Sedna and the Oort Cloud around a migrating Sun

Abstract Recent numerical simulations have demonstrated that the Sun’s dynamical history within the Milky Way may be much more complex than that suggested by its current low peculiar velocity (Sellwood, J.A., Binney, J.J. [2002]. Mon. Not. R. Astron. Soc. 336, 785–796; Roskar, R., Debattista, V.P., Quinn, T.R., Stinson, G.S., Wadsley, J. [2008]. Astrophys. J. 684, L79–L82). In particular, the Sun may have radially migrated through the galactic disk by up to 5–6 kpc (Roskar, R., Debattista, V.P., Quinn, T.R., Stinson, G.S., Wadsley, J. [2008]. Astrophys. J. 684, L79–L82). This has important ramifications for the structure of the Oort Cloud, as it means that the Solar System may have experienced tidal and stellar perturbations that were significantly different from its current local galactic environment. To characterize the effects of solar migration within the Milky Way, we use direct numerical simulations to model the formation of an Oort Cloud around stars that end up on solar-type orbits in a galactic-scale simulation of a Milky Way-like disk formation. Surprisingly, our simulations indicate that Sedna’s orbit may belong to the classical Oort Cloud. Contrary to previous understanding, we show that field star encounters play a pivotal role in setting the Oort Cloud’s extreme inner edge, and due to their stochastic nature this inner edge sometimes extends to Sedna’s orbit. The Sun’s galactic migration heightens the chance of powerful stellar passages, and Sedna production occurs around ∼20–30% of the solar-like stars we study. Considering the entire Oort Cloud, we find its median distance depends on the minimum galactocentric distance attained during the Sun’s orbital history. The inner edge also shows a similar dependence but with increased scatter due to the effects of powerful stellar encounters. Both of these Oort Cloud parameters can vary by an order of magnitude and are usually overestimated by an Oort Cloud formation model that assumes a fixed galactic environment. In addition, the amount of material trapped in outer Oort Cloud orbits ( a  > 20,000 AU) can be extremely low and may present difficulties for traditional models of Oort Cloud formation and long-period comet production.

[1]  Ž. Ivezić,et al.  THE GENESIS OF THE MILKY WAY'S THICK DISK VIA STELLAR MIGRATION , 2010, 1009.5997.

[2]  S. White,et al.  A Universal Density Profile from Hierarchical Clustering , 1996, astro-ph/9611107.

[3]  H. Rix,et al.  Nonaxisymmetric structures in the stellar disks of galaxies , 1995, astro-ph/9505111.

[4]  Martin J. Duncan,et al.  Embedded star clusters and the formation of the Oort Cloud , 2006 .

[5]  P. Weissman The Oort cloud , 1990, Nature.

[6]  T. Quinn,et al.  Gasoline: a flexible, parallel implementation of TreeSPH , 2003, astro-ph/0303521.

[7]  Jan H. Oort,et al.  The structure of the cloud of comets surrounding the Solar System and a hypothesis concerning its origin , 1950 .

[8]  M. Duncan,et al.  Embedded star clusters and the formation of the Oort cloud II. The effect of the primordial solar nebula , 2007 .

[9]  J. Wisdom Symplectic Correctors for Canonical Heliocentric n-Body Maps , 2006 .

[10]  M. Schwamb,et al.  PROPERTIES OF THE DISTANT KUIPER BELT: RESULTS FROM THE PALOMAR DISTANT SOLAR SYSTEM SURVEY , 2010, 1007.2954.

[11]  K. Menten,et al.  TRIGONOMETRIC PARALLAXES OF MASSIVE STAR-FORMING REGIONS. I. S 252 & G232.6+1.0 , 2008, 0811.0595.

[12]  L. Hou,et al.  The spiral structure of our Milky Way Galaxy , 2009, 0903.0721.

[13]  Harold F. Levison,et al.  Dynamics of the Giant Planets of the Solar System in the Gaseous Protoplanetary Disk and Their Relationship to the Current Orbital Architecture , 2007, 0706.1713.

[14]  Julio A. Fernández,et al.  The Buildup of a Tightly Bound Comet Cloud around an Early Sun Immersed in a Dense Galactic Environment: Numerical Experiments , 2000 .

[15]  James Binney,et al.  Chemical evolution with radial mixing , 2008, 0809.3006.

[16]  Julio A. Fernández The Formation of the Oort Cloud and the Primitive Galactic Environment , 1997 .

[17]  M. Duncan,et al.  Embedded star clusters and the formation of the Oort cloud. III. Evolution of the inner cloud during the Galactic phase , 2008 .

[18]  J. Binney,et al.  The uncertainty in Galactic parameters , 2009, 0907.4685.

[19]  Harold F. Levison,et al.  The Origin of Halley-Type Comets: Probing the Inner Oort Cloud , 2000 .

[20]  B. Gladman,et al.  Production of the Extended Scattered Disk by Rogue Planets , 2006 .

[21]  Robert Jedicke,et al.  Pan-STARRS: A Large Synoptic Survey Telescope Array , 2002, SPIE Astronomical Telescopes + Instrumentation.

[22]  Stellar encounters as the origin of distant Solar System objects in highly eccentric orbits , 2004, Nature.

[23]  S. Tremaine,et al.  The Formation and Extent of the Solar System Comet Cloud , 1987 .

[24]  Zeljko Ivezic,et al.  The Milky Way Tomography with SDSS , 2005 .

[25]  K. Tsiganis,et al.  Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets , 2005, Nature.

[26]  J. Binney DYNAMICS OF DISKS , 2007 .

[27]  Harold F. Levison,et al.  Capture of the Sun's Oort Cloud from Stars in Its Birth Cluster , 2010, Science.

