Is Farfarout in interstellar space?

Is Farfarout Interstellar? Unpacking the Orbit of a Distant Solar System Object

Farfarout. The name itself evokes a sense of remoteness, a whispered secret from the frigid outer edges of our solar system. Officially designated 2018 AG37, this distant object, orbiting far beyond Neptune, has captivated astronomers with its exceptionally elongated orbit and its proximity, however fleeting, to our Sun. But the question remains: is Farfarout truly a member of our solar system, or is it merely a passing visitor from the interstellar void?

The answer, unfortunately, isn’t a simple yes or no. Farfarout’s orbit is the key to understanding its status. At its aphelion (farthest point from the Sun), it reaches a staggering 175 astronomical units (AU). One AU is the average distance between the Earth and the Sun; therefore, Farfarout, at its most distant, is 175 times farther from our star than we are. This places it far beyond the Kuiper Belt, the region of icy bodies beyond Neptune, and even beyond the hypothesized inner edge of the Oort Cloud, a theoretical sphere of icy planetesimals surrounding our solar system.

However, the sheer distance alone doesn’t definitively classify it as interstellar. What truly matters is the object’s gravitational binding to the Sun. While 175 AU is incredibly far, Farfarout’s orbit, though highly elliptical, is still demonstrably bound to our Sun. Its perihelion (closest point to the Sun), at a relatively close 27 AU, indicates that the Sun’s gravity is strong enough to keep it tethered, at least for the time being. This is a crucial distinction: interstellar objects, like ‘Oumuamua and 2I/Borisov, exhibit unbound, hyperbolic orbits, meaning they are not gravitationally captured by our Sun and are simply passing through.

The thousand-year journey Farfarout undertakes around the Sun further emphasizes its current solar system residency. This long orbital period suggests a stable, if eccentric, relationship with our star. While gravitational perturbations from passing stars or other celestial bodies could theoretically alter its orbit over vast timescales, current observations don’t indicate any imminent ejection from our solar system.

Therefore, while Farfarout resides at the extreme fringes of our solar system, pushing the boundaries of our understanding of its extent, the evidence currently suggests it’s not interstellar. It’s an incredibly distant member of our own solar family, a testament to the vast, largely unexplored space that lies beyond Neptune, a space where objects like Farfarout continue to challenge our conceptions of planetary systems and their boundaries. Continued observation and analysis of its trajectory are vital to refine our understanding of this distant world and its place within the cosmic neighborhood.