Baffled

Astronomers spent decades looking for objects from outside our own solar system. Then two arrived at once. When should we expect the next one? And what can they teach us?

It emerged from the celestial void in October 2017 – a tiny bright speck on the telescope at Haleakalā Observatory, Hawaii.

Tumbling through space at 57,000mph (90,000 kmph), the object is thought to have come from the direction of Vega, an alien star that resides 147 trillion miles (237 trillion km) away. Possibly shaped like an elongated cigar, possibly formed into an uncannily spaceship-like disc, by the time it was spotted it had already zipped by our own Sun, performed a slick hairpin turn, and begun hurtling off in another direction.

This space anomaly was named 'Oumuamua – pronounced oh-moo-uh-moo-uh – Hawaiian for "a messenger from afar arriving first". Robert Weryk, the astronomer at the University of Hawaii who first detected it, knew immediately from its speed that he was looking at something new to physics. This was no ordinary comet or asteroid, it was an interstellar visitor from a distant, unidentified solar system – the first to have ever been found.

Appropriately for an object with such alien origins, it soon became clear that 'Oumuamua was suitably strange. Two things in particular fixated scientists.

The first was its mysterious acceleration away from the Sun, which was hard to reconcile with many ideas about what it might have been made of. The second was its peculiar shape – by some estimates, it was 10 times as long as it was wide. Before 'Oumuamua, the most elongated known space objects were three times longer than they were wide.  TO READ MORE, CLICK HERE...