The document discusses the criteria for defining planets in our solar system and beyond. It explores size, shape, orbit characteristics, historical classifications, and membership in populations like the Kuiper Belt. While size and orbit were traditionally the main criteria, the discovery of objects like Ceres, Pluto, and exoplanets require considering other factors. The International Astronomical Union is working to develop a definition that accounts for findings both within and beyond our solar system.
6. Solar System Table of Contents:
I. Sun
II. Mercury, Venus, Earth, Mars
III. Asteroid Belt
IV.Jupiter, Saturn, Uranus, Neptune
V. Kuiper Belt (icy asteroids)
VI.Oort Cloud (comets)
7. SIZE SHAPE ORBIT TEMP COMP
Which of the following criteria are
important for defining a planet?
8. Size and Shape: Earth is spherical,
asteroid Gaspra is not.
12,800 kilometers
(avout 8000 miles)
15 kilometers
(about 9 miles)
9. Asteroid Ceres is spherical and about
the size of Texas. Is it a planet?
15. Discovery of Kuiper Belt Objects
• 1992, Jane Luu and David Jewitt
• More than 1,000 KBO’s now known
• 11 Pluto-sized KBO’s
• Pluto is a Kuiper Belt Object
29. Summary
• Object size and orbit main criteria
• Historical context a consideration
(Pluto is already on all of the plastic placemats!)
• Membership in a larger population
will also be a consideration
• Object must be smaller than about
13 x’s Jupiter’s mass
30. For more information:
Discovery of UB 313:
http://www.gps.caltech.edu/~mbrown/
First Discovery of Kuiper Belt Objects:
http://www.ifa.hawaii.edu/faculty/jewitt/kb.html
List of planets orbiting other stars:
http://exoplanet.eu