Julio Ángel Fernández

Julio Ángel Fernández

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Dr. Julio Ángel Fernández Alves (born Montevideo
Montevideo
Montevideo is the largest city, the capital, and the chief port of Uruguay. The settlement was established in 1726 by Bruno Mauricio de Zabala, as a strategic move amidst a Spanish-Portuguese dispute over the platine region, and as a counter to the Portuguese colony at Colonia del Sacramento...

, 5 April 1946) is a Uruguay
Uruguay
Uruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...

an astronomer and member of the department of astronomy at the Universidad de la República in Montevideo
Montevideo
Montevideo is the largest city, the capital, and the chief port of Uruguay. The settlement was established in 1726 by Bruno Mauricio de Zabala, as a strategic move amidst a Spanish-Portuguese dispute over the platine region, and as a counter to the Portuguese colony at Colonia del Sacramento...

. He is also a member of PEDECIBA, (the program for development of basic sciences in Uruguay). From 2005 to 2010, he was the Dean of the Universidad de la Republica's Faculty of Sciences. The asteroid 5996 Julioangel
5996 Julioangel
5996 Julioangel is a main-belt asteroid discovered on July 11, 1983 by E. Bowell at Flagstaff.- External links :*...

 was named after him.

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
Oort cloud
The Oort cloud , or the Öpik–Oort cloud , is a hypothesized spherical cloud of comets which may lie roughly 50,000 AU, or nearly a light-year, from the Sun. This places the cloud at nearly a quarter of the distance to Proxima Centauri, the nearest star to the Sun...

, 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
Scott Tremaine
Scott Duncan Tremaine is a Canadian-born astrophysicist. He is a fellow of the Royal Society of London, the Royal Society of Canada and the National Academy of Sciences. Tremaine is widely regarded as one of the world's leading astrophysicists for his contributions to the theory of solar system...

 in Canada supported the view, and led eventually to the discovery of the Kuiper belt
Kuiper belt
The Kuiper belt , sometimes called the Edgeworth–Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune to approximately 50 AU from the Sun. It is similar to the asteroid belt, although it is far larger—20 times as wide and 20 to 200 times as massive...

. Many astronomers, including David Jewitt, who discovered the belt, believe that Fernandez deserves more credit than anyone else, including Gerard Kuiper
Gerard Kuiper
Gerard Peter Kuiper , Netherlands – December 24, 1973, Mexico City) was a Dutch-American astronomer after whom the Kuiper belt was named.-Early life:...

, 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
IAU
IAU may refer to:*International Astronomical Union*International American University*International American University College of Medicine*International Association of Universities*International Association of Ultrarunners...

's meeting to establish the first definition of "planet". As an alternative to the IAU's draft proposal, which had included Pluto
Pluto
Pluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet in the Solar System and the tenth-most-massive body observed directly orbiting the Sun...

, its moon Charon
Charon (moon)
Charon is the largest satellite of the dwarf planet Pluto. It was discovered in 1978 at the United States Naval Observatory Flagstaff Station. Following the 2005 discovery of two other natural satellites of Pluto , Charon may also be referred to as Pluto I...

 and Ceres among the planets, Fernández's proposed definition reserved the term "planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...

" only for those objects in the Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

 which had cleared their neighbourhoods of planetesimal
Planetesimal
Planetesimals are solid objects thought to exist in protoplanetary disks and in debris disks.A widely accepted theory of planet formation, the so-called planetesimal hypothesis of Viktor Safronov, states that planets form out of cosmic dust grains that collide and stick to form larger and larger...

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's proposal, though the objects were christened "dwarf planets".

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