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Dynamical Behavior of Solar System Objects With 2.8 < TJ < 3.2 Implications for the origin of Main-Belt Comets Nader Haghighipour(IfA, Hawaii) Henry Hsieh (Academia Sinica, Taiwan) P/2012 T1 P/2006 VW139 (Hsieh, …, Haghighipouret al. 2012, 2013)
Elst-Pizzaro SpaceWatch, 1996, Scotti
Elst-Pizzaro SpaceWatch, 1996, Scotti Hsieh, Fernandez, Jewitt 2004 Hsieh & Jewitt, 2002
Tisserand’s Parameter (AsteroidalvsCometary Orbits) Relative encounter velocityof a comet with Jupiter (Vaghi, 1973; Fernandez et al., 2002) Asteroidal/Cometary orbit discriminant (Kresak, 1972) Asteroids TJ> 3 Comets TJ< 3 Jupiter Family Comets 2<TJ < 3 2P/EnckeTJ > 3 107P/Wilson-Harrington
133P/Elst-Pizarro TJ = 3.184 Hsieh, Fernandez, Jewitt 2004
Elst-Pizzaro Eccentricity a = 3.156 (AU) e =0.165 i = 1.39 (deg) TJ = 3.184 a (AU)
Elst-Pizarro, Read, 1999 RE70(Hsieh & Jewitt 2006) TJ = 3.184 TJ = 3.153 TJ = 3.166
Orbits are entirely within asteroid belt Jewitt 2008
Perspective View of the Orbits (MBCs = Orange, Planets = White) Distances in AU DCJ MBC Meeting @ UH 2008-March-04 Courtesy of D. Jewitt
Unstable Unstable (< 30 Myr) May scattered to other orbits in asteroid belt Beagle Family Stable MBCs are native to the asteroid belt(Haghighipour 2009, 2010)
P/2008 R1 (Garradd)(Jewitt, Yang & Haghighipour 2009) TJ = 3.217 P/2008 R1 (GARRADD)
P 2012 T1 (PANSTARRS) (Hsieh, …, Haghighipour, et al. 2013) TJ = 3.135
A Possible Trigger Mechanism: Impact The vent sealing time is unknown. A guess based on the sublimation rate would be 10 -100 yrs of equivalent exposure at 3 AU. Jewitt 2008 DCJ MBC Meeting @ UH 2008-March-04
First 50 000 numbered asteroids (pale blue dots) and all comets catalogued by the Minor Planet Center as of 2014 April 1 (pale red dots)
Dynamics of Objects With 2.8 < TJ < 3.2 A sample of 10,000 test particles Randomly select TJ, a , e from 2.8 < TJ < 3. 2 , 0 < e < 0.99, and a< aJ= 5.204 (AU) Computed the corresponding i needed to produce the selected TJ Arguments of perihelion, longitudes of ascending nodes, and mean anomalies selected randomly Every comet catalogued by the MPC as of Apr 2014
Integrating for 2 Myrs This time scale is chosen to be long enough to span the median lifetime of 4.5 x 105years found by Levison & Duncan (1994) for short-period comets Before ejection from the solar system or collision with the Sun.
a < 2.064 AU 2.064 < a< 3.277 AU a> 3.277 AU
Conclusions • TJ= 3 is not a rigid boundary, • Immediately after the start of asimulation, objects in all three semimajoraxis regions diverge to cover a range of TJvalues both larger than and smaller than 3, • objects in each region have TJ values outside this range for about 50-70% of time with 30-40% of this time with TJ< 3, • The average final TJfor unstable objects are < 3, • A very small number of unstable test particles have terminal TJ> 3, • The average TJfor both stable and unstable test particles in each TJ range are extremely similar.
Implications for the Origin of MBCs Stable MBCs are Native to their current locations 133P/Elst-Pizarro : Themis/Beagle family 176P (1999 RE70) : Themis Family P/2010 R2 (La Sagra) and P/2006 VW139: protected by two- and three-body mean motion resonances with Jupiter and Saturn Unstable MBCs should not be considered representative of their corresponding regions. These bodies are likely only temporarily captured there and originated elsewhere P/2005 U1 (Read) : Scattered MBC probably from Themis family P/2008 R1 (Garradd) : Scattered MBCs from larger distances
P/2008 R1 (Garradd)(Jewitt, Yang & Haghighipour 2009) P/2008 R1 (GARRADD) Unstable (~32 Myr) Scattered object
P/2010 R2 (La Sagra)(Hsieh, Yang, Haghighipour et al 2012) Stable over 100 Myr Native to its current orbit
P/2006 VW139(Hsieh, Yang, Haghighipour et al 2012) Stable over 100 Myr Native to its location 3.0512 3.0516 3.0520 3.02 3.04 3.06 3.08 (AU) (AU)
Conclusions • 133P/Elst-Pizarro is native to its current orbit and belongs to (~2.5 Gyr • old) Themis family and its (< 10 Myr old) Beagle sub-family • 176P (1999 RE70) is native to its orbit and belongs to Themis family • P/2005 U1 (Read), probably from Themis family, is unstable with a • lifetime slightly larger than 20 Myr • P/2008 R1 (Garradd), not native to its orbit, probably scattered into its • current orbit from (larger) distances in the asteroid belt • P/2010 R2 (La Sagra) and P/2006 VW139 are native to their current • location and are protected by two- and three-body mean motion • resonances with Jupiter and Saturn
9:4 2:1 Read RE70 Elst-Pizzaro Eccentricity a (AU)
Activation must have been recent Sublimation Rate Sun’s Brightness Albedo Latent Heat Radial Distance Radius dr/dt ~ 1 m/yr Assuming km-sized MBCs R ~ 3.1 AU A ~ 0.05 T ~ 150 K
Collisional Activation Mass-loss at tail = 0.03 kg/s = d ~ 15 m From observation Radius of the Vent Assuming V ~ 5 km/s, the projectile would be of m-size (Hsieh & Jewitt 2006)
Collision Probability • Disk Model • - Disk consists of m-sized bodies and one MBC (km-size) • Asteroids size distribution: N Dn , n = -2 to -4 • Assuming n = -2.5, Nm / Nkm = 106 • Considered 250,000 m-sized particles • - Disk surface density ~ r -3/2 • Particles’ eccentricity : 0 - 0.5 , randomly distributed • Particles’ inclination : 0 - 25 deg. Randomly distributed • The MBC was assumed to be Elst-Pizzaro
3 4 7 Percentage of collided particles 11 14 18 22 23 24 25 27 28 38 Averaged time between two collisions Averaged Collided Particles = 20% Averaged Collision Rate =1 every 47000 years Averaged Time of Collision (10k years) Semimajor Axis (AU)
Hydrogen-Helium gas envelope Accreting planetesimals of rock and ice Accreting rocky planetesimals Snow line Object a (AU) ei (deg) TJ d (km) Elst-Pizarro (133P/7968) 3.156 0.165 1.39 3.184 5.0 Read (P/2005 U1 ) 3.165 0.253 1.27 3.153 2.2 1999 RE70 (118401) 3.196 0.192 0.24 3.166 4.4