A planet with an amazing orbit around two stars is found

Scientists suspect that there may be a planet in the gas-dust disk that surrounds the Herculis binary system. If so, then it rotates in a plane perpendicular to the one in which the stars orbit each other. 

AC Herculis system. Source: phys.org

Amazing AC Herculis system

A group of scientists led by Rebecca Martin from the Nevada Center for Astrophysics has suggested that a very unusual planet may be hiding in the AC Herculis system. This star, more precisely, a system of two luminaries, is located at a distance of 4,200 light-years from us.

Its main component is a pulsating yellow-white giant, about 2,400 times brighter than the Sun. Not much is known about the second star, except that it is heavier than our luminary. However, scientists have previously established that there is a powerful dust disk around these components.

Now, based on observations, they assume that there is a planet inside the disk that stabilizes it. The conclusion is based on the fact that there is a gap inside this disk that divides it into two parts.

Circumbinary disk and a planet in it. Source: Martin et al. 2023

Circumbinary disk

Systems in which planets orbit two stars at once have been encountered before, but in small numbers. The first of them was discovered in 2019, and since then, scientists have learned about the existence of three more. However, AC Herculis is not interesting for this. The fact is that its disk, and therefore the orbit of the planet, are almost perpendicular to the plane in which the stars orbit each other.

To be precise, the possible orbit of the planet is close to the perpendicular but still differs from it by 9 percent. And this raises a number of questions, firstly, why it does not lie in the same plane with the orbits of the luminaries at all.

In addition, scientists are very surprised by the large distance between the stars in this system, since usually planets orbiting two stars at once do this when the latter is very close. And here, two giant luminaries are circling each other for a period of about 3.5 Earth years.

Also, scientists have never seen a planet orbiting two stars, one of which does not belong to the main sequence but is a giant. The AC Herculis system is extremely unusual, and researchers hope that it will be able to enrich us with new knowledge.

According to phys.org

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