Formation of TRAPPIST-1
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Exploring Exoplanet Populations with NASA's Kepler Mission
SPECIAL FEATURE: PERSPECTIVE PERSPECTIVE SPECIAL FEATURE: Exploring exoplanet populations with NASA’s Kepler Mission Natalie M. Batalha1 National Aeronautics and Space Administration Ames Research Center, Moffett Field, 94035 CA Edited by Adam S. Burrows, Princeton University, Princeton, NJ, and accepted by the Editorial Board June 3, 2014 (received for review January 15, 2014) The Kepler Mission is exploring the diversity of planets and planetary systems. Its legacy will be a catalog of discoveries sufficient for computing planet occurrence rates as a function of size, orbital period, star type, and insolation flux.The mission has made significant progress toward achieving that goal. Over 3,500 transiting exoplanets have been identified from the analysis of the first 3 y of data, 100 planets of which are in the habitable zone. The catalog has a high reliability rate (85–90% averaged over the period/radius plane), which is improving as follow-up observations continue. Dynamical (e.g., velocimetry and transit timing) and statistical methods have confirmed and characterized hundreds of planets over a large range of sizes and compositions for both single- and multiple-star systems. Population studies suggest that planets abound in our galaxy and that small planets are particularly frequent. Here, I report on the progress Kepler has made measuring the prevalence of exoplanets orbiting within one astronomical unit of their host stars in support of the National Aeronautics and Space Admin- istration’s long-term goal of finding habitable environments beyond the solar system. planet detection | transit photometry Searching for evidence of life beyond Earth is the Sun would produce an 84-ppm signal Translating Kepler’s discovery catalog into one of the primary goals of science agencies lasting ∼13 h. -
News Feature: the Mars Anomaly
NEWS FEATURE NEWS FEATURE The Mars anomaly The red planet’s size is at the heart of a rift of ideas among researchers modeling the solar system’s formation. Stephen Ornes, Science Writer The presence of water isn’t the only Mars mystery sci- debate, data, and computer simulations, until re- entists are keen to probe. Another centers around a cently most models predicted that Mars should be seemingly trivial characteristic of the Red Planet: its many times its observed size. Getting Mars to form size. Classic models of solar system formation predict attherightplacewiththerightsizeisacrucialpartof that the girth of rocky worlds should grow with their any coherent explanation of the solar system’sevo- distance from the sun. Venus and Earth, for example, lution from a disk of gas and dust to its current con- should exceed Mercury, which they do. Mars should at figuration. In trying to do so, researchers have been — least match Earth, which it doesn’t. The diameter of the forced to devise models that are more detailed and — RedPlanetislittlemorethanhalfthatofEarth(1,2). even wilder than any seen before. “We still don’t understand why Mars is so small,” Nebulous Notions says astronomer Anders Johansen, who builds com- The solar system began as an immense cloud of dust putational models of planet formation at Lund Univer- and gas called a nebula. The idea of a nebular origin sity in Sweden. “It’s a really compelling question that dates back nearly 300 years. In 1734, Swedish scientist drives a lot of new theories.” and mystic Emanuel Swedenborg—whoalsoclaimed Understanding the planet’s diminutive size is key that Martian spirits had communed with him—posited to knowing how the entire solar system formed. -
Setting the Stage: Planet Formation and Volatile Delivery
Noname manuscript No. (will be inserted by the editor) Setting the Stage: Planet formation and Volatile Delivery Julia Venturini1 · Maria Paula Ronco2;3 · Octavio Miguel Guilera4;2;3 Received: date / Accepted: date Abstract The diversity in mass and composition of planetary atmospheres stems from the different building blocks present in protoplanetary discs and from the different physical and chemical processes that these experience during the planetary assembly and evolution. This review aims to summarise, in a nutshell, the key concepts and processes operating during planet formation, with a focus on the delivery of volatiles to the inner regions of the planetary system. 1 Protoplanetary discs: the birthplaces of planets Planets are formed as a byproduct of star formation. In star forming regions like the Orion Nebula or the Taurus Molecular Cloud, many discs are observed around young stars (Isella et al, 2009; Andrews et al, 2010, 2018a; Cieza et al, 2019). Discs form around new born stars as a natural consequence of the collapse of the molecular cloud, to conserve angular momentum. As in the interstellar medium, it is generally assumed that they contain typically 1% of their mass in the form of rocky or icy grains, known as dust; and 99% in the form of gas, which is basically H2 and He (see, e.g., Armitage, 2010). However, the dust-to-gas ratios are usually higher in discs (Ansdell et al, 2016). There is strong observational evidence supporting the fact that planets form within those discs (Bae et al, 2017; Dong et al, 2018; Teague et al, 2018; Pérez et al, 2019), which are accordingly called protoplanetary discs. -
