Near Earth Near Earth ObjectsObjects
and and
Other Small Other Small BodiesBodies
in the Solar in the Solar SystemSystem
Presented toPresented to
Sandhills Astronomical Sandhills Astronomical SocietySociety
Fayetteville, NCFayetteville, NCFebruary 13, 2008February 13, 2008
Tony VaughnTony Vaughn
What is an Asteroid, Anyway?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 B5In our solar system:
(1) A planet is a celestial body that(a) Is in orbit around the sun,
(b) Has sufficient mass for its self-gravity to overcome rigid-body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and
(c) 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) Is in orbit around the sun,
(b) Has sufficient mass for its self-gravity to overcome rigid-body forces so that it assumes a hydrostatic equilibrium (nearly round) shape,
(c) Has not cleared the neighborhood around its orbit, and
(d) 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 . . .In Short . . .
Small bodies are either comets or asteroidsA 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)
Some ExamplesSome Examples
1 Ceres 1801 Palermo 2 Pallas 1802 Bremen 3 Juno 1804 Lilienthal 4 Vesta 1807 Bremen 5 Astraea 1845 Driesen 6 Hebe 1847 Driesen 7 Iris 1847 London 8 Flora 1847 London 9 Metis 1848 Markree 10 Hygeia 1849 Naples
. . .
5000 IAU 1987 Palomar
StatisticsStatistics
As of January 24, 2008:– 744,278 Registered Asteroids– 173,116 Numbered Asteroids– 14,299 Named Asteroids
Composition of AsteroidsComposition of Asteroids
DefinitionCompositionDistributionNomenclatureNEOs and PHAsObservation
Distribution of AsteroidsDistribution of Asteroids
DefinitionCompositionDistributionNomenclatureNEOs and PHAsObservation
Distribution in the Solar SystemDistribution in the Solar System
Inner Solar SystemMain BeltOuter Solar System
Nomenclature of AsteroidsNomenclature of Asteroids
DefinitionCompositionDistributionNomenclatureNEOs and PHAsObservation
NomenclatureNomenclature
ResponsibilityIndividual 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
ResponsibilityResponsibility
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
ReportingReporting
Minor Planet Circulars (monthly)Minor Planet Circulars Orbit SupplementMinor Planet Circulars SupplementMinor Planet Electronic Circulars (daily)
Individual AsteroidsIndividual 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 FormatProvisional 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 CodesDate Codes
January A B February C D March E F April G H May J K June L M
July N O August P Q September R S October T U November V W December X Y
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.
Serial NumberSerial 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 DesignationPermanent 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 ExampleAn 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
Near-Earth AsteroidsNear-Earth Asteroids
DefinitionCompositionDistributionNomenclatureNEOs and PHAsObservation
Classification by Orbital Classification by Orbital ElementsElements
Orbital Elements OverviewOrbit Size and ShapeOrbital NeighborhoodOrbital Relationships
NEOs and PHAsNEOs and PHAs
Near Earth Objects– Semi-major axis < 1.3 AU
Potentially Hazardous Asteroids– MOID < 0.05 AU– Diameter > 150 m
Families of NEOsFamilies 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
Observation of AsteroidsObservation of Asteroids
DefinitionCompositionDistributionNomenclatureNEOs and PHAsObservation
ObservationObservation
Plan AheadUse a Star Chart Identify nearby stars at several scalesPlot “rulers” visuallyMake drawings or take photos
Asteroid Observing Club– Regular Member– Gold Member
Requirements– 25 (100) asteroids– Observed at least twice– Sketches or photos
Receive certificate (and pin)
Astronomical LeagueAstronomical League
““All I’m saying is All I’m saying is nownow is the time is the time to develop the technology to deflect the to develop the technology to deflect the
asteroid”asteroid”
From a FEMA presentation on Hazard Mitigation Planning
For More InformationFor More Information
Harvard-Smithsonian Center for Astrophysics Monthly Observatory Night – 2008-01-17“Impact! Finding and Tracking Asteroid Threats”Brian Marsden – CfAhttp://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 – 2008-11-08http://www.science.house.gov/publications/hearings_markups_details.aspx?NewsID=2033 (Streaming Webcast in RealMedia)
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