Discovery Hygiea was discovered on the evening of 12 April 1849 by Italian astronomer
Annibale de Gasparis at the
Astronomical Observatory of Capodimonte in
Naples, Italy. On that night he was using the observatory's Reichenbach
equatorial telescope to observe a section of the sky in the 12th
hour of
right ascension, as part of his larger project of
cataloguing stars along the
ecliptic up to the 14th
apparent magnitude. While comparing his observations to the
Berlin Academy's star chart, de Gasparis noticed a starlike object between magnitude 9 and 10 which was not recorded before. Although poor weather prevented further observations for a few days, de Gasparis reobserved the object on 14 and 17 April and confirmed it had moved between these dates. Judging by how much the object had moved, de Gasparis concluded it must be another new
planet between the orbit of
Mars and
Jupiter. De Gasparis announced his discovery to Erasmo Fabri Scarpellini, secretary of the
Correspondenza Scientifica bulletin at
Rome, Italy, who in turn passed on the news to
Heinrich Christian Schumacher, who published it in the
Astronomische Nachrichten journal on 11 May 1849. Hygiea was the first asteroid discovered by de Gasparis and the tenth asteroid discovered in history. He would later discover another six asteroids between 1850 and 1853 and two more during the 1860s.
Name De Gasparis invited
Ernesto Capocci Belmonte, his friend and director of the Capodimonte Observatory, to assign a name to the asteroid as gratitude for his help and advice. Capocci suggested the name
Igea—the Italian spelling of
Hygieia, the
Greek goddess of health and daughter of
Asclepius. De Gasparis added the adjective
Borbonica to Capocci's suggested name, to honor
King Ferdinand II of the
Bourbons of Naples who ruled the
Kingdom of the Two Sicilies and supported the work of the Capodimonte Observatory. Together, de Gasparis and Capocci proposed the name
Igea Borbonica ("Bourbon Hygieia") in a letter forwarded to Ferdinand II on 8 May 1849. De Gasparis's commemoration of the Bourbons may have helped him and Capocci circumvent punishment for their participation in the
liberal movements of 1848. The name
Igea Borbonica was not mentioned in the first communications to the European scientific community. When English astronomer
John Herschel received the news of Hygiea's discovery from his
Neapolitan colleagues, he suggested that
Parthenope would be an apt name for de Gasparis's discovery, as it comes from the siren who founded Naples in Greek mythology. In a letter written to English mathematician
Augustus De Morgan in April 1849, Herschel wrote: Herschel corresponded with other European scientists and astronomers to hear their thoughts on the name Parthenope for de Gasparis's discovery, although by the time he reached out to de Gasparis, Hygiea had already been named one month earlier. When Schumacher, editor of
Astronomische Nachrichten, learned of the name proposed by de Gasparis and Capocci, he complained in a letter addressed to Herschel on 26 June 1849 that it had the Italian spelling instead of the Latin form, as conventionally done for all the other planets. Regardless, de Gasparis recognized Herschel's suggestion and expressed desire to realize Herschel's wish. On 11 May 1850, de Gasparis discovered the asteroid
11 Parthenope and acknowledged Herschel for the name in his announcement. There are multiple variations on the Latin spelling of Hygiea, including
Hygièa,
Hygia, and
Hygea. The modern English form
Hygiea is a less common variant of the name of the goddess, which in Greek is Ὑγίεια (
Hygieia) or Ὑγεῖα (
Hygeia). The name was often spelled
Hygeia (and occasionally
Hygea) by astronomers during the early 1850s, though by the 1860s, the spelling
Hygiea became commonplace. According to the English astronomer
John Russell Hind, the adjective
Borbonica had been dropped by 1852.
