Solar System Origins Research Articles

Meet the primordial asteroid family.

Identification of an ancient family of asteroids may help constrain solar system origins

Col-OSSOS: z-Band Photometry Reveals Three Distinct TNO Surface Types

Abstract Several different classes of trans-Neptunian objects (TNOs) have been identified based on their optical and near-infrared colors. As part of the Colours of the Outer Solar System Origins Survey (Col-OSSOS), we have obtained g-, r-, and z-band photometry of 26 TNOs using Subaru and Gemini Observatories. Previous color surveys have not utilized z-band reflectance, and the inclusion of this band reveals significant surface reflectance variations between sub-populations. The colors of TNOs in g − r and r − z show obvious structure, and appear consistent with the previously measured bi-modality in g − r. The distribution of colors of the two dynamically excited surface types can be modeled using the two-component mixing models from Fraser & Brown. With the combination of g − r and r − z, the dynamically excited classes can be separated cleanly into red and neutral surface classes. In g − r and r − z, the two dynamically excited surface groups are also clearly distinct from the cold classical TNO surfaces, which are red, with and r − z ≲ 0.6, while all dynamically excited objects with similar g − r colors exhibit redder r − z colors. The z-band photometry makes it possible for the first time to differentiate the red excited TNO surfaces from the red cold classical TNO surfaces. The discovery of different r − z colors for these cold classical TNOs makes it possible to search for cold classical surfaces in other regions of the Kuiper Belt and to completely separate cold classical TNOs from the dynamically excited population, which overlaps in orbital parameter space.

OSSOS. VI. Striking Biases in the Detection of Large Semimajor Axis Trans-Neptunian Objects

Abstract The accumulating but small set of large semimajor axis trans-Neptunian objects (TNOs) shows an apparent clustering in the orientations of their orbits. This clustering must either be representative of the intrinsic distribution of these TNOs, or else have arisen as a result of observation biases and/or statistically expected variations for such a small set of detected objects. The clustered TNOs were detected across different and independent surveys, which has led to claims that the detections are therefore free of observational bias. This apparent clustering has led to the so-called “Planet 9” hypothesis that a super-Earth currently resides in the distant solar system and causes this clustering. The Outer Solar System Origins Survey (OSSOS) is a large program that ran on the Canada–France–Hawaii Telescope from 2013 to 2017, discovering more than 800 new TNOs. One of the primary design goals of OSSOS was the careful determination of observational biases that would manifest within the detected sample. We demonstrate the striking and non-intuitive biases that exist for the detection of TNOs with large semimajor axes. The eight large semimajor axis OSSOS detections are an independent data set, of comparable size to the conglomerate samples used in previous studies. We conclude that the orbital distribution of the OSSOS sample is consistent with being detected from a uniform underlying angular distribution.

NASA missions aim at asteroid oddballs.

Lucy and Psyche to explore solar system origins.

Dawes Review 7: The Tidal Downsizing Hypothesis of Planet Formation

AbstractTidal Downsizing scenario of planet formation builds on ideas proposed by Gerard Kuiper in 1951. Detailed simulations of self-gravitating discs, gas fragments, dust grain dynamics, and planet evolutionary calculations are summarised here and used to build a predictive population synthesis. A new interpretation of exoplanetary and debris disc data, the Solar System's origins, and the links between planets and brown dwarfs is offered. Tidal Downsizing predicts that presence of debris discs, sub-Neptune mass planets, planets more massive than ~ 5 Jupiter masses and brown dwarfs should not correlate strongly with the metallicity of the host. For gas giants of ~ Saturn to a few Jupiter mass, a strong host star metallicity correlation is predicted only inwards of a few AU from the host. Composition of massive cores is predicted to be dominated by rock rather than ices. Debris discs made by Tidal Downsizing have an innermost edge larger than about 1 au, have smaller total masses and are usually in a dynamically excited state. Planet formation in surprisingly young or very dynamic systems such as HL Tau and Kepler-444 may be a signature of Tidal Downsizing. Open questions and potential weaknesses of the hypothesis are pointed out.

