I never knew that the Earth had another moon apart from The Moon. But what is this new moon that has decided to steal our already (beautiful) moon of its honour?
If you believed till now that the Earth’s only moon was the Moon, tough luck, you are wrong! Yes, when I found out about Cruithne, I had NO idea that Earth had a second moon. Now is the time when I shall delve further into this mystical moon that hardly any members of the planet have heard about.
Cruithne or 3753 Cruithne is also given other (quite scientific) names like 1983 UH and 1986 TO. Discovered on the 10th of October 1986, Duncan Waldron in Australia, was the man responsible to locate this quasi satellite. A quasi satellite can be very simply described as an object in space that follows the orbit of its planet and is related to this planet when it comes to gravity and the other complexities but is somehow very eccentric in terms of orbiting. Then why is it that after it’s been discovered, we still can’t see it? It wasn’t till 1997 that it was discovered that Cruithne had an orbit way different than that of the Earth. This highly eccentric orbit is better described as a horse shoe kind of orbit.
Here are a few vital stats about Cruithne:
- Diameter: 5 km or 3 miles
- Closest approach to the Earth: 30 times the distance that is between the Earth and the Moon
- Mass: 130,000,000,000,000kg
- Years to complete orbiting around the Earth: 770 years
- Time taken to revolve around sun: About 364 days
- Temperature: 275 Kelvin (About 2 degree Celsius)
So is there any worry of Cruithne and Earth clashing? Looks like not in a long (and I mean LONG) time because the orbit of Cruithne dictates that it follows the Earth in a synchronised way even though scientists claim that Cruithne’s orbit isn’t stable.
What is this about the eccentric orbit? Well, to the sun, Cruithne is an elliptic orbit (which is similar to that of the Earth) which means that it feels like it follows the Earth. But to the Earth, Cruithne looks like it follows a kidney bean/horse shoe kind of orbit because the orbital speed and distance of Cruithne to the Sun is a lot more different than that of the Earths. Because the Earth revolves around the Sun in 365 days and Cruithne revolves in 364, it means that in the long run, it is going to be the Earth that ends up following Cruithne because Cruithne is quicker than the Earth when it comes to revolutions. The process is then reversed and it will feel like Cruithne is catching up with the Earth and so on and so forth. Eventually (with a bunch of complex science descriptions that I didn’t understand) because of the speed and time difference, the horse shoe orbit and the Earth will pull away from each other. This happens because there are gravitational energy exchanges that occur every single time Cruithne and Earth come very close to each other.
Well, enough of the boring sciency bits, now with the more interesting parts. When can you next see Cruithne? Cruithne’s last series of close interactions with the Earth happened in 1902 which isn’t really that long back. The next time there will be a set of close meetings will be in the July of 2292 where the Earth greets Cruithne at a (very tiny) 12.5 million km. Cruithne again meets Earth in what seems like every 380 to 390 years. Shame we can never see it, eh?