[28]  B. Collins,et al.  A UNIFIED THEORY FOR THE EFFECTS OF STELLAR PERTURBATIONS AND GALACTIC TIDES ON OORT CLOUD COMETS , 2010, 1010.0477.

[29]  A SEARCH FOR DISTANT SOLAR SYSTEM BODIES IN THE REGION OF SEDNA , 2009, 0901.4173.

[30]  Joseph M. Hahn,et al.  Completing the inventory of the solar system , 1996 .

[31]  J. Lissauer,et al.  A Widebinary Solar Companion as a Possible Origin of Sedna-like Objects , 2006 .

[32]  S. Tremaine,et al.  The influence of the Galactic tidal field on the Oort comet cloud , 1986 .

[33]  J. Anthony Tyson,et al.  Survey and Other Telescope Technologies and Discoveries , 2002 .

[34]  Harold F. Levison,et al.  Origin of the structure of the Kuiper belt during a dynamical instability in the orbits of Uranus and Neptune , 2007, 0712.0553.

[35]  N. Kaib,et al.  DECREASING COMPUTING TIME WITH SYMPLECTIC CORRECTORS IN ADAPTIVE TIMESTEPPING ROUTINES , 2010, 1011.3830.

[36]  J. Binney Radial mixing in galactic discs , 2002, astro-ph/0203510.

[37]  R. Wielen,et al.  On the birth-place of the Sun and the places of formation of other nearby stars , 1996 .

[38]  Harold F. Levison,et al.  From the Kuiper Belt to Jupiter-Family Comets: The Spatial Distribution of Ecliptic Comets☆ , 1997 .

[39]  N. Kaib,et al.  The formation of the Oort cloud in open cluster environments , 2007, 0707.4515.

[40]  G. Stinson,et al.  Star formation and feedback in smoothed particle hydrodynamic simulations – I. Isolated galaxies , 2006, astro-ph/0602350.

[41]  Dayton L. Jones,et al.  Stellar encounters with the solar system , 2001 .

[42]  Chadwick Trujillo,et al.  Discovery of a Candidate Inner Oort Cloud Planetoid , 2004, astro-ph/0404456.

[43]  G. Stinson,et al.  Riding the Spiral Waves: Implications of Stellar Migration for the Properties of Galactic Disks , 2008, 0808.0206.

[44]  P. A. Dybczy'nski,et al.  Where do long‐period comets come from? Moving through the Jupiter–Saturn barrier , 2011, 1102.0154.

[45]  G. A. Moellenbrock,et al.  TRIGONOMETRIC PARALLAXES OF MASSIVE STAR-FORMING REGIONS. VI. GALACTIC STRUCTURE, FUNDAMENTAL PARAMETERS, AND NONCIRCULAR MOTIONS , 2009, 0902.3913.

[46]  F. Adams The Birth Environment of the Solar System , 2010, 1001.5444.

[47]  David Schlegel,et al.  The Milky Way Tomography with SDSS. I. Stellar Number Density Distribution , 2005, astro-ph/0510520.

[48]  M. Mayor,et al.  The Geneva–Copenhagen Survey of the Solar Neighbourhood , 2004, Publications of the Astronomical Society of Australia.

[49]  Mauri J. Valtonen,et al.  Periodic Modulation of the Oort Cloud Comet Flux by the Adiabatically Changing Galactic Tide , 1995 .

[50]  R. Muller,et al.  Tidal gravitational forces: The infall of “new” comets and comet showers , 1986 .

[51]  The Evolution of Long-Period Comets , 1997, astro-ph/9705153.

[52]  P. Weissman,et al.  Oort Cloud Formation and Dynamics , 2004 .

[53]  H. Rickman,et al.  The key role of massive stars in Oort cloud comet dynamics , 2011 .

[54]  H. Rickman,et al.  Injection of Oort Cloud comets: the fundamental role of stellar perturbations , 2008, 0804.2560.

[55]  N. Kaib,et al.  Oort cloud formation at various Galactic distances , 2010 .

[56]  K. Tsiganis,et al.  Origin of the orbital architecture of the giant planets of the Solar System , 2005, Nature.

[57]  M. E. Brown,et al.  Discovery of a Planetary-sized Object in the Scattered Kuiper Belt , 2005, astro-ph/0508633.

[58]  M. Haywood Radial mixing and the transition between the thick and thin Galactic discs , 2008, 0805.1822.

[59]  R. Davies,et al.  Astronomical Society of the Pacific Conference Series , 2010 .

[60]  Nathan A. Kaib,et al.  Reassessing the Source of Long-Period Comets , 2009, Science.

[61]  P. J. Francis,et al.  The Demographics of Long-Period Comets , 2005, astro-ph/0509074.

[62]  C. Lada,et al.  Embedded Clusters in Molecular Clouds , 2003, astro-ph/0301540.

[63]  J. Stadel Cosmological N-body simulations and their analysis , 2001 .

[64]  Julio A. Fernández,et al.  On The Origin of The High-Perihelion Scattered Disk: The Role of The Kozai Mechanism And Mean Motion Resonances , 2005 .

[65]  S. Tremaine,et al.  The frequency and intensity of comet showers from the Oort cloud , 1987 .

[66]  H. Jahreiss,et al.  Towards a fully consistent Milky Way disc model – I. The local model based on kinematic and photometric data , 2009, 0910.3481.

[67]  C. Flynn,et al.  The local density of matter mapped by hipparcos , 1998, astro-ph/9812404.

[68]  M. Duncan,et al.  A disk of scattered icy objects and the origin of Jupiter-family comets. , 1997, Science.

[69]  A. Just,et al.  Towards a fully consistent Milky Way disc model – II. The local disc model and SDSS data of the NGP region , 2010, 1010.2655.