Astronomy:326732 Nice

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326732 Nice
Discovery[1]
Discovered byLONEOS
Discovery siteAnderson Mesa
Discovery date25 April 2003
Designations
(326732) Nice
Pronunciation/niːs/ NEESS
Named afterNice, France
2003 HB6[1]
Minor planet category
Orbital characteristics[2]
Epoch 21 November 2025 (JD 2461000.5)
Uncertainty parameter 0
|{{{apsis}}}|helion}}4.2605 AU
|{{{apsis}}}|helion}}1.1658 AU
2.7132 AU
Eccentricity0.5703
Orbital period4.4692 yr (1632.37 d)
Mean anomaly348.1798°
Inclination6.6184°
Longitude of ascending node161.6112°
145.8055°
Known satellites1
Earth MOID0.1637 AU
TJupiter3.096
Physical characteristics
Dimensions1.95 ± 0.63 kilometres (1.21 ± 0.39 mi)[3]: 4244 
Sidereal rotation period3.463 h[4]: 27 
X-type or D-type[3]: 4237 
L-type[5]
Color indices:[3]: 4244 
g–r = 0.531±0.015
r–i = 0.190±0.018
i–z = 0.089±0.025
Absolute magnitude (H)17.66 (JPL)[2]


326732 Nice (/niːs/ NEESS; provisional designation 2003 HB6) is a binary near-Earth asteroid. It was discovered on 25 April 2003 by the Lowell Observatory Near-Earth Object Search (LONEOS) project and named after the French city of Nice on 24 February 2025. Classified as an Amor asteroid, it has a diameter of nearly 2 kilometres (1.2 mi) and rotates once every 3.5 hours. It has one known moon; the unnamed satellite's discovery was announced on 18 September 2021.

Discovery and naming

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]

Orbit

An orbital diagram of 326732 Nice, with the orbits of the inner planets and the ecliptic grid shown.

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]

Physical properties

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 

Satellite

Discovery[5]
Discovered byPetr Pravec et al.
Discovery site
Discovery date18 September 2021
Orbital characteristics[4]: 27–28 
Orbital period22.903 h
Physical characteristics
Sidereal rotation period22.903 h (synchronous)[4]: 28 


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 

References

  1. ↑ 1.0 1.1 1.2 "(326732) Nice = 2003 HB6". Minor Planet Center. https://www.minorplanetcenter.net/db_search/show_object?utf8=%E2%9C%93&object_id=326732. Retrieved 25 October 2025. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 "326732 Nice (2003 HB6)". JPL Small-Body Database. NASA/Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=Nice. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Pereira, W. (6 October 2025). "Photometric characterization of near-Earth objects from OASI and CASLEO observations". Monthly Notices of the Royal Astronomical Society 543 (4): 4235–4253. doi:10.1093/mnras/staf1701. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 Warner, Brian D.; Stephens, Robert D. (2022). "On Confirmed and Suspected Binary Asteroids Observed at the Center for Solar System Studies". The Minor Planet Bulletin 49 (1): 22–29. Bibcode: 2022MPBu...49...22W. https://mpbulletin.org/issues/MPB_49-1.pdf. 
  5. ↑ 5.0 5.1 5.2 5.3 5.4 Pravec, Petr (18 September 2021). "(326732) 2003 HB6". IAU Central Bureau for Astronomical Telegrams (5039). Bibcode: 2021CBET.5039....1P. http://www.cbat.eps.harvard.edu/cbet/005000/CBET005039.txt. 
  6. ↑ Minor Planet Center Staff (26 April 2003). "MPEC 2003-H36 : 2003 HB6". Minor Planet Electronic Circular (Minor Planet Center) 2003-H36. Bibcode: 2003MPEC....H...36T. https://minorplanetcenter.net/mpec/K03/K03H36.html. Retrieved 27 October 2025. 
  7. ↑ "M. P. C. 79358". Minor Planet Circulars. Minor Planet Center. 6 May 2012. p. 250. https://minorplanetcenter.net/iau/ECS/MPCArchive/2012/MPC_20120506.pdf. Retrieved 27 October 2025. 
  8. ↑ "WGSBN Bulletin 5, #3". Working Group for Small Bodies Nomenclature. 24 February 2025. https://www.wgsbn-iau.org/files/Bulletins/V005/WGSBNBull_V005_003.pdf. Retrieved 27 October 2025. 
  9. ↑ "Solving solar system quandaries is simple: Just flip-flop the position of Uranus and Neptune" (Press release). Arizona State University. 13 December 2007. Retrieved 2025-02-13.
  10. ↑ "«Un petit morceau de Nice dans l'espace» : pourquoi la capitale azuréenne a un astéroïde à son nom" (in French). Ouest France. 5 March 2025. https://www.ouest-france.fr/sciences/espace/un-petit-morceau-de-nice-dans-lespace-pourquoi-la-capitale-azureenne-a-un-asteroide-a-son-nom-47444662-f9d6-11ef-8548-c974a9e992f2. 
  11. ↑ Duret, Loreena (1 March 2025). ""Je veux faire briller Nice dans l'Espace" : un double astéroïde porte désormais le nom de la capitale azuréenne" (in fr-FR). https://france3-regions.franceinfo.fr/provence-alpes-cote-d-azur/alpes-maritimes/nice/je-veux-faire-briller-nice-dans-l-espace-un-double-asteroide-porte-desormais-le-nom-de-la-capitale-azureenne-3115273.html. 
  12. ↑ "NEO Groups". NASA/JPL Near-Earth Object Program Office. http://neo.jpl.nasa.gov/neo/groups.html. 
  13. ↑ Izawa, M. R. M. (July 2015). "Variability, absorption features, and parent body searches in “spectrally featureless” meteorite reflectance spectra: Case study – Tagish Lake". Icarus 254: 324–332. doi:10.1016/j.icarus.2015.04.013. Bibcode: 2015Icar..254..324I. 



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