In the photo: Left - a map of asteroids known to mankind for 1990 (about 9 thousand objects), on the right - data for 2007 (379 084 objects).
Studying how the Earth temporarily captures asteroids has shown that our planet must have at least one additional moon at any given time.
In 2006, participants in the American astronomical project Catalina Sky Survey drew attention to the fact that a mysterious body had entered the Earth's orbit. The spectrum of this object was remarkably similar to the titanium white that covered the stages of the Saturn 5 rocket. Indeed, a number of rocket stages revolve around the Sun in the vicinity of the Earth.
However, upon closer inspection, the object turned out to be miraculous. 2006 RH120 was a tiny asteroid (only a few meters across). In September 2006, he was captured by the Earth's gravity, and in June 2007, he set off on a further journey in search of more interesting neighbors.
2006 RH120 became the first reliably documented example of a temporary moon.
Mikael Granvik from the University of Hawaii (USA) and his colleagues believe there should be many such examples. Researchers have modeled the Earth-Moon system to understand how often we can count on additional satellites and how long they can stay in orbit.
The answer is very simple. At any given time, at least one natural satellite of a meter diameter must be present in the Earth's orbit. These objects stay there for about 10 months and manage to orbit our planet three times.
Interest in the problem goes beyond academic. NASA has repeatedly stated that it is interested in sending people to the asteroid. What better way to start than with the object in our orbit?
However, finding the right candidate is a difficult task. The asteroids that may become temporary satellites in the near future are very small; it is difficult to see them. Moreover, they are influenced by so many forces that it is almost impossible to predict their capture by the Earth.
Promotional video:
The research results are posted on the arXiv website.