[meteorite-list] Plutoid Chosen as Name for Solar System Objects Like Pluto

[Ron Baalke]

International Astronomical Union
Paris, France

For more information, please contact:

Dr. Edward L.G. Bowell
IAU Division III President
Lowell Observatory, USA
Tel: +1-928-774-3358

Catherine J. Cesarsky
IAU President 
CEA-Saclay DSM / IRFU, France
Phone: +33-1-3024-5090

Dr. Karel A. van der Hucht
IAU General Secretary 
International Astronomical Union, France 
Tel: +31-30-2535729/5600

Mr. Lars Lindberg Christensen
IAU Press Officer
ESA/Hubble, Garching, Germany
Tel: +49-89-32-00-63-06

FOR IMMEDIATE RELEASE: 11 June 2008

IAU0804

Plutoid chosen as name for Solar System objects like Pluto

The International Astronomical Union has decided on the term plutoid as a
name for dwarf planets like Pluto at a meeting of its Executive Committee in
Oslo.

Almost two years after the International Astronomical Union (IAU) General
Assembly introduced the category of dwarf planets, the IAU, as promised, has
decided on a name for transneptunian dwarf planets similar to Pluto. The
name plutoid was proposed by the members of the IAU Committee on Small Body
Nomenclature (CSBN), accepted by the Board of Division III, by the IAU
Working Group for Planetary System Nomenclature (WGPSN) and approved by the
IAU Executive Committee at its recent  meeting in Oslo, Norway. 

Plutoids are celestial bodies in orbit around the Sun at a distance 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. The two known and named plutoids are Pluto and Eris. It is
expected that more plutoids will be named as science progresses and new
discoveries are made.

The dwarf planet Ceres is not a plutoid as it is located in the asteroid
belt between Mars and Jupiter. Current scientific knowledge lends credence
to the belief that Ceres is the only object of its kind. Therefore, a
separate category of Ceres-like dwarf planets will not be proposed at this
time. 

The IAU has been responsible for naming planetary bodies and their
satellites since the early 1900s. The IAU CSBN, who originally proposed the
term plutoid, is responsible for naming small bodies (except satellites of
the major planets) in the Solar System. The CSBN will be working with the
IAU WGPSN to determine the names of new plutoids to ensure that no dwarf
planet shares the name of another small Solar System body. The WGPSN
oversees the assignment of names to surface features on bodies in the Solar
System. These two committees have previously worked together to accept the
names of dwarf planet Eris and its satellite Dysnomia.

In Oslo, members of the IAU also discussed the timing involved with the
naming of new plutoids. Again, following the advice of the Division III
Board and the two Working Groups, it was decided that, for naming purposes,
any Solar System body having (a) a semimajor axis greater than that of
Neptune, and (b) an absolute magnitude brighter than H = +1 magnitude will
be considered to be a plutoid, and be named by the WGPSN and the CSBN.
Name(s) proposed by the discovery team(s) will be given deference. If
further investigations show that the object is not massive enough and does
not qualify as a plutoid, it will keep its name but change category. 

In French plutoid is plutoide, in Spanish plutoide and in Japanese .

Notes

The IAU is the international astronomical organisation that brings together
almost 10 000 distinguished astronomers from all nations of the world. Its
mission is to promote and safeguard the science of astronomy in all its
aspects through international cooperation. The IAU also serves as the
internationally recognised authority for assigning designations to celestial
bodies and the surface features on them. Founded in 1919, the IAU is the
worlds largest professional body for astronomers.

The absolute magnitude H for planets, dwarf planets, comets and asteroids
allows astronomers to compare the brightness of objects as if they all sat
one astronomical unit from the Sun and the Earth and at a phase angle of
zero degrees. In this scale, increasing brightness corresponds to a
decreasing magnitude. Apparently bright objects can have negative magnitudes
while positive magnitudes indicate to dim objects.
 
Links

* IAU website
  http://www.iau.org/
* Information about Pluto and the other dwarf planets
  http://www.iau.org/public_press/themes/pluto/

[NOTE: An image supporting this release is available at
http://www.iau.org/static/archives/images/screen/iau0804a.jpg (97KB)]