Journal articles on the topic 'Planets'
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Kokaia, Giorgi, Melvyn B. Davies, and Alexander J. Mustill. "Effects of capturing a wide-orbit planet on planetary systems: system stability and habitable zone bombardment rates." Monthly Notices of the Royal Astronomical Society 511, no. 2 (December 31, 2021): 1685–93. http://dx.doi.org/10.1093/mnras/stab3659.
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ABSTRACT A large fraction of stars are formed in dense clusters. In the cluster, close encounters between stars at distances less than 100 au are common. It has been shown that during close encounters planets can transfer between stars. Such captured planets will be on different orbits compared to planets formed in the system, often on very wide, eccentric, and inclined orbits. We examine how these captured planets affect Kuiper belt-like planetesimal belts in their new systems by examining the effects on habitable planets in systems containing an outer gas giant. We show that these captured planets can destabilize the belt, and we show that the fraction of the planetesimals that make it past the giant planets into the system to impact the habitable planet is independent of the captured planet’s orbital plane, whereas the fraction of the planetesimals that are removed and the rate at which they are removed depend strongly on the captured planet’s pericentre and inclination. We then examine a wide range of outcomes of planet capture and find that when a Jupiter-mass planet is captured it will in 40 per cent of cases destabilize the giant planets in the system and in 40 per cent of cases deplete the belt in a few Myr, i.e. not posing much risk to life on terrestrial planets that would be expected to develop later. In the final 20 per cent of cases, the result will be a flux of impactors 10–20 times greater than that on Earth that can persist for several Gyr, detrimental to the development of life on the planet.
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Barr, Amy C., Vera Dobos, and László L. Kiss. "Interior structures and tidal heating in the TRAPPIST-1 planets." Astronomy & Astrophysics 613 (May 2018): A37. http://dx.doi.org/10.1051/0004-6361/201731992.
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Context. With seven planets, the TRAPPIST-1 system has among the largest number of exoplanets discovered in a single system so far. The system is of astrobiological interest, because three of its planets orbit in the habitable zone of the ultracool M dwarf. Aims. We aim to determine interior structures for each planet and estimate the temperatures of their rock mantles due to a balance between tidal heating and convective heat transport to assess their habitability. We also aim to determine the precision in mass and radius necessary to determine the planets’ compositions. Methods. Assuming the planets are composed of uniform-density noncompressible materials (iron, rock, H2O), we determine possible compositional models and interior structures for each planet. We also construct a tidal heat generation model using a single uniform viscosity and rigidity based on each planet’s composition. Results. The compositions for planets b, c, d, and e remain uncertain given the error bars on mass and radius. With the exception of TRAPPIST-1c, all have densities low enough to indicate the presence of significant H2O. Planets b and c experience enough heating from planetary tides to maintain magma oceans in their rock mantles; planet c may have surface eruptions of silicate magma, potentially detectable with next-generation instrumentation. Tidal heat fluxes on planets d, e, and f are twenty times higher than Earth’s mean heat flow. Conclusions. Planets d and e are the most likely to be habitable. Planet d avoids the runaway greenhouse state if its albedo is ≳0.3. Determining the planet’s masses within ~0.1–0.5 Earth masses would confirm or rule out the presence of H2O and/or iron. Understanding the geodynamics of ice-rich planets f, g, and h requires more sophisticated modeling that can self-consistently balance heat production and transport in both rock and ice layers.
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Jackson, Brian, Rory Barne, and Richard Greenberg. "Planetary Transits and Tidal Evolution." Proceedings of the International Astronomical Union 4, S253 (May 2008): 217–29. http://dx.doi.org/10.1017/s1743921308026434.
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AbstractTransiting planets are generally close enough to their host stars that tides may govern their orbital and thermal evolution. We present calculations of the tidal evolution of recently discovered transiting planets and discuss their implications. The tidal heating that accompanies this orbital evolution can be so great that it controls the planet's physical properties and may explain the large radii observed in several cases, including, for example, TrES-4. Also, since a planet's transit probability depends on its orbit, it evolves due to tides. Current values depend sensitively on the physical properties of the star and planet, as well as on the system's age. As a result, tidal effects may introduce observational biases in transit surveys, which may already be evident in current observations. Transiting planets tend to be younger than non-transiting planets, an indication that tidal evolution may have destroyed many close-in planets. Also the distribution of the masses of transiting planets may constrain the orbital inclinations of non-transiting planets.
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Franchini, Alessia, Rebecca G. Martin, and Stephen H. Lubow. "Multiplanet disc interactions in binary systems." Monthly Notices of the Royal Astronomical Society 491, no. 4 (November 22, 2019): 5351–60. http://dx.doi.org/10.1093/mnras/stz3175.
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ABSTRACT We investigate the evolution of a multiplanet–disc system orbiting one component of a binary star system. The planet–disc system is initially coplanar but misaligned to the binary orbital plane. The planets are assumed to be giants that open gaps in the disc. We first study the role of the disc in shaping the mutual evolution of the two planets using a secular model for low initial tilt. In general, we find that the planets and the disc do not remain coplanar, in agreement with previous work on the single planet case. Instead, the planets and the disc undergo tilt oscillations. A high-mass disc between the two planets causes the planets and the disc to nodally precess at the same average rate but they are generally misaligned. The amplitude of the tilt oscillations between the planets is larger while the disc is present. We then consider higher initial tilts using hydrodynamical simulations and explore the possibility of the formation of eccentric Kozai–Lidov (KL) planets. We find that the inner planet’s orbit undergoes eccentricity growth for a large range of disc masses and initial misalignments. For a low disc mass and large initial misalignment, both planets and the disc can undergo KL oscillations. Furthermore, we find that sufficiently massive discs can cause the inner planet to increase its inclination beyond 90° and therefore to orbit the binary in a retrograde fashion. The results have important implications for the explanation of very eccentric planets and retrograde planets observed in multiplanet systems.
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Schaefer, Laura K., and Vivien Parmentier. "The Air Over There: Exploring Exoplanet Atmospheres." Elements 17, no. 4 (August 1, 2021): 257–63. http://dx.doi.org/10.2138/gselements.17.4.257.
