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Transcript
Near Earth
Objects
and
Other Small
Bodies
in the
Solar
System
Presented to
Sandhills Astronomical
Society
Fayetteville, NC
February 13, 2008
Tony Vaughn
Overview

Definition
 Composition
 Distribution
 Nomenclature
 NEOs and PHAs
 Observation
What is an Asteroid, Anyway?

Major Bodies
– Sun
– Planets

Minor Bodies
–
–
–
–
–
Natural Satellites
Comets
Asteroids
Meteoroids
Dust
International Astrophysical Union

Founded in 1919.
 Composed of professional astronomers from around the
world at the PhD level and above, actively engaged in
research or education.
 Mission: to promote and safeguard the science of
astronomy in all its aspects through international
cooperation.
 Holds General Assembly Meetings every 3 years.
General Assembly XXVI, Prague, Aug 2006
Resolution B5
In our solar system:
(1) A planet is a celestial body that
(a)
(b)
(c)
Is in orbit around the sun,
Has sufficient mass for its self-gravity to overcome rigid-body
forces so that it assumes a hydrostatic equilibrium (nearly round)
shape, and
Has cleared the neighborhood around its orbit.
General Assembly XXVI, Prague, Aug 2006
Resolution B5 (continued)
(2) A “dwarf planet” is a celestial body that
(a)
(b)
(c)
(d)
Is in orbit around the sun,
Has sufficient mass for its self-gravity to overcome rigid-body
forces so that it assumes a hydrostatic equilibrium (nearly round)
shape,
Has not cleared the neighborhood around its orbit, and
Is not a satellite.
General Assembly XXVI, Prague, Aug 2006
Resolution B5 (continued)
(3) All other objects, except satellites, orbiting the Sun shall
be referred to collectively as
“Small Solar System Bodies.”
These currently include most of the solar system asteroids, most
Trans-Neptunian Objects (TNOs), comets, and other small bodies.
In Short . . .

Small bodies are either comets or asteroids
 A comet is a small body that sometimes has
a coma.
 An asteroid is a small body that has no
atmosphere or outgassing.
– (An asteroid might sometimes be a depleted
comet.)

An asteroid is larger than a meteoroid (10m)
In Short . . .
An asteroid is a big rock in
space.
Some Examples










1
2
3
4
5
6
7
8
9
10
Ceres
Pallas
Juno
Vesta
Astraea
Hebe
Iris
Flora
Metis
Hygeia
1801
1802
1804
1807
1845
1847
1847
1847
1848
1849
Palermo
Bremen
Lilienthal
Bremen
Driesen
Driesen
London
London
Markree
Naples
. . .

5000 IAU
1987
Palomar
Statistics

As of January 24, 2008:
– 744,278 Registered Asteroids
– 173,116 Numbered Asteroids
– 14,299 Named Asteroids
Composition of Asteroids

Definition
 Composition
 Distribution
 Nomenclature
 NEOs and PHAs
 Observation
Taxonomy

C-Class
– Carbonaceous

S-Class
– Silicaceous

M-Class
– Metallic
Distribution of Asteroids

Definition
 Composition
 Distribution
 Nomenclature
 NEOs and PHAs
 Observation
Distribution in the Solar System

Inner Solar System
 Main Belt
 Outer Solar System
Inner Solar System
Outer Solar System
Nomenclature of Asteroids

Definition
 Composition
 Distribution
 Nomenclature
 NEOs and PHAs
 Observation
Nomenclature

Responsibility
 Individual Asteroids
– Provisional Designation
– Permanent Designation

Some Examples
References: http://www.cfa.harvard.edu/iau/info/OldDesDoc.html
http://www.iau.org/MINOR_PLANETS_NAMING.245.0.html
Responsibility

Minor Planet Center (MPC) at the
Smithsonian Astrophysical Observatory
(SAO), under Division III of the IAU.
 Central Bureau for Astronomical Telegrams
(CBAT), under Commission 6 of the IAU.
 Harvard University, Cambridge, MA
Reporting

Minor Planet Circulars (monthly)
 Minor Planet Circulars Orbit Supplement
 Minor Planet Circulars Supplement
 Minor Planet Electronic Circulars (daily)
Individual Asteroids

MPC assigns a provisional designation to
newly discovered asteroids
 Body must have been observed for at least
two separate nights.
 Body must be distinct from existing lists of
known bodies.
Provisional Naming Format

