The head of Harvard University's Astronomy Department is doubling down on his claim from November 2018 that the space rock Oumuamua, the first interstellar object to enter our solar system, which it did in 2017, was an alien probe.
Dr. Avi Loeb was interviewed by Haaretz about his controversial claim, which was made in a paper published in the Astrophysical Journal Letters. Co-author and Harvard astrophysicist Shmuel Bialy had stated, “Currently there is an unexplained phenomena, namely, the excess acceleration of Oumuamua, which we show may be explained by the force of radiation pressure from the sun. However this requires the body to have a very large surface and be very thin, which is not encountered in nature.” The paper stated:
Considering an artificial origin, one possibility is that ‘Oumuamua is a lightsail, floating in interstellar space as a debris from an advanced technological equipment (Loeb 2018). Lightsails with similar dimensions have been designed and constructed by our own civilization, including the IKAROS project and the Starshot Initiative2. The lightsail technology might be abundantly used for transportation of cargo between planets (Guillochon & Loeb 2015) or between stars (Lingam & Loeb 2017). In the former case, dynamical ejection from a planetary System could result in space debris of equipment that is not operational any more 3 (Loeb 2018), and is floating at the characteristic speed of stars relative to each other in the Solar neighborhood. This would account for the various anomalies of ‘Oumuamua, such as the unusual geometry inferred from its lightcurve (Meech et al. 2017; Fraser et al. 2018; Drahus et al. 2018; Belton et al. 2018), its low thermal emission, suggesting high reflectiv ity (Trilling et al. 2018), and its deviation from a Keplerian orbit (Micheli et al. 2018) without any sign of a cometary tail.
Loeb told Haaretz in layman's terms how he suspected that Oumuamua wasn’t a comet:
It was only under consecutive observation for six days, from October 25 to 31 – namely, a week after its discovery. At first they said, Okay, it’s a comet – but no comet tail was visible. Comets are made of ice, which evaporates as the comet approaches the sun. But we didn’t see a trail of gas or dust in Oumuamua. So the thinking was that it must be an asteroid – simply a chunk of stone. But the object rotated on its axis for eight hours, and during that time its brightness changed by a factor of 10, whereas the brightness of all the asteroids that we’re familiar with changes, at most, by a factor of three. If we assume that the light reflection is constant, that means its length is at least 10 times greater than its thickness.
Loeb explained how the information gleaned from the Hubble Space Telescope last June revealing that Oumuamua had accelerated when it passed through our solar system led him to believe alien forces were at work, especially because comets warmed by the sun accelerate as gas escapes, but they also have a comet tail, which Oumuamua did not have. Plus the normal gas emission from a comet causes the comet’s sin rate to change, and that didn’t happen either.
Loeb asserted, “The only hypothesis I could think of is a push from solar radiation pressure. For that to work, the object would have to be very thin, less than a millimeter thick, in other words a type of pancake. In addition, the Spitzer Space Telescope found no evidence of heat emission from the object, and that means that it is at least 10 times more reflective than a typical comet or asteroid. What we have, then, is a thin, flat, shiny object. So I arrived at the idea of a solar sail: A solar sail is a spaceship that uses the sun for propulsion. Instead of using fuel, it is propelled ahead by reflecting light. In fact, it’s a technology that our civilization is developing at this very time.”
Loeb told Haaretz, “I don’t care what people say. It doesn’t matter to me. I say what I think, and if the broad public takes an interest in what I say, that’s a welcome result as far as I’m concerned, but an indirect result. Science isn’t like politics: It is not based on popularity polls.”
Asked if he would have published the article if he didn’t have tenure, Loeb answered:
I suppose not. It’s not just the tenure. I’m head of the astronomy department, and founding director of the Black Hole Initiative [an interdisciplinary center at Harvard dedicated to the study of black holes]. In addition, I’m director of the Board on Physics and Astronomy of the National Academies. So it could be that I’m committing image suicide, if this turns out to be incorrect. On the other hand, if it turns out to be correct, it’s one of the greatest discoveries in human history.
Posting that the race that may have sent the probe may well be extinct by now, Loeb concluded:
As soon as it becomes clear that there really have been many civilizations that have become extinct, I believe that people will learn the right lesson. And if we discover remnants of advanced technologies, they will prove to us that we are only at the start of the road; and that if we don’t continue down that road, we will miss a great deal of what there is to see and experience in the universe. Imagine if cavemen had been shown the smartphone you’re using to record me. What would they have thought about this special rock? Now imagine that Oumuamua is the iPhone, and we are the cavemen. Imagine scientists who are considered the visionaries of reason among the cavemen looking at the device and saying, ‘No, it’s just a rock. A special rock, but a rock. Where do you come off claiming it’s not a rock?’”