Transneptunian Binaries and Collision Families: Probes of our Local Dust Disk

Transcription

1 Transneptunian Binaries and Collision Families: Probes of our Local Dust Disk Susan D. Benecchi, STScI Collaborators: Keith Noll, Will Grundy, Denise Stephens, Hal Levison, and the Deep Ecliptic Survey Team (esp. Marc Buie and Jim Elliot) STScI Public Lecture, 5 May 2009 This work was supported by a NASA grant from STScI under NASA contract NAS

2 Motivation Context Local Dust Disks Asteroid Belt Kuiper Belt Binary KBOs as Test Particles Surface Reflectance ( Color ) Orbits Lightcurves Formation Mechanisms Solar System Formation Model Outline

3 Motivation Context Local Dust Disks Asteroid Belt Kuiper Belt Binary KBOs as Test Particles Surface Reflectance ( Color ) Orbits Lightcurves Formation Mechanisms Solar System Formation Model Outline

4 Motivation Study of objects in our solar system may help us to better understand extra-solar systems. Jupiter-like bodies (atmospheric effects, moons) Dust disks (the results of small body collisions) Small bodies reside throughout the solar system and their positions and characteristics help us to learn about the migration of the giant planets. Binaries allow us to determine the physical properties of objects in the outer solar system.

5 Motivation Context Local Dust Disks Asteroid Belt Kuiper Belt Binary KBOs as Test Particles Surface Reflectance ( Color ) Orbits Lightcurves Formation Mechanisms Solar System Formation Model Outline

6 Dust Disks & exo-planet systems Debes et al. 2008

7 Motivation Context Local Dust Disks Asteroid Belt Kuiper Belt Binary KBOs as Test Particles Surface Reflectance ( Color ) Orbits Lightcurves Formation Mechanisms Solar System Formation Model Outline

8 The Inner Solar System sun Planets (Mercury,Venus, Earth,Mars,Jupiter) Jupiter Trojans Perihelia < 1.3 AU Main belt asteroids Comets *open symbols represent single-opposition objects; solid symbols represent multi-opposition objects Minor Planet Center iau/lists/innerplot.html

9 Asteroid Families Orbits related Physical characteristics related

10 Motivation Context Local Dust Disks Asteroid Belt Kuiper Belt Binary KBOs as Test Particles Surface Reflectance ( Color ) Orbits Lightcurves Formation Mechanisms Solar System Formation Model Outline

11 <1% Mars s maximum apparent diameter (0.1 arcsec) 50,000 times fainter than Mars (V~14) Located at 30 AU (mean semimajor axis ~ 40 AU), it has a 249-year orbit with i = 17º and e = 0.25.

12 Charon 1978, Nix/Hydra 2005 Discovery image of Charon, from a USNO photographic plate (James Christy). Charon is ~ 17 Rpl from Pluto (~ 1 ), synchronous rotation, period of 6.4 days Nix/Hydra discovered in 2005 by HST ( S/2005 P1 & S/2005 P2 ); Distances of 1.85 and 2.09 Charon (V16.9=8) is 1/5 as bright as Pluto (V15.1), Nix/Hydra are A few 1000x fainter than Pluto (V~23) Nix/Hydra are 1/2000-1/ Pluto s mass Buie et al. 2006

13 Las Campanas, Kitt Peak & HST Observatories The Baade & Clay Magellan 6.5-m Telescopes & the Raymond & Beverly Sackler Magellan Instant Camera (MagIC) HST & ACS/HRC Kitt Peak 4-m & Mosaic Camera

14 Deep Ecliptic Survey Observations Box=0.6 x0.6 on the sky ±6.5 of the ecliptic Near Earth: 75 ''/hr Main Belt: ''/hr Centaurs: 5-15 ''/hr Kuiper Belt: 5 ''/hr Millis et al. 2002

15 Context: The Outer Solar System* sun gas-giant planets (Jupiter, Saturn,Uranus, Neptune) Pluto Centaur classical KBO resonant KBO scattered KBO *open symbols represent single-opposition objects; solid symbols represent multi-opposition objects Minor Planet Center iau/lists/outerplot.html

16 Context: The Outer Solar System* sun gas-giant planets (Jupiter, Saturn,Uranus, Neptune) Pluto Centaur classical KBO resonant KBO scattered KBO *open symbols represent single-opposition objects; solid symbols represent multi-opposition objects Minor Planet Center iau/lists/outerplot.html

17

18 Relative Size

19 Surfaces and Colors Verbiscer et al Buie & Grundy 2000

20 Pluto and Charon: Atmospheres Pluto C313.2, Charon Gulbis et al Elliot et al Observers: J.L. Elliot and E.R. Adams, Movie: D. Osip *Not real time. Occultation of C313.2 by Charon as recorded by POETS mounted on the 6.5-m Clay telescope at Las Campanas Observatory. Charon does not have a substantial atmosphere. Pluto has a Nitrogen atmosphere, currently expanding.

