Exiled moons can explain astronomical mysteries

The moons ejected from the orbits around the giant gas exoplanets could explain several astronomical mysteries, suggests an international team of astronomers.

Researchers led by Mario Sucerquia, of the University of Antioquia, Colombia, and Jaime Alvarado-Montes, of the Australian University of Macquarie, have modeled the likely behavior of giant exomons who should form around gigantic planets and discovered that they would be expelled and shipped.

Approximately 50% of these ejected moons would survive immediate expulsion and avoid any subsequent collision with the planet or star, turning into quasi- planets moving around the host star, but in eccentric "Pluto" orbits ".

These rogue moons, called "ploonets" by Sucerquia, Alvarado-Montes and his colleagues, could potentially explain several puzzling phenomena, the least of which is why astronomers have confirmed the existence of at least 4098 exoplanets but not one exomoon.

Most of the planets discovered so far belong to a type known as Hot Jupiters, which primarily reflects the limitations of current detection technology. Previous research indicates that at least some of them should be surrounded by large moons.

Their absence, write the researchers in an article that will soon be published in the journal Monthly Notices from the Royal Astronomical Society, could be explained by a scenario in which the angular momentum between the two bodies makes that the moon escapes the gravitational attraction of its parent.

"These moons would become planetary embryos, or even planets in their own right, with very eccentric orbits," Alvarado-Montes explains.

While admitting that the ploonets remain hypothetical, the researchers believe that their existence would explain several difficult results produced by the Kepler Space Telescope, now retired from NASA.

These include the mysterious immersions in the light curves emanating from a KIC-8462852.

"It's better known as Tabby Star," says Alvarado-Montes, "and the strange changes in its luminous intensity have been observed for years, but are still not understood." Ploonets might be the answer. "

They could also explain apparent evidence of cannibalism between certain stars or the existence of exocomets around others.

Ploonets can therefore be an essential part of the global puzzle, but their existence has not yet been proven.

Sucerquia, Alvarado-Montes and their colleagues recognize that even if they exist, they can deteriorate too quickly to be observed.

"If, on the other hand," they write, "the deadlines are sufficiently large, we could have a real chance of detecting them in the near and medium future".

The document, "Ploonets: Training, Evolution and Detectability of Takedowns", is currently available on arXiv, the pre-print library run by Cornell University in the United States.