Two astronomers have suggested the possibility that the object that has passed through the solar system is of extraterrestrial origin. However, the hypothesis is very unlikely. This is why.
by Gary Dagorn
Among the scientific curiosities that succeed in capturing the attention of the general public without a doubt, extraterrestrial life is certainly one of the most fascinating subjects. The last example so far concerns the astronomical object 1I / 2017 U1, also called "Oumuamua". This comet, or what is considered a comet, was widely discussed in the fall of 2017, when it was discovered, because it is the first object known to be a solar system that must be observed by man. An interstellar object, thus coming from the constellation of the Lyre, approached 45 million kilometers of the sun before it came quickly from the solar system to the constellation Pegasus.
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Who is this intruder of another solar system?
In addition to being certified "Object from elsewhere""Oumuamua" was also surprised by its very unusual shape (ten times longer than wide) as well as its high speed. Curious features that gave him a great profile at that time. After his discovery, on 19 October, several telescopes followed his race through the solar system until he lost his track at the beginning of January 2018, while he was moving away from the sun. the object is relatively small (about a few hundred meters long).
An "exotic" hypothesis
With sixty-six observation data, several teams of astronomers looked at "Oumuamua" to determine its exact nature. Is it an asteroid? A comet? Neither suggests a scientific article submitted to the journal The Astrophysical Journal Letters, but already readable in prepublication. The two authors, co-holders of the Astronomy chair at the University of Harvard, propose a more "exotic" hypothesis, that of an artificial origin and therefore of an extraterrestrial civilization. There was no longer any need to arouse the interest of the press and to mediate the position of the two American astronomers. But it has received sharp criticism, because this hypothesis remains highly unlikely.
The article has not yet been published in the final version
The conclusions of the work of MM. Shmuel Bialy and Abraham Loeb have to be handled carefully, not because they are exotic, but because the formulated hypothesis is not the best explanation for the real nature of "Oumuamua". Besides the fact that the article has not yet been published in the final version and has not been read again and corrected before publication (an element that always requires caution), it quickly rejects the track privileged by other works, according to which "Oumuamua" probably comet.
At the origin of the disagreement about the real nature of this interstellar rock is the fact that the object is faster than it should be, according to the simulations made on the ground. A difference between calculations and observations that surprise astronomers. They conclude that the object has undergone an acceleration that is not due to the natural gravitational influence of the solar system, but to a still unknown factor.
And this very question tries to arrange the study of Shmuel Bialy and Abraham Loeb. But these are based on the assumption that "Oumuamua" is not an active comet and can not have any activity on the surface that can explain the acceleration (such as degassing, for example, a transformation of the ice from a comet into gas on the surface, when the the sun is approaching). In the absence of comet activity, the two astronomers try to explain the velocity of the object by the influence of the solar wind (ie the material streams emitted by the sun at high speed) and conclude that the declaration is valid provided that "Oumuamua" very light, as light as a small asteroid.
Their calculations are correct, because other teams have also estimated that the solar wind can explain the phenomenon, provided that the object is much lighter than anything previously seen with a comparable size. But where they have considered such low density as unlikely, in view of other possible explanations, MM. Bialy and Loeb wonder about a new type of fine and light interstellar object, which we had never seen before, and benefit from it to allow the suggestion of a possible artificial origin to slip away "A possibility that"Oumuamua" a solar spring, traveling in the interstellar space, such as the remains of technologically advanced equipment ".
The hypothesis of two astronomers: there is an alien probe & # 39; in the solar system
Although such an assumption can never be excluded, it has no basis and it is not at all satisfactory for many fellow brothers.
"What they say does not fit with the data"
Work carried out by the team of Italian astronomer Marco Micheli, and published on June 27, 2018 in the magazine nature, demonstrate that "Oumuamua" has a brightness, density and thermal properties similar to those of a comet. Micheli and his colleagues wanted to explain this shift to all possible causes, including the solar wind. The only plausible physical explanation for these astronomers is that of degassing, which implies that the object is indeed a comet. If the telescopes do not detect degassing, the researchers claim that "The absence of observed activity is possible when a comet body is surrounded by a thin insulating sheath" and also emphasize that their hypothesis is consistent with "Acceleration already observed in comets of the solar system".
"The idea of a solar trip can not match what has been observed"
"What MM Loeb and Bialy advance do not match the collected data about the object», said, for his part, Lucie Maquet, astronomer at the Institute of Heaven Mechanics and calculation of ephemeris (IMCCE), interviewed by The world – as a result of which the conclusions of the article would necessarily become invalid. According to her "The idea of a solar trip can not match what has been observed" and the familiar form of "Oumuamua". The researcher also recalls that, if no degassing was observed, it is quite possible that for an interstellar object whose chemical composition is unknown to us, it is otherwise unheated from water in the visible spectrum, such as comets in the water. solar system usually do.
"We always try to observe familiar behavior", she reasons, but "Degassing is impossible to observe if we do not look at the correct wavelengths".
A way to mean that, as popularized by the American cosmologist Carl Sagan, "An extraordinary confirmation requires extraordinary evidence".