Overview

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

OverviewOverview

DefinitionCompositionDistributionNomenclatureNEOs and PHAsObservation

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)

In Short . . .In Short . . .

An asteroid is a big rock in space.

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


TaxonomyTaxonomy

C-Class– Carbonaceous

S-Class– Silicaceous

M-Class– Metallic

Distribution of AsteroidsDistribution of Asteroids


Distribution in the Solar SystemDistribution in the Solar System

Inner Solar SystemMain BeltOuter Solar System

Inner Solar SystemInner Solar System

Outer Solar SystemOuter Solar System

Nomenclature of AsteroidsNomenclature of Asteroids


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

243 Ida243 Ida

45 Eugenia45 Eugenia

216 Kleopatra216 Kleopatra

433 Eros433 Eros

NEAR at 433 ErosNEAR at 433 Eros

Near-Earth AsteroidsNear-Earth Asteroids


Classification by Orbital Classification by Orbital ElementsElements

Orbital Elements OverviewOrbit Size and ShapeOrbital NeighborhoodOrbital Relationships

Orbital Elements OverviewOrbital Elements Overview

Orbit Size and ShapeOrbit Size and Shape

Neighborhood of a PlanetNeighborhood of a Planet

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

Schematic: AtenSchematic: Aten

Earth

Aten

a < 1 AU

Q > 0.983 (Earth’s q )

Schematic ApolloSchematic Apollo

Earth

Apollo

a > 1 AU

q < 1.017 (Earth’s Q )

Schematic AmorSchematic Amor

Earth

Amor

a > 1 AU

1.3 > q > 1.017 AU (Earth’s Q )

Observation of AsteroidsObservation of Asteroids


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)

http://www.science.house.gov/publications/hearings_markups_details.aspx?NewsID=2033




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