14 DAY TRIAL // Though the twin Earth hypothesis has been abandoned a long time ago, some astronomers have not given up the quest of searching for cosmic objects that may accompany Earth in its orbit. Their work paid off too, and recently a team was able to identify an asteroid that meets this criterion.
In the past, people believed that another Earth could exist in the same orbit as our own, except on the other part of the Sun. But astronomers dismissed the idea in the end, saying that the gravitational effects such a planet would have on its neighbors would make it easy to detect.
However, their explanation did not preclude an Earth companion at all. As such, the discovery of asteroid 2010 SO16 did not really come as a surprise to anyone. What was surprising about this space rock is the shape of its orbit.
Astronomers say that the object circles the Sun in the same orbit as our planet does, except its orbit is shaped like a horseshoe. This is very unusual for such an asteroid, Technology Review reports.
The discovery was made by a team of experts at the Armagh Observatory in Northern Ireland, who were led by astronomers Apostolos Christou and David Asher. They say that very few other known near-Earth objects (NEO) have the orbit of this one.
According to calculations, the peculiar orbit this asteroid is in is produced by the interactions it has with our planet, and by the basic laws of celestial mechanics governing orbits in general.
Objects that are located closer to the Sun move faster than those who are farther away. When 2010 SO16 is closer to the star, it moves faster than Earth, and therefore gradually catches up with it.
But when it gets to close, our planet's gravity influences it, dragging the rock towards Earth, and making it move farther away from the Sun. At some point, the asteroid will enter an orbit that is farther away from the star than our planet's is.
It will then begin to move slower, and will lag behind Earth over time. Years later, the two bodies will meet again, only this time it will be our planet that will catch up with the asteroid, triggering the same interaction pattern yet again.
Astronomers calculate that this process takes about 350 years to unfold once. One thing that amazed experts about 2010 SO16 in particular is that it seems to follow its orbit very closely, whereas objects in horseshoe-shaped orbits are generally prone very likely to influenced by larger bodies in space.
The asteroid is now visible from Earth, but is very faint, and special equipment is needed to observe it. “It will remain as an evening object in the sky for several decades to come,” Christou and Asher say.