Water, Habitability, and Detectability Steve Desch
Water, Habitability, and Detectability Steve Desch PI, “Exoplanetary Ecosystems” NExSS team School of Earth and Space Exploration, Arizona State University with Ariel Anbar, Tessa Fisher, Steven Glaser, Hilairy Hartnett, Stephen Kane, Susanne Neuer, Cayman Unterborn, Sara Walker, Misha Zolotov Astrobiology Science Strategy NAS Committee, Beckmann Center, Irvine, CA (remotely), January 17, 2018 How to look for life on (Earth-like) exoplanets: find oxygen in their atmospheres How Earth-like must an exoplanet be for this to work? Seager et al. (2013) How to look for life on (Earth-like) exoplanets: find oxygen in their atmospheres Oxygen on Earth overwhelmingly produced by photosynthesizing life, which taps Sun’s energy and yields large disequilibrium signature. Caveats: Earth had life for billions of years without O2 in its atmosphere. First photosynthesis to evolve on Earth was anoxygenic. Many ‘false positives’ recognized because O2 has abiotic sources, esp. photolysis (Luger & Barnes 2014; Harman et al. 2015; Meadows 2017). These caveats seem like exceptions to the ‘rule’ that ‘oxygen = life’. How non-Earth-like can an exoplanet be (especially with respect to water content) before oxygen is no longer a biosignature? Part 1: How much water can terrestrial planets form with? Part 2: Are Aqua Planets or Water Worlds habitable? Can we detect life on them? Part 3: How should we look for life on exoplanets? Part 1: How much water can terrestrial planets form with? Theory says: up to hundreds of oceans’ worth of water Trappist-1 system suggests hundreds of oceans, especially around M stars Many (most?) planets may be Aqua Planets or Water Worlds How much water can terrestrial planets form with? Earth- “snow line” Standard Sun distance models of distance accretion suggest abundant water. -
The Formation of Jupiter by Hybrid Pebble-Planetesimal Accretion
The formation of Jupiter by hybrid pebble-planetesimal accretion Author: Yann Alibert1, Julia Venturini2, Ravit Helled2, Sareh Ataiee1, Remo Burn1, Luc Senecal1, Willy Benz1, Lucio Mayer2, Christoph Mordasini1, Sascha P. Quanz3, Maria Schönbächler4 Affiliations: 1Physikalisches Institut & Center for Space and Habitability, Universität Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland 2Institut for Computational Sciences, Universität Zürich, Winterthurstrasse 190, 8057 Zürich, Switzerland 3 Institute for Particle Physics and Astrophysics, ETH Zürich, Wolfgang-Pauli-Strasse 27, 8093 Zürich, Switzerland 4Institute of Geochemistry and Petrology, ETH Zürich, Clausiusstrasse 25, 8092 Zürich, Switzerland The standard model for giant planet formation is based on the accretion of solids by a growing planetary embryo, followed by rapid gas accretion once the planet exceeds a so- called critical mass1. The dominant size of the accreted solids (cm-size particles named pebbles or km to hundred km-size bodies named planetesimals) is, however, unknown1,2. Recently, high-precision measurements of isotopes in meteorites provided evidence for the existence of two reservoirs in the early Solar System3. These reservoirs remained separated from ~1 until ~ 3 Myr after the beginning of the Solar System's formation. This separation | downloaded: 6.1.2020 is interpreted as resulting from Jupiter growing and becoming a barrier for material transport. In this framework, Jupiter reached ~20 Earth masses (M⊕) within ~1 Myr and 3 slowly grew to ~50 M⊕ in the subsequent 2 Myr before reaching its present-day mass . The evidence that Jupiter slowed down its growth after reaching 20 M⊕ for at least 2 Myr is puzzling because a planet of this mass is expected to trigger fast runaway gas accretion4,5. -
Formation of the Solar System (Chapter 8)
Formation of the Solar System (Chapter 8) Based on Chapter 8 • This material will be useful for understanding Chapters 9, 10, 11, 12, 13, and 14 on “Formation of the solar system”, “Planetary geology”, “Planetary atmospheres”, “Jovian planet systems”, “Remnants of ice and rock”, “Extrasolar planets” and “The Sun: Our Star” • Chapters 2, 3, 4, and 7 on “The orbits of the planets”, “Why does Earth go around the Sun?”, “Momentum, energy, and matter”, and “Our planetary system” will be useful for understanding this chapter Goals for Learning • Where did the solar system come from? • How did planetesimals form? • How did planets form? Patterns in the Solar System • Patterns of motion (orbits and rotations) • Two types of planets: Small, rocky inner planets and large, gas outer planets • Many small asteroids and comets whose orbits and compositions are similar • Exceptions to these patterns, such as Earth’s large moon and Uranus’s sideways tilt Help from Other Stars • Use observations of the formation of other stars to improve our theory for the formation of our solar system • Use this theory to make predictions about the formation of other planetary systems Nebular Theory of Solar System Formation • A cloud of gas, the “solar nebula”, collapses inwards under its own weight • Cloud heats up, spins faster, gets flatter (disk) as a central star forms • Gas cools and some materials condense as solid particles that collide, stick together, and grow larger Where does a cloud of gas come from? • Big Bang -> Hydrogen and Helium • First stars use this -
