Astronomers of the Center Harvard-Smithsonian for Astrophysics estimate that the elongated shape of the first asteroid, interstellar known, Oumuamua, operates as a sail, which explains their unexpected acceleration.
Speculate with an artificial origin of the object, designed for the reconnaissance trip interstellar by an advanced civilization, but whose mission has finished and you’ve become the waste of a shipwreck.
The study, called ‘how Could the pressure of solar radiation to explain the acceleration of peculiar Oumuamua?’, published in arXiv, was made by Shmuel Bialy, a postdoctoral researcher in the Institute of Theory and Computation, and Abraham Loeb, the director of this center.
Oumuamua was seen for the first time by the survey Pan-STARRS-1 40 days after its passage closest to the Sun (9 September 2017). At this point, I was at about 0.25 AU from the Sun (a quarter of the distance between the Earth and the Sun), and was already out of the Solar System. At that time, astronomers noticed that she seemed to have a high density (indicative of a composition of rock and metal) and that was spinning rapidly.
Although he showed no signs of degassing by passing close to our Sun (which would have indicated that it was a comet), a research team was able to obtain spectra which indicated that Oumuamua was more ice cream than was previously thought. Then, when he began to leave the Solar System, the Hubble Space Telescope took some final images of Oumuamua that revealed some unexpected behavior.
After examining the images, another international team of researchers discovered that Oumuamua had increased in speed, instead of decreasing the speed as expected. The most likely explanation, they said, was that Oumuamua was unloading material from its surface due to solar heating (also known as degassing). The release of this material, which is consistent with the way in which it behaves as a comet, would give the Oumuamua the thrust constant that is needed to achieve this speed increase.
This, Bialy and Loeb offer a counter explanation. If Oumuamua was in fact a comet, why then did not experience outgassing when it was closer to our Sun? In addition, they cite other research which showed that if the degassing is responsible for the acceleration, would also have caused a rapid evolution in the spin of Oumuamua (not observed).
Basically, Bialy and Loeb considered the possibility that Oumuamua could be, in fact, a sailing, a form of spacecraft which depends on the pressure of radiation, to generate propulsion, similar to what you are working on Breaktrough Starshot, the project to send small ships to other systems.
Similar to what is planned for Starshot, this candle light can be sent from another civilization to study our Solar System and search for signs of life. As explained by professor Loeb to Universe Today by e-mail:
“We explain the excess of acceleration of Oumuamua away from the Sun as a result of the force that the Sun exerts on its surface. That this force explain the excess of acceleration measurement, the object must be extremely small, of the order of a fraction of a millimeter of thickness but of tens of meters in size. This makes the object it is light for its surface area and allows it to act as a candle light. Its origin may be natural (in the middle of interstellar or proto-planetary discs) or artificial (such as a probe sent to a reconnaissance mission in the inner region of the Solar System)”.
Based on this, Bialy and Loeb calculated the likely shape, thickness and the mass-area that would have an object as artificial. They also sought to determine if this object could survive in the interstellar space, and whether it could or not to resist the tensile stresses caused by rotation and tidal forces.
What they found was that a candle with only a fraction of a millimeter of thickness (0,3-0,9 mm) would be enough for a sheet of solid material to survive the trip through the entire galaxy, although this largely depends on the mass density of Oumuamua. Thick or thin, this candle could withstand collisions with grains of dust and gas that pervade the interstellar medium, as well as centrifugal forces and of the tide.
In terms of what I would be doing a candle light extraterrestrial, in our Solar System, Bialy and Loeb offer some possible explanations for that. First, they suggest that the probe can be a really sailing late that floats under the influence of gravity and radiation on stellar, similar to waste from the wrecks of ships that float in the ocean. This would help explain why Breakthrough Listen found no evidence of radio transmissions.