by cubefox | 2025-07-11 19:43:23+00:00
> It also means that

No, it doesn't mean that. What makes 'Oumuamua special is not the fact that we didn't see interstellar objects before. It's rather the fact that 'Oumuamua has highly unusual and hard to explain properties. Avi Loeb:

> ‘Oumuamua exhibited a non-gravitational acceleration of 4.92 ± 0.16 × 10^⁻6 m/s² that decreased proportionally to 1/r², where r represents the heliocentric distance, corresponding to a formal ~30 σ detection of non-gravitational acceleration (Micheli et al., 2018). The inverse-square relationship typically indicates radiation pressure or outgassing forces. However, despite extensive observations by the Spitzer Space Telescope, no carbon-based molecules, dust, or thermal emission indicative of cometary outgassing were detected (Trilling et al., 2018). Such a paradox — acceleration without observable mass loss — violates fundamental assumptions about how small bodies behave in the solar system.

> The object’s extreme geometry presented another unprecedented observation. ‘Oumuamua’s brightness varied by a factor of 10 during its 8-hour rotation period, indicating an extreme geometry with an aspect ratio exceeding 10:1 (Drahus et al., 2018; Meech et al., 2017). Such extreme elongation is unprecedented among known Solar System objects, leading to competing interpretations of either a cigar-shaped or pancake-like geometry (Belton et al., 2018; Luu et al., 2020; Mashchenko, 2019; Moro-Martín, 2019a,b; Zhang & Lin, 2020).

> More significantly, ‘Oumuamua entered the Solar System with a velocity remarkably close to the Local Standard of Rest (LSR). The object’s velocity before encountering the Solar System was within approximately 6 km/s of the local median stellar velocity and just 11 km/s from the LSR, with negligible radial and vertical Galactic motion (Mamajek, 2017). Fewer than 1 in 500 stars share such kinematics, making ‘Oumuamua’s near-stationary approach highly improbable for a naturally ejected object from a nearby star system (Loeb, 2022). Natural ejection mechanisms from planetary systems typically impart the host star’s peculiar velocity to expelled bodies, yet ‘Oumuamua appeared to originate from the most kinematically common frame of reference in our Galactic neighborhood (Loeb, 2022; Mamajek, 2017).

> The object’s rotational dynamics added another layer of complexity. ‘Oumuamua displayed non-principal axis rotation, exhibiting a tumbling motion rather than spinning around a single axis. Such a rotational state is unusual for an object that has been traveling through interstellar space for potentially billions of years, as collisions and internal friction should have damped its motion to simple rotation (Belton et al., 2018; Fraser et al., 2018).

> Finally, the object’s slightly red color differed from both typical comets and asteroids. Its spectral properties showed no absorption features that would indicate specific mineral compositions, making it difficult to determine its definite surface composition (Jewitt et al., 2017; Ye et al., 2017). This spectral ambiguity prevented researchers from determining surface composition through standard techniques, leaving the object’s fundamental nature — rocky, icy, or something else entirely — unresolved.

https://avi-loeb.medium.com/scientific-paradigm-resistance-e...