Emily Chan
According to Stephen Lepp, a study co-author and astrophysicist at the University of Nevada, Las Vegas, there were a lot more smaller planetary bodies and debris in the solar system than there are today.
Most of the debris from the moon’s formation likely collided with the Earth or moon, or was thrown past both.
But, some of it could have ended up revolving around the Earth and moon in circumbinary orbits. They would have orbited the poles of the Earth and the moon instead of around their equators.
No stable polar circumbinary orbits around Earth and the moon are present today, but the researchers discovered that such orbits were stable at the time of the formation of the moon.
It wasn’t until after the distance between the moon and Earth stretched to 7.5 times the Earth’s diameter that the orbits ceased to exist.
“Most works on the dynamics of orbits around the Earth-moon system has concentrated on the current orbital configuration,” Rebecca Martin, a study co-author and astrophysicist at the University of Nevada, Las Vegas, said.
“When we found that the current configuration wouldn’t support polar orbits, we decided to look at earlier times when the separation between the Earth and the moon was much smaller.”
In early times, a companion moon or disk in a polar orbit around the moon and Earth might have significantly affected the evolution of the moon-Earth orbit, which could explain its modern-day features.
Even though polar material is long gone now, studies of orbits in exoplanetary systems could clarify some of the dynamics.
The study was accepted for publication in the Astrophysical Journal.
