There's now even more evidence that a bizarre star system perched on the constellation Orion's nose may contain the rarest type of planet in the known universe: a single world orbiting three suns simultaneously.
The star system, known as GW Orionis (or GW Ori) and located about 1,300 light-years from Earth, makes a tempting target for study; with three dusty, orange rings nested inside one another, the system looks like a giant bulls-eye in the sky. In the center of this bull's eye, three stars live, two being locked up in a tight binary orbit with each other, and a third turning broadly around the other two.
Triple star systems are rare in the cosmos, but GW Ori gets stranger as astronomers look closer. In a 2020 paper published in The Astrophysical Journal Letters, researchers closely looked at GW Ori with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile. They discovered that the system's three dust rings are misaligned with one another, with the innermost ring wobbling wildly in its orbit.
The team proposed that a young planet, or the creation, could throw out the gravitational balance of GW Ori's complicated triple-ring arrangement. Thus, if the detection is confirmed, this would be the first triple sun planet (or "circumtriple") of the known universe.
Yet a September 17 article in the Monthly Notices of the Royal Astronomical Society provides new evidence of the existence of this rare planet. The study authors conducted 3D simulations to model how the mysterious gaps in the star system's rings could have formed, based on observations of other dust rings (or "protoplanetary disks") elsewhere in the universe.
The team tested two hypotheses: Either the break-in GW Ori's rings formed from the torque applied by the three twirling stars at the system's center, or the break appeared when a planet instituted within one of the rings.
The researchers concluded that there was not enough turbulence in the rings for the star couple theory to function. On the contrary, the models suggest that the presence of a massive planet the size of Jupiter — or perhaps several planets — is the most plausible explanation for the strange shape and behavior of the rings.
If future observations of the system support that theory, GW Ori may be "the first evidence of a circumtriple planet carving a gap in real-time," lead study author Jeremy Smallwood, from the University of Nevada, Las Vegas, told The New York Times.
Sadly, a hypothetical observer of this maybe-planet wouldn't be able to see all three suns rise and fall in the sky; the two stars at the center of the system move in such a tight binary orbit that they would appear as one excellent star, with the third swooping around them, the researchers said.
But if this were confirmed, the mere existence of this world would prove that planets can form under a broader range of conditions than scientists had previously realized. If three suns and a flickering mixture of dust rings are not enough to foil an emerging planet, who knows what it is.