DOCSLIB.ORG

Forming Close-In Earths and Super-Earths Around Low Mass Stars

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Forming Close-In Earths and Super-Earths Around Low Mass Stars Forging the Vulcans: Forming Close-in Earths and Super-Earths around Low Mass Stars Subhanjoy Mohanty (Imperial College London) Jonathan Tan (University of Florida, Gainesville) VIEW FROM KEPLER-62F: artist’s impression Some Examples of Transiting Planets P=10.3d Kepler 62 bcdef: 5 planets around a Solar-type star, , M~4.3M R=1.97R♁ ♁ with 2 Super-Earths in the Habitable Zone M ≲ 9 M♁ BORUCKI et al. 2013 P=13.0d R=3.15R♁ , M~13.5M♁ M ≲ 4 M♁ P=22.7d R=3.43R♁ , M~6.1M♁ M ≲14 M♁ P=32.0d R=4.52R♁ , M~8.4M♁ M ≲ 36 M♁ P=46.7d R=2.61R♁ , M~2.3M♁ M ≲ 35 M♁ P=118.4d R=3.66R♁ , M <300M♁ Kepler 11 bcdefg: 6 Close-packed Low-mass, Low-density planets around a Solar-type star LISSAUER et al. 2011 Statistics around Solar-type Stars ~50% of Solar- type stars have close-in Earths & super-Earths ~50% of M dwarfs have PETIGURA et al. 2013 close-in Earths & super-Earths Statistics around Red Dwarfs (very low-mass stars) DRESSING et al. 2013 Formation Mechanisms Problem with normal MMSN: Not enough solid material at small radii to form multiple close-in super-Earths in situ 1. Formation at larger radii, followed by radial migration. But: produces planets trapped near mean motion resonances, while no such preference observed in close-in super-Earths 2. Planet-planet scattering, followed by tidal circularization. But: cannot explain low-dispersion in orbital inclinations 3. In-situ formation from disk with Σ > ΣMMSN . But: significant fraction of such disks would be grav. unstable 4. Preferential enrichment of inner disk in solids, followed by in-situ formation (Hansen & Murray ‘13; Chatterjee & Tan ‘14). MRI-driven Disk Accretion stellar X-ray ionization (Gammie 1996) (Chatterjee & Tan 2014) Current Treatment Only Qualitative treatment so far of location and strength of Pressure Barrier at Dead Zone Inner Boundary (DZIB): Assumes: (e.g., Chatterjee & Tan ‘14; Kretke et al. ‘09) 1. Ad hoc location of DZIB at T ~ 1200K 2. α-disk structure with some specified Mdot, with ad hoc α in MRI-active zone and a step change in α change across the DZIB BUT: Disk structure + B-field determines MRI-driven α, which In turn determines Mdot ! heating and disk structure ! COUPLED PROBLEM: for steady-state: Must solve disk structure and MRI eqns simultaneously Conditions for Ang. Mom. Transport by B-Fields 2 α = 1/(2β)= PB / 2Pg (where PB = B /4π) (Wardle 2007) (Mohanty, Ercolano & Turner 2013) Active Disk Equations STRUCTURE (Xiao et al in prep, adapted from CT14 and FKR, for α-disk model): (assume vertically isothermal) 0 0 1/2 1/2 Cs,vert = (kT / μmp) , zH = (2) (cs / Ω) 2 2 ρ = ρ0 exp[-(z/zH) ], P = P0 exp[-(z/zH) ] IONIZATION: Saha Equation at T for Na, K + dust + chemical network 2 α (B): Sol. to MRI eqns. for various B, for given structure and ionization (α = PB / 2Pg , PB = B /4π) 2 Mdot (B): Mdot = B h / 4Ω (~ 2π αPgh / Ω) α FLOOR Next Steps 1. Insert derived MRI-disk structure / α into hydro simulations (FARGO), to derive planet mass / gap opening (including vertical B-fields => smaller gap-opening mass) 2. Reinsert gap properties (width, height) into MRI calculations to derive Dead Zone retreat due to stellar X-rays, and location of new pressure boundary. 3. Reinsert into FARGO to calculate new planet mass / gap opening; repeat cycles 2 & 3 (until dust in disk runs out). 4. Repeat 1-3 including more accurate chemistry, for different Mdot and Mstar, to get planetary masses and separations as a function of Mdot and Mstar; compare statistically to Kepler (and later TESS etc) stats to validate. 5. Understand why Vulcans do NOT form around the 50% of low-mass stars. How to NOT Form Vulcans 1. HALL EFFECT: In the presence of an external field, can either enhance the MRI or quench it, depending on whether the field is aligned or anti-aligned with the spin-axis of the disk. Quenching the MRI in the inner disk removes the pressure trap (low-α continues in the mid-plane all the way to the disk inner truncation radius) and stops Vulcan formation. 2. Stellar magnetic fields are just such an external field in the inner disk. Generated in the stellar interior, so magnetic axis should be independent of spin-axis of the disk: 50% aligned, 50% anti-aligned: ⇒ Vulcans present around half the low-mass stars, absent in other half 3. Midplane in the inner disk is usually dominated by Ohmic resistivity, so Hall effect wouldn’t apply. BUT Hall dominates when the dust fraction becomes very small, so IS very important within dust sublimation radius. Conclusions 1. ~50% of all low mass stars: both solar-types and M dwarfs, have multiple Earth / super-Earth size planets at P < ~50-100d (Vulcans) 2. Inward migration of pebbles due to radial drift (gas-drag), followed by in-situ planet formation in an MRI-drive pressure trap at the DZIB, appears an excellent way to form the Vulcans. 3. Conversely, MRI-quenching by disk Hall effect due to stellar fields can explain why these planets are NOT formed in ~50% of low-mass stellar systems (e.g., in Solar System). 4. Detailed MRI calculations, coupled to hydrodynamic simulations, necessary to contruct a quantitative and testable model; underway.. 5. Comparisions to detailed data (Kepler, followed by TESS, CHEOPS) required to validate the model; will carry out… HST Spitzer Kepler Keck VLT PRESENT NEAR-FUTURE (5-10 yrs) JWST PLATO TESS GMT TMT ELT The End.
