Interstellar object
This term can also be applied to an object that is on an interstellar trajectory but is temporarily passing close to a star, such as certain asteroids and comets (that is, exoasteroids and exocomets[1][2]).
The discovery of ʻOumuamua inspired the tentative identification of CNEOS 2014-01-08, also known as the Manus Island fireball, as an interstellar object that impacted the Earth by astronomers Amir Siraj and Avi Loeb in 2019.
[29] Until the discovery of 'Oumuamua, the fact that no comet with a speed greater than the Sun's escape velocity[30] had been observed was used to place upper limits to their density in interstellar space.
[2] A more recent estimate by David C. Jewitt and colleagues, following the detection of 'Oumuamua, predicts that "The steady-state population of similar, ~100 m scale interstellar objects inside the orbit of Neptune is ~1×104, each with a residence time of ~10 years.
[1] Amir Siraj and Avi Loeb demonstrated that the Oort Cloud could have been formed from ejected planetesimals from other stars in the Sun's birth cluster.
[34][35][36] 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.
[30][41] Recent research suggests that asteroid 514107 Kaʻepaokaʻawela may be a former interstellar object, captured some 4.5 billion years ago, as evidenced by its co-orbital motion with Jupiter and its retrograde orbit around the Sun.
[46] 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.
[48] 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.
This is only a suggestion, as ʻOumuamua might very well have lost all surface volatiles to eons of cosmic radiation exposure in interstellar space, developing a thick crust layer after it was expelled from its parent system.
[58] On 13 September 2019, the Gran Telescopio Canarias obtained a low-resolution visible spectrum of 2I/Borisov that revealed that this object has a surface composition not too different from that found in typical Oort Cloud comets.
[63] 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 July 28, 2006.
[64] In November 2018, Harvard astronomers Amir Siraj and Avi Loeb reported that there should be hundreds of 'Oumuamua-size interstellar objects in the Solar System, based on calculated orbital characteristics, and presented several centaur candidates such as 2017 SV13 and 2018 TL6.
[65] Both researchers have proposed methods for increasing the discovery rate of interstellar objects that include stellar occultations, optical signatures from impacts with the moon or the Earth's atmosphere, and radio flares from collisions with neutron stars.
[4] After declassifying the data in April 2022,[75] the U.S. Space Command, based on information collected from its planetary defense sensors, confirmed the velocity of the potential interstellar meteor.
In November 2022, a paper was published, claiming the anomalous properties (including its high strength and strongly hyperbolic trajectory) of CNEOS 2014-01-08 are better described as measurement error rather than genuine parameters.
[91] Different mission durations and their velocity requirements were explored with respect to the launch date, assuming direct impulsive transfer to the intercept trajectory.
[92] In case that no suitable comet is identified during its 3-year wait, the spacecraft could be tasked to intercept an interstellar object in short notice, if reachable.
