Is it plausible to expect a close encounter of the Earth with a yet undiscovered astronomical object in the next few years?

TL;DR

This paper assesses the likelihood of an undiscovered astronomical object entering the inner solar system in the next few years, concluding it is highly implausible due to required unrealistically high velocities and current observational constraints.

Contribution

It provides a combined analytical and numerical analysis showing that a nearby undiscovered object cannot reach Earth in two years without possessing unphysical speeds, given current observational bounds.

Findings

An undiscovered object would need to travel at near-light speeds to reach Earth in 2 years.

Such high velocities are inconsistent with known astrophysical objects like hypervelocity stars.

Current observational limits strongly suggest no such object is on a collision course in the near future.

Abstract

We analytically and numerically investigate the possibility that a still undiscovered body X, moving along an unbound hyperbolic path from outside the solar system, may penetrate its inner regions in the next few years posing a threat to the Earth. By conservatively using as initial position the lower bounds on the present-day distance dX of X dynamically inferred from the gravitational perturbations induced by it on the orbital motions of the planets of the solar system, both the analyses show that, in order to reach the Earth's orbit in the next 2 yr, X should move at a highly unrealistic speed v, whatever its mass MX is. For example, by assuming for it a solar (MX =M_Sun) or brown dwarf mass (MX = 80mJup), now at not less than dX = 11-6 kau (1 kau=1000 astronomical units), v would be of the order of 6-10% and 3-5% of the speed of light c, respectively. By assuming larger present-day distances for X, on the basis of the lacking of direct observational evidences of electromagnetic origin for it, its speed would be even higher. Instead, the fastest solitary massive objects known so far, like hypervelocity stars (HVSs) and supernova remnants (SRs), travel at v = 0.002-0.005c, having acquired so huge velocities in some of the most violent astrophysical phenomena like interactions with supermassive galactic black holes and supernova explosions. It turns out that the orbit of the Earth would not be macroscopically altered by a close (0.2 au) passage of such an ultrafast body X in the next 2 yr. On the contrary, our planet would be hurled into the space if a Sun-sized body X would encounter it by moving at v/c = 10^-4. On the other hand, this would imply that such a X should be now at just 20-30 au, contrary to all direct observational and indirect dynamical evidences.