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The atmospheric composition for a rocky exoplanet will depend strongly on the planet’s bulk composition and orbital position. Nontraditional gases may be present in the atmospheres of exceptionally hot planets. Atmospheres of more clement planets will depend on the abundance of volatiles acquired during planet formation and atmospheric removal processes, including escape, condensation, and reaction with the surface. To date, observations of exoplanet atmospheres have focused on giant planets, but future space-and ground-based observatories will revolutionize the precision and spectral resolution with which we can probe an exoplanet’s atmosphere. This article consolidates lessons learned from the study of giant planet atmospheres, and points to the observations and challenges on the horizon for terrestrial planets.
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Garrido-Deutelmoser, Juan, Cristobal Petrovich, Leonardo Krapp, Kaitlin M. Kratter, and Ruobing Dong. "Substructures in Protoplanetary Disks Imprinted by Compact Planetary Systems." Astrophysical Journal 932, no. 1 (June 1, 2022): 41. http://dx.doi.org/10.3847/1538-4357/ac6bfd.
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Abstract The substructures observed in protoplanetary disks may be the signposts of embedded planets carving gaps or creating vortices. The inferred masses of these planets often fall in the Jovian regime despite their low abundance compared to lower-mass planets, partly because previous works often assume that a single substructure (a gap or vortex) is caused by a single planet. In this work, we study the possible imprints of compact systems composed of Neptune-like planets (∼10–30 M ⊕) and show that long-standing vortices are a prevalent outcome when their interplanetary separation (Δa) falls below ∼8 times H p—the average disk’s scale height at the planet’s locations. In simulations where a single planet is unable to produce long-lived vortices, two-planet systems can preserve them for at least 5000 orbits in two regimes: (i) fully shared density gaps with elongated vortices around the stable Lagrange points L 4 and L 5 for the most compact planet pairs (Δa ≲ 4.6 H p), and (ii) partially shared gaps for more widely spaced planets (Δa ∼ 4.6–8 H p) forming vortices in a density ring between the planets through the Rossby wave instability. The latter case can produce vortices with a wide range of aspect ratios down to ∼3 and can occur for planets captured into the 3:2 (2:1) mean-motion resonances for disks’ aspects ratios of h ≳ 0.033 (h ≳ 0.057). We suggest that their long lifetimes are sustained by the interaction of spiral density waves launched by the neighboring planets. Overall, our results show that the distinguishing imprint of compact systems with Neptune-mass planets are long-lived vortices inside the density gaps, which in turn are shallower than single-planet gaps for a fixed gap width.
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Kozhanov, T. S., and Nizyarov N. "Mathematical Theory of Motion of Revolving Axes on the Surface of Planets." International Astronomical Union Colloquium 178 (2000): 619–22. http://dx.doi.org/10.1017/s0252921100061790.
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Let a planet perform translational and rotational motions in the field of solar attraction. Let’s assume that the observer on the surface of the planet, knows (even approximately) an orbit and variations of orientation. It is necessary to clarify the motion of the instanteous rotation axis on the planet’s surface from the observer’s point of view on the planet’s surface.1. The coordinate system, to describe the translational and rotational motions of planets around the Sun we shall take into account the properties of orbits of solar system planets, namely: 1)All planets move in the same direction as the Sun revolves.2)At the present time, from June until December the Earth’s inhabitants see the north pole of the Sun and during the second half of year the southern one (Beleckei 1975, Menzel 1959).
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Li, Gongjie. "Tilting Planets during Planet Scattering." Astrophysical Journal Letters 915, no. 1 (June 25, 2021): L2. http://dx.doi.org/10.3847/2041-8213/ac0620.
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Fang, Julia, and Jean-Luc Margot. "PREDICTING PLANETS INKEPLERMULTI-PLANET SYSTEMS." Astrophysical Journal 751, no. 1 (April 30, 2012): 23. http://dx.doi.org/10.1088/0004-637x/751/1/23.
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Rauer, Heike, and Artie Hatzes. "Extrasolar planets and planet formation." Planetary and Space Science 55, no. 5 (April 2007): 535. http://dx.doi.org/10.1016/j.pss.2006.09.001.
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Maldonado, R. F., E. Villaver, A. J. Mustill, and M. Chávez. "Disentangling the parameter space: the role of planet multiplicity in triggering dynamical instabilities on planetary systems around white dwarfs." Monthly Notices of the Royal Astronomical Society 512, no. 1 (February 22, 2022): 104–15. http://dx.doi.org/10.1093/mnras/stac481.
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ABSTRACT Planets orbiting intermediate- and low-mass stars are in jeopardy as their stellar hosts evolve to white dwarfs (WDs) because the dynamics of the planetary system changes due to the increase of the planet:star mass ratio after stellar mass-loss. In order to understand how the planet multiplicity affects the dynamical stability of post-main sequence (MS) systems, we perform thousands of N-body simulations involving planetary multiplicity as the variable and with a controlled physical and orbital parameter space:equal-mass planets; the same orbital spacing between adjacent planet’s pairs; and orbits with small eccentricities and inclinations. We evolve the host star from the MS to the WD phase following the system dynamics for 10 Gyr. We find that the fraction of dynamically active simulations on the WD phase for two-planet systems is $10.2^{+1.2}_{-1.0}$–$25.2^{+2.5}_{-2.2}$ ${{\rm per\,cent}}$ and increases to $33.6^{+2.3}_{-2.2}$–$74.1^{+3.7}_{-4.6}$ ${{\rm per\,cent }}$ for the six-planet systems, where the ranges cover different ranges of initial orbital separations. Our simulations show that the more planets the system has, the more systems become unstable when the star becomes a WD, regardless of the planet masses and range of separations. Additional results evince that simulations with low-mass planets (1, 10 M⊕) lose at most two planets, have a large fraction of systems undergoing orbit crossing without planet losses, and are dynamically active for Gyr time-scales on the WD’s cooling track. On the other hand, systems with high-mass planets (100, 1000 M⊕) lose up to five planets, preferably by ejections, and become unstable in the first few hundred Myr after the formation of the WD.
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Cloutier, R., N. Astudillo-Defru, X. Bonfils, J. S. Jenkins, Z. Berdiñas, G. Ricker, R. Vanderspek, et al. "Characterization of the L 98-59 multi-planetary system with HARPS." Astronomy & Astrophysics 629 (September 2019): A111. http://dx.doi.org/10.1051/0004-6361/201935957.
