Interstellar meteoroids based on meteor observations: persistent controversies

Introduction

This presentation will demonstrate the sensitivity of meteoroid orbit determination to errors in meteor measurements. Both parameters, speed and radiant, influence the computed heliocentric velocity of a meteoroid prior to encountering Earth, thus impacting its orbit determination. Whether a meteoroid's orbit is closed or open relative to the Sun determines its nature and origin. Unambiguously identifying an interstellar meteoroid therefore necessitates understanding the validity limits provided by uncertainties in these parameters. However, uncertainties in meteor databases are often underestimated or unknown. We introduce a general tool for estimating the accuracy of determined uncertainties in the data.

Hyperbolic excess velocities

Meteor observations provide direct insights into the original extraterrestrial material that formed our solar system and its distribution in Earth's vicinity and beyond. Detecting an interstellar meteoroid could offer clues about the materials in our nearby solar environment or the building blocks of exoplanetary systems.

However, the sole indicator of a particle's interstellar origin is a hyperbolic meteoroid orbit relative to the Sun, while the expected hyperbolic excess of a meteoroid's heliocentric velocity closely approximates the common uncertainty in velocity determination. Consequently, unambiguously identifying an interstellar meteoroid is exceedingly challenging, requiring a comprehensive examination of potential biases and errors.

The accuracy of the data determines the relevance of the conclusions drawn from the scientific results obtained from observed data, especially in meteor astronomy, where the orbit of an object prior to its encounter with Earth is derived from a phenomenon lasting only a few seconds in the atmosphere. Here, we demonstrate how the measured geocentric parameters, including both the meteor velocity v and the angular elongation ε of its apparent radiant from the Earth's apex, impact the resulting meteoroid orbit.

Kresaks’ diagram

It is possible to display both geocentric quantities (v and ε) of a meteor and observe the heliocentric orbit of the meteoroid on the same plot. As introduced by Lubor Kresak and Margita Kresakova in 1976 [1], such a diagram facilitates sufficiently accurate estimations to distinguish between various types of orbits. Hence, such a display is very useful when analyzing hyperbolic orbits [2]. For each hyperbolic meteor, it is possible to estimate the uncertainties in speed and radiant position, which may have shifted the event beyond the parabolic limit. But it is also useful for verifying whether the uncertainties of the dataset as a whole are not underestimated. If so, the spread of meteors in the data smoothly continues beyond the parabolic limit to much higher values than the uncertainties should have allowed [3].

The recent well-known case of an interstellar meteoroid candidate

A notable example is the fireball detected by U.S. Government sensors on January 8, 2014. Based on its parameters, provided in the CNEOS^A catalog, the meteoroid exhibits a hyperbolic excess velocity, leading to its proposal as a candidate for an interstellar meteoroid [4]. Reports also suggest that fragments of this fireball were found on the ocean floor near Papua New Guinea, further supporting its potential interstellar origin [5]. The case has been re-analyzed in connection with the entire catalog, and it has been concluded that, based on the available data, there is no evidence to support the interstellar origin of any of the nominally hyperbolic fireballs from this data [6].

Acknowledgements. This work was supported by the Slovak Grant Agency for Science, grant No. 2/0009/22.

References

[1] Kresak, L. and Kresakova, M., 1976, BAC, 27, 106

[2] Hajdukova, M., Sterken V.J., and Wiegert, P., 2019, in Meteoro-ids: Sources of Meteors on Earth and Beyond, CUP, 235

[3] Barghini, D., Durisova, S., Koten, P., and Hajdukova, M., 2024, in preparation

[4] Siraj, A. and Loeb, A., 2022, Astrophys. J., 939, 53

[5] Siraj, A., Loeb, A., and Gallaudet, T. 2022, arXiv e-prints, arXiv:2208.00092

[6] Hajdukova, M., Stober, G., Barghini, D., Koten, P., Vaubaillon, J., Sterken, V.J., Durisova, S., Jackson, A., and Desch, S., 2024, in preparation

^Ahttps://cneos.jpl.nasa.gov/fireballs/