Planet Formation by Pebble Accretion in Ringed Disks A
A&A 638, A1 (2020) https://doi.org/10.1051/0004-6361/202037983 Astronomy & © A. Morbidelli 2020 Astrophysics Planet formation by pebble accretion in ringed disks A. Morbidelli Département Lagrange, University of Nice – Sophia Antipolis, CNRS, Observatoire de la Côte d’Azur, Nice, France e-mail: [email protected] Received 19 March 2020 / Accepted 9 April 2020 ABSTRACT Context. Pebble accretion is expected to be the dominant process for the formation of massive solid planets, such as the cores of giant planets and super-Earths. So far, this process has been studied under the assumption that dust coagulates and drifts throughout the full protoplanetary disk. However, observations show that many disks are structured in rings that may be due to pressure maxima, preventing the global radial drift of the dust. Aims. We aim to study how the pebble-accretion paradigm changes if the dust is confined in a ring. Methods. Our approach is mostly analytic. We derived a formula that provides an upper bound to the growth of a planet as a function of time. We also numerically implemented the analytic formulæ to compute the growth of a planet located in a typical ring observed in the DSHARP survey, as well as in a putative ring rescaled at 5 AU. Results. Planet Type I migration is stopped in a ring, but not necessarily at its center. If the entropy-driven corotation torque is desaturated, the planet is located in a region with low dust density, which severely limits its accretion rate. If the planet is instead near the ring’s center, its accretion rate can be similar to the one it would have in a classic (ringless) disk of equivalent dust density. -
University of Groningen Evaluating Galactic Habitability Using High
University of Groningen Evaluating galactic habitability using high-resolution cosmological simulations of galaxy formation Forgan, Duncan; Dayal, Pratika; Cockell, Charles; Libeskind, Noam Published in: International Journal of Astrobiology DOI: 10.1017/S1473550415000518 IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Final author's version (accepted by publisher, after peer review) Publication date: 2017 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Forgan, D., Dayal, P., Cockell, C., & Libeskind, N. (2017). Evaluating galactic habitability using high- resolution cosmological simulations of galaxy formation. International Journal of Astrobiology, 16(1), 60–73. https://doi.org/10.1017/S1473550415000518 Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license. More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne- amendment. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. -
Why Should We Care About TRAPPIST-1?
PUBLISHED: 27 MARCH 2017 | VOLUME: 1 | ARTICLE NUMBER: 0104 news & views EXOPLANETS Why should we care about TRAPPIST-1? The discovery of a system of six (possibly system we’ve found with terrestrial planets seven) terrestrial planets around the tightly packed together and in resonance. TRAPPIST-1 star, announced in a paper Their orbits are also all co-planar, as the by Michaël Gillon and collaborators image shows, and luckily for us this orbital (Nature 542, 456–460; 2017) attracted a plane passes through the line of sight great deal of attention from researchers between us and TRAPPIST-1: all these as well as the general public. Reactions planets are ‘transiting’. This is much more ranged from the enthusiastic — already than a simple technical detail, as it allows us hypothesizing a string of inhabited to characterize all their atmospheres — an planets — to those who felt that it essential step to understand their climate didn’t add anything substantial to our and propensity for habitability. current knowledge of exoplanets and Finally and maybe most importantly, was ultimately not worth the hype. The these planets are distributed over all of cover of the Nature issue hosting the the three zones related to different phases paper (pictured), made by Robert Hurt, (IPAC) HURT NASA/JPL-CALTECH/ROBERT of water, as cleverly represented by the a visualization scientist at Caltech, is a illustration. However, this information, fine piece of artwork, but it also helps us They can thus be called ‘terrestrial’ without linked to the concept of habitable or in assessing the actual relevance of the any qualms about terminology. -
1 on the Origin of the Pluto System Robin M. Canup Southwest Research Institute Kaitlin M. Kratter University of Arizona Marc Ne