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Aims. L 98-59 (TIC 307210830, TOI-175) is a nearby M3 dwarf around which TESS revealed three small transiting planets (0.80, 1.35, 1.57 Earth radii) in a compact configuration with orbital periods shorter than 7.5 days. Here we aim to measure the masses of the known transiting planets in this system using precise radial velocity (RV) measurements taken with the HARPS spectrograph. Methods. We considered both trained and untrained Gaussian process regression models of stellar activity, which are modeled simultaneously with the planetary signals. Our RV analysis was then supplemented with dynamical simulations to provide strong constraints on the planets’ orbital eccentricities by requiring long-term stability. Results. We measure the planet masses of the two outermost planets to be 2.42 ± 0.35 and 2.31 ± 0.46 Earth masses, which confirms the bulk terrestrial composition of the former and eludes to a significant radius fraction in an extended gaseous envelope for the latter. We are able to place an upper limit on the mass of the smallest, innermost planet of <1.01 Earth masses with 95% confidence. Our RV plus dynamical stability analysis places strong constraints on the orbital eccentricities and reveals that each planet’s orbit likely has e < 0.1. Conclusions. L 98-59 is likely a compact system of two rocky planets plus a third outer planet with a lower bulk density possibly indicative of the planet having retained a modest atmosphere. The system offers a unique laboratory for studies of planet formation, dynamical stability, and comparative atmospheric planetology as the two outer planets are attractive targets for atmospheric characterization through transmission spectroscopy. Continued RV monitoring will help refine the characterization of the innermost planet and potentially reveal additional planets in the system at wider separations.
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Yu, Fangyuan, and Dong Lai. "Free-floating Planets, Survivor Planets, Captured Planets, and Binary Planets from Stellar Flybys." Astrophysical Journal 970, no. 1 (July 1, 2024): 97. http://dx.doi.org/10.3847/1538-4357/ad4f81.
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Abstract In star clusters, close stellar encounters can strongly impact the architecture of a planetary system or even destroy it. We present a systematic study of the effects of stellar flybys on two-planet systems. When such a system experiences flybys, one or both planets can be ejected, forming free-floating planets (FFPs), captured planets (CPs) around the flyby star, and free-floating binary planets (BPs); the remaining single-surviving planets (SSPs) can have their orbital radii and eccentricities greatly changed. Through numerical experiments, we calculate the formation fractions (or branching ratios) of FFPs, SSPs, CPs, and BPs as a function of the pericenter distance of the flyby, and use them to derive analytical expressions for the formation rates of FFPs, SSPs, CPs and BPs in general cluster environments. We find that the production rates of FFPs and SSPs are similar (for the initial planet semimajor axis ratio a 1/a 2 = 0.6–0.8), while the rate for CPs is a few times smaller. The formation fraction of BPs depends strongly on a 1/a 2 and on the planet masses. For Jupiter-mass planets, the formation fraction of BPs is always less than 1% (for a 1/a 2 = 0.8) and typically much smaller (≲0.2% for a 1/a 2 ≲ 0.7). The fraction remains less than 1% when considering 4M J planets. Overall, when averaging over all flybys, the production rate of BPs is less than 0.1% of that of FFPs. We also derive the velocity distribution of FFPs produced by stellar flybys, and the orbital parameter distributions of SSPs, CPs, and BPs. These results can be used in future studies of exotic planets (including FFPs) and planetary systems.
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Gunell, Herbert, Romain Maggiolo, Hans Nilsson, Gabriella Stenberg Wieser, Rikard Slapak, Jesper Lindkvist, Maria Hamrin, and Johan De Keyser. "Why an intrinsic magnetic field does not protect a planet against atmospheric escape." Astronomy & Astrophysics 614 (June 2018): L3. http://dx.doi.org/10.1051/0004-6361/201832934.
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The presence or absence of a magnetic field determines the nature of how a planet interacts with the solar wind and what paths are available for atmospheric escape. Magnetospheres form both around magnetised planets, such as Earth, and unmagnetised planets, like Mars and Venus, but it has been suggested that magnetised planets are better protected against atmospheric loss. However, the observed mass escape rates from these three planets are similar (in the approximate (0.5–2) kg s−1 range), putting this latter hypothesis into question. Modelling the effects of a planetary magnetic field on the major atmospheric escape processes, we show that the escape rate can be higher for magnetised planets over a wide range of magnetisations due to escape of ions through the polar caps and cusps. Therefore, contrary to what has previously been believed, magnetisation is not a sufficient condition for protecting a planet from atmospheric loss. Estimates of the atmospheric escape rates from exoplanets must therefore address all escape processes and their dependence on the planet’s magnetisation.
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Marcy, Geoffrey W., R. Paul Butler, Steven S. Vogt, and Debra A. Fischer. "Extrasolar Planets and Prospects for Terrestrial Planets." Symposium - International Astronomical Union 213 (2004): 11–24. http://dx.doi.org/10.1017/s0074180900192903.
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Examination of ∼2000 sun–like stars has revealed 97 planets (as of 2002 Nov), all residing within our Milky Way Galaxy and within ∼200 light years of our Solar System. They have masses between 0.1 and 10 times that of Jupiter, and orbital sizes of 0.05–5 AU. Thus planets occupy the entire detectable domain of mass and orbits. News & summaries about extrasolar planets are provided at: http://exoplanets.org. These planets were all discovered by the wobble of the host stars, induced gravitationally by the planets, causing a periodicity in the measured Doppler effect of the starlight. Earth–mass planets remain undetectable, but space–based missions such as Kepler, COROT and SIM may provide detections of terrestrial planets within the next decade.The number of planets increases with decreasing planet mass, indicating that nature makes more small planets than jupiter–mass planets. Extrapolation, though speculative, bodes well for an even larger number of earth–mass planets. These observations and the theory of planet formation suggests that single sun–like stars commonly harbor earth–sized rocky planets, as yet undetectable. The number of planets increases with increasing orbital distance from the host star, and most known planets reside in non–circular orbits. Many known planets reside in the habitable zone (albeit being gas giants) and most newly discovered planets orbit beyond 1 AU from their star. A population of Jupiter–like planets may reside at 5–10 AU from stars, not easily detectable at present. The sunlike star 55 Cancri harbors a planet of 4–10 Jupiter masses orbiting at 5.5 AU in a low eccentricity orbit, the first analog of our Jupiter, albeit with two large planets orbiting inward.To date, 10 multiple–planet systems have been discovered, with four revealing gravitational interactions between the planets in the form of resonances. GJ 876 has two planets with periods of 1 and 2 months. Other planetary systems are “hierarchical”, consisting of widely separated orbits. These two system architectures probably result from gravitational interactions among the planets and between the planets and the proto-planetary disk out of which they formed.
