As if opening a cosmic Russian nesting doll, astronomers peeked into the center of the Milky Way and discovered what looked like a miniature spiral galaxy, swirling finely around a large star.
The star – located about 26,000 light-years from Earth near the dense and dusty galactic center – is about 32 times more massive than the Sun and is located inside a huge disk of swirling gas, known as the “protostellar disk”. (The disk itself measures about 4,000 astronomical units of latitude – or 4,000 times the distance between the Earth and the Sun).
Such disks are widespread in the universe, serving as a stellar fuel that helps young stars grow into big, bright suns over millions of years.
But astronomers have never seen a galaxy like this before: a miniature galaxy orbiting dangerously close to the center of our galaxy.
How did this mini-spiral come about and are there any more like it?
The answers may lie in a mysterious object, about three times the size of the Earth’s sun, lurking just outside the orbit of the spiral disk, according to a new study published May 30 in the journal Natural astronomy.
Using high-definition observations from the Atacama Large Millimeter / Submillimeter Array (ALMA) telescope in Chile, the researchers found that the disk did not appear to move in a way that would give it its natural spiral shape.
above: Schematic representation of the history of the accretion disk and the intrusion object. The three diagrams starting from the lower left are numerical simulation images, which show the system at the time of the overflight event, 4,000 years later and 8,000 years after the event. The upper right image was taken from an ALMA observation, showing a spiral disk and two objects around it, corresponding to a system 12,000 years after the event.
Instead, they wrote, the disk appears to have been literally disturbed by an imminent collision with another body – probably a mysterious object the size of a triple sun that is still visible nearby.
To test this hypothesis, the team calculated a dozen potential orbits for the mysterious object, and then ran a simulation to see if any of those orbits could bring the object close enough to the protostellar disk to turn it into a spiral.
They discovered that if the object had followed a specific trajectory, it could have passed the disk about 12,000 years ago, disturbing the dust just enough to result in the colorful spiral shape seen today.
“The nice overlap between analytical calculations, numerical simulations, and ALMA observations provides strong evidence that spiral arms on a disk are relics of an intrusive object’s flyover,” said study co-author Lu Xing, a research associate in Shanghai. The Astronomical Observatory of the Chinese Academy of Sciences, it is stated in the announcement.
In addition to offering the first direct images of a protostellar disk in the galactic center, this study shows that external objects can turn star disks into spiral shapes that are usually only seen on the galactic scale.
And since the center of the Milky Way is millions of times denser with stars than our galaxy neck, it is likely that near-failure events occur at the galactic center fairly regularly, the researchers said.
This means that the center of our galaxy may be overloaded with miniature spirals, which are just waiting to be discovered. Scientists may not get to the center of this cosmic nesting doll for a long, long time.
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This article was originally published by Live Science. Read the original article here.
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