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Near Earth Objects and Other Small Bodies in the Solar System Presented to Sandhills Astronomical Society Fayetteville, NC February 13, 2008 Tony Vaughn.

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Presentation on theme: "Near Earth Objects and Other Small Bodies in the Solar System Presented to Sandhills Astronomical Society Fayetteville, NC February 13, 2008 Tony Vaughn."— Presentation transcript:

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2 Near Earth Objects and Other Small Bodies in the Solar System Presented to Sandhills Astronomical Society Fayetteville, NC February 13, 2008 Tony Vaughn

3 Overview Definition Composition Distribution Nomenclature NEOs and PHAs Observation

4 What is an Asteroid, Anyway? Major Bodies – Sun – Planets Minor Bodies – Natural Satellites – Comets – Asteroids – Meteoroids – Dust

5 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.

6 General Assembly XXVI, Prague, Aug 2006 Resolution B5 In 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.

7 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.

8 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.

9 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)

10 In Short... An asteroid is a big rock in space.

11 Some Examples 1Ceres1801Palermo 2Pallas1802Bremen 3Juno1804Lilienthal 4Vesta1807Bremen 5Astraea1845Driesen 6Hebe1847Driesen 7Iris1847London 8Flora1847London 9Metis1848Markree 10Hygeia1849Naples... 5000 IAU1987Palomar

12 Statistics As of January 24, 2008: – 744,278 Registered Asteroids – 173,116 Numbered Asteroids – 14,299 Named Asteroids

13 Composition of Asteroids Definition Composition Distribution Nomenclature NEOs and PHAs Observation

14 Taxonomy C-Class – Carbonaceous S-Class – Silicaceous M-Class – Metallic

15 Distribution of Asteroids Definition Composition Distribution Nomenclature NEOs and PHAs Observation

16 Distribution in the Solar System Inner Solar System Main Belt Outer Solar System

17 Inner Solar System

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19 Outer Solar System

20 Nomenclature of Asteroids Definition Composition Distribution Nomenclature NEOs and PHAs Observation

21 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

22 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

23 Reporting Minor Planet Circulars (monthly) Minor Planet Circulars Orbit Supplement Minor Planet Circulars Supplement Minor Planet Electronic Circulars (daily)

24 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.

25 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 TA 1 ) = 26 th object discovered during the first two weeks of October, 2007.

26 Date Codes January AB February CD March EF April GH May JK June LM July NO August PQ September RS October TU November VW December XY Second half of the month begins on the 16 th. Some older asteroids used I in place of J, but modern usage replaces the I with the standard J.

27 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

28 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).

29 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

30 243 Ida

31 45 Eugenia

32 216 Kleopatra

33 433 Eros

34 NEAR at 433 Eros

35 Near-Earth Asteroids Definition Composition Distribution Nomenclature NEOs and PHAs Observation

36 Classification by Orbital Elements Orbital Elements Overview Orbit Size and Shape Orbital Neighborhood Orbital Relationships

37 Orbital Elements Overview

38 Orbit Size and Shape

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40 Neighborhood of a Planet

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43 NEOs and PHAs Near Earth Objects – Semi-major axis < 1.3 AU Potentially Hazardous Asteroids – MOID < 0.05 AU – Diameter > 150 m

44 Families of NEOs Atiras – Orbit inside Earth’s orbit – a < 1 AU Q < 0.983 AU Atens – Aphelion within Earth’s orbit – a 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

45 Schematic: Aten Earth Aten a < 1 AU Q > 0.983 (Earth’s q )

46 Schematic Apollo Earth Apollo a > 1 AU q < 1.017 (Earth’s Q )

47 Schematic Amor Earth Amor a > 1 AU 1.3 > q > 1.017 AU (Earth’s Q )

48 Observation of Asteroids Definition Composition Distribution Nomenclature NEOs and PHAs Observation

49 Observation Plan Ahead Use a Star Chart Identify nearby stars at several scales Plot “rulers” visually Make drawings or take photos

50 Asteroid Observing Club – Regular Member – Gold Member Requirements – 25 (100) asteroids – Observed at least twice – Sketches or photos Receive certificate (and pin) Astronomical League

51 “All I’m saying is now is the time to develop the technology to deflect the asteroid” From a FEMA presentation on Hazard Mitigation Planning

52 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=2033http://www.science.house.gov/publications/hearings_markups_details. aspx?NewsID=2033 (Streaming Webcast in RealMedia)

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