OSSOS. IV. DISCOVERY OF A DWARF PLANET CANDIDATE IN THE 9:2 RESONANCE WITH NEPTUNE

ABSTRACT We report the discovery and orbit of a new dwarf planet candidate, 2015 RR245, by the Outer Solar System Origins Survey (OSSOS). The orbit of 2015 RR245 is eccentric (e = 0.586), with a semimajor axis near 82 au, yielding a perihelion distance of 34 au. 2015 RR245 has and absolute magnitude for an assumed albedo of p V = 12%, the object has a diameter of ∼670 km. Based on astrometric measurements from OSSOS and Pan-STARRS1, we find that 2015 RR245 is securely trapped on ten-megayear timescales in the 9:2 mean-motion resonance with Neptune. It is the first trans-Neptunian object (TNO) identified in this resonance. On hundred-megayear timescales, particles in 2015 RR245-like orbits depart and sometimes return to the resonance, indicating that 2015 RR245 likely forms part of the long-lived metastable population of distant TNOs that drift between resonance sticking and actively scattering via gravitational encounters with Neptune. The discovery of a 9:2 TNO stresses the role of resonances in the long-term evolution of objects in the scattering disk and reinforces the view that distant resonances are heavily populated in the current solar system. This object further motivates detailed modeling of the transient sticking population.

THE OUTER SOLAR SYSTEM ORIGINS SURVEY. I. DESIGN AND FIRST-QUARTER DISCOVERIES

We report the discovery, tracking and detection circumstances for 85 trans-Neptunian objects (TNOs) from the first 42 deg$^{2}$ of the Outer Solar System Origins Survey (OSSOS). This ongoing $r$-band Solar System survey uses the 0.9 deg$^{2}$ field-of-view MegaPrime camera on the 3.6 m Canada-France-Hawaii Telescope. Our orbital elements for these TNOs are precise to a fractional semi-major axis uncertainty $<0.1\%$. We achieve this precision in just two oppositions, as compared to the normal 3-5 oppositions, via a dense observing cadence and innovative astrometric technique. These discoveries are free of ephemeris bias, a first for large trans-Neptunian surveys. We also provide the necessary information to enable models of TNO orbital distributions to be tested against our TNO sample. We confirm the existence of a cold "kernel" of objects within the main cold classical Kuiper belt, and infer the existence of an extension of the "stirred" cold classical Kuiper belt to at least several AU beyond the 2:1 mean motion resonance with Neptune. We find that the population model of Petit et al. (2011) remains a plausible representation of the Kuiper belt. The full survey, to be completed in 2017, will provide an exquisitely characterized sample of important resonant TNO populations, ideal for testing models of giant planet migration during the early history of the Solar System.

OSSOS III—RESONANT TRANS-NEPTUNIAN POPULATIONS: CONSTRAINTS FROM THE FIRST QUARTER OF THE OUTER SOLAR SYSTEM ORIGINS SURVEY

ABSTRACT The first two observational sky “blocks” of the Outer Solar System Origins Survey (OSSOS) have significantly increased the number of well characterized observed trans-Neptunian objects (TNOs) in Neptune's mean motion resonances. We describe the 31 securely resonant TNOs detected by OSSOS so far, and we use them to independently verify the resonant population models from the Canada–France Ecliptic Plane Survey (CFEPS), with which we find broad agreement. We confirm that the 5:2 resonance is more populated than models of the outer solar system's dynamical history predict; our minimum population estimate shows that the high-eccentricity (e &gt; 0.35) portion of the resonance is at least as populous as the 2:1 and possibly as populated as the 3:2 resonance. One OSSOS block was well suited for detecting objects trapped at low libration amplitudes in Neptune's 3:2 resonance, a population of interest in testing the origins of resonant TNOs. We detected three 3:2 objects with libration amplitudes below the cutoff modeled by CFEPS; OSSOS thus offers new constraints on this distribution. The OSSOS detections confirm that the 2:1 resonance has a dynamically colder inclination distribution than either the 3:2 or 5:2 resonances. Using the combined OSSOS and CFEPS 2:1 detections, we constrain the fraction of 2:1 objects in the symmetric mode of libration to 0.2–0.85; we also constrain the fraction of asymmetric librators in the leading island, which has been theoretically predicted to vary depending on Neptune's migration history, to be 0.05–0.8. Future OSSOS blocks will improve these constraints.

