In 2017, astronomers and the whole world were surprised to learn that an interstellar object (called um Oumuamua) passed Earth on its way to the outer solar system. After numerous studies were carried out, scientists left scratching their heads as to what kind of object it was – what assumptions, ranging from a comet or from an asteroid to a comet fragment or even an extraterrestrial solar sail!
But one of the greatest conclusions of this event was the discovery that such objects regularly pass through our solar system (and some remain). And, as it turns out, astronomers from NASA, ESA and the International Scientific Optical Network (ISON) have announced the discovery of what could be the second interstellar object! Could this be um Oumuamua 2.0? And if so, what secrets can this represent?
The new object received the designation C / 2019 Q4 (Borisov) in honor of Gennady Borisov, an astronomer of the Crimean Astrophysical Observatory, who first discovered this object on August 30. NASA's intelligence system, which tracks recently discovered asteroids and comets as part of the Near Earth Object Research Center (CNEOS), indicated that it soon had an unusual orbit.
A few days later, the famous astronomer Marco Mikeli – from the ESA Near-Earth Object Coordination Center (NEOCC) – was able to obtain images of the object through ISON. Mikeli, attributed to the discovery of several NEOs, also performed several measurements of the position of the object using data provided by the Canadian-French-Hawaiian Telescope (CHFT) in Manua Kea, Hawaii.
ESA now analyzes all available data and plans more observations in order to better understand the path of the object and its origin. But, based on its eccentricity, it seems that this object could be an interstellar visitor, although this remains to be said definitively. As Mikeli explained:
"Now we are working to get more observations of this unusual object., We need to wait a few days to really find out its origin by observations that either confirm the current thesis about its interstellar nature, or perhaps radically change our understanding.".
It is currently known that C / 2019 Q4 is a relatively large and active comet that has a diameter of several kilometers. It is expected that it will approach the Sun in early December, reaching a distance of about 300 million km (186 million miles), or slightly more than twice the distance between the Earth and the Sun (2 AU). This distance will lead him beyond the orbit of Mars, and therefore does not meet the definition of a near-Earth object (NEO).
Assuming C / 2019 Q4 is a comet, it will begin to radiate gas as soon as it reaches the closest point in its path around our Sun. This will be caused by an increase in temperature on its surface, as a result of which its frozen volatile substances (i.e. water, carbon dioxide, methane, ammonia) will sublimate and be released. Astronomers will be able to confirm that the object is actually a comet based on the halo (or “tail”) that will be received.
Since it is known that comets remain stable at a distance of about 3 AU (448.8 million Km; miles) from the Sun, it is fair to say that gas must be released in C / 2019 Q4. It was here that Oumuamua began to confuse scientists who did not experience degassing, despite the fact that they reached a distance of 38.1 million km (23.7 million miles) from the sun.
Nevertheless, he managed to accelerate at the exit from the solar system, which corresponded to the behavior of the comet. This is what led some scholars to think that um Oumuamua could actually be an artificial object, or at least a celestial object that a person had never encountered before. This is what makes interstellar objects such a prize.
Unsurprisingly, scientists are so excited that another interstellar object seems to have entered our solar system. That is why many are looking for low-cost, quick deployment concepts for spaceships that could meet with these objects and explore them. If only C / 2019 Q4 arrived in our solar system in a few years, the ESA mission Comet Interceptor could do just that.
This mission is part of Cosmic Vision, ESA's long-term vision for space exploration, which includes “fast-class” missions that can come close to transitional phenomena (such as comets). The Comet Interceptor proposal (based on ‘Oumuamua) provides for three spacecraft that will be the first to visit a comet or interstellar object when it begins to penetrate the inner solar system.
In any case, if further observations show that C / 2019 Q4 is indeed of interstellar origin, this will mean that our solar system has been visited by at least two such objects for so many years. This indicates that such bodies are much more common than previously thought, and this also means that we will have many opportunities to study them in the future!
Further reading: ESA