Three years have been passed since Oumuamua (11/2017 U1), the first unknown interstellar object was observed in our solar system on October 19, 2017, by the University of Hawaii’s Pan-STARRS1 telescope, which is used to find asteroids and comets near our planet. The strange, cigar-shaped object moving through our solar system at incredible speed and ridiculous inclination is still creating a curiosity towards the astronomers in our world, making them ask ‘what the object actually is.’ A few hundred feet long, but very thin, shaped like a giant space cigar with a reddish hue, reminiscent of the object were first thought to be an asteroid, a rock shed by another star system, or a comet. However, based on the survey properties and the single detection, it has suggested that the large variations in its apparent magnitude and the non-trivial periodicity of the lightcurve show an extreme aspect ratio of at least 5:1, an unprecedented value for previously known asteroids and comets in the Solar System. Moreover, scientists have decided that there was a lack of visible comet activity, such as cyanide gas emission, typically seen in outgassing from comets formed.

The biggest characteristic of Omuamua is that it has a complex rotational motion. Oumuamua is moving on an open hyperbolic trajectory with an eccentricity of 1.23 through our solar system, which is why astronomers were quickly able to identify it as an interstellar object.

ESO's VLT Sees `Oumuamua Getting a Boost | ESO
Fig 1. Predicted path of Oumuamua and the new course (ESA)

From the article published in the Harvard Smithsonian Center for Astrophysics, they have suggested that Oumuamua’s non-gravitational acceleration best suggests the best fit model of acceleration by radian pressure. They have also explored maximum distance for interstellar travel, momentum and energy transfer and tidal forces to back up their explanation for its acceleration. However, this requires a very small mass to area ratio by near 0.1 gcm-2which gives a typical mass density of 1-3 gcm-2and thickness of 0.9-0.3mm. They have also found that although very thin, such an object can travel over galactic distances, maintaining its momentum and withstanding collisional destruction by dust-grains and gas, as well as centrifugal and tidal forces.

While this scenario can explain may naturally explain the peculiar acceleration of Oumuamua, it opens up another question of what kind of material has such a small mass-to-area ratio. If radiation pressure is the accelerating force, then ‘Oumuamua represents a new class of thin interstellar material, which may be produced in different ways, including naturally, an unknown process in the ISM or even an artificial origin. There is a possibility that Oumuamua is one of the debris from advanced technological equipment and even if it is an exotic scenario, it may be the evidence of an operational probe sent intentionally to the Earth by an alien civilization. This still remains a questionnaire, still in discussion.


Amy Yeobin Han
Amy Yeobin Han

Student of NLCS Jeju
Member of NLCS Jeju Science and Engineering at Elite Universities Society (SEEUS)


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