We perform $N$-body simulations of the early phases of open cluster evolution including a large population of planetesimals, initially arranged in Kuiper-belt like discs around each star. Using a new, 4th-order and time-reversible $N$-body code on Graphics Processing Units (GPUs), we evolve the whole system under the stellar gravity, i.e. treating planetesimals as test particles, and consider two types of initial cluster models, similar to IC348 and the Hyades, respectively. In both cases, planetesimals can be dynamically excited, transferred between stars or liberated to become free-floating (such as A/2017 U1 or 'Oumuamua) during the early cluster evolution. We find that planetesimals captured from another star are not necessarily dynamically distinct from those native to a star. After an encounter both native and captured planetesimals can exhibit aligned periastrons, qualitatively similar to that seen in the Solar system and commonly thought to be the signature of Planet 9. We discuss the implications of our results for both our Solar system and exoplanetary systems.
A 2000-2017 set of long-period comets with high-quality orbits of perihelion distance <1 AU is used to show that the objects that perish shortly before perihelion are nearly exclusively the Oort Cloud comets, especially those with perihelia within 0.6 AU of the Sun, intrinsically fainter, and dust poor. Their propensity for disintegration is much higher than predicted by Bortle's perihelion survival rule, prompting the author to propose a new synoptic index to be tested in future prognostication efforts. By their susceptibility to demise near the Sun, the nuclei of Oort Cloud comets differ dra…
1I/'Oumuamua is the first detected interstellar interloper. We test the hypothesis that it is representative of a background population of exo-Oort cloud objects ejected under the effect of post-main sequence mass loss and stellar encounters. We do this by comparing the cumulative number density of interstellar objects inferred from the detection of 1I/'Oumuamua to that expected from these two clearing processes. We consider the 0.08--8 M$_{\odot}$ mass range, take into account the dependencies with stellar mass, Galactocentric distance, and evolutionary state, and consider a wide range of siz…
The outer solar system exhibits an anomalous pattern of orbital clustering, characterized by an approximate alignment of the apsidal lines and angular momentum vectors of distant, long-term stable Kuiper belt objects. One explanation for this dynamical confinement is the existence of a yet-undetected planetary-mass object, "Planet Nine (P9)". Previous work has shown that trans-Neptunian objects, which originate within the scattered disk population of the Kuiper belt, can be corralled into orbital alignment by Planet Nine's gravity over ~Gyr timescales, and characteristic P9 parameters have bee…
Microlensing is generally thought to probe planetary systems only out to a few Einstein radii. Microlensing events generated by bound planets beyond about 10 Einstein radii generally do not yield any trace of their hosts, and so would be classified as free floating planets (FFPs). I show that it is already possible, using adaptive optics (AO), to constrain the presence of potential hosts to FFP candidates at separations comparable to the Oort Cloud. With next-generation telescopes, planets at Kuiper-Belt separations can be probed. Next generation telescopes will also permit routine vetting for…
We analyse the origin of three Centaurs with perihelia in the range 15 AU to 30 AU, inclinations above 70 deg and semi-major axes shorter than 100 AU. Based on long-term numerical simulations we conclude that these objects most likely originate from the Oort cloud rather than the Kuiper Belt or Scattered Disc. We estimate that there are currently between 1 and 200 of these high-inclination, high-perihelion Centaurs with absolute magnitude H<8.
