A single sub-km Kuiper Belt object from a stellar Occultation in archival data

Department of Astronomy, 249-17, California Institute of Technology, Pasadena, California 91125, USA.
Nature (Impact Factor: 41.46). 12/2009; 462(7275):895-7. DOI: 10.1038/nature08608
Source: PubMed

ABSTRACT The Kuiper belt is a remnant of the primordial Solar System. Measurements of its size distribution constrain its accretion and collisional history, and the importance of material strength of Kuiper belt objects. Small, sub-kilometre-sized, Kuiper belt objects elude direct detection, but the signature of their occultations of background stars should be detectable. Observations at both optical and X-ray wavelengths claim to have detected such occultations, but their implied abundances are inconsistent with each other and far exceed theoretical expectations. Here we report an analysis of archival data that reveals an occultation by a body with an approximately 500-metre radius at a distance of 45 astronomical units. The probability of this event arising from random statistical fluctuations within our data set is about two per cent. Our survey yields a surface density of Kuiper belt objects with radii exceeding 250 metres of 2.1(-1.7)(+4.8) x 10(7) deg(-2), ruling out inferred surface densities from previous claimed detections by more than 5sigma. The detection of only one event reveals a deficit of sub-kilometre-sized Kuiper belt objects compared to a population extrapolated from objects with radii exceeding 50 kilometres. This implies that sub-kilometre-sized objects are undergoing collisional erosion, just like debris disks observed around other stars.

Download full-text


Available from: Shay Zucker, Sep 27, 2015
19 Reads
  • Source
    • "This is an important issue, since it relates to the total mass of distinct TNO populations and the origin and evolution of SPCs as small TNOs that penetrate the inner solar system after evolving over millions of years from trans-Neptunian distances (e.g., Jewitt 2002). In the near future, the observation of TNOs of cometary size (typically a few kilometers in diameter) will probably rely on stellar occultations (Cooray & Farmer 2003; Roques et al. 2003; Schlichting et al. 2009) or highly-sensitive survey programs (Larsen et al. 2007; Yoshida et al. 2011). 3.3 Identifying groups of TNOs in orbital space: Motivations and goals What are the main classes of TNOs, and what are their boundaries in orbital element space? "
    [Show abstract] [Hide abstract]
    ABSTRACT: Trans-Neptunian objects (TNOs) are icy/rocky bodies that move beyond the orbit of Neptune in a region known as the trans-Neptunian belt (or Edgeworth-Kuiper belt). In contrast to the predictions of accretion models that feature protoplanetary disk planetesimals evolving on dynamically cold orbits (with both very small eccentricities, e, and inclinations, i), in reality TNOs exhibit surprisingly wide ranges of orbital eccentricities and inclinations. Several theoretical models have addressed the origin and orbital evolution of the main dynamical classes of TNOs, but none have successfully reproduced them all. In addition, none have explained several objects on peculiar orbits, or provided insightful predictions, without which a model cannot be tested properly against observations. Based on extensive simulations of planetesimal disks with the presence of the four giant planets and huge numbers of modeled planetesimals, I explore in detail the dynamics of the TNOs, in particular their (un)stable regions over timescales comparable to the age of the solar system, and the role of resonances across the entire trans-Neptunian region. I also propose that, along with the orbital history of the giant planets, the orbital evolution of primordial embryos (massive planetesimals comparable to Mars-Earth masses) can explain the fine orbital structure of the trans-Neptunian belt, the orbits of Jovian and Neptunian Trojans, and possibly the current orbits of the giant planets. Those primordial embryos were ultimately scattered by the giant planets, a process that stirred both the orbits of the giant planets and the primordial planetesimal disk to the levels observed at 40-50 AU. In particular, the main constraints provided by the trans-Neptunian belt are optimally satisfied if at least one such primordial embryo (planetoid) survived in the outskirts of the solar system.
    12/2012; 1(3). DOI:10.5047/meep.2012.00103.0121
  • Source
    • "There remains debate as to the origin of this distribution at the largest sizes (Durda et al. 1998; Bottke et al. 2005; Morbidelli et al. 2009), but it is recognised that these populations have undergone, and continue to undergo, collisional evolution which means that their size distributions should also extend down to dust sizes. Exactly how the distributions extrapolate down is less well constrained (e.g., Schlichting et al. 2009). However, dust is seen in the inner Solar System that migrates inwards past the Earth due to Poynting-Robertson drag (Leinert & Grün 1990; Dermott et al. 2001), though it is debated as to whether this dust has an asteroidal or cometary origin (Durda & Dermott 1997; Nesvorn´y et al. 2010). "
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a new scheme for determining the shape of the size distribution, and its evolution, for collisional cascades of planetesimals undergoing destructive collisions and loss processes like Poynting-Robertson drag. The scheme treats the steady state portion of the cascade by equating mass loss and gain in each size bin; the smallest particles are expected to reach steady state on their collision timescale, while larger particles retain their primordial distribution. For collision-dominated disks, steady state means that mass loss rates in logarithmic size bins are independent of size. This prescription reproduces the expected two phase size distribution, with ripples above the blow-out size, and above the transition to gravity-dominated planetesimal strength. The scheme also reproduces the expected evolution of disk mass, and of dust mass, but is computationally much faster than evolving distributions forward in time. For low-mass disks, P-R drag causes a turnover at small sizes to a size distribution that is set by the redistribution function (the mass distribution of fragments produced in collisions). Thus information about the redistribution function may be recovered by measuring the size distribution of particles undergoing loss by P-R drag, such as that traced by particles accreted onto Earth. Although cross-sectional area drops with 1/age^2 in the PR-dominated regime, dust mass falls as 1/age^2.8, underlining the importance of understanding which particle sizes contribute to an observation when considering how disk detectability evolves. Other loss processes are readily incorporated; we also discuss generalised power law loss rates, dynamical depletion, realistic radiation forces and stellar wind drag.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The size distribution and total mass of objects in the Oort Cloud have important implications to the theory of planets formation, including the properties of, and the processes taking place in the early solar system. We discuss the potential of space missions like Kepler and CoRoT, designed to discover transiting exo-planets, to detect Oort Cloud, Kuiper Belt and main belt objects by occultations of background stars. Relying on published dynamical estimates of the content of the Oort Cloud, we find that Kepler's main program is expected to detect between 0 and ~100 occultation events by deca-kilometer-sized Oort Cloud objects. The occultations rate depends on the mass of the Oort cloud, the distance to its "inner edge", and the size distribution of its objects. In contrast, Kepler is unlikely to find occultations by Kuiper Belt or main belt asteroids, mainly due to the fact that it is observing a high ecliptic latitude field. Occultations by Solar System objects will appear as a photometric deviation in a single measurement, implying that the information regarding the time scale and light-curve shape of each event is lost. We present statistical methods that have the potential to verify the authenticity of occultation events by Solar System objects, to estimate the distance to the occulting population, and to constrain their size distribution. Our results are useful for planning of future space-based exo-planet searches in a way that will maximize the probability of detecting solar system objects, without hampering the main science goals. Comment: Submitted to ApJL, 5 pages, 1 figure
    The Astrophysical Journal Letters 12/2009; DOI:10.1088/2041-8205/711/1/L7 · 5.34 Impact Factor
Show more