If you could fly two billion miles in the direction of the Pegasus constellation, and knew where to look, you would find a thin, flat object, about the size of a football field and up to ten times more reflective than the average comet. If you watched it for a while, you would notice that it is tumbling as it moves away from the sun, turning end over end roughly every seven hours.
This object passed the Earth in October 2017. As it began its return to interstellar space, the Canadian astronomer Robert Weryk identified it among the images from what was then the world’s most powerful camera, a telescope in Hawaii called Pan-STARRS1. The astronomers in Hawaii called it ‘Oumuamua, a Hawaiian word meaning “first scout from a distant place”.
‘Oumuamua was the subject of great excitement. It was the first object humans have observed travelling through the solar system from interstellar space. But it also became controversial: its shape, the way in which it approached us, and the way it moved away are not consistent with the behaviour of an asteroid or comet. For 11 days, the world’s telescopes searched for meaning from this strange visitor.
A year later, the debate about ‘Oumuamua intensified when one of the world’s foremost astronomers, Avi Loeb, submitted a paper to the Astrophysical Journal Letters. In it, Loeb and his colleague, Shmuel Bailey, argued that ‘Oumuamua’s strange properties indicated that it was “a new class of thin interstellar material, either produced naturally, through a yet unknown process […] or of an artificial origin”. Since then, Loeb has maintained that the most rational, conservative explanation is that ‘Oumuamua was produced by an alien civilisation.
We will almost certainly never see ‘Oumuamua again, because it is heading away from the solar system at 30 kilometres a second. But Loeb says scientists must prepare now for what happens when the next such object arrives, as he believes it will very soon. If he is right, these objects surround us in numbers that are almost unimaginable.
Avi Loeb is a fast talker; he has the rapid fluency of someone who has spent decades giving lectures, but there is also an unpractised enthusiasm to his speech. He keeps the accent of his native Israel, though he has lived in the US since 1988, when he took a fellowship at Princeton University. His first interview was with the famous physicist Freeman Dyson, who was also well known for theorising about alien civilisations.
Loeb spent almost a decade as chair of Harvard’s astronomy department, the longest any scientist has held that position. He has made or helped to make a number of major breakthroughs in our understanding of the universe, including different ways of detecting exoplanets – planets orbiting stars other than the sun. He has correctly predicted incredible phenomena, such as stars that streak across the depths between galaxies at nearly half a billion miles an hour. He is the founding director of Harvard’s Black Hole Initiative, part of the Event Horizon Telescope project that in April 2019 presented to the world the first photograph of a black hole. [ … ]