On the Origin of the Pluto System Robin M. Canup Southwest Research Institute Kaitlin M. Kratter University of Arizona Marc Neveu NASA Goddard Space Flight Center / University of Maryland The goal of this chapter is to review hypotheses for the origin of the Pluto system in light of observational constraints that have been considerably refined over the 85-year interval between the discovery of Pluto and its exploration by spacecraft. We focus on the giant impact hypothesis currently understood as the likeliest origin for the Pluto-Charon binary, and devote particular attention to new models of planet formation and migration in the outer Solar System. We discuss the origins conundrum posed by the system’s four small moons. We also elaborate on implications of these scenarios for the dynamical environment of the early transneptunian disk, the likelihood of finding a Pluto collisional family, and the origin of other binary systems in the Kuiper belt. Finally, we highlight outstanding open issues regarding the origin of the Pluto system and suggest areas of future progress. 1. INTRODUCTION For six decades following its discovery, Pluto was the only known Sun-orbiting world in the dynamical vicinity of Neptune. An early origin concept postulated that Neptune originally had two large moons – Pluto and Neptune’s current moon, Triton – and that a dynamical event had both reversed the sense of Triton’s orbit relative to Neptune’s rotation and ejected Pluto onto its current heliocentric orbit (Lyttleton, 1936). This scenario remained in contention following the discovery of Charon, as it was then established that Pluto’s mass was similar to that of a large giant planet moon (Christy and Harrington, 1978). -
The Planetary Luminosity Problem:" Missing Planets" and The
Draft version March 27, 2020 Typeset using LATEX twocolumn style in AASTeX62 The Planetary Luminosity Problem: \Missing Planets" and the Observational Consequences of Episodic Accretion Sean D. Brittain,1, ∗ Joan R. Najita,2 Ruobing Dong,3 and Zhaohuan Zhu4 1Clemson University 118 Kinard Laboratory Clemson, SC 29634, USA 2National Optical Astronomical Observatory 950 North Cherry Avenue Tucson, AZ 85719, USA 3Department of Physics & Astronomy University of Victoria Victoria BC V8P 1A1, Canada 4Department of Physics and Astronomy University of Nevada, Las Vegas 4505 S. Maryland Pkwy. Las Vegas, NV 89154, USA (Received March 27, 2020; Revised TBD; Accepted TBD) Submitted to ApJ ABSTRACT The high occurrence rates of spiral arms and large central clearings in protoplanetary disks, if interpreted as signposts of giant planets, indicate that gas giants form commonly as companions to young stars (< few Myr) at orbital separations of 10{300 au. However, attempts to directly image this giant planet population as companions to more mature stars (> 10 Myr) have yielded few successes. This discrepancy could be explained if most giant planets form \cold start," i.e., by radiating away much of their formation energy as they assemble their mass, rendering them faint enough to elude detection at later times. In that case, giant planets should be bright at early times, during their accretion phase, and yet forming planets are detected only rarely through direct imaging techniques. Here we explore the possibility that the low detection rate of accreting planets is the result of episodic accretion through a circumplanetary disk. We also explore the possibility that the companion orbiting the Herbig Ae star HD 142527 may be a giant planet undergoing such an accretion outburst. -
Strong Accretion on a Deuterium-Burning Brown Dwarf? F
Astronomy & Astrophysics manuscript no. GY11* c ESO 2010 June 27, 2010 Strong accretion on a deuterium-burning brown dwarf? F. Comeron´ 1, L. Testi1, and A. Natta2 1 ESO, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Munchen,¨ Germany e-mail: [email protected] 2 Osservatorio Astrofisico di Arcetri, INAF, Largo E. Fermi 5, I-50125 Firenze, Italy Received ; accepted ABSTRACT Context. The accretion processes that accompany the earliest stages of star formation have been shown in recent years to extend to masses well below the substellar limit, and even to masses close to the deuterium-burning limit, suggesting that the features characteristic of the T Tauri phase are also common to brown dwarfs. Aims. We discuss new observations of GY 11, a young brown dwarf in the ρ Ophiuchi embedded cluster. Methods. We have obtained for the first time low resolution long-slit spectroscopy of GY 11 in the red visible region, using the FORS1 instrument at the VLT. The spectral region includes accretion diagnostic lines such as Hα and the CaII infrared triplet. Results. The visible spectrum allows us to confirm that GY 11 lies well below the hydrogen-burning limit, in agreement with earlier findings based on the near-infrared spectral energy distribution. We obtain an improved derivation of its physical parameters, which −3 suggest that GY 11 is on or near the deuterium-burning phase. We estimate a mass of 30 MJup, a luminosity of 6 × 10 M , and a temperature of 2700 K. We detect strong Hα and CaII triplet emission, and we estimate from the latter an accretion rate M˙ acc = −10 −1 9:5 × 10 M yr , which places GY 11 among the objects with the largest M˙ acc=M∗ ratios measured thus far in their mass range.