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Chen, Cheng, Rebecca G. Martin, Stephen H. Lubow, and C. J. Nixon. "Tilted Circumbinary Planetary Systems as Efficient Progenitors of Free-floating Planets." Astrophysical Journal Letters 961, no. 1 (January 1, 2024): L5. http://dx.doi.org/10.3847/2041-8213/ad17c5.
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Abstract The dominant mechanism for generating free-floating planets has so far remained elusive. One suggested mechanism is that planets are ejected from planetary systems due to planet–planet interactions. Instability around a single star requires a very compactly spaced planetary system. We find that around binary star systems instability can occur even with widely separated planets that are on tilted orbits relative to the binary orbit due to combined effects of planet–binary and planet–planet interactions, especially if the binary is on an eccentric orbit. We investigate the orbital stability of planetary systems with various planet masses and architectures. We find that the stability of the system depends upon the mass of the highest-mass planet. The order of the planets in the system does not significantly affect stability, but, generally, the most massive planet remains stable and the lower-mass planets are ejected. The minimum planet mass required to trigger the instability is about that of Neptune for a circular orbit binary and a super-Earth of about 10 Earth masses for highly eccentric binaries. Hence, we suggest that planet formation around inclined binaries can be an efficient formation mechanism for free-floating planets. While most observed free-floating planets are giant planets, we predict that there should be more low-mass free-floating planets that are as of yet unobserved than higher-mass planets.
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Lee, Man Hoi, D. Fabrycky, and D. N. C. Lin. "Evidence for Solid Planets from Kepler's Near-Resonance Systems." Proceedings of the International Astronomical Union 8, S293 (August 2012): 100–105. http://dx.doi.org/10.1017/s1743921313012623.
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AbstractThe multiple-planet systems discovered by the Kepler mission show an excess of planet pairs with period ratios just wide of exact commensurability for first-order resonances like 2:1 and 3:2. In principle, these planet pairs could be in resonance if their orbital eccentricities are sufficiently small, because the width of first-order resonances diverges in the limit of vanishingly small eccentricity. We consider a widely-held scenario in which pairs of planets were captured into first-order resonances by migration due to planet-disk interactions, and subsequently became detached from the resonances, due to tidal dissipation in the planets. In the context of this scenario, we find a constraint on the ratio of the planet's tidal dissipation function and Love number that implies that some of the Kepler planets are likely solid. However, tides are not strong enough to move many of the planet pairs to the observed separations, suggesting that additional processes are at play.
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Marcy, Geoffrey W., and Andrew W. Howard. "The occurrence and the distribution of masses and radii of exoplanets." Proceedings of the International Astronomical Union 6, S276 (October 2010): 3–12. http://dx.doi.org/10.1017/s1743921311019867.
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AbstractWe analyze the statistics of Doppler-detected planets and Keplere-detected planet candidates of high integrity. We determine the number of planets per star as a function of planet mass, radius, and orbital period, and the occurrence of planets as a function of stellar mass. We consider only orbital periods less than 50 days around Solar-type (GK) stars, for which both Doppler and Kepler offer good completeness. We account for observational detection effects to determine the actual number of planets per star. From Doppler-detected planets discovered in a survey of 166 nearby G and K main sequence stars we find a planet occurrence of 15+5−4% for planets with M sin i = 3–30 ME and P < 50 d, as described in Howard et al. (2010). From Keplere, the planet occurrence is 0.130 ± 0.008, 0.023 ± 0.003, and 0.013 ± 0.002 planets per star for planets with radii 2–4, 4–8, and 8–32 RE, consistent with Doppler-detected planets. From Keplere, the number of planets per star as a function of planet radius is given by a power law, df/dlog R = kRRα with kR = 2.9+0.5−0.4, α = −1.92 ± 0.11, and R = RP/RE. Neither the Doppler-detected planets nor the Keplere-detected planets exhibit a “desert” at super-Earth and Neptune sizes for close-in orbits, as suggested by some planet population synthesis models. The distribution of planets with orbital period, P, shows a gentle increase in occurrence with orbital period in the range 2–50 d. The occurrence of small, 2–4 RE planets increases with decreasing stellar mass, with seven times more planets around low mass dwarfs (3600–4100 K) than around massive stars (6600–7100 K).
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Nagasawa, Makiko, Shigeru Ida, and Taisuke Bessho. "The formation of close-in planets by the slingshot model." Proceedings of the International Astronomical Union 3, S249 (October 2007): 279–84. http://dx.doi.org/10.1017/s1743921308016700.
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AbstractWe investigated the efficiency of planet scatterings in producing close-in planets by a direct inclusion of the dynamical tide effect into the simulations. We considered a system consists of three Jovian planets. Through a planet-planet scattering, one of the planets is sent into shorter orbit. If the eccentricity of the scattered planet is enough high, the tidal dissipation from the star makes the planetary orbit circular. We found that the short-period planets are formed at about 30% cases in our simulation and that Kozai mechanism plays an important role. In the Kozai mechanism, the high inclination obtained by planet-planet scattering is transformed to the eccentricity. It leads the pericenter of the innermost planet to approach the star close enough for tidal circularization. The formed close-in planets by this process have a widely spread inclination distribution. The degree of contribution of the process for the formation of close-in planets will be revealed by more observations of Rossiter-McLaughlin effects for transiting planets.
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Velgas, Lev Borisovich, and Liia Lvovna Iavolinskaia. "Seven main discoveries, rigorously proven." Interactive science, no. 6 (40) (June 21, 2019): 103–5. http://dx.doi.org/10.21661/r-496981.
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We are striving to prove that all planets rotate around their axis due to their satellites. Rotation of the collateral gravitation is analogous for all the planets, for the Sun as well. The Sun, as well as every single planet, can have multiple satellites. Satellite and planet’s collateral gravitation, if it moves because of satellite’s movement around the orbit, rotates the planet or the Sun. The article proves that collateral gravitation of the Moon and the Earth, that moves around the Earth due to Moon’s movement around the Earth, rotates the Earth around it’s axis.
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Wilhelm, Caitlyn, Rory Barnes, Russell Deitrick, and Rachel Mellman. "The Ice Coverage of Earth-like Planets Orbiting FGK Stars." Planetary Science Journal 3, no. 1 (January 1, 2022): 13. http://dx.doi.org/10.3847/psj/ac3b61.
