326732 Nice

Nice was discovered by the Lowell Observatory Near-Earth-Object Search (LONEOS) project at Anderson Mesa on 25 April 2003.^[1] It was given the provisional designation 2003 HB₆, and its discovery was announced in a Minor Planet Electronic Circular the next day.^[6] Once its orbit was sufficiently determined, it was numbered (326732) by the Minor Planet Center on 6 May 2012.^[7]

On 24 February 2025, the asteroid was given the name Nice by the Working Group for Small Bodies Nomenclature (WGSBN). The asteroid was named in honor of the city of Nice, France, which was founded by Greek colonists in 350 BCE. The city was declared a UNESCO World Heritage Site in 2021, and it is home to the Côte d'Azur Observatory, whose planetary science team has been well-involved in asteroid research.^[8]: 16 The city is also the namesake for the Nice model, which proposes that the giant planets migrated to their current orbits from a more compact configuration early in the Solar System's history.^[9] The name was proposed by planetary scientist Patrick Michel, principal investigator of the ESA's Hera mission. The mission aims to study the effects of NASA's Double Asteroid Redirection Test impact on Dimorphos, a moon of 65803 Didymos.^[10] Michel stated that his naming proposal aimed to bring recognition to Nice's contributions to astronomy.^[11]

Nice orbits the Sun with a semi-major axis (a) of 2.71 astronomical units (AU), completing one orbit every 4.47 years. It has an orbital inclination of 6.62° with respect to the ecliptic plane. Due to its orbital eccentricity of 0.57, its distance to the Sun along its orbit varies from 4.26 AU at aphelion to 1.17 AU at perihelion.^[2] It is classified as a near-Earth asteroid (NEA), and it is a member of the Amor asteroids—NEAs whose orbits lie entirely outside Earth's (a > 1.0 AU) but have perihelia under 1.3 AU.^[2][12]

Nice has a diameter of 1.95 ± 0.63 kilometres (1.21 ± 0.39 mi).^[3]: 4244 It is either an X-type, D-type, or L-type asteroid.^{[3]: 4237 [5]} Spectrally, Nice closely resembles the Tagish Lake meteorite, and may be its source object.^[13]: 331

Analysis of Nice's lightcurve, or fluctuations in its observed brightness as it rotates, indicates that it has a rotation period of 3.463 hours.^[4]: 27 Its rotation period lies close to the spin barrier, which lies at 2.2 hours. The spin barrier is the critical rotation period below which a strengthless rubble pile asteroid with a bulk density of 2.2 g/cm³ would structurally fail due to the centrifugal force.^[3]: 4240

Nice has one known satellite, making it a binary asteroid. It was discovered by a team of astronomers led by Petr Pravec in photometric observations taken at Ondrejov Observatory and the European Southern Observatory between 10 August and 15 September 2021. Its discovery was announced through the Central Bureau Electronic Telegrams on 18 September of that year.^[5] The satellite currently has no name or official designation.^[2]

Mutual eclipses indicate that the satellite is 0.23±0.02 times the size of Nice. The satellite's lightcurve suggests that it has a slightly elongated shape, with an a/b ratio of 1.4±0.2.^[5] It orbits with a period of 22.903 hours and is synchronously tidally locked to Nice.^{[4]: 27–28}