First stars that could significantly perturb comet motion are finally found (1911.01735v1)

Abstract: Since 1950 when Oort published his paper on the structure of the cloud of comets it is believed that stars passing near this hypothetical cometary reservoir play an important role in the dynamical evolution of long period comets and injecting them into the observability region of the Solar System. The aim of this paper is to discuss two cases in which the data obtained from observations were used and stellar perturbations (of different intensity, strong case of C/2002 A3 LINEAR and weaker case of C/2013 F3 PANSTARRS) on cometary motion were detected. Using the best available data from the Gaia DR2 catalogue and some other sources we searched for close stellar passages near the Sun. Our study took into account that some of the stars are parts of multiple systems. Over 600 stars or systems that approached or will approach the Sun closer than 4.0 pc were found. Having the list of perturbers completed we studied their influence on a sample of 277 Oort spike comets that were observed since 1901 and discovered that two comets might have their orbits fundamentally changed due to a close stellar encounter. Our results show how much different the dynamical evolution of comets would have looked when their motion was considered only in the Galactic potential. Uncertainties both in stellar and cometary data were carefully taken into account. Our analysis indicates that the occurrence of stellar perturbations on cometary motions is very rare and the uncertainties of these effects are hard to estimate.

• The paper uses Gaia DR2 and other data to identify over 600 stars potentially perturbing Oort Cloud comets, numerically integrating orbits under galactic and stellar influences.
• Key findings highlight two specific cases, comets C/2002 A3 LINEAR and C/2013 F3 PANSTARRS, where identified stars like HD 7977 likely caused significant orbital changes.
• The study validates theoretical models of stellar influence on Oort cloud comets and emphasizes the need for future data like Gaia releases to improve accuracy in modeling multi-body interactions.

Analysis of Stellar Perturbations on Cometary Trajectories

The research paper under analysis investigates the influence of nearby stellar passages on the trajectories of long period comets (LPCs) within the Solar System, employing observational data and the Gaia DR2 catalogue to identify such celestial events. This paper represents a significant contribution to our understanding of the dynamical evolution of comets, particularly those that originate in the Oort Cloud. The authors attempt to identify individual stars that might act as significant perturbers of observed comet orbits, focusing on two specific instances: the comets C/2002 A3 LINEAR and C/2013 F3 PANSTARRS.

Methodology and Data Utilization

The paper emphasizes the use of data from the Gaia DR2 catalogue, complemented by additional observational data, to identify stars that have or will pass within 4.0 parsecs of the Sun. Through this comprehensive astronomical survey, the authors have amassed a list of over 600 stars or stellar systems that potentially exert gravitational effects on the Solar System's cometary constituents. At the center of their analysis is a sample of 277 Oort spike comets, which the authors extended to include objects observed since 1901, offering a broad temporal frame for their investigation.

Key to the method was the numerical integration of cometary orbits, a procedure carried out under both Galactic potential influences and perturbative effects from identified stars. This approach offers a contrast to simpler models that rely on Galactic tides alone, providing a broader context for assessing comet dynamics. The paper highlights that this level of analysis was previously hindered by the limited availability of precise parallax and radial velocity measurements before the Gaia mission.

Findings: Stellar Induced Orbital Changes

The paper's findings provide timely insights into the rare but profound impact of close stellar encounters on comet orbits. Two significant cases are highlighted where stellar encounters may have altered cometary trajectories:

1. C/2002 A3 LINEAR: The research identifies HD 7977 as a stellar body that exerted a considerable perturbative force, with the closest recorded approach at around 740 au. This stellar interaction may have transitioned the comet from being an Oort cloud object to a potentially observable comet with a drastically altered orbit, aligning with the Oort proposition about stellar influences injecting comets into observable zones.
2. C/2013 F3 PANSTARRS: The investigation into Star B, though impacted by higher uncertainty due to less robust astrometric data, suggests a similarly transformative interaction took place, raising the comet's previous perihelion to a distance that aligns it more closely with known Oort cloud dynamics.

Implications and Future Considerations

These observations substantiate long-held theoretical models concerning the influence of stellar activity on Oort cloud comets, though the authors acknowledge the complexity and rarity of such events. Furthermore, the paper highlights an ongoing issue in celestial mechanics: the challenge of accurately accounting for dynamical variables due to data limitations, both historical and present.

The research underscores the potential for upcoming data releases, such as those expected from Gaia's further data releases to significantly enhance our understanding of such dynamical systems. These data are anticipated to improve the precision of astrometric and kinematic measurements, thus enriching capacity to track multi-body interactions over extensive periods.

The paper makes a case for continued surveillance and detailed examination of stellar encounters, proposing that future works integrate data on binary and multiple star systems to mitigate the complexity of motion models. With Gaia's mission ongoing, the anticipations remain that more comprehensive datasets will refine the accuracy of solar neighborhood models, offering richer insights into the mechanisms that govern the dynamical pathways of comets in our cosmic vicinity.