A1 14 Comets

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Miller's Astronomy 1 lecture notes on Comets

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A1 14 Comets

  1. 1. Kuiper Belt (Pluto) LACC: §12.3, 12.4, 13.3 • Understand how the various object in the outer solar system are classified • Understand what conditions and processes shaped these objects • Know the dwarf planets: Pluto, Eris. An attempt to answer the “big questions”: what is out there? Are we alone? Thursday, April 8, 2010 1
  2. 2. Transneptunian Objects (TNOs) 8 Largest Top row are all artist's dwarf planets conceptions http://www.astronomynow.com/ThomasMuellerInterview.html Thursday, April 8, 2010 2
  3. 3. The Outer Solar System http://www.cfa.harvard.edu/iau/lists/OuterPlot.html Thursday, April 8, 2010 3
  4. 4. Trans-Neptunian Objects While wikipedia is not as reliable as a .gov or .edu site, this illustration was too good to pass up. http://en.wikipedia.org/wiki/Trans-Neptunian_object Thursday, April 8, 2010 4
  5. 5. Centaurs 95P/Chiron, the first official Centaur P/2004 A1 centaur, around 200 km (LONEOS) http://www.hohmanntransfer.com/mn/07/img/ http://www.aanda.org/index.php? index.html option=article&access=standard&I temid=129&url=/articles/aa/full/ 2006/48/aa5189-06/ aa5189-06.right.html The largest known centaur is (10199) Chariklo at 200--250 km. http://aas.org/archives/BAAS/v37n3/dps2005/446.htm Thursday, April 8, 2010 5
  6. 6. Kuiper Belt Objects: Pluto The IAU members gathered at the 2006 General Assembly agreed that a "planet" is defined as 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 cleared the neighborhood around its orbit. http://www.iau.org/public_press/ http://apod.nasa.gov/apod/ap010319.html news/detail/iau0603/ Thursday, April 8, 2010 6
  7. 7. KBO and Dwarf Planet Pluto Little is known about Pluto's atmosphere, but it probably consists primarily of nitrogen with some carbon monoxide and methane. It is extremely tenuous, the surface pressure being only a few microbars. Pluto's atmosphere may exist as a gas only when Pluto is near its perihelion; for the majority of Pluto's long year, the atmospheric gases are frozen into ice. Near perihelion, it is likely that some of the atmosphere escapes to space perhaps even interacting with Charon. NASA mission planners want to arrive at Pluto while the atmosphere is still unfrozen. http://www.solarviews.com/eng/pluto.htm Thursday, April 8, 2010 7
  8. 8. Pluto and Charon: A binary planetary system? This model system has been artificially lit and reoriented so that its equator lies in a horizontal plane. The scale of time has been altered so that 2 days of simulated time pass in 1 second of real time. http://www.planetsalive.com/?planet=Pluto&tab=E Thursday, April 8, 2010 8
  9. 9. Currently, the largest KBO / SDO: Eris known dwarf planet is (136199) Eris. Eris is just slightly larger than Pluto, but orbits as far as twice Pluto's distance from the Sun. Eris is shown above in an image taken by a 10-meter Keck Telescope from Hawaii, USA. Like Pluto, Eris has a moon, which has been officially named by the International Astronomical Union as (136199) Eris I (Dysnomia). Eris was discovered in 2003, and is likely composed of frozen water-ice and methane. Currently, the only other officially designated "dwarf planet" is (1) http://apod.nasa.gov/apod/ap060918.html Ceres. Thursday, April 8, 2010 9
  10. 10. Dwarf Planets on Parade http://www.windows.ucar.edu/tour/link=/our_solar_system/dwarf_planets/images/ five_dwarfs_earth_luna_big_jpg_image.html&edu=high Thursday, April 8, 2010 10
  11. 11. Dwarf Planets to Scale Three dwarf planets along side some well known moons. (There are other moons and dwarf planets within this size range that are not shown.) Eris http://astro.berkeley.edu/~basri/defineplanet/ Thursday, April 8, 2010 11
  12. 12. Kuiper Belt (Pluto) LACC: §12.3, 12.4, 13.3 • Understand how the various object in the outer solar system are classified: Centaurs, Kuiper Belt Objects, Scattered Disk Objects • Understand what conditions and processes shaped these objects: formed outside orbit of Neptune, near collisions throw them out of the Kuiper Belt--Centaurs, SDOs, rogue planet? • Know the dwarf planets: Pluto (w/ Charon, Hydra, and Nix), Eris (w/ Dysnomia) is largest. An attempt to answer the “big questions”: what is out there? Are we alone? Thursday, April 8, 2010 12
