Could Schloz's Star(s) Passed Within 20,000 AU of the Sun 70,000 Years Ago?

The Closest Known Flyby of a Star to the Solar System

Authors:

Mamajek et al

Abstract:

Passing stars can perturb the Oort Cloud, triggering comet showers and potentially extinction events on Earth. We combine velocity measurements for the recently discovered, nearby, low-mass binary system WISE J072003.20-084651.2 ("Scholz's star") to calculate its past trajectory. Integrating the Galactic orbits of this ∼0.15 M⊙ binary system and the Sun, we find that the binary passed within only 52+23−14 kAU (0.25+0.11−0.07 parsec) of the Sun 70+15−10 kya (1σ uncertainties), i.e. within the outer Oort Cloud. This is the closest known encounter of a star to our solar system with a well-constrained distance and velocity. Previous work suggests that flybys within 0.25 pc occur infrequently (∼0.1 Myr−1). We show that given the low mass and high velocity of the binary system, the encounter was dynamically weak. Using the best available astrometry, our simulations suggest that the probability that the star penetrated the outer Oort Cloud is ∼98%, but the probability of penetrating the dynamically active inner Oort Cloud (<20 among="" be="" binary="" blockquote="" caused="" cloud="" comets="" discovery="" dynamically="" flux="" flyby="" highlights="" impact="" important="" is="" kau="" likely="" long-period="" lurking="" may="" nearby="" negligible="" of="" on="" oort="" perturbers="" recent="" stars.="" system="" that="" the="" this="" while="">