A plutoid, or ice dwarf, is a trans-Neptunian dwarf planet: that is, a body orbiting beyond Neptune that is large enough to be rounded in shape. The term was adopted by part of the International Astronomical Union (IAU), but has been rejected by another and is not widely used by astronomers.

There are thought to be a hundred or so plutoids in the Solar System, although only four have been formally designated as such to date.

The IAU developed this category of astronomical objects as a consequence of its 2006 resolution defining the word "planet". The IAU's formal definition of 'plutoid,' announced 11 June 2008, is: :Plutoids are celestial bodies in orbit around the Sun at a semi-major axis greater than that of Neptune that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape, and that have not cleared the neighbourhood around their orbit. Satellites of plutoids are not plutoids themselves.

Accordingly, in the language of mathematical set theory, plutoids can be thought of as the intersection of the set of dwarf planets and the set of trans-Neptunian objects.

In light of the difficulty of remotely ascertaining hydrostasis, the IAU only formally confers "dwarf planet" (and by extension, "plutoid") status to those bodies whose minimum estimated size is substantially greater than what is generally thought necessary to guarantee hydrostatic equilibrium. , Pluto, , , and are the only objects officially recognized as plutoids, while upwards of seventy more bodies that currently lack formal recognition are thought likely to meet the definition, and can expect formal recognition at some time in the future.

Alan Stern of the Southwest Research Institute believes the outer planets show signs of collisions with plutoids 1,000 to 2,000 kilometers in diameter: Uranus could have been tipped off its axis by a plutoid, and Triton, the largest moon of Neptune, is probably a captured plutoid from the Kuiper belt.

History of the term

On August 24, 2006, the IAU decided to re-classify Pluto as a dwarf planet, requiring that a planet must "clear the neighbourhood around its orbit."

The General Assembly of the IAU further resolved:

This new category had been proposed under the name "''pluton''" or a "''plutonian object''" earlier in the General Assembly. The former was rejected, in part because "pluton" is actually a pre-existing geological term, and many geological experts wrote in complaints pointing this out. "Pluton" was dropped midway through the Assembly and was abandoned in the final draft resolution (6b); "Plutonian object" failed to win majority approval on a 183–186 vote in the IAU General Assembly on August 24, 2006.

The definition of the category also fluctuated during its early stages. When first proposed, the category (then named "pluton") defined members as planets whose rotation period around the Sun was more than 200 Julian years, and whose orbit was more highly inclined and more elliptical than a traditional planetary orbit. Once it had been counter-proposed to strip Pluto of planet status, this category of Pluto-like objects was then applied to dwarf planets that met the conditions of being trans-Neptunian and "like Pluto" in terms of period, inclination, and eccentricity. Ultimately, the final resolution left the formal definition, like the name, to be established at a later date.

Following the IAU General Assembly, the name "plutoid" was proposed by the members of the IAU Committee on Small Body Nomenclature (CSBN), accepted by the Board of Division III, and approved by the IAU Executive Committee at its meeting in Oslo, Norway, on 11 June 2008. The term was announced after the Executive Committee meeting, along with a greatly simplified definition: all trans-Neptunian dwarf planets are plutoids. However, due to a communication error, the IAU Working Group for Planetary System Nomenclature (WG-PSN) was not consulted, and they subsequently rejected the term.

As of 2009, the term had not been widely accepted by the scientific community, with the term ''ice dwarf (planet)'' sometimes used instead.

Analogous terminology

Prior to the emergence of the term "plutoid" as an IAU-sanctioned categorization, there had been some attempts at applying a title for this class of object.

The term ''"ice dwarf"'' saw some adoption as a near-synonym to the eventual term "plutoid". "Ice dwarf", however, also saw some use as an umbrella term for all so-called "distant minor planets" (trans-Neptunian objects plus centaurs) or other, broad applications; one attempted definition was that an ice dwarf "is larger than the nucleus of a normal comet and icier than a typical asteroid". There are large numbers of such objects in the Oort cloud and the Kuiper belt. However, it is not clear whether all so-categorized ice dwarfs are actually icier than icy asteroids such as Ceres (now considered a dwarf planet). Nonetheless, Ceres is sometimes called a ''terrestrial dwarf'' to distinguish it from Pluto and Eris.

