Companions of Earth: minimoons, quasi-satellites and horseshoes
- Written by Tanya Hill, Honorary Fellow of the University of Melbourne and Senior Curator (Astronomy), Museum Victoria
The Earth's only steadfast companion.Adrian Kingsley-Hughes/flickr, CC BY-NC-SAThe Earth has one steadfast companion – the moon has been locked in orbit around the Earth since its violent formation more than four billion years ago.
However, Earth’s gravity can also tug on small nearby objects – the near-earth asteroids –...