21 Motivation Context Local Dust Disks Asteroid Belt Kuiper Belt Binary KBOs as Test Particles Surface Reflectance ( Color ) Orbits Lightcurves Formation Mechanisms Solar System Formation Model Outline

22 Binaries binary orbit -> system mass. ( m p + m ) s = 4" 2 a 3 GP 2 diameters assuming an albedo, p. WATER ICE I PARTIALLY HYDRATED ROCK d = 2r" R p 10#0.2 ( m kbo +$% #m sun ) Density -> Suggest composition. WATER ICE I + HYDRATED ROCK BASELINE PLUTO 1180 km, 1.85 g cm 3 DIFFERENTIATED ROCK FRACTION=0.65 ICE II + HYDRATED ROCK BASELINE CHARON 625 km, 1.75 g cm 3 UNDIFFERENTIATED ROCK FRACTION=0.55 " = 4 3 )# + % * + $ d p 2 m p + m s & ( ' 3 # + d & s % ( $ 2 ' 3,. -. / McKinnon et al 1997

23 Solar System Binary Inventory 35 near-earth asteroids 1 with two satellites 8 Mars crossing asteroids 63 main-belt asteroids 4 with two satellites each 2 Jupiter Trojan asteroids 71 trans-neptunian objects 1 with two satellites, 1 with three satellites

24 Size and Distance Characteristics d p ~100 km, s ~20000 km d p ~2300 km, s ~8000 km d p ~100 km, s ~1000 km d p ~1 km, s ~2.5 km Margot 2004

25 Ground based observations Magellan 2001 Oct 11 0."4 seeing s= 0."61±0."01 m=0.70±0.05 M R =21.8 Classical < 4 arcsec > 2003 QY 90 Magellan 2003 Oct 23 0."47 seeing s=0."41±0. "02 m=0.2±0.2 M R = 23.0 Classical 2005 EO 304 Magellan 2005 Apr 15 0."7 seeing s=2."67±0."06 m=1.2±0.1 M R = 22.5 Classical 2003 UN 284 DES 2003 Oct 24 1."0 seeing s=2."01±0."11 m=0.59±0.21 M R =23.2 Classical

26 HST ACS/HRC observations 2001 FL 185 s= 0."065±0."014 m=0.8±0.1 M R =22.9 Classical < 1 arcsec > s=0."109±0."002 m=1.47±0.04 M R = 19.5 Centaur 1999 OJ 4 s=0."097±0."004 m=0.19±0.09 M R = 22.6 Classical 2002 GZ 31 s=0."070±0."009 m=1.0±0.2 M R =22.2 Scattered Noll et al. 2007

27 Observability of Kuiper Belt Binaries Modified from Kern & Elliot 2006, ApJL

28 HST Binaries Frequency of binaries Noll et al The Solar system beyond Neptune The number of binaries increases with decreasing separation. Currently 71 TNBs Kern & Elliot 2006, ApJL HST data points: Noll et al. 2002, Stephens & Noll 2005 and Brown et al.

29 Inventory of KBOs & Binaries Resonant objects Fraction binary +4 > 5.5 "2 Scattered objects

30 Classical objects Gulbis et al. 2006, Icarus) 9 +7 "4 % KBO Orbital Pole Positions (after Elliot et al. 2005, Fig 19) "6 % Adapted from Noll et al. 2007, The Solar System Beyond Neptune

31 Motivation Context Local Dust Disks Asteroid Belt Kuiper Belt Binary KBOs as Test Particles Surface Reflectance ( Color ) Orbits Lightcurves Formation Mechanisms Solar System Formation Model Outline

32 Binary Colors HST/WFPC2 and HST/ACS, 6 programs Filters: F606W ~ V and F814W ~ I 22 objects Analyzed data with standard HST pipeline and iterative PSF fitting of binary images with Tiny Tim models.

33 Component Comparison Primary and secondary components are identical in color. Correlated with Spearman Rank probability of %. Benecchi et al. 2009

34 Binaries and (assumed) single TNOs Comparison K-S Test > Probability the distribution is the same for (assumed) singles and binaries > 98.8% (for all objects) > % (Use same classification distribution) Benecchi et al MBOSS (Hainaut & Delsanti 2002) and HST (Stephens et al. 2007) Color surveys

35 Take away points Colors Summary Binaries are key objects for determining physical characteristics of objects throughout the Solar System disk. Colors/spectra of KBOs may give some indication of composition and migration in the disk. Binary companions have the same colors as each other Binaries have the same color distribution as (apparent) single TNOs. Possible Explanations Composition Environment Ejecta Exchange (Stern 2008) Particle Irradiation (Richardson & Schwadron 2008) Meteorite Gardening (Jewitt & Luu 2001) Binaries are primordial. They formed throughout the disk and were transported to their current locations in the same way as (apparent) single TNOs.