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Abstract The photometric and spectroscopic signatures of habitable planets orbiting FGK stars may be modulated by surface ice coverage. To estimate its frequency and locations, we simulated the climates of hypothetical planets with a 1D energy balance model and assumed that the planets possess properties similar to modern Earth (mass, geography, atmosphere). We first simulated planets with fixed rotational axes and circular orbits, finding that the vast majority (≳ 90%) of planets with habitable surfaces are free of ice. For planets with partial ice coverage, the parameter space for ice caps (interannual ice located at the poles) is about as large as that for “ice belts” (interannual ice located at the equator), but belts only persist on land. We then performed simulations that mimicked perturbations from other planets by forcing sinusoidal orbital and rotational oscillations over a range of frequencies and amplitudes. We assume initially ice-free surfaces and set the initial eccentricity distribution to mirror known exoplanets, while the initial obliquity distribution matches planet formation predictions, i.e., favoring 90°. For these dynamic cases, we find again that ∼90% of habitable planets are free of surface ice for a range of assumptions for ice’s albedo. Planets orbiting F dwarfs are three times as likely to have ice caps than belts, but for planets orbiting K and G dwarfs ice belts are twice as likely as caps. In some cases, a planet’s surface ice can cycle between the equatorial and polar regions. Future direct imaging surveys of habitable planets may be able to test these predictions.
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Navarro, Thomas, Timothy M. Merlis, Nicolas B. Cowan, and Natalya Gomez. "Atmospheric Gravitational Tides of Earth-like Planets Orbiting Low-mass Stars." Planetary Science Journal 3, no. 7 (July 1, 2022): 162. http://dx.doi.org/10.3847/psj/ac76cd.
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Abstract Temperate terrestrial planets orbiting low-mass stars are subject to strong tidal forces. The effects of gravitational tides on the solid planet and that of atmospheric thermal tides have been studied, but the direct impact of gravitational tides on the atmosphere itself has so far been ignored. We first develop a simplified analytic theory of tides acting on the atmosphere of a planet. We then implement gravitational tides into a general circulation model of a static-ocean planet in a short-period orbit around a low-mass star—the results agree with our analytic theory. Because atmospheric tides and solid-body tides share a scaling with the semimajor axis, we show that there is a maximum amplitude of the atmospheric tide that a terrestrial planet can experience while still having a solid surface; Proxima Centauri b is the poster child for a planet that could be geophysically Earth-like but with atmospheric tides more than 500× stronger than Earth’s. In this most extreme scenario, we show that atmospheric tides significantly impact the planet’s meteorology—but not its climate. Two possible modest climate impacts are enhanced longitudinal heat transport and cooling of the lowest atmospheric layers. The strong radiative forcing of such planets dominates over gravitational tides, unlike moons of cold giant planets, such as Titan. We speculate that atmospheric tides could be climatologically important on planets where the altitude of maximal tidal forcing coincides with the altitude of cloud formation and that the effect could be detectable for non-Earth-like planets subject to even greater tides.
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Kramm, Ulrike, Nadine Nettelmann, and Ronald Redmer. "Constraining planetary interiors with the Love number k2." Proceedings of the International Astronomical Union 6, S276 (October 2010): 482–84. http://dx.doi.org/10.1017/s1743921311020898.
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AbstractFor the solar sytem giant planets the measurement of the gravitational moments J2 and J4 provided valuable information about the interior structure. However, for extrasolar planets the gravitational moments are not accessible. Nevertheless, an additional constraint for extrasolar planets can be obtained from the tidal Love number k2, which, to first order, is equivalent to J2. k2 quantifies the quadrupolic gravity field deformation at the surface of the planet in response to an external perturbing body and depends solely on the planet's internal density distribution. On the other hand, the inverse deduction of the density distribution of the planet from k2 is non-unique. The Love number k2 is a potentially observable parameter that can be obtained from tidally induced apsidal precession of close-in planets (Ragozzine & Wolf 2009) or from the orbital parameters of specific two-planet systems in apsidal alignment (Mardling 2007). We find that for a given k2, a precise value for the core mass cannot be derived. However, a maximum core mass can be inferred which equals the core mass predicted by homogeneous zero metallicity envelope models. Using the example of the extrasolar transiting planet HAT-P-13b we show to what extend planetary models can be constrained by taking into account the tidal Love number k2.
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Sotiriadis, Sotiris, Anne-Sophie Libert, and Sean N. Raymond. "Formation of terrestrial planets in eccentric and inclined giant planet systems." Astronomy & Astrophysics 613 (May 2018): A59. http://dx.doi.org/10.1051/0004-6361/201731260.
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Aims. Evidence of mutually inclined planetary orbits has been reported for giant planets in recent years. Here we aim to study the impact of eccentric and inclined massive giant planets on the terrestrial planet formation process, and investigate whether it can possibly lead to the formation of inclined terrestrial planets. Methods. We performed 126 simulations of the late-stage planetary accretion in eccentric and inclined giant planet systems. The physical and orbital parameters of the giant planet systems result from n-body simulations of three giant planets in the late stage of the gas disc, under the combined action of Type II migration and planet-planet scattering. Fourteen two- and three-planet configurations were selected, with diversified masses, semi-major axes (resonant configurations or not), eccentricities, and inclinations (including coplanar systems) at the dispersal of the gas disc. We then followed the gravitational interactions of these systems with an inner disc of planetesimals and embryos (nine runs per system), studying in detail the final configurations of the formed terrestrial planets. Results. In addition to the well-known secular and resonant interactions between the giant planets and the outer part of the disc, giant planets on inclined orbits also strongly excite the planetesimals and embryos in the inner part of the disc through the combined action of nodal resonance and the Lidov–Kozai mechanism. This has deep consequences on the formation of terrestrial planets. While coplanar giant systems harbour several terrestrial planets, generally as massive as the Earth and mainly on low-eccentric and low-inclined orbits, terrestrial planets formed in systems with mutually inclined giant planets are usually fewer, less massive (<0.5 M⊕), and with higher eccentricities and inclinations. This work shows that terrestrial planets can form on stable inclined orbits through the classical accretion theory, even in coplanar giant planet systems emerging from the disc phase.
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Fitzmaurice, Evan, David V. Martin, and Daniel C. Fabrycky. "Sculpting the circumbinary planet size distribution through resonant interactions with companion planets." Monthly Notices of the Royal Astronomical Society 512, no. 4 (March 21, 2022): 5023–36. http://dx.doi.org/10.1093/mnras/stac741.
