An artist’s impression of the warped disc at the center of the triple star system, (
​(Credit: ESO/L. Calçada, Exeter/Kraus et al)

Over the years, astronomers have found many planetary systems with two or even three stars. However, the planets within the systems typically orbited a single star. Now, researchers may have found a gaseous exoplanet that orbits its three suns simultaneously!

“Unlike our Solar System, which consists of a solitary star, it is believed that half of all-star systems consist of two or more stars that are gravitationally bound to each other,” said Dr. Jeremy Smallwood, lead author and a recent Ph.D. graduate in astronomy from the University of Nevada, Las Vegas (UNLV). “But no planet orbiting three stars — in a circumtriple orbit — has ever been discovered. Perhaps until now.”

A composite image from ALMA and the Very Large Telescope of the triple star system GW Orionis (Image Credit: ESO/ Exeter/ Kraus et al., ALMA (ESO/NAOJ/NRAO).

The distant planet is part of GW Orionis. The young star system is located 1,300 light-years from Earth in the constellation Orions. It is surrounded by three massive rings of dust and debris from which a planet can form. At the center lie three stars — two of which (GW Ori A and B) orbit each other closely while the third (GW Ori C) circles the pair from a distance.

In 2020, UNLV researchers observing GW Orionis with the Atacama Large Millimeter/submillimeter Array (ALMA) — one of the world's most powerful radio telescopes — noticed that its rings were not aligned. They also featured a massive gap in between. Even more intriguing, the innermost ring was twisted at a weird angle to the others.

An ALMA image of GW Orionis, showing the rings (left). A SPHERE image of the system, with the shadow of the inner ring cast on the rest of the disc (right) (Credit: ALMA (ESO/NAOJ/NRAO), ESO/Exeter/Kraus, et al.)

After exploring multiple possible scenarios and performing a comprehensive analysis, the team concluded that the unusual features indicated the presence of at least one massive gas planet. Furthermore, the researchers, who published their findings in the journal Monthly Notices of the Royal Astronomical Society on September 17, 2021, suggest that the yet-to-be-seen planet orbits all three stars at the same time. Such a planet would not only have had to form under highly hostile conditions but also be strong enough to withstand the gravitational pull of its three suns. Smallwood and his team next hope to use the ALMA telescope to obtain concrete evidence of the planet’s existence.

“It’s really exciting because it makes the theory of planet formation really robust,” Smallwood said. “It could mean that planet formation is much more active than we thought, which is pretty cool.”

However, those hoping to see three dramatic sunrises and sunsets on this supposed planet will be disappointed. The researchers say the two stars at the center move in synch and most likely appear as one big star, while the third most likely swoops around them.

Resources: Livescience.com, CNN.com, Sciencedaily.com