Interstellar Meteors are Outliers in Material Strength

TL;DR

This paper identifies interstellar meteors as outliers with unusually high material strength in fireball data, suggesting they originate from a distinct population with implications for interstellar material abundance.

Contribution

It reports the detection of two interstellar meteors with exceptional material strength and analyzes their significance as outliers in the CNEOS fireball catalog.

Findings

IM1 and IM2 are the top 1 and 3 in material strength among catalog objects.

IM1 and IM2 are outliers at 3.5σ and 2.6σ levels, respectively.

Interstellar meteors may contain about 40% of refractory elements in meter-scale objects.

Abstract

The first interstellar meteor larger than dust was detected by US government sensors in 2014, identified as an interstellar object candidate in 2019, and confirmed by the Department of Defense in 2022. Here, we describe an additional interstellar object candidate in the CNEOS fireball catalog, and compare the implied material strength of the two objects, referred to here as IM1 and IM2, respectively. IM1 and IM2 are ranked 1 and 3 in terms of material strength out of all 273 fireballs in the CNEOS catalog. Fitting a log-normal distribution to material strengths of objects in the CNEOS catalog, IM1 and IM2 are outliers at the levels of $3.5 \sigma$ and $2.6 \sigma$, respectively. The random sampling and Gaussian probabilities, respectively, of picking two objects with such high material strength from the CNEOS catalog, are $\sim 10^{-4}$ and $\sim 10^{-6}$. If IM2 is confirmed, this implies that interstellar meteors come from a population with material strength characteristically higher than meteors originating from within the solar system. Additionally, we find that if the two objects are representative of a background population on random trajectories, their combined detections imply that $\sim 40\%$ of all refractory elements are locked in meter-scale interstellar objects. Such a high abundance seemingly defies a planetary system origin.