Two scientists from the Harvard-Smithsonian Center for Astrophysics have proposed that ‘Oumuamua, the first object born outside the solar system discovered, could be an extraterrestrial probe intentionally sent to explore our system. They made their speculations public last week in an article they added to the org prepublication repository and sent to The Astrophysical Journal Letters. In it, they detail new calculations on the movement of the object, which, according to the authors, suggests that it would be a solar sailboat. His claims, however, have met with skepticism from other researchers who have studied the strange Oumuamua.

The conclusions of scientists from the Harvard-Smithsonian Center for Astrophysics, Shmuel Bialy and Abraham Loeb, are based on the fact that when Oumuamua passed close to the sun at full speed, it experienced a small acceleration that cannot be explained by gravitational attraction. This data was revealed by another investigation led by the monitoring center for near-Earth objects of the European Space Agency (ESA), published in Nature last June, which concluded that the acceleration was due to a typical phenomenon in comets, known as degassing, when these icy bodies are heated, they release a cloud of gases and dust under pressure, the so-called coma. The impulse of the coma, then, would have been what pushed Oumuamua closer to the sun. That led them to conclude that the interstellar object must be a comet or similar body.

However, Bialy and Loeb propose that the acceleration was not due to a coma, since it was not observed, but to radiation pressure, a weak force that all objects experience when the photons that makeup light hit them. . For radiation pressure to cause significant acceleration in an object, however, it must either be very thin or very thin and have a very large surface area. This type of structure is that of solar sails, a technology that is being investigated on Earth as a means of propulsion for interstellar space missions. One of the main projects underway is the Breakthrough Starshot initiative, of which Abraham Loeb chairs the scientific advisory committee.

Bialy and Loeb, therefore, suggest that their results are compatible with the fact that Oumuamua is an artificial structure built by an alien civilization, perhaps a residue of space technology. Or “alternatively, a more exotic scenario is that Oumuamua is a fully operational spacecraft intentionally sent to the vicinity of Earth by an extraterrestrial civilization, “they write in the article on org. This claim is supported by the argument that, in its journey at breakneck speed, it approached both the sun and Earth on a very unusual trajectory.

However, the researchers who discovered the acceleration of ‘Oumuamua as it passed close to the sun reiterate that their explanation is more plausible than that of Bialy and Loeb. “In our Nature article, we already considered the possibility that the pressure of solar radiation caused the non-gravitational acceleration that we found, something that Bialy and Loeb do not mention in their article,” explains by email Karen Meech, of the Institute of Astronomy of the University of Hawaii and co-author of the research. However, we concluded that the density that [radiation pressure] would have implied, thousands of times less than that of water, or the thickness, at most a few millimeters, were a much less plausible explanation than the cometary degassing we proposed ” even if the comma was not observed, Marco Micheli, from the European Space Agency (ESA) monitoring center for near-Earth objects in Frascati, Italy.

also argues by email, who was the lead author of that study. Meech and Micheli also point out that the results of the calculations they presented are very similar to those of Bialy and Loeb. On the other hand, the way of reflecting the light of ‘Oumuamua by its rotation would not be compatible with the solar sail shape, according to Karen Meech. We see this phenomenon [degassing] causing icy comets to accelerate all the time, so radiation pressure is not needed to explain it, ”agrees Alan Fitzsimmons, Queen’s University Center for Research in Astrophysics in Belfast. United). Fitzsimmons led one of the first investigations to reveal the oddities in nature of ‘Oumuamua, published in Nature Astronomy in 2017.

Radiation pressure could be the dominant one in a body with such a curious shape,” says Josep Maria Trigo, a researcher at the Institut de Ciències de l’Espai (IEEC-CSIC), asteroid expert and scientific communicator. However, “without having explored the object closely, we may be far from finding a 100% convincing answer about its nature,” says Trigo by email. It is important to emphasize that with the observations to date we cannot conclusively determine what caused the detected non-gravitational acceleration”, acknowledges Karen Meech and adds that in their article they have already pointed out that only in situ observations, already unfeasible due to the distance to the found the object, could clear all doubts about the nature of ‘Oumuamua. Meech also recommends caution when interpreting the article by researchers from the Harvard-Smithsonian Center for Astrophysics, since it has not yet been accepted for publication in The Journal of Astrophysical Letters, an indispensable first step for the scientific community to consider that the results are reliable.

For now, the majority opinion is that it is not an object of artificial origin, much less a ship built by an extraterrestrial civilization. “All the scientists I know who have worked on this firmly believe that ‘Oumuamua is a fragment of natural material ejected from another star system. The most likely explanation is that it is a planetesimal [a precursor to the formation of planets] of the formation process of a solar system, although other natural phenomena have been suggested, Meech says. “No, I don’t think it’s an alien probe,” he adds. Everything we’ve discovered about this object so far is consistent with it being a natural frozen body, kicked out of another system,” agrees Fitzsimmons. “It would be wonderful if it were true that it is an alien spacecraft, but unfortunately this is probably not the case this time.

I think it could be an unusual object, produced naturally by another planetary system, says Josep Maria Trigo. Regarding the assertions of Bialy and Loeb, Trigo values that “they are speculations that require strong evidence, but it is extremely good that they provoke debate. It is the first time that we can study – briefly – an interstellar object and, given that it is a groundbreaking case, it will certainly be debated at all levels . As Carl Sagan used to say, ‘extraordinary claims require extraordinary evidence,’ and I don’t think this article presents them,” concludes Marco Micheli. The same phrase was quoted by Karen Meech and Josep Maria Trigo when questioned about the speculations of Bialy and Loeb.