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ABSTRACT Resonant locking of two planets is an expected outcome of convergent disc migration. The planets subsequently migrate together as a resonant pair. In the context of circumbinary planets, the disc is truncated internally by the binary. If there were only a single planet, then this inner disc edge would provide a natural parking location. However, for two planets migrating together in resonance there will be a tension between the inner planet stopping at the disc edge and the outer planet continuing to be torqued inwards. In this paper, we study this effect, showing that the outcome is a function of the planet–planet mass ratio. Smaller outer planets tend to be parked in a stable exterior 2:1 or 3:2 resonance with the inner planet, which remains near the disc edge. Equal or larger mass outer planets tend to push the inner planet past the disc edge and too close to the binary, causing it to be ejected or sometimes flipped to an exterior orbit. Our simulations show that this process may explain an observed dearth of small (<3 R⊕) circumbinary planets, since small planets are frequently ejected or left on long-period orbits, for which transit detection is less likely. This may also be an effective mechanism for producing free-floating planets and interstellar interlopers like ‘Oumuamua.
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Jackson, Brian, Richard Greenberg, and Rory Barnes. "Tidal evolution of close-in extra-solar planets." Proceedings of the International Astronomical Union 3, S249 (October 2007): 187–96. http://dx.doi.org/10.1017/s1743921308016591.
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AbstractThe distribution of eccentricities e of extra-solar planets with semi-major axes a > 0.2 AU is very uniform, and values for e are generally large. For a < 0.2 AU, eccentricities are much smaller (most e < 0.2), a characteristic widely attributed to damping by tides after the planets formed and the protoplanetary gas disk dissipated. We have integrated the classical coupled tidal evolution equations for e and a backward in time over the estimated age of each planet, and confirmed that the distribution of initial e values of close-in planets matches that of the general population for reasonable tidal dissipation values Q, with the best fits for stellar and planetary Q being ∼ 105.5 and ∼ 106.5, respectively. The current small values of a were only reached gradually due to tides over the lifetimes of the planets, i.e., the earlier gas disk migration did not bring all planets to their current orbits. As the orbits tidally evolved, there was substantial tidal heating within the planets. The past tidal heating of each planet may have contributed significantly to the thermal budget that governed the planet's physical properties, including its radius, which in many cases may be measured by observing transit events. Here we also compute the plausible heating histories for a few planets with anomalously large measured radii, including HD 209458 b. We show that they may have undergone substantial tidal heating during the past billion years, perhaps enough to explain their large radii. Theoretical models of exoplanet interiors and the corresponding radii should include the role of large and time-variable tidal heating. Our results may have important implications for planet formation models, physical models of “hot Jupiters”, and the success of transit surveys.
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Walsh, Kevin J. "Forming terrestrial planets and delivering water." Proceedings of the International Astronomical Union 11, A29B (August 2015): 427–30. http://dx.doi.org/10.1017/s174392131600572x.
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AbstractBuilding models capable of successfully matching the Terrestrial Planet's basic orbital and physical properties has proven difficult. Meanwhile, improved estimates of the nature of water-rich material accreted by the Earth, along with the timing of its delivery, have added even more constraints for models to match. While the outer Asteroid Belt seemingly provides a source for water-rich planetesimals, models that delivered enough of them to the still-forming Terrestrial Planets typically failed on other basic constraints - such as the mass of Mars.Recent models of Terrestrial Planet Formation have explored how the gas-driven migration of the Giant Planets can solve long-standing issues with the Earth/Mars size ratio. This model is forced to reproduce the orbital and taxonomic distribution of bodies in the Asteroid Belt from a much wider range of semimajor axis than previously considered. In doing so, it also provides a mechanism to feed planetesimals from between and beyond the Giant Planet formation region to the still-forming Terrestrial Planets.
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Ricard, Yanick, and Frédéric Chambat. "Mass–Radius Relationships and Contraction of Condensed Planets by Cooling or Despinning." Astrophysical Journal 967, no. 2 (May 30, 2024): 163. http://dx.doi.org/10.3847/1538-4357/ad4113.
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Abstract Condensed planets contract or expand as their temperature changes. With the exception of the effect of phase changes, this phenomenon is generally interpreted as being solely related to the thermal expansivity of the planet’s components. However, changes in density affect pressure and gravity and, consequently, the planet’s compressibility. A planet’s radius is also linked to its rate of rotation. Here again, changes in pressure, gravity, and compressibility are coupled. In this article we clarify how the radius of a condensed planet changes with temperature and rotation, using a simple and rigorous thermodynamic model. We consider condensed materials to obey a simple equation of state which generalizes a polytopic EoS as temperature varies. Using this equation, we build simple models of condensed planet’s interiors including exoplanets, derive their mass–radius relationships, and study the dependence of their radius on temperature and rotation rate. We show that it depends crucially on the value of ρ s gR/K s (ρ s being surface density, g gravity, R radius, K s surface incompressibility). This nondimensional number is also the ratio of the dissipation number which appears in compressible convection and the Gruneïsen mineralogic parameter. While the radius of small planets depends on temperature, this is not the case for large planets with large dissipation numbers; Earth and a super-Earth like CoRoT-7b are in something of an intermediate state, with a moderately temperature-dependent radius. Similarly, while the radius of these two planets is a function of their rotation rates, this is not the case for smaller or larger planets.
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Sikora, James, Jason Rowe, Saugata Barat, Jacob L. Bean, Madison Brady, Jean-Michel Désert, Adina D. Feinstein, et al. "Updated Planetary Mass Constraints of the Young V1298 Tau System Using MAROON-X." Astronomical Journal 165, no. 6 (May 24, 2023): 250. http://dx.doi.org/10.3847/1538-3881/acc865.
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Abstract The early K-type T-Tauri star, V1298 Tau (V = 10 mag, age ≈ 20–30 Myr) hosts four transiting planets with radii ranging from 4.9 to 9.6 R ⊕. The three inner planets have orbital periods of ≈8–24 days while the outer planet’s period is poorly constrained by single transits observed with K2 and the Transiting Exoplanet Survey Satellite (TESS). Planets b, c, and d are proto–sub-Neptunes that may be undergoing significant mass loss. Depending on the stellar activity and planet masses, they are expected to evolve into super-Earths/sub-Neptunes that bound the radius valley. Here we present results of a joint transit and radial velocity (RV) modeling analysis, which includes recently obtained TESS photometry and MAROON-X RV measurements. Assuming circular orbits, we obtain a low-significance (≈2σ) RV detection of planet c, implying a mass of 19.8 − 8.9 + 9.3 M ⊕ and a conservative 2σ upper limit of <39 M ⊕. For planets b and d, we derive 2σ upper limits of M b < 159 M ⊕ and M d < 41 M ⊕, respectively. For planet e, plausible discrete periods of P e > 55.4 days are ruled out at the 3σ level while seven solutions with 43.3 < P e/d < 55.4 are consistent with the most probable 46.768131 ± 000076 days solution within 3σ. Adopting the most probable solution yields a 2.6σ RV detection with a mass of 0.66 ± 0.26 M Jup. Comparing the updated mass and radius constraints with planetary evolution and interior structure models shows that planets b, d, and e are consistent with predictions for young gas-rich planets and that planet c is consistent with having a water-rich core with a substantial (∼5% by mass) H2 envelope.
