Finding the Comets Knocked Into the Inner Solar System by Past StellarEncounters

Finding the imprints of stellar encounters in long-period comets

Authors:

Feng et al

Abstract:

The Solar system's Oort cloud can be perturbed by the Galactic tide and by individual passing stars. These perturbations can inject Oort cloud objects into the inner parts of the Solar system, where they may be observed as the long-period comets (periods longer than 200 yr). Using dynamical simulations of the Oort cloud under the perturbing effects of the tide and 61 known stellar encounters, we investigate the link between long-period comets and encounters. We find that past encounters were responsible for injecting at least 5 per cent of the currently known long-period comets. This is a lower limit due to the incompleteness of known encounters. Although the Galactic tide seems to play the dominant role in producing the observed long-period comets, the non-uniform longitude distribution of the cometary perihelia suggests the existence of strong – but as yet unidentified – stellar encounters or other impulses. The strongest individual future and past encounters are probably HIP 89825 (Gliese 710) and HIP 14473, which contribute at most 8 and 6 per cent to the total flux of long-period comets, respectively. Our results show that the strength of an encounter can be approximated well by a simple proxy, which will be convenient for quickly identifying significant encounters in large data sets. Our analysis also indicates a smaller population of the Oort cloud than is usually assumed, which would bring the mass of the solar nebula into line with planet formation theories.

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="">

HIP 85605 is Will Pass by the Solar System at 8,000 AU in 1/4 to 1/2 Million Years From now

It’s known as HIP 85605, one of two stars that make up a binary in the Hercules constellation roughly 16 light years away. And if a recent research paper produced by Dr. Coryn Bailer-Jones of the Max Planck Institute for Astronomy in Heidelberg, Germany is correct, it is on a collision course with our Solar System.

Now for the good news: according to Bailer-Jones’ calculations, the star will pass by our Solar System at a distance of 0.04 parsecs, which is equivalent to 8,000 times the distance between the Earth and the Sun (8,000 AUs). In addition, this passage will not affect Earth or any other planet’s orbit around the Sun. And perhaps most importantly of all, none of it will be happening for another 240,000 to 470,000 years from now.

“Even though the galaxy contains very many stars,” Bailor-Jones told Universe Today via email, “the spaces between them are huge. So even over the (long) life of our galaxy so far, the probability of any two stars have actually collided — as opposed to just coming close — is extremely small.”

However, in astronomical terms, that still counts as a near-miss. In a universe that is 46 billion light years in any direction – and that’s just the observable part of it – an event that is expected to take place just 50 light days away is considered to be pretty close. And in the context of space and time, a quarter of a million to half a million years is the very near future.

link.

I do wonder about the Sun's orbital perturbation from the encounter though.

Oh and this is to be followed by Gliese 710 in around 1.3 million years at 20,000 AU.