A close encounter between two strange objects at the heart of the Milky Way produced something that astronomers have never seen before.
Observers have found what seems to be a miniature spiral galaxy shimmering delicately around a highly luminous star in the center of the Milky Way.
Around 26,000 light-years from Earth, near the dense galactic center, researchers have discovered what is described as an early O-Type Star, which is about 32 times more massive than the Sun, moving inside a disk of swirling gas known as a protostellar disk.
Four thousand astronomical units diameter is the disk’s diameter, 4,000 times that of the Earth to the Sun.
Based on this discovery, massive early-O-type stars must go through an accretion disk-dominated phase of formation, and this conclusion is valid for the unique environment of the Galactic Center.
Over millions of years, stellar disks fuel young stars into becoming enormous, bright suns. However, astronomers have never witnessed anything like this before: a miniature galaxy orbiting dangerously close to the heart of our own galaxy.
In what way did this mini-spiral form? Could there be more like it?
According to a new study in Nature Astronomy, answers may lie in a mysterious object, about three times as massive as Earth’s Sun, lurking just outside the spiral disk’s orbit.
The researchers observed with the Atacama Large Millimeter/submillimeter Array telescope in Chile and determined that the disk appears not to be moving in such a way as to give it a spiral shape. Instead, researchers speculate that the disk may have been shaken up after colliding with another body nearby, perhaps the strange triple-sun-sized object still visible near it.
This hypothesis was verified by calculating a dozen possible orbits for the mystery object before evaluating whether any of those orbits brought it close enough to the protostellar disk for it to become a spiral. The scientists found that the object could have crossed the disk about 12,000 years ago by following a specific path, spreading enough dust to result in today’s spiral shape.
Spirals here, spirals there
These researchers demonstrate that external objects are capable of transforming stellar disks into spiral structures that are normally only seen on a galactic scale.
Researchers say this type of event will likely happen quite frequently in the galactic center due to the dense star population in the Milky Way center, which is millions of times greater than in our suburb of the galaxy.
Therefore, it is likely that our galaxy’s center is packed with miniature spirals just waiting to be discovered.
“The nice match among analytical calculations, the numerical simulation, and the ALMA observations provide robust evidence that the spiral arms in the disk are relics of the flyby of the intruding object,” explained Dr. Lu Xing, an associate researcher from the Shanghai Astronomical Observatory (SHAO) of the Chinese Academy of Sciences.
In addition, the Galactic Center is an important and unique environment for the formation of stars. Aside from the supermassive black hole Sgr A*, the Galactic Center contains massive reservoirs of molecular gas, primarily molecular hydrogen (H2), the raw material for star formation. As soon as gravitational collapse begins, stars begin to form.
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