Julio Ángel Fernández Alves (born 5 April 1946) is a

Uruguay Uruguay, officially the Oriental Republic of Uruguay, is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast, while bordering the Río de la Plata to the south and the A ...

an astronomer and teacher, member of the department of astronomy at the

Universidad de la República The University of the Republic (, sometimes ''UdelaR'') is a public research university in Montevideo, Uruguay. It is the country's oldest and largest university, as well as one of the largest public universities in South America in terms of en ...

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 ...

. He is also a member of PEDECIBA, (the program for development of basic sciences in Uruguay), and the Uruguayan Society of Astronomy. From 2005 to 2010, he was the Dean of the Universidad de la Republica's Faculty of Sciences. The asteroid 5996 Julioangel, discovered in 1983, was named after him. He is an active researcher of the Researchers National System of Uruguay. Fernandez is member of the National Academy of Sciences of the United States.

Kuiper belt

In 1980, in his paper ''On the existence of a comet belt beyond Neptune'', Fernández proposed that periodic comets arrived too frequently into the inner Solar System to be accounted for solely by having arrived from the

Oort cloud The Oort cloud (pronounced or ), sometimes called the Öpik–Oort cloud, is scientific theory, theorized to be a cloud of billions of Volatile (astrogeology), icy planetesimals surrounding the Sun at distances ranging from 2,000 to 200,000 A ...

, and that a trans-Neptunian belt of comets at around 50 AU would be required to explain them. Subsequent computer models by Martin Duncan, Tom Quinn and Scott Tremaine in Canada supported the view, and led eventually to the discovery of the

Kuiper belt The Kuiper belt ( ) is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...

. David Jewitt, who discovered the belt, believes that Fernández deserves more credit than anyone else, including

Gerard Kuiper Gerard Peter Kuiper ( ; born Gerrit Pieter Kuiper, ; 7 December 1905 – 23 December 1973) was a Dutch-American astronomer, planetary scientist, selenographer, author and professor. The Kuiper belt is named after him. Kuiper is consi ...

, for predicting its existence. He has subsequently published many papers on the trans-Neptunian population.

Definition of planet

In 2006, Fernández 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 In Greek mythology, Charon or Kharon ( ; ) is a psychopomp, the ferryman of the Greek underworld. He carries the souls of those who have been given funeral rites across the rivers Acheron and Styx, which separate the worlds of the living and ...

and Ceres among the planets, Fernández with his Uruguayan colleague

Gonzalo Tancredi Gonzalo Tancredi (born 8 March 1963) is an Uruguayan astronomer and full professor in the Department of Astronomy at the University of the Republic in Montevideo, Uruguay. He is an active member of the International Astronomical Union (IAU) and ...

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." The event originated the word "Plutoed," which was selected as the "word of the year 2006" by the

American Dialect Society The American Dialect Society (ADS), founded in 1889, is a learned society "dedicated to the study of the English language in North America, and of other languages, or dialects of other languages, influencing it or influenced by it." The Society p ...

Books

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References

{{DEFAULTSORT:Fernandez, Julio Angel Uruguayan astronomers Uruguayan people of Spanish descent 1946 births Living people Academic staff of the University of the Republic (Uruguay) Foreign associates of the National Academy of Sciences