The initial Galactic velocity vector for the recently discovered hyperbolic asteroid 1I/'Oumuamua (A/2017 U1) is calculated for before its encounter with our solar system. The latest orbit (JPL-13) shows that 'Oumuamua has eccentricity > 1 at 944σ\, significance (1.19936 +- 0.00021), i.e. clearly unbound. Assuming no non-gravitational forces, the object's inbound Galactic velocity was U, V, W = -11.457, -22.395, -7.746 (+-0.009, +-0.009, +-0.011) km/s (U towards Galactic center), with total heliocentric speed 26.32 +- 0.01 km/s. When the velocity is compared to the local stars, 'Oumuamua can b…
The recent discovery by Pan-STARRS1 of 1I/2017 U1 (`Oumuamua), on an unbound and hyperbolic orbit, offers a rare opportunity to explore the planetary formation processes of other stars, and the effect of the interstellar environment on a planetesimal surface. 1I/`Oumuamua's close encounter with the inner Solar System in 2017 October was a unique chance to make observations matching those used to characterize the small-body populations of our own Solar System. We present near-simultaneous g$^\prime$, r$^\prime$, and J photometry and colors of 1I/`Oumuamua from the 8.1-m Frederick C. Gillett Gem…
We study the dynamical properties of objects in hyperbolic orbits passing through the inner Solar system in the context of two different potential sources: interstellar space and the Oort cloud. We analytically derive the probability distributions of eccentricity, $e$, and perihelion distance, $q$, for each source and estimate the numbers of objects produced per unit of time as a function of these quantities. By comparing the numbers from the two sources, we assess which origin is more likely for a hyperbolic object having a given eccentricity and perihelion distance. We find that the likeliho…
Small-Body Science with the Nautilus Space Observatory: From Cislunar Space Resilience to Mapping the Kuiper-Belt-to-Oort-Cloud Transition
Massachusetts Institute of Technology（麻省理工学院）；Space Science Institute（太空科学研究所）；Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）；Steward Observatory, The University of Arizona（亚利桑那大学斯蒂沃德天文台）；Lunar and Planetary Laboratory, University of Arizona（亚利桑那大学月球与行星实验室）；Alien Earths Team, NASA ICAR/NExSS（NASA ICAR/NExSS 外星地球团队）；Space Telescope Science Institute（空间望远镜科学研究所）
We present an updated dynamical and statistical analysis of outer Oort cloud cometary evidence suggesting the sun has a wide-binary Jovian mass companion. The results support a conjecture that there exists a companion of mass ~ 1-4 M_Jup orbiting in the innermost region of the outer Oort cloud. Our most restrictive prediction is that the orientation angles of the orbit normal in galactic coordinates are centered on the galactic longitude of the ascending node Omega = 319 degree and the galactic inclination i = 103 degree (or the opposite direction) with an uncertainty in the normal direction s…
The recently discovered first interstellar object 1I/2017 U1 (`Oumuamua) has brightness that varies by a factor of 10, a range greater than that of any Solar System asteroid, a spectrum characteristic of Type D asteroids, and no evidence of evaporating volatiles, contrary to expectation for exo-Oort clouds. This object was the first example of the proposed "Jurads", objects depleted in volatiles and ejected from planetary systems during the post-main sequence evolution of their parent star. I suggest that heating by the star's giant stage fluidized a precursor cometary object as volatiles esca…
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-k…
Born as ice-rich planetesimals, cometary nuclei were gravitationally scattered onto their current orbits in the Kuiper Belt and the Oort Cloud during the giant planets' dynamical instability in the early stages of our Solar System's history. Here, we model the thermal evolution of planetesimals during and after the giant planet instability. We couple an adapted thermal evolution model to orbital trajectories provided by \textit{N}-body simulations to account for the planetesimals' orbital evolution, a parameter so far neglected by previous thermal evolution studies. Our simulations demonstrate…
A distant, massive planet in the outer solar system has recently been proposed to explain some observed features of extreme trans-Neptunian objects (TNOs). Here we use N-body simulations of the formation of the Kuiper belt and Oort cloud as well as a survey simulator to compare models of the solar system with and without a 9th planet to one another as well as to observations. The main mechanism for TNOs to be deposited into the distant ($a$ > au), detached ($q$ > au) region of the Kuiper Belt in the 8-planet model is Kozai-Lidov oscillation of objects in mean motion resonances (MMR) with Neptu…
This paper considers the dynamics of scattering of planetesimals or planetary embryos by a planet on a circumstellar orbit. We classify six regions in the planet's mass versus semimajor axis parameter space according to the dominant outcome for scattered objects: ejected, accreted, remaining, escaping, Oort Cloud, depleted Oort Cloud. We use these outcomes to consider which planetary system architectures maximise the observability of specific signatures, given that signatures should be detected first around systems with optimal architectures (if such systems exist in nature). Giant impact debr…
This chapter reviews accretion models for Kuiper belt objects (KBOs), discussing in particular the compatibility of the observed properties of the KBO population with the streaming instability paradigm. Then it discusses how the dynamical structure of the KBO population, including the formation of its 5 sub-components (cold, hot, resonant, scattered and fossilized), can be quantitatively understood in the framewok of the giant planet instability. We also establish the connections between the KBO population and the Trojans of Jupiter and Neptune, the irregular satellites of all giant planets, t…
