Monday, 23 February 2009

Cruithne - do we really need two moons?

I’ve recruited a moon-bitch. I say “I’ve recruited”, I haven’t. One – let’s call it Christophe Philipps – has thrown itself at me like a…like a…well, sort of like a moon-bitch. Philipps (moon-bitchi are addressed by surname) serves me well. Once it fetches my slippers and newspaper, it goes to work sourcing the choicest cuts of moon-fact for my readers. Here’s its latest lead. It’s about the moon that man forgot. Thank you, Philipps.

Fathi Namouni – also probably the first words Sir Patrick Moore said to his dad as a baby – studied at a London university in the mid 1980s. While there he looked into Earth’s second moon. But credit goes to Dr Wiegert, Dr Innanen and Dr Mikkola for discovering Earth’s other companion. Ok, that’s the simple version. Read on for a little more detail.

Cruithne – pronounced “Cruithne” – is actually an asteroid. I lied. But its “companion” orbit makes it a bit like our moon. The moon is our only moon. Its close orbit (220,000 miles is very close in space) and regular motion bound by our gravity means it’s our one true satellite (another slight lie when you understand both the moon and Earth orbit a common point of gravity somewhere around the Earth’s core, but not situated centrally). Cruithne (aka Asteroid 3753) is locked in orbit with Earth. It loops around its orbit in a horseshoe shape – tagging along with us; imagine it like a drunk satellite, swaying in and out. It’s a bit like a moon but not enough to earn it the name.

Our asteroid passed closest to us in 1997. Only those with telescopes had the pleasure. The rest of us will have to wait another 770 years for it to return to its 1997 position. But Cruithne will only be with us for 5,000 years before it breaks away from us. I say let’s boycott Asteroid 3753 and concentrate on moon #1: maybe even write a book about her.

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