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Louden, Emma M., Gregory P. Laughlin, and Sarah C. Millholland. "Tidal Dissipation Regimes among the Short-period Exoplanets." Astrophysical Journal Letters 958, no. 2 (November 23, 2023): L21. http://dx.doi.org/10.3847/2041-8213/ad0843.
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Abstract The efficiency of tidal dissipation provides a zeroth-order link to a planet’s physical properties. For super-Earth and sub-Neptune planets in the range R ⊕ ≲ R p ≲ 4R ⊕, particularly efficient dissipation (i.e., low tidal quality factors) may signify terrestrial-like planets capable of maintaining rigid crustal features. Here, we explore global constraints on planetary tidal quality factors using a population of planets in multiple-planet systems whose orbital and physical properties indicate susceptibility to capture into secular spin–orbit resonances. Planets participating in secular spin–orbit resonance can maintain large axial tilts and significantly enhanced heating from obliquity tides. When obliquity tides are sufficiently strong, planets in low-order mean-motion resonances can experience resonant repulsion (period ratio increase). The observed distribution of period ratios among transiting planet pairs may thus depend nontrivially on the underlying planetary structures. We model the action of resonant repulsion and demonstrate that the observed distribution of period ratios near the 2:1 and 3:2 commensurabilities implies Q values spanning from Q ≈ 101–107 and peaking at Q ≈ 106. This range includes the expected range in which super-Earth and sub-Neptune planets dissipate (Q ≈ 103–104). This work serves as a proof of concept for a method of assessing the presence of two dissipation regimes, and we estimate the number of additional multitransiting planetary systems needed to place any bimodality in the distribution on a strong statistical footing.
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Lazzoni, C., S. Desidera, F. Marzari, A. Boccaletti, M. Langlois, D. Mesa, R. Gratton, et al. "Dynamical models to explain observations with SPHERE in planetary systems with double debris belts." Astronomy & Astrophysics 611 (March 2018): A43. http://dx.doi.org/10.1051/0004-6361/201731426.
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Context. A large number of systems harboring a debris disk show evidence for a double belt architecture. One hypothesis for explaining the gap between the debris belts in these disks is the presence of one or more planets dynamically carving it. For this reason these disks represent prime targets for searching planets using direct imaging instruments, like the Spectro-Polarimetric High-constrast Exoplanet Research (SPHERE) at the Very Large Telescope.Aim. The goal of this work is to investigate this scenario in systems harboring debris disks divided into two components, placed, respectively, in the inner and outer parts of the system. All the targets in the sample were observed with the SPHERE instrument, which performs high-contrast direct imaging, during the SHINE guaranteed time observations. Positions of the inner and outer belts were estimated by spectral energy distribution fitting of the infrared excesses or, when available, from resolved images of the disk. Very few planets have been observed so far in debris disks gaps and we intended to test if such non-detections depend on the observational limits of the present instruments. This aim is achieved by deriving theoretical predictions of masses, eccentricities, and semi-major axes of planets able to open the observed gaps and comparing such parameters with detection limits obtained with SPHERE.Methods. The relation between the gap and the planet is due to the chaotic zone neighboring the orbit of the planet. The radial extent of this zone depends on the mass ratio between the planet and the star, on the semi-major axis, and on the eccentricity of the planet, and it can be estimated analytically. We first tested the different analytical predictions using a numerical tool for the detection of chaotic behavior and then selected the best formula for estimating a planet’s physical and dynamical properties required to open the observed gap. We then apply the formalism to the case of one single planet on a circular or eccentric orbit. We then consider multi-planetary systems: two and three equal-mass planets on circular orbits and two equal-mass planets on eccentric orbits in a packed configuration. As a final step, we compare each couple of values (Mp, ap), derived from the dynamical analysis of single and multiple planetary models, with the detection limits obtained with SPHERE.Results. For one single planet on a circular orbit we obtain conclusive results that allow us to exclude such a hypothesis since in most cases this configuration requires massive planets which should have been detected by our observations. Unsatisfactory is also the case of one single planet on an eccentric orbit for which we obtained high masses and/or eccentricities which are still at odds with observations. Introducing multi planetary architectures is encouraging because for the case of three packed equal-mass planets on circular orbits we obtain quite low masses for the perturbing planets which would remain undetected by our SPHERE observations. The case of two equal-mass planets on eccentric orbits is also of interest since it suggests the possible presence of planets with masses lower than the detection limits and with moderate eccentricity. Our results show that the apparent lack of planets in gaps between double belts could be explained by the presence of a system of two or more planets possibly of low mass and on eccentric orbits whose sizes are below the present detection limits.
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Dvorak, R., E. Pilat-Lohinger, E. Bois, B. Funk, F. Freistetter, and L. Kiseleva-Eggleton. "Planets in Double Stars: The ϒ Cephei System." International Astronomical Union Colloquium 191 (August 2004): 222–26. http://dx.doi.org/10.1017/s0252921100008800.
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AbstractUp to now we have evidence for some 15 planets moving in double stars. They are all of the so-called S-type, which means that they are orbiting one of the primaries. Only two of the binaries have separations in the order of the distances where the planets in our Solar system orbit the Sun, namely Gliese 86 and ϒ Cep. In this study we investigate the stability of the recently discovered planet in ϒ Cep with respect to the orbital parameters of the binary and of the planet. Additionally we check the region inside and outside the planet’s orbit (a = 2.1 AU). Even when the mass of an additional planet in 1 AU would be in the order of that of Jupiter, the discovered planet would be in a stable orbit.
