Bizarre spiral object found swirling around Milky Way's center

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It looks like a tiny galaxy, but it's just one big star.

An illustration of the mysterious spiral's history, showing (from bottom to top) its evolution 12,000 years ag, 8,000 years ago, 4,000 years ago, and today.
An illustration of the mysterious spiral's history, showing (from bottom to top) its evolution 12,000 years ago, 8,000 years ago, 4,000 years ago, and today. (Image credit: SHAO)

As if cracking open a cosmic Russian nesting doll, astronomers have peered into the center of the Milky Way and discovered what appears to be a miniature spiral galaxy, swirling daintily around a single large star.

The star — located about 26,000 light-years from Earth near the dense and dusty galactic center — is about 32 times as massive as the sun and sits within an enormous disk of swirling gas, known as a "protostellar disk." (The disk itself measures about 4,000 astronomical units wide — or 4,000 times the distance between Earth and the sun).

How did this mini-spiral come to be, and are there more like it out there? The answers may lie in a mysterious object, about three times as massive as Earth's sun, lurking just outside the spiral disk's orbit, according to a new study published May 30 in the journal Nature Astronomy.

Using high-definition observations taken with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile, the researchers found that the disk doesn't appear to be moving in a way that would give it a natural spiral shape. Rather, they wrote, the disk seems to have been literally stirred up by a near-collision with another body — possibly the mysterious triple-sun-sized object that's still visible nearby it.

"The nice match among analytical calculations, the numerical simulation and the ALMA observations provides robust evidence that the spiral arms in the disk are relics of the flyby of the intruding object," study co-author Lu Xing, an associate researcher from the Shanghai Astronomical Observatory of the Chinese Academy of Sciences, said in a statement.

Besides offering the first direct images of a protostellar disk in the galactic center, this study shows that external objects can whip stellar disks into spiral shapes typically only seen on the galactic scale. 

And because the center of the Milky Way is millions of times denser with stars than our neck of the galaxy, it's likely that near-miss events like this occur in the galactic center pretty regularly, the researchers said. That means our galaxy's center may be overloaded with miniature spirals, only waiting to be discovered. Scientists may not reach the center of this cosmic nesting doll for a long, long time.

Originally published on Live Science.

Brandon Specktor
Brandon Specktor
Editor

Brandon is the space / physics editor at Live Science. With more than 20 years of editorial experience, his writing has appeared in The Washington Post, Reader's Digest, CBS.com, the Richard Dawkins Foundation website and other outlets. He holds a bachelor's degree in creative writing from the University of Arizona, with minors in journalism and media arts. His interests include black holes, asteroids and comets, and the search for extraterrestrial life.