On October 19, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) in Hawaii announced the first detection of an interstellar object, called 1I / 2017 U1 (aka "Oumuamua). following months, numerous follow-up observations were made to find out more about this visitor, as well as resolving the dispute that it was a comet and an asteroid.
Rather than settling the dispute, further observations have only deepened the mystery, also giving rise to suggestions that could be an extra-terrestrial solar sail. For this reason, scientists are very interested in finding other examples of objects similar to Oumuamua. According to a recent study by a group of Harvard astrophysicists, it is possible that interstellar objects enter our system and end up falling into our sun somehow regularly.
The study, "Raising the fire on" Oumuamua, "appeared recently online and was presented for publication at the Astrophysical Journal Letters . The study was conducted by John Forbes – a colleague at the Harvard-Smithsonian Center for Astrophysics & Institute for Theory and Computation (ITC) – and Prof. Abraham Loeb – the Director of ITC, the Frank B. Baird Jr. Prof. of Science and the president of the department of astronomy of the Harvard University.
To recap, when & # 39; Oumuamua was first discovered, the object was about 0.25 AU from the sun and already exited the solar system. Based on its trajectory, it was concluded that "Oumuamua was of extra-solar origin, rather than being a long-term object originating from the Oort cloud.The astronomers also noted that it seemed to have a high density (indicative of a rocky and metallic composition) and that it turned quickly
This gave rise to the theory that, rather than being an interstellar comet, "Oumuamua was actually an interstellar asteroid. This was consistent with the fact that he did not experience any degeneration or form a tail when he made his approach closer to the sun. However, while Oumuamua began to leave the solar system, another research group noticed that he had experienced a speed increase.
This strange behavior once again led scientists to hypothesize that "Oumuamua could be a comet, since it tasted as a result of solar heating would explain its sudden change of speed." Unfortunately, between the fact that the object had not experienced any degeneration closer to the sun, or experienced a rapid evolution in its turn (which accompanies the sudden release of material), scientists were once again at a loss.
As noted, this gave rise to # 39; idea that "Oumuamua could actually be a light sail, which was originally proposed in another study by Prof. Loeb and Shmuel Bialy (a postdoctoral research with the ITC). Basically, a light sail is a form of spacecraft that is based on the pressure of radiation to generate propulsion, which would explain why the object accelerated when moving away from the sun.
Regardless of its true nature, the fact that & # 39; Oumuamua has challenged the classification has made it a subject of great interest As Loeb said in the Today universe:
"The discovery of & # 39. Oumuamua allows us to calibrate the abundance of interstellar objects of its size, based on the investigation time and the sensitivity of the Pan STARRS telescopes.There should be approximately one quadrillion (10 15 ) such objects per star in the Milky Way. A small fraction of these objects passes near Jupiter and kicks enough to remain trapped in the System System. "
In a previous study, Prof. Loeb and Manasvi Lingam (a postdoc researcher) with the ITC) calculated that the solar system is home to approximately 6,000 trapped interstellar objects. In a follow-up study, Loeb and Amir Siraj identified four candidates for a possible study and indicated that many others will probably be found with the Large Synoptic Survey Telescope (LSST) – which could also be studied from a robotic mission in the next future.
"This is a way to learn about the structure and composition of interstellar objects similar to Oumuamua," Loeb said. "In our new document we proposed instead to study the steam produced when these objects pass near the sun and are evaporated by intense solar heat.We calculated the probability of this happening, bearing in mind that" Oumuamua showed no sign of comet tail or carbon-based gas because it did not pass close enough to the sun. "
This proposal would build on the established tradition of examining the spectra of comets when they pass near the sun to learn more about their origins by determining the rates of water production, diatomic carbon (C 2 ) , cyanide (CN) and amino radicals (NH 2) – as well as the dynamic properties of the comet – scientists are able to determine which part of the protoplanetary disk was probably formed in the comet.
this to bodies in the solar system, Forbes and Loeb sought to limit the frequency with which interstellar visitors pass close to our sun.This consisted of using the known orbit of & # 39; Oumumua and the Monte Carlo method. (where random sampling is used to obtain numerical values) to determine the expected distribution of the orbits of interstellar objects near the sun.
From this, they were able to to obtain estimates on how often objects collide with our sun, and how many of these are probably of interstellar origin. As Loeb said:
"We have discovered that such objects collide with the sun once every 30 years, while about 2 passages in the orbit of Mercury each year.We have identified the preferred orientations for the orbits of interstellar objects and we have concluded that at least one of the objects of the solar system are of extrasolar origin. "
Forbes and Loeb have also identified the probable orbital orientations that extrasolar objects would have in our solar system, using data from the International Celestial Reference System (ICRS). As in the previous study conducted by Loeb and Lingam, they also identified some known objects in the solar system that have these orientations.
These were extracted from NASA's JPL Small-Body database, most of which belong to the Kreutz group – a family of sungrazing comets that have orbits that bring them extremely close to the perihelion sun. Of these, Forbes and Loeb identify some that could be of interstellar origin based on the inclination of their orbits.
"In the future, many interstellar objects will be discovered by LSST," Loeb said. "Another telescope with the potential to discover comets in the sun is the next Daniel K Inoue Solar Telescope (DKIST), which is located right next to the Pan STARRS observatory on Mount Haleakala in Hawaii, and DKIST will observe the high-spatial sun and temporal resolution and is equipped with multiple spectra-polarimeters. DKIST's ability to study comets in the sun may be limited by the lack of a coronograph to block sunlight, but its unprecedented sensitivity and resolution can lead to interesting discoveries . " This latest study could help inform future studies of interstellar objects, which could reveal what types of conditions are present in extrasolar systems without having to send robotic missions to study them directly. Assuming that some of these objects are artificial in nature, they could also solve the Fermi paradox.
Since the discovery of & # 39; Oumuamua (and our inability to solve the question of its true nature), scientists have been impatient to find another interstellar object in our solar system for study. To know that there are already some, and that could be studied very early, is an exciting prospect. In any case, we find ourselves to learn a lot about this universe that we inhabit.
Could it Oumuamua be an extraterrestrial solar sail?