Exoplanet orbiting three stars discovered in a first

Since its discovery announced last fall, the GW Orionis star system, located 1,300 light years from Earth in the constellation Orion, has aroused the curiosity of scientists. It must be said that this group of three stars flanked by a large disk of dust and gas, atypically shaped, is nothing ordinary. Imagine three suns surrounded by two rings clearly separated by a void, one of which is tilted 38 degrees from the other. How could something so strange happen?

At first, its discoverers imagined that the gravitational interactions between the stars of this strange team could be at the origin of the tearing of its so-called protoplanetary disk (because planets can form there). A thesis that has just been called into question by a study recently published in the scientific journal Monthly Notices of the Royal Astronomical Society.

According to its authors, the combined gravity of the three stars cannot be sufficient to explain the observations. However, the international team of researchers including a French astrophysicist is making another very attractive hypothesis. The tearing of the disk of gas and dust would actually be the result of a large Jupiter-type exoplanet (or even several) which would be digging this breach in real time. What would be unheard of!

A unique case
Especially since, among the more than 4,700 exoplanets known to date, the vast majority orbit a single star like the Earth around the Sun, a few make their rounds near two, but none so far have ‘has three. A first case had been mentioned in 2016, with HD 131399Ab, but it was finally revealed to be a star and not an exoplanet.

If there is a planet that digs its groove in GW Orionis’s disc, it is therefore the very first known to orbit three stars simultaneously. This reinforces the idea that planets can originate in all star systems, even the most exotic of them.

It remains to provide direct proof of the existence of this planet. This, according to the authors of the study, could be done during an observation campaign already planned with the Alma telescope and the Very Large Telescope of the European Southern Observatory (ESO) in all next months.

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