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Giovanni Domenico Maraldi
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Giovanni Domenico Maraldi, referred to as Maraldi II

A portrait of Giovanni Domenico Maraldi – with the permission of Castello Maraldi

Giovanni Domenico Maraldi was born on the 17th April 1709 in Perinaldo, at that time in the county of Nice. He was the son of Angela Francesca Allavena and Giovanni Domenico Maraldi or Marvaldi, the latter being the brother of Giacomo Filippo Maraldi – who has come to be known as Maraldi I – who was, in turn, a nephew of Giovanni Domenico Cassini – Cassini I. Giovanni Domenico Maraldi – also known by the French form of his name as Jean Dominique Maraldi – is generally referred to as Maraldi II.

Giovanni initially studied with the Jesuits in San Remo, then travelled to join the now crowded Cassini household in Paris from Italy in the Spring of 1727. His uncle, Phillipe, sadly died two years later, the result of this being that Giovanni was drawn to working with Jacques Cassini, Cassini II. Giovanni became a member of the Academy of Sciences in 1731. The Observatory was now so crowded with astronomers that Giovanni had to sleep in the wide embrasure of an upper storey window.

J D Cassini

It appears that he enjoyed working not only with his uncle, Cassini II, but also with Nicolas Louis de La Caille, who arrived in 1737. The following year Maraldi and La Caille were commissioned by Cassini II to survey the coast from Nantes to Bayonne, his work continuing on a number of projects. In 1744 survey work was published under Maraldi’s name, much of the work having been carried out with the assistance of La Caille, which Maraldi acknowledged. La Caille continued working until his death in 1762 at the age of 49, leaving all his notes to his great friend, Giovanni Maraldi.

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Giovanni worked with his cousin, Cassini de Thury – Cassini III – between 1732 and 1740 on establishing the boundaries of France and producing a map of 180 sheets.

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Beginning work in Paris with Jupiter’s fourth moon, he carried out geodesic measurements using the eclipse times of Jupiter’s moons to determine longitudes, and obtaining a longitude difference between Greenwich and Paris of 9m 23s (the modern value being 9m 20.93s).

Giovanni Domenico also carried out observations of several comets:

  • (the first comet of 1742 (C/1742 C1, 1742),
  • the great comet of 1743-4 discovered by Klinkenberg and De Chéseaux (C/1743 X1, 1744),
  • De Chéseaux’s comet of 1746 (C/1746 P1, 1747),
  • Halley’s comet of 1759,
  • Klinkenberg’s comet of 1762 (C/1762 K1, 1762), and
  • Messier’s comet of 1769 (C/1769 P1, 1769),

as well as calculating cometary orbits. In addition he made observations of the transits of Mercury and Venus.

In 1735 Giovanni Domenico was given the responsibility for publishing 25 volumes of the Connaissance des Temps, additionally publishing Lacaille’s catalog of southern stars, Coelum Australe Stelliferum.

In September 1746 he observed De Chéseaux’s comet of that year together with Jacques Cassini. While doing so, he discovered two globular clusters:

  • M15 in Pegasus on the 7th September 1746, and
  • M2 in Aquarius on the 11th September 1746 (Maraldi 1746). He continued to track the comet until the evening of December 5.

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Retirement to Perinaldo

Giovanni Domenico Maraldi’s previously robust health began to deteriorate in 1763 and, in April 1770, with his health worsening, he requested and obtained permission to return to Perinaldo, Italy. He took with him optical instruments and continued to carry out observations based on his previous interests, particularly Jupiter’s satellites, in the clearer air of Perinaldo until around 1785.

He died in Perinaldo on the 14th November 1788 where he is buried.

Jean Dominque Cassini, in his ‘Mémoires pour servir à l'histoire des science et à celle de l'Observatoire royal de Paris’, wrote that Maraldi died at the age of seventy-six following a ‘type of black illness’ that came and went every three months over a period of three years, and fortified by his religion.

He was honoured, together with his uncle, by the naming of the Moon crater Maraldi (19.4N, 34.9E, 39 km diameter, in 1935). I understand that he is not separately mentioned in the naming of the Mars crater Maraldi (62.0S, 32.0 W, 124km diameter, in 1973), which may honour his uncle only.

Delambre (1827) mentions a third Maraldi (Jaques-Philippe, Maraldi III, 1746-1797) who made some observations of planetary satellites at Perinaldo, though I have been able to discover little about him.

Giacomo Filippo Maraldi   |   top   |   Giovanni Filippo Maraldi

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