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Why a Small Red Rock is Fascinating Astronomers
And other news from space and physics this week
It’s not, normally, the kind of thing that attracts much attention. A few million miles from Earth lies a small red rock, roughly forty meters across, tumbling gently around the Sun. Astronomers, you might think, would have more interesting things to look at.
And yet the astronomical world is strangely interested by this rock. Telescopes spend days trained on it, watching its every twist and turn. Space agencies are busy planning missions to visit it and designing probes to descend to its surface before bringing bits of it back home.
That’s because Kamo’oalewa, as the rock is known, occupies a special and almost unique status. Kamo’oalewa is a “quasi-moon”, an object that technically orbits the Sun but spends much of its time close to the Earth. Five such quasi-moons are known, and Kamo’oalewa happens to be the closest and most stable of them.
Astronomers first spotted it in 2016, using a telescope in Hawaii, and soon realised that Kamo’oalewa always hovers just in front or just behind our planet. For most quasi-moons this is a temporary arrangement. They spend just a few years or decades close to Earth, before drifting away into the depths of space.
