The Origin of
Stars, Planets, and
Life in the Universe
Dr. Natalie Batalha
nbatalha@science.sjsu.edu
Poll Question:
How many planets
are there in our
Solar System?
Taking an Inventory of the Solar System
Pluto
Neptune
Comet
Mars
Sun
Uranus
Earth
Venus
Mercury
Jupiter
Saturn
http://www.cfa.harvard.edu/iau/lists/InnerPlot.html
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)
Which of the following criteria are
important for defining a planet?
SIZE SHAPE ORBIT TEMP COMP
Size and Shape: Earth is spherical,
asteroid Gaspra is not.
12,800 kilometers
(avout 8000 miles)
15 kilometers
(about 9 miles)
Asteroid Ceres is spherical and about
the size of Texas. Is it a planet?
Moon
Mercury
Mars
Io
Europa
Ganymede
Pluto
Callisto
Definition so far:
a) Orbits the Sun;
b) Is at least as large as Pluto.
Ceres
YES
Ganymede
NO
YES
NO
Orbital Characteristics
Earth
Mercury
Mars
Pluto
Uranus
7°
Venus
17°
Saturn
Jupiter
Neptune
Poll Question:
Why is Pluto’s orbit
different from those of
the other 8 planets?
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
How to Find Kuiper Belt Objects
The Orbits of Some Kuiper Belt Objects
Artist’s Depiction of UB313
Credit: Robert Hurt (IPAC)
UB313
(1500 miles)
Should UB313 be the 10th
Planet in the Solar System?
Yes
No
Which of the following criteria are
important for defining a planet?
Size
Orbit
History
Population
193 planets orbiting other
stars (a total of 155 systems)
have been identified to date.
What do they tell us?
Most are in elliptical orbits
Gas giants are
seen orbiting
very close to
their parent
star!
Copyright © 1998-2006 Lynette R. Cook
Three planets all within 0.2 AU
(Mercury orbits at 0.4 AU!)
Giant planets with 10x’s the mass of
Jupiter.
Copyright © 1998-2006 Lynette R. Cook, All Rights Reserved
The International
Astronomical Union is
working to craft a definition
that satisfies both Solar
System and Extra-Solar
System findings.
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
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