It was announced alongside nine other Jovian moons on 17 July 2018 and was provisionally designated S/2018 J 1 by the Minor Planet Center, after observations were collected over a long enough time span to confirm the satellite's orbit.

[3] Ersa is part of the Himalia group, a tight cluster of prograde irregular moons of Jupiter that follow similar orbits to Himalia at semi-major axes between 11–12 million km (6.8–7.5 million mi) and inclinations between 26–31°.

[5] With an estimated diameter of 3 km (1.9 mi) for an absolute magnitude of 15.9, it is one of the smallest known members of the Himalia group.

[6] The name was suggested in a naming contest held by the Carnegie Institute on Twitter,[7] where more than twenty tweets suggested the name, including Aaron Quah (@8603103) who submitted the name first, StSauveur_MoonsProject (@StSauMoons) that are the 12th grade students of Saint Sauveur High School in Redon, France, the fifth grade at Hillside Traditional Academy in British Columbia, Canada (submitted on their behalf by @mrgrouchypants), and a 4-year-old child who sang a song about Ersa (submitted on his behalf by @Thoreson).

On average, Ersa orbits Jupiter at a semi-major axis of about 11,401,000 km (7,084,000 mi) at an inclination of about 29.1° with respect to the ecliptic.