ʻOumuamua
Object Velocity km/s # of observations and obs arc
90377 Sedna 1.99 196 in 9240 days
C/1980 E1 ( Bowell ) 2.96 179 in 2514 days
C/1997 P2 ( Spacewatch ) 2.96 94 in 49 days
C/2010 X1 ( Elenin ) 2.96 2222 in 235 days
C/2012 S1 ( ISON ) 2.99 6514 in 784 days
C/2008 J4 ( McNaught ) 4.88 22 in 15 days
1I/2017 U1 ( ʻOumuamua ) 26.5 121 in 34 days
Observations -- Trajectory
Seen from Earth , the apparent trajectory makes annual retrograde loops in the sky , with its origin in Lyra , temporarily moving south of the ecliptic between 2 September and 22 October 2017 , and moving northward again towards its destination in Pegasus . ʻOumuamua 's hyperbolic trajectory over the Solar System ʻOumuamua appears to have come from roughly the direction of Vega in the constellation Lyra . [ 41 ] [ 42 ] [ 47 ] [ 48 ] The incoming direction of motion of ʻOumuamua is 6° from the solar apex ( the direction of the Sun 's movement relative to local stars ) , which is the most likely direction for approaches from objects outside the Solar System . [ 47 ] [ 49 ] On 26 October , two precovery observations from the Catalina Sky Survey were found dated 14 and 17 October . [ 50 ] [ 39 ] A two-week observation arc had verified a strongly hyperbolic trajectory . [ 7 ] [ 36 ] It has a hyperbolic excess velocity ( velocity at infinity , v ∞ { \displaystyle v_ { \infty } \ ! } ) of 26.33 km/s ( 94,800 km/h ; 58,900 mph ) , its speed relative to the Sun when in interstellar space . [ d ] ʻOumuamua speed relative to the Sun [ 51 ] Distance Date Velocitykm/s 2300 AU 1605 26.34 1000 AU 1839 26.35 100 AU 2000 26.67 10 AU 2016 29.50 1 AU 9 August 2017 49.67 Perihelion 9 September 2017 87.71 1 AU 10 October 2017 49.67 10 AU 2019 29.51 100 AU 2034 26.65 1000 AU 2196 26.36 2300 AU 2430 26.32 By mid-November , astronomers were certain that it was an interstellar object . [ 52 ] Based on observations spanning 34 days , ʻOumuamua 's orbital eccentricity is 1.20 , the highest ever observed [ 53 ] [ 10 ] until 2I/Borisov was discovered in August 2019 . An eccentricity exceeding 1.0 means an object exceeds the Sun 's escape velocity , is not bound to the Solar System and may escape to interstellar space . While an eccentricity slightly above 1.0 can be obtained by encounters with planets , as happened with the previous record holder , C/1980 E1 , [ 53 ] [ 54 ] [ f ] ʻOumuamua 's eccentricity is so high that it could not have been obtained through an encounter with any of the planets in the Solar System . Even undiscovered planets in the Solar System , if any should exist , could not account for ʻOumuamua 's trajectory nor boost its speed to the observed value . For these reasons , ʻOumuamua can only be of interstellar origin . [ 55 ] [ 56 ] Animation of ʻOumuamua passing through the Solar System
ʻOumuamua (, ) is the first known interstellar object detected passing through the Solar System. Formally designated 1I/2017 U1, it was discovered by Robert Weryk using the Pan-STARRS telescope at Haleakala Observatory, Hawaii, on 19 October 2017, 40 days after it passed its closest point to the Sun on 9 September. When it was first observed, it was about from Earth (about 85 times as far away as the Moon), and already heading away from the Sun. ʻOumuamua is a small object estimated to be between long, with its width and thickness both estimated to range between . It has a dark red colour, similar to objects in the outer Solar System. ʻOumuamua showed no signs of being a comet coma (atmosphere) despite its close approach to the Sun, but exhibited non-gravitational acceleration. Nonetheless, the object could be a remnant of a disintegrated rogue comet (or exocomet), according to a NASA scientist. The object has a rotation rate similar to the average spin rate seen in Solar System asteroids, but is more elongated than all but a few other natural bodies. While a strengthless object (rubble pile) would require it to be of a density similar to rocky asteroids, a small amount of internal strength similar to icy comets would allow a relatively low density. ʻOumuamua is tumbling, rather than smoothly rotating, and is moving so fast relative to the Sun that there is no chance it originated in the Solar System. It also means that ʻOumuamua cannot be captured into a solar orbit, so it will eventually leave the Solar System and resume traveling through interstellar space. ʻOumuamua's planetary system of origin, and the amount of time it has spent traveling amongst the stars, are unknown.