Unconfirmed interstellar objects within the solar system

by Wm. Robert Johnston
last updated 1 Feburary 2020

This page lists proposed and unconfirmed interstellar objects within the solar system. For confirmed interstellar objects see these pages:

(514107) 2015 BZ509

In May 2018 Namouni and Morais (2018) concluded that asteroid (514107) 2015 BZ509 was of interstellar origin based on integration of its orbit over long integration time periods. 2015 BZ509 is coorbital with Jupiter but with a retrograde orbit--semimajor axis of 5.140 AU, eccentricity of 0.3807, and inclination of 163.0°. The conclusion is based on finding that the current orbit is stable for multi-billion year timescales combined with the understanding that "planet formation models cannot produce such a primordial large inclination orbit." Currently, interstellar origin of (514107) 2015 BZ509 is at least in part model dependent.

Eight centaurs

In February 2019 Siraj and Loeb (2019) reported that eight Centaur-like asteroids had high probabilities of having been captured from interstellar space based on comparison of their orbits to orbits of hypothetical objects modeled as captured from interstellar space. These are (with estimated sizes):

The interpretation of interstellar origin for these objects is probabilistic, applying to the population of objects in similar orbits but not being definitive for any individual object.

8 January 2014 bolide

In April 2019 Siraj and Loeb (2019) proposed that a bolide observed on 8 January 2019 was of interstellar origin. The meteor, observed by U.S. satellites and reported in the CNEOS catalog had an estimated size of 0.5 meters and exploded in the atmosphere northeast of Papua New Guinea with an energy of 0.1 kilotons (CNEOS, 2019). The finding that it was of interstellar origin is based on backwards propagation using the CNEOS reported trajectory. Due to uncertainties in CNEOS trajectory data the identification is unconfirmed.


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Last modified 1 February 2020.
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