Most known trans-Neptunian objects (TNOs) gravitationally scattering off the giant planets have orbital inclinations consistent with an origin from the classical Kuiper belt, but a small fraction of these "scattering TNOs" have inclinations that are far too large (i > 45 deg) for this origin. These scattering outliers have previously been proposed to be interlopers from the Oort cloud or evidence of an undiscovered planet. Here we test these hypotheses using N-body simulations and the 69 centaurs and scattering TNOs detected in the Outer Solar Systems Origins Survey and its predecessors. We co…
Most comets are volatile-rich bodies that have recently entered the inner solar system following long-term storage in the Kuiper belt and the Oort cloud reservoirs. These reservoirs feed several distinct, short-lived "small body" populations. Here, we present new measurements of the optical colors of cometary and comet-related bodies including long-period (Oort cloud) comets, Damocloids (probable inactive nuclei of long-period comets) and Centaurs (recent escapees from the Kuiper belt and precursors to the Jupiter family comets). We combine the new measurements with published data on short-per…
Microlensing and occultation are generally studied in the geometric optics limit. However, diffraction may be important when recently discovered Kuiper-Belt objects (KBOs) occult distant stars. In particular the effects of diffraction become more important as the wavelength of the observation and the distance to the KBO increase. For sufficiently distant and massive KBOs or Oort cloud objects not only is diffraction important but so is gravitational lensing. For an object similar to Eris but located in the Oort cloud, the signature of gravitational lensing would be detected easily during an oc…
In its 16 years of scientific measurements, the Spitzer Space Telescope performed a number of ground breaking and key infrared measurements of Solar System objects near and far. Targets ranged from the smallest planetesimals to the giant planets, and have helped us reform our understanding of these objects while also laying the groundwork for future infrared space-based observations like those to be undertaken by the James Webb Space Telescope in the 2020s. In this first Paper, we describe how the Spitzer Space Telescope advanced our knowledge of Solar System formation and evolution via observ…
The chance discovery of the first interstellar minor body, 1I/2017 U1 (`Oumuamua), indicates that we may have been visited by such objects in the past and that these events may repeat in the future. Unfortunately, minor bodies following nearly parabolic or hyperbolic paths tend to receive little attention: over 3/4 of those known have data-arcs shorter than 30 d and, consistently, rather uncertain orbit determinations. This fact suggests that we may have observed interstellar interlopers in the past, but failed to recognize them as such due to insufficient data. Early identification of promisi…
The detached object Sedna is likely at the inner edge of the Oort cloud, more precisely the inner Oort cloud (IOC). Until recently it was the sole member of this population. The recent discovery of the detached object 2012 VP113 has confirmed that there should be more objects in this region. Three additional IOC candidates with orbits much closer to Neptune have been proposed in the past decade since Sedna's discovery: 2000 CR105, 2004 VN112 and 2010 GB174. Sedna and 2012 VP113 have perhelia near 80 AU and semi-major axes over 250 AU. The latter three have perihelia between 44 AU and 50 AU and…
We simulate the formation and evolution of Oort clouds around the 200 nearest stars (within 16pc according to the Gaia DR2) database. This study is performed by numerically integrating the planets and minor bodies in orbit around the parent star and in the Galactic potential. The calculations start 1\,Gyr ago and continue for 100Myr into the future. In this time frame, we simulate how asteroids (and planets) are ejected from the star's vicinity and settle in an Oort cloud and how they escape the local stellar gravity to form tidal steams. A fraction of 0.0098 to 0.026 of the asteroids remain b…
Several lines of observational evidence suggest that white dwarfs receive small birth kicks due to anisotropic mass loss. If other stars possess extrasolar analogues to the Solar Oort cloud, the orbits of comets in such clouds will be scrambled by white dwarf natal kicks. Although most comets will be unbound, some will be placed on low angular momentum orbits vulnerable to sublimation or tidal disruption. The dusty debris from these comets will manifest itself as an IR excess temporarily visible around newborn white dwarfs; examples of such disks may already have been seen in the Helix Nebula,…
We study the development of activity in the incoming long-period comet C/2017 K2 over the heliocentric distance range 9 < r_H < 16 AU. The comet continues to be characterized by a coma of sub-millimeter and larger particles ejected at low velocity. In a fixed co-moving volume around the nucleus we find that the scattering cross-section of the coma is related to the heliocentric distance by a power law with heliocentric index $s = 1.14\pm0.05$. This dependence is significantly weaker than the inverse square variation of the insolation as a result of two effects. These are, first, the heliocentr…
