C/2018 V1 (Machholz–Fujikawa–Iwamoto)

Lore & Background

The comet was discovered by three amateur astronomers: Donald Machholz in Colfax, California, USA, and independently by Shigehisa Fujikawa and Masayuki Iwamoto in Japan. Their combined observations led to the comet's name, Machholz–Fujikawa–Iwamoto. It was estimated to be between 8th and 10th magnitude from mid-November to mid-December 2018, making it visible in a small telescope. The current orbit determination is based on 750 observations over a 37-day observation arc.

Reader's Guide

C/2018 V1 (Machholz–Fujikawa–Iwamoto) holds significance as a comet with a slightly hyperbolic trajectory and a 72.6% probability of having an extrasolar provenance, meaning it likely originated outside the Solar System, although an origin in the Oort Cloud remains possible. Its present-day barycentric orbital eccentricity is greater than 1, indicating it is currently escaping the Solar System and heading toward interstellar space. The comet was discovered by three amateur astronomers, highlighting the continued role of citizen scientists in astronomical discovery. Its visibility in small telescopes from mid-November to mid-December 2018 allowed many observers to track it. The comet's legacy includes its inclusion in lists of parabolic comets and its connection to other comets such as 72P/Denning–Fujikawa and C/1983 J1 (Sugano–Saigusa–Fujikawa).

Did You Know?

• The comet was visually discovered on 7 November 2018 by Donald Machholz using an 18.5-inch reflecting telescope.
• It was independently co-discovered by Shigehisa Fujikawa and Masayuki Iwamoto.
• Its barycentric orbital eccentricity is greater than 1, so it is currently escaping the Solar System.

Discovery by an Amateur and the MOSS Survey

French amateur astronomer Claudine Rinner made the find on the night of 21 December 2017, working remotely with the 0.5-metre reflecting telescope at the Oukaïmeden Observatory near Marrakesh, Morocco. Her observation was one product of the Morocco Oukaïmeden Sky Survey, a program directed by Zouhair Benkhaldoun at Cadi Ayyad University that targets the detection and orbital characterization of small Solar System bodies. At the moment of discovery the object sat roughly 1.1 astronomical units from Earth, glimmering at magnitude 19.8 in the constellation Gemini. It was the sixth near-Earth asteroid catalogued by the MOSS effort. Rinner's detection was promptly forwarded to the Minor Planet Center's Near-Earth Object Confirmation Page, where follow-up observations from several observatories over the next six days allowed a preliminary orbit to be computed. The object was formally announced in a Minor Planet Electronic Circular on 27 December 2017. Later, archivists at the Mount Lemmon Survey and Pan-STARRS1 identified earlier frames from 14 and 12 December 2017 respectively, pushing the known observation record back a full week before Rinner's discovery.

The 2018 Close Approach and Radar Imaging

On 21 June 2018 at 20:53 UTC, the binary pair swept past Earth at a distance of roughly 5.96 million kilometres—about 15.5 lunar distances—moving at a relative speed of 15.5 kilometres per second. The object's apparent brightness crested near magnitude 15, far too dim for unaided eyes, and it traced a path of 0.51 degrees per hour across the constellation Andromeda, sitting 66 degrees from the Sun in the sky. What made this encounter truly remarkable was the level of detail captured: radar teams at Arecibo and Green Bank conducted concurrent observations that resolved the two components in high fidelity, while the Goldstone Solar System Radar contributed its own independent data set. Each member of the pair measured approximately 0.9 kilometres in diameter and appeared to be of similar mass, confirming the binary nature of the system. After its flyby of Earth, the object continued outward on its elongated orbit, slipping past Mars at a distance of about 6.6 million kilometres before heading toward its aphelion beyond the asteroid belt.

A Comet in Asteroid's Clothing

Although catalogued as a near-Earth asteroid, 2017 YE5 carries the hallmarks of a long-dead comet. Its orbit is extremely elongated, with an eccentricity of 0.71 that swings it from 0.82 astronomical units at perihelion all the way out to 4.82 AU at aphelion—well beyond the outer edge of the main asteroid belt. The full circuit takes 4.73 years. At its farthest point the object drifts close enough to Jupiter's orbit, with a minimum intersection distance of 0.42 AU, that the gas giant's gravity has almost certainly sculpted its path over countless cycles. The tell-tale numerical fingerprint is its Tisserand parameter of 2.877, a value squarely in the range associated with comets rather than typical asteroids. Spectroscopic work carried out in 2018 using both optical and infrared wavelengths painted a consistent picture: a dark, reddish surface with very low reflectance, matching the D-type spectral class long linked to cometary nuclei. Taken together, these clues lead researchers to suspect that 2017 YE5 is best understood as an extinct or dormant Jupiter-family comet that has shed its volatile ices and now masquerades as a rocky body.

Classification, Nomenclature, and the Question of Danger

Because its orbit crosses Earth's path while its average solar distance exceeds one astronomical unit, 2017 YE5 falls under the Apollo group of near-Earth objects. Its minimum orbital intersection distance with Earth is roughly 0.021 AU—about eight lunar distances—which, combined with an absolute magnitude bright enough to satisfy the threshold, earns it the label of a potentially hazardous asteroid from the Minor Planet Center. Yet the label is purely statistical: trajectory calculations show the pair will not come within twelve lunar distances of our planet for at least the next two centuries. After a thorough refinement of its orbital elements, the object was struck from the JPL Sentry Risk Table on 6 January 2018, effectively closing the book on any realistic impact scenario. On the nomenclature front, the body still carries only its provisional designation, 2017 YE5, which encodes the discovery date and marks it as the 130th object found in the second half of December 2017. A permanent minor-planet number remains out of reach because the observation arc spans just 270 days; the Minor Planet Center requires at least four oppositions before a number—and the right to a name—can be assigned.