  13. 13. LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe, 3rd ed. • Ch 12, pp. 286: 6. Due at the beginning of next class period. Test covering chapters 10-13 next class period. Be working your Solar System project. Thursday, April 8, 2010 13
  14. 14. Comets LACC: §12.3, 12.4, 13.3 • Know how Meteorites are classified: composition (laboratory analysis) • Understand under what conditions and processes the comets formed: formed outside orbit of Neptune, near collisions alter throw them out of the Kuiper Belt • Know what Comets tell us about the conditions and processes shaped our solar system: Comets tell us about our solar system: composition and history. An attempt to answer the “big questions”: what is Thursday, April 8, 2010 14
  15. 15. Comets http://cometography.com/lcomets/2006p1.html Thursday, April 8, 2010 15
  16. 16. Comet Halley http://lpmpjogja.diknas.go.id/kc/c/comet/comet.htm Thursday, April 8, 2010 16
  17. 17. Oort Cloud: Morphology 100 000 AU is about 1.5 light years. The closest star, Proxima Centauri, is 4.2 lightyears away. http://www.nature.com/nature/journal/v424/n6949/fig_tab/nature01725_ft.html Thursday, April 8, 2010 17
  18. 18. Kuiper Belt vs. Oort Cloud http://www.nature.com/nature/journal/v424/n6949/fig_tab/nature01725_ft.html Thursday, April 8, 2010 18
  19. 19. The Parts of a Comet http://www.galaxyexplorers.org/newsletter/comet_fun_facts.asp Thursday, April 8, 2010 19
  20. 20. A Sun Grazing Comt ...Comet SOHO-6, one of numerous sungrazing comets...as its head enters the equatorial solar wind region. It eventually plunged into the Sun. ... 23 December 1996.... The field of view of this coronagraph encompasses 8.4 million kilometers (5.25 million miles) of the inner heliosphere. http://sohowww.nascom.nasa.gov/gallery/images/xmascomet.html Thursday, April 8, 2010 20
  21. 21. Comet Tails http://www.nasa.gov/lb/audience/forkids/home/CS_Ten_Facts_About_Comets.html Thursday, April 8, 2010 21
  22. 22. Comets: Composition Conventional wisdom is that “Comets are ... dirty snowballs or "icy mudballs". They are a mixture of ices (both water and frozen gases) and dust that for some reason didn't get incorporated into planets when the solar system was formed. This makes them very interesting as samples of the early history of the solar system.” (http://www.nineplanets.org/comets.html) However, data from the Startdust mission “...implies that while the comets contain ices that formed at the edge of the solar system, the rocky materials that actually make up the bulk of a comet's mass actually formed in the hottest possible conditions. The inner solar system can be thought of as a factory producing rocky materials that were distributed outwards to all the bodies and regions of the solar system.” (http://stardust.jpl.nasa.gov/news/ news113.html) Thursday, April 8, 2010 22
  23. 23. Comets: Composition One of the most remarkable particles found in the Stardust collection is a particle named after the Inca Sun God Inti. Inti is collection of rock fragments that are all related in mineralogical, isotopic and chemical composition to rare components in meteorites called "Calcium Aluminum Inclusions" or CAI's for short. CAI's are the oldest materials that formed in the solar system and they contain a remarkable set of minerals that form at extremely high temperature. In addition to these same minerals, Inti also has tiny inclusions that may have been the first generation of solids to condense from hot gas in the early solar system. These include compounds of titanium, vanadium and nitrogen (TiN and VN) as well as tiny nuggets of platinum, osmium, ruthenium, tungsten and molybdenum. In certain chemical environments and at high enough temperature in the early solar system these exotic materials were the only solid materials that could survive without being vaporized. http://stardust.jpl.nasa.gov/news/news113.html Thursday, April 8, 2010 23
  24. 24. Comets on Parade Temple 1 9 km 0.6 gm/cm3 http://www.sciencenews.org/articles/20050910/bob9.asp Borrelly 8 km Wild 2 5 km 0.36 gm/cm3 http://www.aas.org/publications/baas/v36n4/dps2004/317.htm http://sse.jpl.nasa.gov/planets/profile.cfm? Object=Comets&Display=Gallery Thursday, April 8, 2010 24
  25. 25. Comet Halley The nucleus of Comet Halley is approximately 16x8x8 kilometers. The density of Halley's nucleus is very low: about 0.1 gm/cm3 indicating that it is probably porous, perhaps because it is largely dust remaining after the ices have sublimed away. (http:// www.nineplanets.org/halley.html) http://apod.nasa.gov/apod/ap961210.html Thursday, April 8, 2010 25