Two parts: date of discovery + serial number

Date indicates year and half month:
YYYY X
– Four digit year
– Letter, A-Y, for half month (12 mos x 2 = 24 characters) , no I, Z

Serial number is numerical, but expressed in a mixed base,
and reversed order.
– An alphabetic character ranging A-Z (excluding I)
– An optional number starting at 1, increasing w/o bound.
Example: 2007 TA1 (= 2007 TA1 ) = 26th object discovered
during the first two weeks of October, 2007.
Date Codes






January
February
March
April
May
June
A
C
E
G
J
L
B
D
F
H
K
M






July
August
September
October
November
December
N
P
R
T
V
X
Second half of the month begins on the 16th.
Some older asteroids used I in place of J, but
modern usage replaces the I with the standard J.
O
Q
S
U
W
Y
Serial Number
Think “Place Value,” but in base 25.
 Designation has two “places,” one in base 25, the other in
infinite base, but represented as base 10 (decimal).
 LSB is one alphabetic character {A=0, Z=24}
 MSB is numeric
 To convert to a normal decimal number, N:
N = MSB x 25 + LSB + 1

e.g.:
2007 TU24
N = 24 x 25 + U{=19} + 1 = 620
Permanent Designation

Assigned when orbit is determined to
acceptable predictability (normally two or
more full periods).
 Simple serial number.
 In addition, discoverer is invited to suggest
a name, to be approved by the Committee
on Small Body Nomenclature (CSBN).
An Example

Three names:
– Provisional: 1929 CD
– Permanent: 1664
– Unique Name: Felix


Fourth discovery in
February 1929 by E.
Delporte at Uccle, BE
Combined designation:
– (1664) Felix

Also known as
– 1936 AD
– 1947 FC
– 1949 WC
– 1954 DD
– 1956 TV
– 1961 AE
243 Ida
45 Eugenia
216 Kleopatra
433 Eros
NEAR at 433 Eros
Near-Earth Asteroids

Definition
 Composition
 Distribution
 Nomenclature
 NEOs and PHAs
 Observation
Classification by Orbital
Elements

Orbital Elements Overview
 Orbit Size and Shape
 Orbital Neighborhood
 Orbital Relationships
Orbital Elements Overview
Orbit Size and Shape
Orbit Size and Shape
Neighborhood of a Planet
Neighborhood of a Planet
Neighborhood of a Planet
NEOs and PHAs

Near Earth Objects
– Semi-major axis < 1.3 AU

Potentially Hazardous Asteroids
– MOID < 0.05 AU
– Diameter > 150 m
Families of NEOs

Atiras
–
–

Orbit inside Earth’s orbit
a < 1 AU Q < 0.983 AU
Atens
–
–

Aphelion within Earth’s orbit
a < 1 AU Q > 0.983 AU
Apollos
–
–

Perihelion within Earth’s orbit
a > 1 AU q < 1.017 AU
Amors
–
–
Orbit outside Earth’s orbit
a > 1 AU 1.017 < q < 1.3 AU
Schematic: Aten
Aten
a < 1 AU
Q > 0.983 (Earth’s
Earth
q)
Schematic Apollo
Apollo
a > 1 AU
q < 1.017 (Earth’s
Earth
Q)
Schematic Amor
Amor
a > 1 AU
1.3 > q > 1.017 AU (Earth’s
Earth
Q)
Observation of Asteroids

Definition
 Composition
 Distribution
 Nomenclature
 NEOs and PHAs
 Observation
Observation

Plan Ahead
 Use a Star Chart
 Identify nearby stars at several scales
 Plot “rulers” visually
 Make drawings or take photos
Astronomical League

Asteroid Observing Club
– Regular Member
– Gold Member

Requirements
– 25 (100) asteroids
– Observed at least twice
– Sketches or photos

Receive certificate (and pin)
From a FEMA
presentation on
Hazard
Mitigation
Planning
“All I’m saying is now is the time
to develop the technology to deflect the asteroid”
For More Information

Harvard-Smithsonian Center for Astrophysics
Monthly Observatory Night – 2008-01-17
“Impact! Finding and Tracking Asteroid Threats”
Brian Marsden – CfA
http://www.cfa.harvard.edu/events/mon_video_archive08.html

US House Committee on Science and Technology
Hearing on NEOs – Status of the Survey Program and Review of
NASA’s Report to Congress – 2008-11-08
http://www.science.house.gov/publications/hearings_markups_details.
aspx?NewsID=2033 (Streaming Webcast in RealMedia)
End