36 Motivation Context Local Dust Disks Asteroid Belt Kuiper Belt Binary KBOs as Test Particles Surface Reflectance ( Color ) Orbits Lightcurves Formation Mechanisms Solar System Formation Model Outline

37 Sample Images (2000 QL 251 )

38 3 orbits Orbit Refinement: (42355) Typhon/Echidna 4 orbits P = ± days a = 1628 ± 29 km e = ± M s = (9.49 ± 0.52) kg r = g cm "0.17 Grundy et al. 2008

39 Orbits P=56.470±0.031 P=137.33±0.18 P=125.61±0.13 P=84.114±0.038 P=22.041±0.004 P=97.044±0.099 Grundy et al. 2009, Icarus. Orbital periods are in days.

40 Derived Quantities Grundy et al. 2009, Icarus.

41 Comparison: observed & physical properties Grundy et al Benecchi et al. 2008, ACM

42 Motivation Context Local Dust Disks Asteroid Belt Kuiper Belt Binary KBOs as Test Particles Surface Reflectance ( Color ) Orbits Lightcurves Formation Mechanisms Solar System Formation Model Outline

43 Possible lightcurves Single object with a single spot Single object, multiple spots

44 Elongated Object Assumptions: Object is a triaxial ellipsoid. Rotation axis of the object is to the line of sight of the body. A P-P of the lightcurve is an appropriate estimate of the axis ratio of the elongation. a b =100.4A P"P S min =πac S max =πbc

45 Eclipsing Binary

46 HST color variability Benecchi et al. 2009

47 (47171) 1999TC 36 lightcurve component a Benecchi et al, 2009 in preparation combined (a+b)

48 Longer-duration ground based lightcurves (88611) Teharon Multiple night observations Color variability search Kern 2005, Thesis P=5.50±0.02 A=0.22±0.02 Reduced χ 2 =0.99 Kern 2005, Thesis

49 Detailed lightcurves: 2001QG 298 and (136108) Haumea Sheppard & Jewitt, 2004 Takahaski & Ip, 2005 Lacerda et al. 2008

50 Motivation Context Local Dust Disks Asteroid Belt Kuiper Belt Binary KBOs as Test Particles Surface Reflectance ( Color ) Orbits Lightcurves Formation Mechanisms Solar System Formation Model Outline

51 Proposed Binary KBO Formation Models Updated from Kern 2005, Thesis

52 Motivation Context Local Dust Disks Asteroid Belt Kuiper Belt Binary KBOs as Test Particles Surface Reflectance ( Color ) Orbits Lightcurves Formation Mechanisms Solar System Formation Model Outline

53 Solar System Formation: the Nice model Figure from Gomes 2003, EMP Model: Series of papers by Morbidelli, Levison, Gomes, Tsiganis, 2005

54 The Nice model (animation) Gomes et al Giant planets (Jupiter- Neptune) are in circular orbits surrounded by a belt of icy objects. Gaps appear in the proto- Kuiper Belt, much like the Kirkwood gaps in the main asteroid belt. The three outer planets expand outward, and the belt of planetesimals spread out a bit. Everything goes crazy just after the chronometer reaches 878 million years when Saturn and Jupiter reach a 2:1 orbital resonance.

55 Nice model comparison to observations 4. The giant planet irregular satellites. 5. The Late Heavy Bombardment. 6. The Kuiper belt. 1. The correct giant planet orbits. 2. The correct Trojans (Jupiter and Neptune). 3. The D-type asteroids.

56 Take away points Summary The Asteroid and Kuiper Belts are local dust disks and studies of them may be able to provide insight for models of extra solar planetary disks. Binaries and multiple systems provide the best environment to obtain physical measurements of these remote places in our Solar System. Methods of study: orbits, colors, lightcurves, occultations Binary companions have the same colors as each other Binaries have the same color distribution as (apparent) single TNOs. At least 2 multiple systems in the Kuiper Belt (Pluto, Haumea) and similar numbers in the Asteroid belt. Binaries are primordial. They formed throughout the disk and were transported to their current locations in the same way as (apparent) single TNOs.

57 New Horizons: Pluto encounter 2015 final stop the Kuiper Belt Jupiter science worked as planned: Io Tvashtar Plume February 28, 2007

58 Thanks for listening. Questions?