There is now more evidence that the strange star system perched in the nose of the constellation Orion may contain the rarest type of planet in the known universe: one tiny exoplanet orbiting three suns simultaneously.
The star system, known as GW Orionis (or GW Ori), located about 1,300 light-years from Earth, is a tempting target for study. With three dusty orange rings intertwined with each other, the system literally looks like a giant bull’s eye (circles at which people shoot arrows in an attempt to hit the center of the target) in the sky.
In the middle of these circles live 3 stars, two of which are trapped in a narrow binary orbit with each other, and the third orbits widely around the other two stars.
Scientists took a closer look at GW Ori using the Atacama Large Millimeter/submillimeter Array Telescope (ALMA) in Chile, in a study published in 2020 in The Astrophysical Journal Letters. They discovered that the system’s three dust rings are actually out of balance with each other, with the innermost ring swinging violently in its orbit.
The team suggested that a small planet could upset the gravitational balance of the three complex ring arrangement in GW Ori. If the discovery is confirmed, it will be the first triple-sun (or “round”) planet in the known universe.
Now, a paper published September 17 in the journal Monthly Notices of the Royal Astronomical Society provides new evidence for the existence of this rare planet. The research team ran a 3D simulation to model how mysterious gaps in the star system’s rings might form, based on observations of other dust rings (or “protoplanetary disks”) elsewhere in the universe.
The team tested two hypotheses: either the gap in the rings of GW Ori formed from the torque (rotational force) applied by the three rotating stars at the center of the system, or it appeared when a planet formed within one of the rings.
The scientists concluded that there was not enough turbulence in the rings for the stellar moment theory to work. Instead, simulations suggest that a massive Jupiter-sized planet, or possibly several, is the most likely explanation for the rings’ strange shape and behavior.
If future observations of the system support this theory, GW Ori may be “the first evidence of a circular planet digging a hole in real time,” senior study author Jeremy Smallwood of the University of Nevada, Las Vegas, told the New York Times.