List of plutoid candidates

At present, the International Astronomical Union classifies four objects as plutoids:dubious dp|Pluto, dp|Eris, dp|Haumea, and dp|Makemake; dozens of others are thought likely to be plutoids. The qualifying feature is that plutoids must "have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical shape)."citenews|publisher=International Astronomical Union|title=IAU 2006 General Assembly: Result of the IAU Resolution votes|url=http://www.iau.org/iau0603.414.0.html|year=2006|accessdate=2008-01-26] [citeweb|url=http://solarsystem.nasa.gov/planets/profile.cfm?Object=Dwarf&Display=OverviewLong|title=Dwarf Planets|publisher=NASA|accessdate=2008-01-22] cite press release|url=http://www.iau.org/public_press/news/release/iau0804/|title=Plutoid chosen as name for Solar System objects like Pluto] Except for Pluto, observations are insufficient for direct classification. However, based on present knowledge of how icy bodies gravitationally relax into equilibrium shapes, there are a significant number of potential candidates amongst the population of trans-Neptunian objects (TNOs).citeweb|url=http://web.gps.caltech.edu/~mbrown/dwarfplanets/|author=Mike Brown|title=The Dwarf Planets|accessdate=2008-01-20] There are about 70 candidates now, but it is possible that this number will increase to 2000.

Changes to IAU naming procedures

The IAU has modified its nomenclature procedures such that objects considered highly likely to be plutoids receive differing treatment when receiving names than other TNOs. Objects that have an absolute magnitude less than +1 (and hence a mathematically-delimited minimum diameter of 838 kmcite web
title=Conversion of Absolute Magnitude to Diameter for Minor Planets
publisher=Department of Physics & Astronomy (Stephen F. Austin State University)
author=Dan Bruton
url=http://www.physics.sfasu.edu/astro/asteroids/sizemagnitude.html
accessdate=2008-06-13] ) will be overseen by two rather than one naming committee. This procedural decision has no direct bearing on the object's formal classification as a plutoid, but once so named, they are for all practical purposes accepted as such. Makemake and Haumea are the only TNOs to have proceeded through the naming process as presumed plutoids.

Plutoid candidates

Mike Brown estimates that at a diameter somewhere between 200 and 400 km, an icy body relaxes into hydrostatic equilibrium. Following is a list of TNOs that Brown thinks likely qualify as dwarf planets since he estimates they have diameters of at least 400km. However, diameter estimates vary widely, and they are therefore ordered here by their absolute magnitudes, "H," rather than diameter. Theoretical minimum diameters correspond to a maximum albedo of 1. Although many TNOs are thought to be dark, and therefore substantially larger than this lower limit, Eris has a high albedo of 0.8–0.9, and the Haumea family are also thought to be bright. (See albedo.)

With diameters above 900km

These TNOs are at least 900 km across in Brown's estimation.

References

External links

* [http://adsabs.harvard.edu/abs/2008Icar..195..851T Which are the Dwarfs in the Solar System?] Tancredi,G; Favre,S. Icarus, Volume 195, Issue 2, p. 851-862.

ee also

* List of trans-Neptunian objects