New comet is our second interstellar visitor

Enlarge / Comet C/2019 Q4 (Borisov). Note the fuzzy appearance and faint tail. (credit: Canada-France-Hawaii Telescope)

Due to complicated gravitational interactions from planets and other bodies, it's expected that our Solar System has ejected various small bodies like comets and asteroids. Since exosolar systems are likely to do the same, it's thought that the vast distances of interstellar space are sparsely populated by these small bodies. As such, we should expect one of these objects to wander through our Solar System, an expectation that was confirmed in 2017 with the arrival of 'Oumuamua, an odd, cigar-shaped object that shot through the Solar System at an extreme angle.

Now, just two years later, we seem to have our second. Officially termed C/2019 Q4 (Borisov), the comet is approaching the inner Solar System at an angle that almost certainly indicates it didn't originate here.

Hyperbolic orbits

Right now, there's not much public information about C/2019 Q4 (Borisov). A press release from the Jet Propulsion Lab provides some basic details. Discovered on August 30, it takes its name from Gennady Borisov, who spotted it from an observatory in the Crimea. Since then, observations have firmed up its orbit, indicating that it will make its closest approach to the Sun in December, passing no closer than Mars' orbit.