Symbol and designation As with the other previously discovered asteroids, Hygiea was given an
astronomical symbol as a way of representing it. The symbol for Hygiea was proposed by de Gasparis in a letter addressed to Hind on 4 November 1850, in which he wrote, "The symbol of Hygeia is a serpent (like a Greek
ζ) crowned with a star." Visually, de Gasparis's symbol for Hygiea is depicted as: (U+1F779 in
Unicode 17.0). The serpent, particularly when
drinking from a bowl, is a traditional symbol of the goddess Hygieia (cf. U+1F54F 🕏). However, perhaps due to the late announcement of Hygiea's intended symbol, it was not used in following astronomical
almanacs such as the
Berliner Astronomisches Jahrbuch in 1850 and the
Nautical Almanac and Astronomical Ephemeris in 1852, marking the first time an asteroid was listed without its symbol in these almanacs. American astronomer
Benjamin Apthorp Gould interpreted Hygiea's symbol as a
rod of Asclepius, depicting it as a serpent coiled around a staff in a January 1852 publication of the
Astronomical Journal: (U+2695 ⚕). Both symbols of Hygiea soon became obsolete, as the number of asteroids discovered had grown too much for each to have unique symbols. In 1851
Johann Franz Encke proposed a different identification system, suggesting using a number corresponding to the order of discovery enclosed in a small circle—for Hygiea it would be ⑩. Astronomers began adopting Encke's circled number scheme in scientific publications, though as the number of asteroids discovered grew, astronomers eventually switched to enclosing the number in
parentheses, which became the modern
minor-planet designation scheme. In the case of Hygiea, its modern minor planet designation would be
(10) Hygiea or
10 Hygiea. The
Minor Planet Center uses the
minor planet provisional designations A849 GA and
A900 GA for Hygiea, though these are only retrospective extensions of the new-style provisional designation scheme established in 1925. While the provisional designation A849 GA refers to the discovery date of Hygiea, the designation A900 GA refers to the date when Hygiea was serendipitously observed and catalogued (as
Arequipa 38) by the
Harvard College Observatory's photographic
sky survey at
Arequipa, Peru in 1900. Hygiea has seen some minor
astrological use, though its symbol was confused once again, with Asclepsius's rod replaced by
Mercury's
caduceus: , though in a more elaborate form (U+2BDA ⯚) than the caduceus symbol of the planet Mercury. The caduceus has long been mistaken for the rod of Asclepius (see
caduceus as a symbol of medicine).
Classification listed Hygiea as a potential planet. While the first four asteroids discovered—
Ceres (1801),
Pallas (1802),
Juno (1804), and
Vesta (1807)—were considered planets during the first half of the 19th century (with some astronomers continuing to consider them as such until the end of the century), the discovery of Hygiea occurred when the classification of asteroids was already evolving. Hygiea was referred to as a
planet in the following years after its discovery, though by 1852 astronomers have also called Hygiea a
minor planet or an
asteroid. These terms were introduced prior to Hygiea's discovery and became more used with the discovery of more asteroids beginning in the 1850s. From the second half of the 19th century, asteroids began to be treated in a predominantly collective way, grouped according to orbital or spectral characteristics, with less attention to the individual object. In 2006, the
International Astronomical Union's (IAU) committee for
drafting a new definition of planet had considered classifying Hygiea among the planets or the newly-coined category of
dwarf planets, if it were found that the asteroid is massive enough to be shaped predominantly by
hydrostatic equilibrium. This proposal for the definition of planet has since been revised and adopted to decree that a planet must orbit the Sun, have sufficient mass to attain a spherical shape by hydrostatic equilibrium, and
clear its neighbourhood; objects that satisfy all but the last criterion are considered dwarf planets. Since 2019, telescope images have resolved Hygiea's nearly spherical shape, suggesting that it may have reached hydrostatic equilibrium. Because Hygiea already orbits the Sun and is located in the asteroid belt where it has not cleared its orbital neighborhood, Hygiea's nearly spherical shape could qualify it as a dwarf planet, according to Pierre Vernazza and collaborators who studied Hygiea with telescope imaging. If so, Hygiea could be the smallest dwarf planet known. However, the IAU has not yet officially classified Hygiea as a dwarf planet. == Orbit ==