"Ice dwarf" as a term for an icy planetary body that generally orbits beyond Neptune was coined as part of a conception of a threefold division of the Solar System into inner ''terrestrial planets'', central ''gas giants'', and outer ''ice dwarfs'', of which Pluto was the principal member. This conception foreshadowed the reclassification of Pluto to dwarf planet and plutoid after the discovery of Eris.

Naming process for plutoids

With the creation of the term "dwarf planet", some ambiguity was created as to which of two IAU bodies would be responsible for naming dwarf planets. Eris had been named through the IAU Committee on Small Body Nomenclature and the IAU Working Group for Planetary System Nomenclature working in cooperation with one another. Along with announcing the name "plutoid", the IAU decision of 11 June 2008 institutionalized this cooperative process involving the two bodies in the naming of new plutoids. In keeping with minor planet naming guidelines, priority will be given to names proposed by the discovery teams, and plutoids may not share a name with a small Solar System body.

Complications related to "dwarf planet" definition

When the definition of "dwarf planet" was instated at the IAU General Assembly of 2006, Ceres, Pluto and Eris were identified by name as the initial members of the dwarf planet class. However, precise regulations as to how hydrostatic equilibrium would be measured were left undefined for the time being. Without an official procedure for calculating the lower bound of size to be a "dwarf planet", no further bodies could be formally recognized as either dwarf planets or plutoids.

It was noted that the naming process would remain stalled without such rules, and that even with them, few of these bodies can be imaged with sufficient resolution to determine their shapes. Therefore, the IAU announced that for naming purposes, a trans-Neptunian object will be ''assumed to be a plutoid'' if it has ''an absolute magnitude brighter than H = +1 magnitude''.

Mathematically, the smallest possible object that could possess an absolute magnitude of +1 (a perfectly reflective one with an albedo of 1) would be 838 km in diameter. It is highly unlikely that any body of this size or larger, regardless of composition, would not also surpass whatever threshold is ultimately adopted as proof of hydrostatic equilibrium. That said, if it turns out upon further investigation that an object named as if it were a plutoid has ''not'' achieved hydrostatic equilibrium, the IAU has stated it will be reclassified, but keep its name.

This decision allowed for the naming of Makemake and Haumea, and their formal recognition as plutoids and dwarf planets, bringing the number of IAU-accepted plutoids to four. However, the (co)discoverer of Eris, Makemake, and Haumea, Mike Brown, estimates that between 100 and 400 ''known'' bodies are plutoids, and that there are many more that have yet to be discovered. See list of dwarf planet candidates.

See also

References

;Notes ;References

Category:Dwarf planets

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name	Ned McGowan
background	non_vocal_instrumentalist
born	1970
instrument	Flute, Contrabass Flute
genre	Contemporary classical music
occupation	Composer
label	Karnatic Lab Records
website	Homepage of Ned McGowan }}

Ned McGowan (1970) is an American composer and flutist based in Amsterdam.

“McGowan’s music strives for an idiom in which various musics – American popular, European classical and avant-garde, Carnatic, a fascination with proportionally intricate rhythms, the use of microtones in the search for new subtleties of melody – and many others, rub against each other and generate new meanings.” - musicologist Bob Gilmore.

Education

After finishing studies in flute at the San Francisco Conservatory and the Cleveland Institute of Music, he moved to Amsterdam in 1994 to continue his research. Over the course of eight years, he studied both flute and composition in Amsterdam and The Hague, exploring a wide range of subjects – from extended techniques to Carnatic forms and rhythms, from jazz improvisation to West-African drumming. His compositional voice was profoundly influenced by these experiences, even though he never directly follows any of these traditions stylistically.

