Have Aliens Found Us? A Harvard Astronomer on the Mysterious Interstellar Object ‘Oumuamua
On October 19, 2017, astronomers at the University of Hawaii spotted a strange object travelling through our solar system, which they later described as “a red and extremely elongated asteroid.” It was the first interstellar object to be detected within our solar system; the scientists named it ‘Oumuamua, the Hawaiian word for a scout or messenger. The following October, Avi Loeb, the chair of Harvard’s astronomy department, co-wrote a paper (with a Harvard postdoctoral fellow, Shmuel Bialy) that examined ‘Oumuamua’s “peculiar acceleration” and suggested that the object “may be a fully operational probe sent intentionally to Earth’s vicinity by an alien civilization.” Loeb has long been interested in the search for extraterrestrial life, and he recently made further headlines by suggesting that we might communicate with the civilization that sent the probe. “If these beings are peaceful, we could learn a lot from them,” he told Der Spiegel.
I recently spoke by phone with Loeb, who was frustrated that scientists saw ‘Oumuamua too late in its journey to photograph the object. “My motivation for writing the paper is to alert the community to pay a lot more attention to the next visitor,” he told me. During our conversation, which has been edited and condensed for clarity, we discussed why Loeb thinks we need to consider the possibility that ‘Oumuamua was sent by aliens, the dangers of unscientific speculation, and what belief in an advanced extraterrestrial civilization has in common with faith in God.
Your explanation of why ‘Oumuamua might be an interstellar probe may be hard for laypeople to understand. Why might this be the case, beyond the fact that lots of things are possible?
There is a Scientific American article I wrote where I summarized six strange facts about ‘Oumuamua. The first one is that we didn’t expect this object to exist in the first place. We see the solar system and we can calculate at what rate it ejected rocks during its history. And if we assume all planetary systems around other stars are doing the same thing, we can figure out what the population of interstellar objects should be. That calculation results in a lot of possibilities, but the range is much less than needed to explain the discovery of ‘Oumuamua.
There is another peculiar fact about this object. When you look at all the stars in the vicinity of the sun, they move relative to the sun, the sun moves relative to them, but only one in five hundred stars in that frame is moving as slow as ‘Oumuamua. You would expect that most rocks would move roughly at the speed of the star they came from. If this object came from another star, that star would have to be very special.