Interstellar object

With the first discovery of an interstellar object in the Solar System, the IAU has proposed a new series of small-body designations for interstellar interlopers, the I numbers, similar to the comet numbering system. The Minor Planet Center will assign the numbers. Provisional designations for interstellar objects will be handled using the C/ or A/ prefix (comet or asteroid), as appropriate. ==Overview==

Astronomers estimate that several interstellar objects of extrasolar origin (like ʻOumuamua) pass inside the orbit of Earth each year, and that 10,000 are passing inside the orbit of Neptune on any given day. Interstellar comets occasionally pass through the inner Solar System Both researchers proposed a search for ʻOumuamua-like objects which are trapped in the Solar System as a result of losing orbital energy through a close encounter with Jupiter. It is possible for objects orbiting a star to be ejected due to interaction with a third massive body, thereby becoming interstellar objects. Such a process was initiated in the early 1980s when C/1980 E1, initially gravitationally bound to the Sun, passed near Jupiter and was accelerated sufficiently to reach escape velocity from the Solar System. This changed its orbit from elliptical to hyperbolic and made it the most eccentric known object at the time, with an eccentricity of 1.057. The detection of ʻOumuamua crossing the inner Solar System confirms the possibility of a material link with exoplanetary systems. File:Uncertain size-frequency distribution of interstellar visitors.jpg|thumb|Interstellar visitors in the Solar System cover the whole range of sizes – from kilometer large objects down to submicron particles. Also, interstellar dust and meteoroids carry with them valuable information from their parent systems. Detection of these objects along the continuum of sizes is, however, not evident. The smallest interstellar dust particles are filtered out of the Solar System by electromagnetic forces, while the largest ones are too sparse to obtain good statistics from in situ spacecraft detectors. Discrimination between interstellar and interplanetary populations can be a challenge for intermediate (0.1–1 micrometer) sizes. These can vary widely in velocity and directionality. The identification of interstellar meteoroids, observed in the Earth's atmosphere as meteors, is highly challenging and requires high accuracy measurements and appropriate error examinations. Otherwise, measurement errors can transfer near-parabolic orbits over the parabolic limit and create an artificial population of hyperbolic particles, often interpreted as of interstellar origin. In May 2023, astronomers reported the possible capture of other interstellar objects in Near Earth Orbit (NEO) over the years. ==Solar System interlopers==

Confirmed 1I/2017 U1 (ʻOumuamua) , the first confirmed interstellar object, discovered in 2017 A dim object was discovered on 19 October 2017, by the Pan-STARRS telescope, at an apparent magnitude of 20. The observations showed that it follows a strongly hyperbolic trajectory around the Sun at a speed greater than the solar escape velocity, in turn meaning that it is not gravitationally bound to the Solar System and likely to be an interstellar object. 3I/ATLAS A third object was discovered by ATLAS on 1 July 2025, just inside the orbit of Jupiter at a distance of 4.5 AU from the Sun. It has a record-setting eccentricity of 6.14. The object came to perihelion on 29 October 2025 11:36 UT at a distance of from the Sun. Both inbound and outbound, the object has an interstellar velocity (v_\infty) of around 58 km/s. Unconfirmed (C/1996 B2) might be a former interstellar object captured by the Solar System Some other objects have been thought to be possible interstellar interlopers. The situation : In 2007, Afanasiev et al. reported the likely detection of a multi-centimeter intergalactic meteor hitting the atmosphere above the Special Astrophysical Observatory of the Russian Academy of Sciences on 28 July 2006. In November 2018, Harvard astrophysicists Amir Siraj and Avi Loeb reported that there should be hundreds of ʻOumuamua-size interstellar objects in the Solar System, based on calculated orbital characteristics, and presented several centaur candidates such as and . These are all orbiting the Sun, but may have been captured in the distant past. In May 2023, astronomers reported the possible capture of other interstellar objects in Near Earth Orbit (NEO) over the years, and still other experts found Earth-related explanations for the purported meteorite impact instead. 2014 interstellar meteor CNEOS 2014-01-08 was a meteor with a mass of 0.46 tons and width of , which burned up in the Earth's atmosphere on 8 January 2014. A 2019 preprint suggested this meteor had been of interstellar origin. It had a heliocentric speed of and an asymptotic speed of , and it exploded at 17:05:34 UTC near Papua New Guinea at an altitude of . After declassifying the data in April 2022, the U.S. Space Command, based on information collected from its planetary defense sensors, confirmed the velocity of the potential interstellar meteor. In 2023, The Galileo Project completed an expedition to retrieve small fragments of the apparently peculiar Claims about their findings have been doubted by their peers according to a report in The New York Times. Further related studies were reported on 1 September 2023. Other astronomers doubt the interstellar origin because the meteoroid catalog used does not report uncertainties on the incoming velocity. ==Hypothetical missions==

With current space technology, close visits and orbital missions are challenging due to interstellar interlopers' high speeds, though not impossible. The Initiative for Interstellar Studies (i4is) launched in 2017 Project Lyra to assess the feasibility of a mission to ʻOumuamua. If no suitable comet is identified during its 3-year endurance, the spacecraft could be tasked to intercept a reachable interstellar interloper at short notice. ==See also==