Newsgroup: it.scienza.astronomia
Titolo: Quanti pianeti?

Alla fine, di tutte le ipootesi fatte, che altro non erano che tali, anche 
se qualcuno su questo newsgroup pensava a qualcosa di ufficiale e definitivo 
(nonché catastrofico!), questo è quello che è uscito fuori dai tanto derisi 
astronomi della IAU: 
http://www.corriere.it/Primo_Piano/Scienze_e_Tecnologie/2006/08_Agosto/24/pluto.shtml
 ; 
e ancora:
http://edition.cnn.com/2006/TECH/space/08/24/pluto.ap/index.html
Come al solito, prima di cominciare a sparlare e sputare sentenze precoci, 
sarebbe meglio informarsi sull'ufficialità delle notizie, per evitare 
l'imbarazzo finale.
Se qualcuno ha altri link in cui si spiegano meglio le motivazioni della 
decisione, è pregato di segnalarli.
A presto!
Daniele Gasparri
Perugia (Italy)
www.danielegasparri.com
 

 decisione, è pregato di segnalarli.
come segnalavo a Sao67174, "La" fonte ufficiale, il daily GA newspaper:
http://astro.cas.cz/nuncius/nsiii_09.pdf
 (da 
http://www.astronomy2006.com/
)
Ultima pagina, vedi anche "250 words for/against".
Final Version of Resolution on the Definition of a Planet
--------------------------------------------------------
At the second session of the General Assembly which will be held 14:00
Thursday August 24 in the Congress Hall, members of
the IAU will vote on the resolutions presented here. There will be separate
sequential votes on Resolution 5A and Resolution 5B.
Similarly, there will be separate votes on Resolutions 6A and 6B. Resolution
5A is the principal defi nition for the IAU usage of
"planet" and related terms. Resolution 5B adds the word "classical" to the
collective name of the eight planets Mercury through
Neptune. Resolution 6A creates for IAU usage a new class of objects, for
which Pluto is the proto-type. Resolution 6B introduces
the name "plutonian objects" for this class. The Merriam-Webster dictionary
defi nes "plutonian" as: Main Entry: plu.to.ni.an
- Pronunciation: plü-'tO-nE-&n - Function: adjective - Usage: often
capitalized - : of, relating to, or characteristic of Pluto or
the lower world. Resolutions Committee members will be available at the IAU
Exhibit (situated in the exhibition area, 2nd fl oor of
Congress Hall, Foyer 2) from 13:00-13:30 today (Thursday). However, only
minor corrections can be accommodated at this stage.
A French version of the Resolutions will be available at the door.
IAU Resolution: Defi
nition of a Planet in the Solar System
Contemporary observations are changing our understanding of planetary
systems, and it is important that our nomenclature for
objects refl ect our current understanding. This applies, in particular, to
the designation 'planets'. The word 'planet' originally
described 'wanderers' that were known only as moving lights in the sky.
Recent discoveries lead us to create a new defi nition, which
we can make using currently available scientifi c information.
Resolution 5A
The IAU therefore resolves that planets and other bodies in our Solar System
be defi ned into three distinct categories in the
following way:
(1) A planet1 is a celestial body that (a) is in orbit around the Sun, (b)
has suffi cient mass for its self-gravity to overcome rigid
body forces so that it assumes a hydrostatic equilibrium (nearly round)
shape, and (c) has cleared the neighbourhood around its orbit.
(2) A dwarf planet is a celestial body that (a) is in orbit around the Sun,
(b) has suffi cient mass for its self-gravity to overcome
rigid body forces so that it assumes a hydrostatic equilibrium (nearly
round) shape2, (c) has not cleared the neighbourhood around its
orbit, and (d) is not a satellite.
(3) All other objects3 orbiting the Sun shall be referred to collectively as
"Small Solar System Bodies".
1 The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn,
Uranus, and Neptune.
2 An IAU process will be established to assign borderline objects into
either dwarf planet and other categories.
3 These currently include most of the Solar System asteroids, most
Trans-Neptunian Objects (TNOs), comets, and other small bodies.
Resolution 5B
Insert the word "classical" before the word "planet" in Resolution 5A,
Section (1), and footnote 1. Thus reading:
(1) A classical planet1 is a celestial body . . .
and
1 The eight classical planets are: Mercury, Venus, Earth, Mars, Jupiter,
Saturn, Uranus, and Neptune.
IAU Resolution: Pluto
Resolution 6A
The IAU further resolves:
Pluto is a dwarf planet by the above defi nition and is recognized as the
prototype of a new category of trans-Neptunian objects.
Resolution 6B
The following sentence is added to Resolution 6A:
This category is to be called "plutonian objects."


La questione sembra si sia risolta nei migliore dei modi per il nostro 
Sistema Solare.
Al contrario, non leggo alcun accenno ai pianeti extrasolari (faccio fatica 
a leggere l'inglese, ho dato poco più di un'occhiata ai documenti...). Se 
così fosse, IMHO la questione sarebbe chiusa... a metà.
Questa è la definizione "eliocentrica" di pianeta. In sostanza non è venuta 
fuori quella
definizione "universale" che mi aspettavo da questo congresso. Forse era 
meglio indicare
anche una massa minima e una massima.
Non è questione di leziosità, ma se si definisce pianeta un corpo con orbita 
poco ellittica, metti caso che si scopre un pianeta extrasolare con forte 
eccentricità, allora che si fa? Non lo si chiama più pianeta o si 
ridefinisce la parola?
Cieli sereni
-- 
Lorenzo Preti
http://digilander.libero.it/luranz
 

 Cieli sereni