  26. 26. Shoemaker-Levy 9 struck Jupiter in 1994 http://apod.nasa.gov/apod/ap001105.html Thursday, April 8, 2010 26
  27. 27. Meteor Showers are Caused by Comets When Earth’s orbit passes through a trail of comet debris, there are many meteors visible in a single night--a meteor shower.  The Earth passes through the meteoroids from the comet in the same place each year as it goes around the Sun, so meteor showers occur annually. For example, every August we can see the beautiful Perseid meteor shower, caused by the dusty trail that Comet Swift-Tuttle left behind. http://cse.ssl.berkeley.edu/SegwayEd/lessons/cometstale/com2place.html Thursday, April 8, 2010 27
  28. 28. Meteor Showers http://csep10.phys.utk.edu/astr161/lect/meteors/showers.html More extensive listings of meteor showers can be found, e.g. http://csep10.phys.utk.edu/astr161/lect/meteors/shower_list.html Thursday, April 8, 2010 28
  29. 29. Comets LACC: §12.3, 12.4, 13.3 • Understand what conditions and processes shaped the comets: rocky materials -- inner solar system, icy materials -- outer solar system • Know what Comets tell us about our solar system: potentially unchanged since they formed, they reveal the early solar system’s composition and condition. • Understand how meteor showers are related to comets: Earth passes through/near a comet’s orbit and encounters its dust. An attempt to answer the “big questions”: what is out there? Are we alone? Thursday, April 8, 2010 29
  30. 30. LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe, 3rd ed. • Ch 12, pp. 286: 4. Due at the beginning of next class period. Test covering chapters 10-13 next class period. Be working your Solar System project. Thursday, April 8, 2010 30
  31. 31. Review for the Test 3 of 5: The Outer Solar System [10 pts] Identify objects from a picture. [10 pts] Asteroids, Comets, etc. • Jupiter. Saturn, Uranus, Neptune • Location: asteroids--asteroid belt, Trojan asteroids • Io, Europa, Ganymede, Callisto, Titan, Triton (some meteorites came from the Luna, Mars, • asteroids, comets (parts: nucleus, coma, dust tail, Vesta); transneptunian objects--Centaurs (between ion tail), Pluto (w/ Charon, Nix, and Hydra) Jupiter and Neptune), Kuiper belt (50 - 100 AU, outside the orbit of Neptune), Oort Comet Cloud [10 pts] Jupiter, Saturn, Uranus, Neptune (random elliptical orbits out to 100,000 AU • Physical properties: mass, size, composition, ring • Composition: asteroids--C, S, and M type; systems meteorites--iron, stoney iron, stoney (includes • Orbital properties: axial tilt (Uranus is on its side), carbonaceous chondrites)); comets--parts length of day, length of year, distance from the sun (nucleus, coma, tail (ion and dust)) • Atmospheres: composition (H, He, etc.), clouds • Notable: Minor Planets--Ceres, Pluto (w/ moons), (H2O, (NH4)SH, NH3, CH4) depending on the Eris; Centaurs--Chiron; Ida w/ moon Dactyl; different molecules’ condensation temperatures comet Shoemaker-Levy 9 [10 pts] Moons of Jupiter: Io, Europa, Ganymede, Callisto, [10 pts] Solar System Evolution Saturn: Titan; and Neptune Triton. • Ring Systems: composition (ices, rocky material), • Physical and orbital properties: mass, size, origin (moons wander inside Roche limit, debris composition (Europa and Ganymede may have from meteor impacts on small moons), evolution significant water oceans under their crust), (shepherd moons keep them tidy, orbital distance from their planet, Triton orbits resonances with major moons), bright vs dark backwards, Rhea might have rings (young & icy vs old & dusty) • Surface features: craters (esp. Callisto), volcanic • Outer planet’s moons (differentiation?), KBOs, activity (Io, Triton, Enceladus), what causes these comets: icy--outside frost line moons to be geologically active (tidal forces, • Undifferentiated asteroids are the oldest objects erupting substances may not be not lava) known (over 4.5 billion years old); differentiated • Titan’s atmosphere: composition (N2, 1.6 bars), asteroids may be parts of early planetesimals; methane (CH4) seas and rain? asteroids and comets are samples of the early solar system containing organic compounds like amino acids--the building blocks of life Thursday, April 8, 2010 31

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