Gonzalo Tancredi (born 8 March 1963) is an

Uruguayan Uruguayans () are people identified with the country of Uruguay, through citizenship or descent. Uruguay is home to people of different ethnic origins. As a result, many Uruguayans do not equate their nationality with ethnicity, but with citizen ...

astronomer An astronomer is a scientist in the field of astronomy who focuses on a specific question or field outside the scope of Earth. Astronomers observe astronomical objects, such as stars, planets, natural satellite, moons, comets and galaxy, galax ...

and full professor in the Department of Astronomy at the University of the Republic in

Montevideo Montevideo (, ; ) is the capital city, capital and List of cities in Uruguay, largest city of Uruguay. According to the 2023 census, the city proper has a population of 1,302,954 (about 37.2% of the country's total population) in an area of . M ...

, Uruguay. He is an active member of the

International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

(IAU) and investigator at Los Molinos Observatory. His 2010 evaluation of potential dwarf planets was considered by the IAU, though never acted on. The Themistian asteroid 5088 Tancredi has been named after him.

Definition of planet

In 2006, Tancredi was one of a number of dissenters at the

IAU The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

's meeting to establish the first definition of "planet. " As an alternative to the IAU's draft proposal, which had included

Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of Trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Su ...

, its moon Charon and Ceres among the planets, Tancredi with his Uruguayan colleague Julio Ángel Fernández proposed a definition where they reserved the term "

planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...

" only for those objects in the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

which had cleared their neighbourhoods of

planetesimal Planetesimals () are solid objects thought to exist in protoplanetary disks and debris disks. Believed to have formed in the Solar System about 4.6 billion years ago, they aid study of its formation. Formation A widely accepted theory of pla ...

s, describing those objects which had not cleared their orbits yet retained a spherical shape as "planetoids." The IAU's final definition incorporated much of Fernández and Tancredi's proposal, though the objects were christened "

dwarf planet A dwarf planet is a small planetary-mass object that is in direct orbit around the Sun, massive enough to be hydrostatic equilibrium, gravitationally rounded, but insufficient to achieve clearing the neighbourhood, orbital dominance like the ...

s."

References

External links

Gonzalo Tancredi – Departamento de Astronomía, Instituto de Física, Facultad de Ciencias, Montevideo, URUGUAY

1963 births Living people Uruguayan astronomers Academic staff of the University of the Republic (Uruguay) {{Uruguay-scientist-stub