OSSOS. II. A SHARP TRANSITION IN THE ABSOLUTE MAGNITUDE DISTRIBUTION OF THE KUIPER BELT’S SCATTERING POPULATION

ABSTRACT We measure the absolute magnitude, H, distribution, dN(H) ∝ 10 αH , of the scattering Trans-Neptunian Objects (TNOs) as a proxy for their size-frequency distribution. We show that the H-distribution of the scattering TNOs is not consistent with a single-slope distribution, but must transition around H g ∼ 9 to either a knee with a shallow slope or to a divot, which is a differential drop followed by second exponential distribution. Our analysis is based on a sample of 22 scattering TNOs drawn from three different TNO surveys—the Canada–France Ecliptic Plane Survey, Alexandersen et al., and the Outer Solar System Origins Survey, all of which provide well-characterized detection thresholds—combined with a cosmogonic model for the formation of the scattering TNO population. Our measured absolute magnitude distribution result is independent of the choice of cosmogonic model. Based on our analysis, we estimate that the number of scattering TNOs is (2.4–8.3) × 105 for H r &lt; 12. A divot H-distribution is seen in a variety of formation scenarios and may explain several puzzles in Kuiper Belt science. We find that a divot H-distribution simultaneously explains the observed scattering TNO, Neptune Trojan, Plutino, and Centaur H-distributions while simultaneously predicting a large enough scattering TNO population to act as the sole supply of the Jupiter-Family Comets.

Discovery and spectroscopy of the young jovian planet 51 Eri b with the Gemini Planet Imager.

Directly detecting thermal emission from young extrasolar planets allows measurement of their atmospheric compositions and luminosities, which are influenced by their formation mechanisms. Using the Gemini Planet Imager, we discovered a planet orbiting the ~20-million-year-old star 51 Eridani at a projected separation of 13 astronomical units. Near-infrared observations show a spectrum with strong methane and water-vapor absorption. Modeling of the spectra and photometry yields a luminosity (normalized by the luminosity of the Sun) of 1.6 to 4.0 × 10(-6) and an effective temperature of 600 to 750 kelvin. For this age and luminosity, "hot-start" formation models indicate a mass twice that of Jupiter. This planet also has a sufficiently low luminosity to be consistent with the "cold-start" core-accretion process that may have formed Jupiter.

European Space Agency announces comet landing site

Scientists believe that comets hold clues to the solar system's origins, and soon they will be one step closer to unlocking these secrets. Last week, the European Space Agency announced that the spacecraft Rosetta will deploy its lander, Philae, to land on the “head” of the comet 67/P Churyumov‐Gerasimenko at candidate site J. Project scientists have been racing to choose an ideal landing site since Rosetta arrived at the comet on 6 August. This event will mark the first landing mission on a comet.

Earth: Surprise found in comet dust: Odd mineral offers clues to solar system's origins

Earth: Surprise found in comet dust: Odd mineral offers clues to solar system's origins

Long Trek to Solar System's Last Frontier Begins

PLANETARY SCIENCENext week, a NASA spacecraft sets off to find out whether Pluto and the Kuiper belt hold the key to the solar system's origins. ([Read more][1].) [1]: http://www.sciencemag.org/cgi/content/full/311/5758/172

The cryo-penetrator: An approach to exploration of icy bodies in the solar system

The nuclei of comets and the small icy moons of the outer planets are thought to be the most primitive objects in the solar system. Because of their pristine nature, in-situ measurements of composition, temperature, and mechanical properties will be a powerful tool in realization of one of NASA's major objectives: determination of the Solar System's origins and evolution.Cryo penetrators are a new class of penetrator vehicle investigated intensively since 1985 for NASA's Comet Rendezvous/Asteroid Flyby (CRAF) mission. They are specifically optimized for penetration and operation in icy bodies at temperatures below 150 degrees K. The CRAF studies were directed at investigation of comet nuclei, but the same design should be applicable to the icy moons of the outer planets and, with appropriate delivery systems, (similar to those envisioned for NASA's MESUR mission) to the Martian polar caps.This paper describes the design of a cryopenetrator based on the CRAF Configuration and designed for in-situ measurements of a comet nucleus as part of the Comet Nucleus Penetrator (CNP) Discovery mission. The ROSETTA nucleus rendezvous mission recently selected by ESA is another potential cryo penetrator application.