Astronomers may have discovered the first known planet orbiting 3 stars

The artistic animation of GW Orion. Credit: ESO / Exeter / Kraus et al./L. Calçada

The potential discovery of a circumtriple planet has implications for strengthening our understanding of the formation of planets.

In a distant star system – just 1,300 light years from Earth – researchers and colleagues at UNLV may have identified the first known planet to orbit three stars.

Unlike our solar system, which consists of a lone star, it is believed that half of all star systems, like GW Ori where astronomers have observed the new phenomenon, consist of two or more stars that are gravitationally related to them. to each other.

But no planet orbiting three stars – a circumptriple orbit – has ever been discovered. Maybe until now.

An image of GW Orionis, a triple star system with a mysterious hole in its surrounding dust rings. UNLV astronomers hypothesize the presence of a massive planet in space, which would be the first planet ever discovered to orbit three stars. The image on the left, provided by the Atacama Large Millimeter / submillimeter Array (ALMA) telescope, shows the annular structure of the disc, with the innermost ring separated from the rest of the disc. Observations on the right image show the shadow of the innermost ring over the rest of the disc. UNLV astronomers have used observations from ALMA to build a complete model of the star system. Credit: ALMA (ESO / NAOJ / NRAO), ESO / Exeter / Kraus et al.

Using observations from the powerful Atacama Large Millimeter / submillimeter Array (ALMA), UNLV astronomers analyzed the three dust rings observed around the three stars, which are essential to the formation of the planets.

But they found a substantial, but puzzling, loophole in the circumtriple disc.

The research team investigated different origins, including the possibility that the gap was created by the gravitational couple of the three stars. But after building a complete model of GW Ori, they discovered that the most likely and fascinating explanation for space in the disk is the presence of one or more massive planets, Jupiter-like in nature. The gas giants, according to Jeremy Smallwood, senior author and recent doctorate. graduates in astronomy from UNLV, are usually the first planets to form within a star system. Terrestrial planets like Earth and March to follow.

The planet itself cannot be seen, but the discovery – highlighted in a September study in the Monthly notices from the Royal Astronomical Society – suggests that this is the first circumtriple planet ever discovered. Further observations from the ALMA telescope are expected in the coming months, which could provide direct evidence of the phenomenon.

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

Reference: “GW Ori: circumtriple rings and planets” by Jeremy L Smallwood, Rebecca Nealon, Cheng Chen, Rebecca G Martin, Jiaqing Bi, Ruobing Dong and Christophe Pinte, September 17, 2021, Monthly notices from the Royal Astronomical Society.
DOI: 10.1093 / mnras / stab2624