Our familiar Moon is not the only thing orbiting the Earth! In addition to all of the man-made satellites (and there are a lot of them), a few other tiny moons have recently been discovered, and there may be a lot more of them. It appears that these extra moons fall into two categories: space junk and lost asteroids. A cluster of external links, below, tell the story:
Space junk
- New
‘moon’ found around Earth [BBC, 11 September 2002]
Object known as JOO2E3, captured by Earth in 2002 - Earth’s
new ‘moon’ is space junk [BBC, 12 September 2002]
Follow-up to article cited above - Earth’s
new moon [cooltech.iafrica.com, 13 September 2002]
Refers to space object JOO2E3, noted above; also mentions Cruithne (see below)
Cruithne (pronounced “croo-EEN-ya”), a near-earth asteroid
Although Cruithne is often said to be “Earth’s second moon”, its orbit is in fact around the Sun, not the Earth. The catch is that it takes nearly the same length of time to orbit the Sun as the Earth does (but not exactly), so it manages a near approach to the Earth about every 770 years. To make matters more complex, its orbit is not in the same plane as the Earth’s.
- More
Moons Around Earth? It’s Not So Loony
[Space.com, 29 October 1999]
Discussion of Cruithne, a captured asteroid which is now said to be sort of a permanent satellite of Earth - Lost
asteroid is Earth’s new moon, say experts [Electronic Telegraph,
25 January 2000]
Another discussion of Cruithne - Wikipedia’s
article on 3753 Cruithne
Declares it to be actually in orbit around the Sun - Near-Earth Asteroid 3753 Cruithne
- Another article on Cruithne and other near-Earth asteroids
- Cruithne,
Earth’s “second moon”
Includes simulations of its orbit - Have
astronomers discovered Earth’s second moon?
[Curious About Astronomy]
Discussion of Cruithne’s orbit and possible future
Three other lost asteroids
- Earth’s
New Travelling Companion: Quasi-Satellite Discovered
[Space.com, 21 October 2002]
Article on 2002 AA29, a captured asteroid - A
new “moon” for Earth [Astronomy.com, May 22, 2004]
Refers to 2004 GU9, another asteroid; also mentions another called 2003 YN107 - Earth’s
‘quasi-moon’ is wayward asteroid
[New Scientist, 28 March 2004]
Discussion of three stray asteroids