For a short time, our planet was orbited by a second, small nature satellite. But now a veteran observer says that Asteroid 2020 CD3 has been “thrown back into orbit around the sun” and tailors us on our annual trip around our star.
The small asteroid is probably just about the size of a large appliance or compact car and it was first discovered in February, but astronomers believe it is probably stuck in orbit around the earth for at least a year, if not longer.
Bill Gray, who created a software package that astronomers use to track nearby asteroids and comets, told me that he is certain that our minimum moon has returned to the sun rather than our planet. He explained that 2020 CD3 probably came in for a near earth passage without enough energy to escape the gravitational pull of our planet and wound up in orbit for a while by the combined gravity of the earth and the moon.
Gray called the runway the temporarily trapped object ”a slightly complicated dance around the earth and the moon. “
That dance has a chance to collide with one or the other object, but in the case of the CD, it ultimately allowed it to “steal” some energy from the earth and the moon, allowing it to escape back to a longer orbit around the sun. .
Now our former moon is behind us on our own orbit and gradually becomes weaker.
“CD3’s new orbit takes a little over a year to get around the sun,” Gray explained. “It’s a bit like two cars sharing a track, where one (the earth, in this case) finishes laps just a little faster than the other and gradually moves forward.”
At some point we will actually leave 2020 CD3 – Gray says it will happen next in March 2044 – but this pass will not be close enough for the space rock to be captured again.
“It’s hard to predict that point, but there will probably be closer approaches every 25 years or so,” Gray said. “Eventually, one of these close approaches will be close enough and in the right direction for it to be caught again. And probably lost again, unless it hits the earth or moon during the process. At some point in the next hundred thousand years it will probably happen. “
Such an impact would probably not amount to much more than a few fireballs in the sky when a once proud moon burns in the atmosphere.
But there are probably many other minimum months between and then.
We know of a few other objects besides 2020 CD3 that have been temporarily captured in recent decades. It has probably happened many other times during the long history of our planet and will surely come again.