Massive planets may be orbiting the young triple star GW Orionis

Astronomers have found strong evidence of a massive planet (or planets) (the first planet (s) in a circumtriple orbit) in a three-star hierarchical system called GW Orionis (GW Ori).

GW Ori, also known as HD 244138 and HIC 25689, is about 1,312 light-years away in the constellation Orion.

It is a three-star hierarchical system, with a binary star (GW Ori A and B) at a separation of approximately 1 AU (astronomical units) and a tertiary stellar companion (GW Ori C) at a projected distance. of about 8 AU.

It is one million years old and houses a misaligned circumflex protoplanetary disk.

“Unlike our solar system, which consists of a lone star, it is believed that half of all stellar systems consist of two or more stars that are gravitationally bound together,” said Dr. Jeremy Smallwood of the Department of Physics and Astronomy from the University of Nevada and colleagues.

“But no planet has ever been discovered orbiting three stars – in a circumtric triple orbit. Maybe until now. ”

This composite image shows the ALMA and SPHERE / VLT observations of the disk around GW Orionis. The ALMA (blue) image shows the ringed structure of the disk, with the innermost ring (part of which is visible as an oblong point in the center of the image) separated from the rest of the disk. Observations of the sphere (red-orange) allowed astronomers to see for the first time the shadow of this ring deeper inside the rest of the disk, which allowed them to reconstruct its deformed shape. Image credit: ALMA / ESO / NAOJ / NRAO / University of Exeter / Kraus et al.

This composite image shows the ALMA and SPHERE / VLT observations of the disk around GW Orionis. The ALMA (blue) image shows the ringed structure of the disk, with the innermost ring (part of which is visible as an oblong point in the center of the image) separated from the rest of the disk. Observations of the sphere (red-orange) allowed astronomers to see for the first time the shadow of this ring deeper inside the rest of the disk, which allowed them to reconstruct its deformed shape. Image credit: ALMA / ESO / NAOJ / NRAO / University of Exeter / Kraus et al.

Using observations from the Atacama Large Millimeter / Submillimeter (ALMA) matrix, astronomers analyzed three previously observed dust rings around the GW Ori system.

They identified a substantial, but disconcerting, gap at 100 AU and misalignments between each of the rings.

They investigated different origins, including the possibility that the gap was created by the gravitational pair of the three stars.

But after building a complete model of GW Ori, they found that the most likely and fascinating explanation for disk space is the presence of one or more massive planets.

“Gas giants are usually the first planets to form within a star system. They follow terrestrial planets like Earth and Mars, “Dr. Smallwood said.

“The planet itself cannot be seen, but the finding suggests that this is the first orbital planet ever discovered.”

New observations of ALMA are expected in the coming months, which could provide direct evidence of the circumtriple planet (s).

“It’s really exciting because it makes the theory of the formation of the planet really robust,” Dr. Smallwood said.

“It could mean that planet formation is much more active than we thought, which is pretty cool.”

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