Astronomers have discovered yet another alien visitor to the Solar System.

This one appears to be a comet, a ball of dust, ice and various volatile materials. It is rapidly approaching the sun and has just passed within the orbit of Jupiter. The object, designated Comet 3I/ATLAS, has an estimated diameter of about 20 kilometres. It is moving at around 240,000 kilometres an hour, which means it is not a member of our Solar System. It is moving far too fast to be held by the Sun's gravity.

That means it has come in from interstellar space, will fly past the Sun and return to the abyss. If we consider the chances of one of these lonely interstellar wanderers randomly drifting into the Solar System, and that this has happened at least three times in the last few years, there must be a lot of them.

These bodies probably originated in the same way as their counterparts in our Solar System—from the collapse of a cloud of gas and dust. If so, they would start their existence cosily orbiting a newly- born star........

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