Load more

Recommended publications
  • 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.
    [Show full text]
  • Formation of TRAPPIST-1
    EPSC Abstracts Vol. 11, EPSC2017-265, 2017 European Planetary Science Congress 2017 EEuropeaPn PlanetarSy Science CCongress c Author(s) 2017 Formation of TRAPPIST-1 C.W Ormel, B. Liu and D. Schoonenberg University of Amsterdam, The Netherlands ([email protected]) Abstract start to drift by aerodynamical drag. However, this growth+drift occurs in an inside-out fashion, which We present a model for the formation of the recently- does not result in strong particle pileups needed to discovered TRAPPIST-1 planetary system. In our sce- trigger planetesimal formation by, e.g., the streaming nario planets form in the interior regions, by accre- instability [3]. (a) We propose that the H2O iceline (r 0.1 au for TRAPPIST-1) is the place where tion of mm to cm-size particles (pebbles) that drifted ice ≈ the local solids-to-gas ratio can reach 1, either by from the outer disk. This scenario has several ad- ∼ vantages: it connects to the observation that disks are condensation of the vapor [9] or by pileup of ice-free made up of pebbles, it is efficient, it explains why the (silicate) grains [2, 8]. Under these conditions plan- TRAPPIST-1 planets are Earth mass, and it provides etary embryos can form. (b) Due to type I migration, ∼ a rationale for the system’s architecture. embryos cross the iceline and enter the ice-free region. (c) There, silicate pebbles are smaller because of col- lisional fragmentation. Nevertheless, pebble accretion 1. Introduction remains efficient and growth is fast [6]. (d) At approx- TRAPPIST-1 is an M8 main-sequence star located at a imately Earth masses embryos reach their pebble iso- distance of 12 pc.
    [Show full text]
  • 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.
    [Show full text]
  • 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
    [Show full text]
  • 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.
    [Show full text]
  • 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.
    [Show full text]
  • 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.
    [Show full text]
  • 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.
    [Show full text]
  • Lecture 32 Planetary Accretion –
    Lecture 32 Planetary Accretion – Growth and Differentiation of Planet Earth Reading this week: White Ch 11 (sections 11.1 -11.4) Today – Guest Lecturer, Greg Ravizza 1. Earth Accretion 2. Core Formation – to be continued in Friday’s lecture Next time The core continued, plus, the origin of the moon GG325 L32, F2013 Growth and Differentiation of Planet Earth Last lecture we looked at Boundary Conditions for earth's early history as a prelude to deducing a likely sequence of events for planetary accretion. Today we consider three scenarios for actual accretion: homogeneous condensation/accretion, followed by differentiation – Earth accretes from materials of the same composition AFTER condensation, followed by differentiation heterogeneous condensation/accretion (partial fractionation of materials from each other) before and during planetary buildup – Earth accretes DURING condensation, forming a differentiated planet as it grows. something intermediate between these two end-members GG325 L32, F2013 1 Growth and Differentiation of Planet Earth Both homogeneous and heterogeneous accretion models require that the core segregates from the primitive solid Earth at some point by melting of accreted Fe. The molten Fe sinks to the Earth’s center because it is denser than the surrounding silicate rock and can flow through it in the form of droplets. However, the original distribution of the Fe and the size and character of the iron segregation event differ between these two models. GG325 L32, F2013 Heterogeneous accretion Earth builds up first from cooling materials (initially hot and then cool). This requires a very rapid build up of earth, perhaps within 10,000 yrs of the initiation of condensation.
