help

Planets and Dwarf Planets

-- | October 30, 2012

Question: Although Pluto has already been classified as a dwarf planet, I do know that there are still some people out there who consider Pluto to be a planet. What is your take on it? Do you think Pluto should still be considered a planet? Why? — Ansley

Answer: In 2006 the International Astronomical Union decided that celestial objects must meet the following conditions in order to be classified as planets:

The object must be in orbit around a star, while not being itself a star,
The object must be massive enough for its own gravity to pull it into a nearly spherical shape, and
The object must have cleared the neighborhood around its orbit.

The last criterion is the one that Pluto fails to meet, mainly because Pluto has a moon, Charon, that is about half its size. In the end, this is all just a refinement of the term “planet” which allows for the proper characterization of objects which are not really asteroids, but also not quite planets. There are currently 5 IAU-recognized dwarf planets: Pluto, Ceres, Eris, Haumea, and Makemake.

Jeff Mangum

The National Radio Astronomy Observatory is a facility of the U.S. National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
	Founded in 1956, the NRAO provides state-of-the-art radio telescope facilities for use by the international scientific community. NRAO telescopes are open to all astronomers regardless of institutional or national affiliation. Observing time on NRAO telescopes is available on a competitive basis to qualified scientists after evaluation of research proposals on the basis of scientific merit, the capability of the instruments to do the work, and the availability of the telescope during the requested time. NRAO also provides both formal and informal programs in education and public outreach for teachers, students, the general public, and the media.
	The U.S. National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 "to promote the progress of science; to advance the national health, prosperity, and welfare; to secure the national defense..."
	AUI collaborates with the scientific community and research sponsors to plan, build, and operate cutting-edge facilities. We cultivate excellence, deliver value, enhance education, and engage the public.