For the past three years, there’s been a second moon orbiting around the Earth. Don’t feel too bad for not noticing, though – scientists only detected it two weeks ago.
On the 15th of February, scientists working on the Catalina Sky Survey (which tracks near-Earth objects) recorded a bright rock orbiting the Earth. This turned out to be an asteroid, which has been given the not-very-catchy name of ‘2020 CD3’. One of the discoverers, Kacper Wierzchos, tweeted that “this is just the second asteroid known to orbit Earth”, out of the million that have been discovered.
The reason it took so long to discover is that the asteroid is only 1.9-3.5 metres across. This means we only learnt of our new moon a couple of months before it leaves us – simulations predict that it will get thrown out of orbit in April. A similar thing happened to our last mini-moon in 2007, since captured asteroids don’t have stable orbits.
Lachlan Writes Science 