    [Show full text]
  • 4. Planet Formation
    4. Planet formation So, where did all these planetary systems come from? Planets form in disks Reviews of how solar system formed: Lissauer (1993) Recent reviews of planet formation: Papaloizou & Terquem (2006); also Lissauer+, Durisen +, Nagasawa+, Dominik+ in Protostars and Planets V There are 14 observations formation models have to explain (Lissauer 1994), two of which are: • planets orbits are circular, coplanar, and in same direction • formation took less than a few Myr Planets form in circumstellar disks in a few Myr The idea that planets form in circumstellar disks (the solar nebula) goes back to Swedenborg (1734), Kant (1755) and Laplace (1796) Star Formation Basic picture (Shu et al. 1987): Stars form from the collapse of clouds of gas and sub-micron sized dust in the interstellar medium After ~1 Myr end up with a star and protoplanetary disk extending ~100 AU This disk disappears in ~10 Myr and is the site of planet formation Planet formation models There are two main competing theories for how planets form: • Core accretion (Safronov 1969; Lissauer 1993; Wetherill, Weidenschilling, Kenyon,…) • Gravitational instability (Kuiper 1951; Cameron 1962; Boss, Durisen,…) The core accretion models are more advanced, and this is how terrestrial planets formed, although models not without problems The origin of the giant planets, and of extrasolar planets, is still debated, but core accretion models reproduce most observations 0. Starting conditions Proto-stellar disk is composed of same material as star, since meteorites have same composition
    [Show full text]
  • Habitability of the Early Earth: Liquid Water Under a Faint Young Sun Facilitated by Strong Tidal Heating Due to a Nearby Moon
    Habitability of the early Earth: Liquid water under a faint young Sun facilitated by strong tidal heating due to a nearby Moon Ren´eHeller · Jan-Peter Duda · Max Winkler · Joachim Reitner · Laurent Gizon Draft July 9, 2020 Abstract Geological evidence suggests liquid water near the Earths surface as early as 4.4 gigayears ago when the faint young Sun only radiated about 70 % of its modern power output. At this point, the Earth should have been a global snow- ball. An extreme atmospheric greenhouse effect, an initially more massive Sun, release of heat acquired during the accretion process of protoplanetary material, and radioactivity of the early Earth material have been proposed as alternative reservoirs or traps for heat. For now, the faint-young-sun paradox persists as one of the most important unsolved problems in our understanding of the origin of life on Earth. Here we use astrophysical models to explore the possibility that the new-born Moon, which formed about 69 million years (Myr) after the ignition of the Sun, generated extreme tidal friction { and therefore heat { in the Hadean R. Heller Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 G¨ottingen, Germany E-mail: [email protected] J.-P. Duda G¨ottingenCentre of Geosciences, Georg-August-University G¨ottingen, 37077 G¨ottingen,Ger- many E-mail: [email protected] M. Winkler Max Planck Institute for Extraterrestrial Physics, Giessenbachstraße 1, 85748 Garching, Ger- many E-mail: [email protected] J. Reitner G¨ottingenCentre of Geosciences, Georg-August-University G¨ottingen, 37077 G¨ottingen,Ger- many G¨ottingenAcademy of Sciences and Humanities, 37073 G¨ottingen,Germany E-mail: [email protected] L.
    [Show full text]
  • The Nature of the Giant Exomoon Candidate Kepler-1625 B-I René Heller
    A&A 610, A39 (2018) https://doi.org/10.1051/0004-6361/201731760 Astronomy & © ESO 2018 Astrophysics The nature of the giant exomoon candidate Kepler-1625 b-i René Heller Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany e-mail: [email protected] Received 11 August 2017 / Accepted 21 November 2017 ABSTRACT The recent announcement of a Neptune-sized exomoon candidate around the transiting Jupiter-sized object Kepler-1625 b could indi- cate the presence of a hitherto unknown kind of gas giant moon, if confirmed. Three transits of Kepler-1625 b have been observed, allowing estimates of the radii of both objects. Mass estimates, however, have not been backed up by radial velocity measurements of the host star. Here we investigate possible mass regimes of the transiting system that could produce the observed signatures and study them in the context of moon formation in the solar system, i.e., via impacts, capture, or in-situ accretion. The radius of Kepler-1625 b suggests it could be anything from a gas giant planet somewhat more massive than Saturn (0:4 MJup) to a brown dwarf (BD; up to 75 MJup) or even a very-low-mass star (VLMS; 112 MJup ≈ 0:11 M ). The proposed companion would certainly have a planetary mass. Possible extreme scenarios range from a highly inflated Earth-mass gas satellite to an atmosphere-free water–rock companion of about +19:2 180 M⊕. Furthermore, the planet–moon dynamics during the transits suggest a total system mass of 17:6−12:6 MJup.
    [Show full text]