Scientists have been stumped as to why they are yet to find an exomoon – a moon found outside the solar system. The latest theory suggests that moons orbiting huge planets could be kicked out of the planet’s orbit, creating a new planet – or a ‘ploonet’ as it is being dubbed. To understand more about this, scientists ran computer simulations on exoplanets colloquially known as hot Jupiters.
These exoplanets are the size of Jupiter – the solar system’s largest planet – but as close to their host star as Mercury.
The simulations found that these large planets often start much farther out, and then drift over billions of years towards their stars.
However, as the massive celestial bodies float towards the star, one of two things usually happens to their moons, according to a team from the University of Antioquia in Colombia.
The simulations show that 44 percent of the moons come crashing to the planet, while 48 percent leave their planet’s orbit and takes an orbit around their host star, thus creating a ploonet.
Six percent of the moons are eaten by the star and a small two percent are kicked out of the planetary system altogether.
The researchers write in the study published in arXiv: “If large exomoons form around migrating giant planets which are more stable (eg. those in the Solar System), what happens to these moons after migration is still under intense research.
“This paper explores the scenario where large regular exomoons escape after tidal-interchange of angular momentum with its parent planet, becoming small planets by themselves. We name this hypothetical type of object a ploonet.”
However, the same thing could happen to Earth’s moon.
Mario Sucerquia of the University of Antioquia in Colombia told New Scientist: “Earth’s tidal strength is gradually pushing the moon away from us at a rate of about 3 centimetres a year. Therefore, the moon is indeed a potential ploonet once it reaches an unstable orbit.”
But as the Moon leaves Earth, it slows down the planet’s rotation, which could have devastating consequences.
Earth’s rotation is slowing as our planet uses energy to keep the tide ahead of the Moon’s orbit.
Our planet keeps the tide slightly ahead of the lunar satellite, which keeps the ecosystem in check and sloshes oceans from continent to continent.
However, to do this, the Earth uses kinetic energy – something which is finite.
This means Earth’s orbit is slightly slowing down as it runs out of energy, and the consequences could be catastrophic.
A slower rotating globe leads to stronger and more frequent earthquakes – exactly why this is the case is unclear, but experts believe it could be down to changes in the Earth’s core which ultimately has an effect on the surface.
Research from Roger Bilham of the University of Colorado in Boulder and Rebecca Bendick of the University of Montana in Missoula looked at earthquakes with a magnitude higher than seven since 1900.
The duo found five years since the turn of the 20th century where there were significantly more 7.0 earthquakes – all of which were years that earth’s rotation speed had slowed down slightly.
Prof Bilham said: “In these periods, there were between 25 to 30 intense earthquakes a year.
“The rest of the time the average figure was around 15 major earthquakes a year.
“The correlation between Earth’s rotation and earthquake activity is strong and suggests there is going to be an increase in numbers of intense earthquakes.”