Sky-plane velocity distributions of interstellar objects and implications for their detection
- 1Department of Physics and Astronomy, Michigan State University , East Lansing, MI 48824 ,
Abstract
In the past decade, three macroscopic-scale interstellar objects have been discovered, implying that a larger Galactic population exists. In this paper, we investigate the possibility that the rapid sky-plane velocities of interstellar objects may preclude their discovery. We provide an analytic solution for the apparent sky motion of an object on an arbitrary orbit observed at an arbitrary location that is more efficient and requires less overhead than the numerical approach. This formula is applied to evaluate the typical sky motion of an interstellar object as a function of its orbit and limiting magnitude/distance. We generate three synthetic populations of ∼105 interstellar objects within heliocentric spheres of radii 1.2, 3.0, and 5.0 au, and calculate the sky motion for these objects when they reach a range of limiting magnitudes for multiple populations of interstellar asteroids and comets. The sky motions of the three known interstellar objects are broadly characteristic of populations with similar absolute magnitudes. Moreover, the intrinsically brighter objects reach detection magnitude thresholds at lower on-sky speeds than the dim objects, and active comets at even lower speeds for the same apparent magnitudes. The tails of these distributions extend to speeds faster than the discovery motion of 1I. Therefore, the potentially rapid sky motion of interstellar objects should be taken into account when attempting to link hyperbolic trajectories in survey data.
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BibTeX
@article{walker2026skyplane,
title = {{Sky-plane velocity distributions of interstellar objects and implications for their detection}},
author = {Cassidy E Walker and Darryl Z Seligman},
journal = {Monthly Notices of the Royal Astronomical Society},
year = {2026},
month = sep,
doi = {10.1093/mnras/stag1866},
url = {https://academic.oup.com/mnras/article/doi/10.1093/mnras/stag1866/8855711},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Sky-plane velocity distributions of interstellar objects and implications for their detection
AU - Cassidy E Walker
AU - Darryl Z Seligman
PY - 2026
DA - 2026/09/30
JO - Monthly Notices of the Royal Astronomical Society
DO - 10.1093/mnras/stag1866
UR - https://academic.oup.com/mnras/article/doi/10.1093/mnras/stag1866/8855711
AB - In the past decade, three macroscopic-scale interstellar objects have been discovered, implying that a larger Galactic population exists. In this paper, we investigate the possibility that the rapid sky-plane velocities of interstellar objects may preclude their discovery. We provide an analytic solution for the apparent sky motion of an object on an arbitrary orbit observed at an arbitrary location that is more efficient and requires less overhead than the numerical approach. This formula is applied to evaluate the typical sky motion of an interstellar object as a function of its orbit and limiting magnitude/distance. We generate three synthetic populations of ∼10^5 interstellar objects within heliocentric spheres of radii 1.2, 3.0, and 5.0 au, and calculate the sky motion for these objects when they reach a range of limiting magnitudes for multiple populations of interstellar asteroids and comets. The sky motions of the three known interstellar objects are broadly characteristic of populations with similar absolute magnitudes. Moreover, the intrinsically brighter objects reach detection magnitude thresholds at lower on-sky speeds than the dim objects, and active comets at even lower speeds for the same apparent magnitudes. The tails of these distributions extend to speeds faster than the discovery motion of 1I. Therefore, the potentially rapid sky motion of interstellar objects should be taken into account when attempting to link hyperbolic trajectories in survey data.
SN - 0035-8711
SN - 1365-2966
ER -