Omuamua-formally known as 1I/2017 U1 is the first known object from another star system to visit our solar system.It was discovered by Robert Weryk using PAN-STARRS 1 telescope of the Haleakala observatory in Hawaii on October 19,2017.On the time of it's discovery it was already moving away from the solar system giving the astronomers a very small window through time to observe the object.
The object is speculated to be an artifact from the origin of a star system .Some astronomers argue that it may be a leftover from a supernova explosion .Others put forward an idea that it is a remnant of a disintegrated rogue comet(exo-comet) .Even an alien object speculation about Omuamua being a thin solar sail exists .Its parent planetary system and the time it spent in its interstellar voyage is unknown.
'Omuamua' is a Hawaiian word which translates to 'a messenger from afar arriving first'.It was initially named 'Rama' after the alien spacecraft in the 1973 sci-fi novel Rendezvous with Rama by Arthur C. Clarke.
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| Artist's Concept |
When observing the variation of brightness of Omuamua , it was noted that the brightness varied by a factor of 10 ;as it rotates around its axis every 7.3 hours; which is a bit unusual.Such a pattern can only be showed by a body with a large ratio between length and width.So it was concluded that Omuamua is an elongated object with it's length between 100 &1000 m and its width and thickness between 35 & 167 m.It executes a complex motion by rotating in two axis while tumbling.On spectroscopic analysis ;Omuamua had a dark red color similar to other objects from outer space.
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| Illustration of the rotation of Omuamua and the variation of brightness. |
| Trajectory of Omuamua |
The velocity of the body was too high to be captured into the earths orbit.It took a hyperbolic trajectory entering the orbit of mercury and gaining momentum from the sun's gravitational force.It didn't exhibit Coma but exhibited non gravitational acceleration which is weird . A recent paper on astrophysics stated that it may be an extraterrestrial solar sail as it acted on the inverse square law. The acceleration observed was related in inverse squares to the distance from the sun .So it is consistent with a push from solar radiation pressure.
But the inverse square law is also consistent with Comet out-gassing; since the radiation from the sun vaporizes the frozen materials creating a jet of gases.But no visible observations were made of the comet out-gassing effect which will produce a Coma. Also an comet out-gassing would change the axis considerably that will cause the object to disintegrate.
Omuamua and such bodies from outer space gives us a chance to study about the early life of a solar system and how it develops into systems like ours.