In addition to having given masterclasses and workshops on composition, flute and non-western techniques, Ned has worked as coordinator of the Crossing Borders seminar at the Amsterdam School of the Arts and taught Advanced Rhythm at the Conservatory of Amsterdam.

Composing

McGowan’s piece Tools, winner of the Henriette Bosmans Prize from the Dutch Composer’s Union GeNeCo, was described as “brutal and humorous” (GeNeCo, 2004), while at the same time “packed with discreet acoustic rooms, some more resonant than others, but all proving that... subtlety pays off” (Guy Livingston, Paris Transatlantic, 2006).

His compositions have been played throughout Europe, North America and Australia, at MATA Festival (New York), Ought-One (Vermont), Aspen Music Festival (Colorado), The American Music Week in Bulgaria, the Gaudeamus Music Week, the North Sea Jazz Festival, the Klap op de Vuurpijl, and the Grachten Festival (Amsterdam). Ensembles and festivals who have commissioned McGowan include the Dutch Radio Chamber Orchestra, the Zephyr String Quartet, Calefax reed quintet, the Axyz Ensemble, Duo Vertigo, the Netherlands Flute Orchestra and Hexnut.

He is also highly active in fostering the Amsterdam musical community through the Karnatic Lab Foundation, an organization he founded with Gijs Levelt in 1999 to promote both composed and improvised new music. This umbrella organization runs a monthly concert series, programs a yearly festival with international guests, and has its own record label Karnatic Lab Records and house ensembles: Axyz, a contemporary music ensemble, Spinifex Orchestra, a nine piece jazz ensemble, and McGowan’s own quintet, Hexnut.

Flute Playing

As a flute player, Ned McGowan plays a variety of styles with ensembles such as Hexnut, and Messing with PVC. In 2007, his specific fascination with Carnatic music led to an extended stay in India studying performance, rhythm and composition. In the last five years Ned McGowan has taken an interest in the contrabass flute, as it opens up the bass musical role in addition to the more common melodic role of the flute. His April 2008 Carnegie Hall debut, as soloist in his own contrabass flute concerto "Bantammer Swing" with the American Composers Orchestra, was well received as one of the only pieces in this genre.

Selected Compositions

Heads or Tails (2008) - Jazz band Bantammer Swing (2008) - Concerto for contrabass flute and chamber orchestra Hymn (2008) - Improvising string quartet Fantasy on an improvisation of Ravi Shankar (2007) - Wind ensemble Spectra (2007) - Solo contrabass flute/flute and flute orchestra Tempest in a Teapot (2006) - Orchestra Devil’s Dust (2006) - String Quartet Alap (2005) - Soprano and ensemble Wood Burn (A)(2005) - Reed quintet/Wood Burn (B) (2005) - Chamber ensemble Workshop (2004) - Alto Recorder and tape Tools (2003) - Mixed quartet; Winner Henriette Bosmans Prize, 2003, Netherlands Urban Turban (2001)- Two marimbas; also arranged for: mixed trio/quartet; saxophone and marimba; jazz ensemble. Stone Soup (2001) - Jazz ensemble Moonrise (1998) - Flute; Finalist Gaudeamus Foundation Prize, 1999 Melting Igloos (1998) - Mixed quartet; Finalist Gaudeamus Foundation Prize, 2000 Man in Tights (2009) - Ned's new composition for anglo concertina quintet, inspired by Recorder maker and concertina aficionado Adrian Brown

Discography

Hexnut (2007) Tools (2006) Nandi Dasaru (2005) Non Sequitur (2005) Paximadi (2005) Rickshaw Chase (2001)

External links

Homepage of Ned McGowan

Karnatic Lab

Karnatic Lab Records

Category:1970 births Category:Dutch composers Category:American composers Category:21st-century classical composers Category:People from Amsterdam Category:Living people

de:Ned McGowan