Editing Definition of planet (section)

== Acceptance of the IAU definition ==
[[File:Outersolarsystem objectpositions labels comp.png|thumb|Plot of the positions of all known [[Kuiper belt objects]], set against the outer planets, as of 2000.]]

Among the most vocal proponents of the IAU's decided definition are [[Michael E. Brown|Mike Brown]], the discoverer of Eris; [[Steven Soter]], professor of astrophysics at the [[American Museum of Natural History]]; and [[Neil deGrasse Tyson]], director of the [[Hayden Planetarium]].

In the early 2000s, when the Hayden Planetarium was undergoing a $100&nbsp;million renovation, Tyson refused to refer to Pluto as the ninth planet at the planetarium.<ref>{{Cite web|author1=Space com Staff|date=February 2, 2001|title=Astronomer Responds to Pluto-Not-a-Planet Claim|url=https://www.space.com/1925-astronomer-responds-pluto-planet-claim.html|access-date=March 29, 2023|website=Space.com|language=en}}</ref> He explained that he would rather group planets according to their commonalities rather than counting them. This decision resulted in Tyson receiving large amounts of hate mail, primarily from children.<ref>''[[The Colbert Report]]'', August 17, 2006</ref> In 2009, Tyson [[The Pluto Files|wrote a book]] detailing the demotion of Pluto.

In an article in the January 2007 issue of ''[[Scientific American]]'', Soter cited the definition's incorporation of current theories of the [[formation and evolution of the Solar System]]; that as the earliest [[protoplanet]]s emerged from the swirling dust of the [[protoplanetary disc]], some bodies "won" the initial competition for limited material and, as they grew, their increased gravity meant that they accumulated more material, and thus grew larger, eventually outstripping the other bodies in the Solar System by a very wide margin. The asteroid belt, disturbed by the gravitational tug of nearby Jupiter, and the Kuiper belt, too widely spaced for its constituent objects to collect together before the end of the initial formation period, both failed to "win" the accretion competition.

When the numbers for the "winning" objects are compared to those of the "losers", the contrast is striking; if Soter's concept that each planet occupies an "orbital zone"{{Ref label|B|b|none}} is accepted, then the least orbitally dominant planet, Mars, is larger than all other collected material in its orbital zone by a factor of 5100. Ceres, the largest object in the asteroid belt, only accounts for one third of the material in its orbit; Pluto's ratio is even lower, at around 7 percent.<ref name=Soter>{{Cite journal|title=What is a Planet?|author= Steven Soter|journal=The Astronomical Journal |volume= 132|issue= 6|pages= 2513–2519|date=August 16, 2006|arxiv= astro-ph/0608359|bibcode = 2006AJ....132.2513S |doi = 10.1086/508861 |s2cid= 14676169}}</ref> Mike Brown asserts that this massive difference in orbital dominance leaves "absolutely no room for doubt about which objects do and do not belong."<ref name=Brown>{{cite web|title=The Eight Planets|author=Michael E. Brown|work=Caltech|url=http://www.gps.caltech.edu/~mbrown/eightplanets/|year=2006| access-date=February 21, 2007}}</ref>