The upcoming commencement of the Vera C. Rubin Observatory's Legacy Survey of Space of Time (LSST) will greatly enhance the discovery rate of interstellar objects (ISOs). `Oumuamua and Borisov were the first two ISOs confirmed in the Solar system, although the first interstellar meteor may have been discovered earlier. We discuss the properties of `Oumuamua and Borisov and explore the expected abundance of ISOs as a function of size in the solar neighborhood. We compare the expected abundance of ISOs to that of objects in the Oort cloud, and draw conclusions about the mass budget per star that…
The discovery of the intact minor planet embedded in the debris disc orbiting SDSS J1228+1040 raises questions about the dynamical history of the system. Further, the recent passage of the potentially interstellar object 1I/'Oumuamua within the solar system has re-ignited interest in minor body flux through exoplanetary systems. Here, we utilize the new analytical formalism from Grishin, Perets and Avni (2019) to estimate the rate at which the gaseous components of typical white dwarf discs trap an exo-planetesimal. We compare the types of captured orbits which arise from planetesimals origina…
Recent observations indicate that >99% of the small bodies in the Solar System reside in its outer reaches --- in the Kuiper Belt and Oort Cloud. Kuiper Belt bodies are probably the best preserved representatives of the icy planetesimals that dominated the bulk of the solid mass in the early Solar System. They likely contain preserved materials inherited from the protosolar cloud, held in cryogenic storage since the formation of the Solar System. Despite their importance, they are relatively underrepresented in our extraterrestrial sample collections by many orders of magnitude ($\sim$10$^{13}…
We calculate the gamma-ray albedo due to cosmic-ray interactions with debris (small rocks, dust, and grains) in the Oort Cloud. We show that under reasonable assumptions a significant proportion of what is called the "extragalactic gamma-ray background" could be produced at the outer frontier of the solar system and may be detectable by the Large Area Telescope, the primary instrument on the Fermi Gamma-Ray Space Telescope. If detected it could provide unique direct information about the total column density of material in the Oort Cloud that is difficult to access by any other method. The sam…
Gas has been detected in many exoplanetary systems ($>$10 Myr), thought to be released in the destruction of volatile-rich planetesimals orbiting in exo-Kuiper belts. In this letter, we aim to explore whether gas is also expected in the Kuiper belt (KB) in our Solar System. To quantify the gas release in our Solar System, we use models for gas release that have been applied to extrasolar planetary systems, as well as a physical model that accounts for gas released due to the progressive internal warming of large planetesimals. We find that only bodies larger than about 4 km can still contain C…
The Primordial Disk of small icy planetesimals, once located at 15-30 AU from the Sun, was disrupted by giant planet migration in the early Solar System. The Primordial Disk thereby became the source region of objects in the current-day Kuiper Belt, Scattered Disk, and Oort Cloud. I present the thermophysics code "Numerical Icy Minor Body evolUtion Simulator", or NIMBUS, and use it to study the thermophysical evolution of planetesimals in the Primordial Disk prior to its disruption. Such modelling is mandatory in order to understand the behaviour of dynamically new comets from the Oort Cloud, …
We have been conducting a survey for distant solar system objects beyond the Kuiper Belt edge (~50 AU) with new wide-field cameras on the Subaru 8 meter and CTIO 4 meter telescopes. We are interested in the orbits of objects that are decoupled from the giant planet region in order to understand the structure of the outer solar system, including whether a massive planet exists beyond a few hundred AU as first reported by Trujillo and Sheppard (2014). In addition to discovering extreme trans-Neptunian objects detailed elsewhere, we have found several objects with high perihelia (q>40 AU) that di…
The orbital architecture of the Solar System is thought to have been sculpted by a dynamical instability among the giant planets. During the instability a primordial outer disk of planetesimals was destabilized and ended up on planet-crossing orbits. Most planetesimals were ejected into interstellar space but a fraction were trapped on stable orbits in the Kuiper belt and Oort cloud. We use a suite of N-body simulations to map out the diversity of planetesimals' dynamical pathways. We focus on two processes: tidal disruption from very close encounters with a giant planet, and loss of surface v…
We have computed trajectories, distances and times of closest approaches to the Sun by stars in the Solar neighbourhood with known position, radial velocity and proper motions. For this purpose we have used a full potential model of the Galaxy that reproduces the local z-force, the Oort constants, the local escape velocity, and the rotation curve of the Galaxy. From our sample we constructed initial conditions, within observational uncertainties, with a Monte Carlo scheme for the twelve most suspicious candidates because of their small tangential motion. We find that the star Gliese 710 will h…
We examine a low energy mechanism for the transfer of meteoroids between two planetary systems embedded in a star cluster using quasi-parabolic orbits of minimal energy. Using Monte Carlo simulations, we find that the exchange of meteoroids could have been significantly more efficient than previously estimated. Our study is relevant to astrobiology as it addresses whether life on Earth could have been transferred to other planetary systems in the solar system's birth cluster and whether life on Earth could have been transferred here from beyond the solar system. In the solar system, the timesc…
