|Discovered by||Edward L. G. Bowell|
|Discovery date||11 February 1980|
|Orbital characteristics A|
(3 January 1982)
|Observation arc||6.88 years|
|Aphelion||~75000 AU (inbound)|
|Eccentricity||1.057 (hyperbolic trajectory)|
1.053 (epoch 1984+)
|Orbital period||~7.1 million years (epoch 1950)|
Ejection (epoch 1977+)
|Last perihelion||12 March 1982|
C/1980 E1 is a non-periodic comet discovered by Edward L. G. Bowell on 11 February 1980 and which came closest to the Sun (perihelion) in March 1982. It is leaving the Solar System on a hyperbolic trajectory due to a close approach to Jupiter. Since its discovery only 1I/ʻOumuamua and 2I/Borisov have been identified with a faster such trajectory.
Before entering the inner Solar System for a 1982 perihelion passage, C/1980 E1 had a barycentric (epoch 1950-Jan-01) orbit with an aphelion of 75,000 AU (1.2 ly), and a period of approximately 7.1 million years.
As the comet was approaching on 9 December 1980, it passed within 0.228 AU of Jupiter, which accelerated the comet briefly giving an (epoch 1981-Jan-09) eccentricity of 1.066. The comet came to perihelion on 12 March 1982, when it had a velocity of 23.3 km/s (52,000 mph) with respect to the Sun. Since the epoch of 1977-Mar-04, C/1980 E1 has had a barycentric eccentricity greater than 1, keeping it on a hyperbolic trajectory that will eject it from the Solar System. Objects in hyperbolic orbits have a negative semimajor axis, giving them a positive orbital energy. After leaving the Solar System, C/1980 E1 will have an interstellar velocity () of 3.77 km/s.[a] The Minor Planet Center does not directly list a semimajor axis for this comet.
The escape velocity from the Sun at Neptune's orbit is 7.7 km/s. By June 1995, the comet was passing Neptune's orbit at 30.1 AU from the Sun continuing its ejection trajectory at 8.6 km/s. Since February 2008, the comet has been more than 50 AU from the Sun.
Emission of OH (hydroxide) was observed pre-perihelion while the comet was nearly 5 AU from the Sun. CN (cyanide) was not detected until the comet was near perihelion. The comet nucleus was estimated to have a radius of several kilometers. The surface crust was probably a few meters thick.