Comet C/2020 F3 (NEOWISE)

Comet C/2020 F3 (NEOWISE) was discovered in March 2020 by the NEOWISE infrared space telescope and reached perihelion on 3 July 2020, passing well inside the orbit of Mercury. It survived that approach intact, and through July it became the brightest comet seen from the northern hemisphere since Hale-Bopp in 1997 — bright enough to pick out by eye in a dark sky.

Two tails are visible here, and they form in different ways. The broad, gently curving tail is dust released as solar heating vaporises ice from the nucleus; once free, the grains are pushed outward by radiation pressure and lag behind along the comet’s orbit. The narrow bluish streak is the ion tail, gas ionised by ultraviolet sunlight and carried straight away from the Sun by the solar wind, which is why the two tails point in noticeably different directions. The blue colour comes from carbon monoxide ions fluorescing in sunlight.

Its orbit is long enough that it will not return for roughly 6,800 years.