[Paper Review] Transit of Luyten 726-8 within 1 ly from Epsilon Eridani

Igor Yu. Potemine|arXiv (Cornell University)|Apr 9, 2010

Stellar, planetary, and galactic studies2 references3 citations

TL;DR

This paper uses astrometric and radial velocity data to simulate stellar encounters, revealing that Luyten 726-8AB will pass within 0.93 ly of Epsilon Eridani in approximately 31.5 kyr. The close encounter, lasting over 4.6 kyr within 1 ly, may perturb Epsilon Eridani's hypothetical Oort cloud, offering an explanation for unusual orbits of trans-Neptunian objects like Sedna.

ABSTRACT

This is one of results from our program of massive simulations of close encounters for all nearby stars. Epsilon Eridani is an extremely interesting star having one confirmed planet and multiple asteroid and debris belts. It should have a quite massive Oort cloud as well. Deltorn et al. searched for past Nemesis encounters of $\varepsilon$ Eri. In this paper we show that, according to current astrometric data, an other famous nearby star Luyten 726-8AB (=BL/UV Ceti) will pass at $\lesssim$ 0.93 ly from Epsilon Eridani in $\approx$ 31.5 kyr. So, it will probably pierce through the outer part of the hypothetical Oort cloud of $ε$ Eri. BL/UV Ceti has only about 20 percent of the solar mass. Nevertheless, it could influence directly some long-period comets of Epsilon Eridani. The duration of mutual transit of two star systems within 1 ly from each other is $\gtrsim$ 4.6 kyr. Our simulations show that stellar encounters within 1 ly might be more frequent than previously thought. It could explain Proxima's peculiar trajectory with respect to $α$ Cen AB or even Sedna's trajectory in the solar system.

Motivation & Objective

• To investigate the dynamical impact of close stellar encounters on the outer regions of planetary systems.
• To determine the timing and distance of the closest approach between Epsilon Eridani and Luyten 726-8AB using precise astrometric data.
• To assess the duration and significance of mutual transit within 1 ly for stellar systems with potential gravitational perturbations.
• To explore whether such encounters could explain peculiar trajectories of objects like Proxima Centauri or Sedna.

Proposed method

• Utilized HIP2 and RECONS astrometric data for Epsilon Eridani and Luyten 726-8AB to compute relative position vectors in galactic coordinates.
• Applied radial velocity measurements from PCRV, Malaroda et al., and GCRV to refine space velocity vectors of both stars.
• Calculated the time and distance of closest approach using vector-based formulas involving scalar products and the speed of light.
• Computed the duration of mutual transit within 1 ly using a derived formula based on relative motion and minimum approach distance.
• Performed simulations using multiple radial velocity assumptions for BL/UV Ceti to assess uncertainty in encounter parameters.
• Evaluated the gravitational influence of Luyten 726-8AB on Epsilon Eridani's hypothetical Oort cloud due to its proximity and mass.

Experimental results

Research questions

• RQ1 What is the minimum distance and timing of the closest approach between Epsilon Eridani and Luyten 726-8AB?
• RQ2 How long will the two stellar systems remain within 1 ly of each other?
• RQ3 Could such a close encounter perturb long-period comets in Epsilon Eridani's hypothetical Oort cloud?
• RQ4 Might this encounter explain the unusual orbital characteristics of Sedna or Proxima Centauri?
• RQ5 How frequently do stellar encounters within 1 ly occur, and what are their dynamical implications?

Key findings

• Luyten 726-8AB will pass within 0.93 ± 0.01 ly of Epsilon Eridani in approximately 31.5 ± 0.2 kyr.
• The duration of mutual transit within 1 ly is estimated at 4.6 kyr, increasing to 6.4 kyr if BL/UV Ceti's radial velocity is assumed to be +25 km/s.
• Despite its low mass (about 20% of the Sun's), Luyten 726-8AB is capable of gravitationally perturbing long-period comets in Epsilon Eridani's outer system.
• The encounter is expected to penetrate the outer regions of Epsilon Eridani's hypothetical Oort cloud, potentially altering comet orbits.
• Stellar encounters within 1 ly may be more frequent than previously thought, offering a plausible mechanism for anomalous trajectories of distant solar system objects.
• The results suggest that such encounters could explain the peculiar orbital dynamics of Sedna and Proxima Centauri relative to Alpha Centauri AB.