterious triple-sun-sized object that is still visible nearby.
If the object followed a specific path, it could have skimmed past the disk about 12,000 years ago, disturbing the dust enough to result in the vivid spiral shape we see today.
“The good combination of analytical calculations, numerical simulation and ALMA observations provide strong evidence that the spiral arms in the disk are relics of the intruding object’s flyby,” said Lu Xing, Research Associate at the Chinese Academy Astronomical Observatory. of Sciences and co-author of the work.
Surprises in the galactic center
Using ALMA observations, the research team achieved a resolution of 40 milliarcseconds. Using these high-resolution, high-sensitivity ALMA observations, the team discovered an accretion disk in the galactic center. They successfully reproduced the entire history of the object flying through the disk more than 10,000 years ago, when it would have caused spirals in the disk. The discovery suggests that early massive O-type stars go through a formation phase involving accretion disks, and this conclusion holds true for the unique environment of the galactic center.
Most striking of all, the two spiral arms of the disk are visible. Such arms are usually found in spiral galaxies, but rarely in protostellar disks. Spiral arms in accretion disks usually form due to fragmentation induced by gravitational instability.
“This finding demonstrates that accretion disks in the early evolutionary stages of star formation are subject to frequent dynamical processes, such as flybys, and these processes can substantially influence star and planet formation. The formation of this massive protostar is similar to that of its lower-mass cousins like the Sun, with accretion disks and flyby events involved. Although stellar masses are different, certain physical mechanisms in star formation could be the same. This provides important clues in resolving the mystery of the formation of massive stars”, the experts conclude.
Could this represent that the center of our galaxy is teeming with miniature spirals just like this one waiting to be discovered?
Referencia: Lu, X., Li, GX., Zhang, Q. et al. A massive Keplerian protostellar disk with flyby-induced spirals in the Central Molecular Zone. Nat Astron (2022). https://doi.org/10.1038/s41550-022-01681-4
