Exomoons May Become Quasi-planets

New research by astronojers Mario
Sucerquia of Universidad de Antioquia, Colombia, and Jaime Alvarado-Montes from
Australia's Macquarie University has shown that moons ejected from orbits
around gas giant exoplanets could explain several astronomical mysteries. They
modelled the likely behaviour of giant exomoons predicted to form around
massive planets – and discovered that they would be expelled and sent packing.
Roughly 50% of these ejected
moons would survive both the immediate expulsion and avoid any subsequent
collision with the planet or the star, ending up as quasi-planets travelling
around the host star, but in eccentric “Pluto-like” orbits.
These rogue moons – dubbed
“ploonets” by Sucerquia, Alvarado-Montes and colleagues – could potentially
explain several puzzling phenomena, not the least of which is why astronomers
have so far confirmed the existence of at least 4098 exoplanets, but not a
single exomoon.
Most of the planets discovered
thus far are of a type known as Hot Jupiters, a fact that reflects mainly the
limits of current detection technology. Previous research indicates that at
least some of these should be orbited by large moons.
Their absence, the researchers
write in a paper soon to be published in the journal Monthly Notices of the
Royal Astronomical Society, could be explained by a scenario in which the
angular momentum between the two bodies results in the moon escaping the
gravitational pull of its parent.
“These moons would become
planetary embryos, or even fully-fledged planets, with highly eccentric orbits
of their own,” explains Alvarado-Montes.
Did Jupiter once have ‘ploonets’?
Original Image: NASA/Johns Hopkins University Applied Physics
Laboratory/Southwest Research Institute/Goddard Space Flight Center
While conceding that ploonets
remain hypothetical, the researchers say their existence would offer a possible
explanation for several challenging results produced by NASA’s now-retired
Kepler space telescope.
These include the puzzling dips
in the light-curves emanating from a formally known as KIC-8462852.
“It’s better known as Tabby
Star,” says Alvarado-Montes, “and the strange changes in its light intensity
have been observed for years, but are still not understood. Ploonets could be
the answer.”
They might also explain apparent evidence of cannibalism
between some stars, or the existence of “exocomets” around others.
Ploonets, thus, may be a vital
piece of the planetary puzzle, but, as yet, their existence remains unproven.
Sucerquia, Alvarado-Montes and
colleagues concede that even if they do exist, they may deteriorate too rapidly
to ever be observed.
“If, on the other hand,” they
write, “the timescales are large enough, we could have real chances to detect
them in the near and middle future.”
The paper is currently available on arXiv, the preprint
library maintained by Cornell University in the US.
Source: https://www.mq.edu.au/newsroom/2019/07/12/exiled-moons-may-explain-astronomical-mysteries/
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