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Veras, Dimitri, Michael Efroimsky, Valeri V. Makarov, Gwenaël Boué, Vera Wolthoff, Sabine Reffert, Andreas Quirrenbach, Pier-Emmanuel Tremblay, and Boris T. Gänsicke. "Orbital relaxation and excitation of planets tidally interacting with white dwarfs." Monthly Notices of the Royal Astronomical Society 486, no. 3 (May 1, 2019): 3831–48. http://dx.doi.org/10.1093/mnras/stz965.
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Abstract Observational evidence of white dwarf planetary systems is dominated by the remains of exo-asteroids through accreted metals, debris discs, and orbiting planetesimals. However, exo-planets in these systems play crucial roles as perturbing agents, and can themselves be perturbed close to the white dwarf Roche radius. Here, we illustrate a procedure for computing the tidal interaction between a white dwarf and a near-spherical solid planet. This method determines the planet’s inward and/or outward drift, and whether the planet will reach the Roche radius and be destroyed. We avoid constant tidal lag formulations and instead employ the self-consistent secular Darwin–Kaula expansions from Boué & Efroimsky (2019), which feature an arbitrary frequency dependence on the quality functions. We adopt wide ranges of dynamic viscosities and spin rates for the planet in order to straddle many possible outcomes, and provide a foundation for the future study of individual systems with known or assumed rheologies. We find that (i) massive Super-Earths are destroyed more readily than minor planets (such as the ones orbiting WD 1145+017 and SDSS J1228+1040), (ii) low-viscosity planets are destroyed more easily than high-viscosity planets, and (iii) the boundary between survival and destruction is likely to be fractal and chaotic.
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Brasser, R., A. C. Barr, and V. Dobos. "The tidal parameters of TRAPPIST-1b and c." Monthly Notices of the Royal Astronomical Society 487, no. 1 (May 4, 2019): 34–47. http://dx.doi.org/10.1093/mnras/stz1231.
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Abstract The TRAPPIST-1 planetary system consists of seven planets within 0.05 au of each other, five of which are in a multiresonant chain. These resonances suggest the system formed via planet migration; subsequent tidal evolution has damped away most of the initial eccentricities. We used dynamical N-body simulations to estimate how long it takes for the multiresonant configuration that arises during planet formation to break. From there we use secular theory to pose limits on the tidal parameters of planets b and c. We calibrate our results against multilayered interior models constructed to fit the masses and radii of the planets, from which the tidal parameters are computed independently. The dynamical simulations show that the planets typically go unstable 30 Myr after their formation. Assuming synchronous rotation throughout, we compute $\frac{k_2}{Q} \gtrsim 2\times 10^{-4}$ for planet b and $\frac{k_2}{Q} \gtrsim 10^{-3}$ for planet c. Interior models yield (0.075–0.37) × 10−4 for TRAPPIST-1b and (0.4–2) × 10−4 for TRAPPIST-1c. The agreement between the dynamical and interior models is not too strong, but is still useful to constrain the dynamical history of the system. We suggest that this two-pronged approach could be of further use in other multiresonant systems if the planet’s orbital and interior parameters are sufficiently well known.
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S. Guimarães, Eduardo. "The Beginning of The Nuclear Universe and The Theory of Orbital Superconductivity of The Celestial Bodies." JOURNAL OF ADVANCES IN PHYSICS 14, no. 2 (June 5, 2018): 5442–48. http://dx.doi.org/10.24297/jap.v14i2.7406.
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This article is a logical and rational analysis of the original nuclear matter, and of the structure that gave rise to the space architecture of the universe with galaxies, stars, the system of planets and moons, and arrives to original and inedited conclusions.
After the so-called Big Bang of the universe arose the space, a new time count and the nuclear universe, governed by the actions of the physical properties of nuclear superconductivity space.
The actions of the physical properties of superconductivity nuclear matter generate the spatial phenomenon of orbital superconductivity, which creates the orbit and space distance of the orbit between the moons with their planets, between the planets with their star, forming the system of planets, and among the stars creating the architecture of the galaxy.
4 The actions of the physical properties of superconductivity nuclear matter also generate the spatial phenomenon of gravity superconductivity, which creates the form and distance of gravity in moons, planets, planets, stars and comets, creating the actions of physics of the star and planet with gravity superconductivity.
The actions of the physical properties of superconductivity nuclear matter also generates the spatial phenomenon of nuclear superconductivity of magnetism, which creates the magnetic pole and the spatial distance of the magnetic field.
The nucleus of all stars, planets, moons, are made of matter, called, by mass of energy nuclear of superconductivity.
All the materials that exist in the nuclear universe are produced, through the atomic decomposition of nuclear matter of superconductivity.
The atomic decomposition of superconductivity nuclear matter reduces the nucleus and nuclear energy of spatial superconductivity.
In the reduction of superconductivity nuclear energy there is a loss of the orbital superconductivity property of the moon and the planet.
In the loss of the orbital superconductivity property of the moon and the planet, the moon is attracted by the superconductivity of the planet and reduces orbit until attracted by the superconductivity of the planet's gravitational field.
The fall of the moon will destroy the planet or produce a crater because of the size of the planet.
The fall of the moon on Jupiter will create an immense nuclear crater in which the diameter and depth will measure the extension of thousands of kilometers.
The fall of the moon on Mars will create an immense nuclear explosion, and will destroy the planet.
Majority of the planets of the galaxies and the universe have a time schedule of self-destruction in the fall of the moons.
Most of the planets in the solar system have a time schedule of self-destruction in the fall of the moons.
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Lissauer, Jack J. "Formation, Frequency and Spacing of Habitable Planets." International Astronomical Union Colloquium 161 (January 1997): 289–97. http://dx.doi.org/10.1017/s0252921100014809.
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AbstractModels of planet formation and of the orbital stability of planetary systems are described and used to discuss estimates of the abundance of habitable planets which may orbit stars within our galaxy. Modern theories of star and planet formation, which are based upon observations of the Solar System and of young stars and their environments, predict that most single stars should have rocky planets in orbit about them. Terrestrial planets are believed to grow via pairwise accretion until the spacing of planetary orbits becomes large enough that the configuration is stable for the age of the system. Giant planets orbiting within or near the habitable zone could either prevent terrestrial planets from forming, destroy such planets or remove them from habitable zones. The implications of the giant planets found in recent radial velocity searches for the abundances of habitable planets are discussed.
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Fabrycky, Daniel C. "What to Expect from Transiting Multiplanet Systems." Proceedings of the International Astronomical Union 4, S253 (May 2008): 173–79. http://dx.doi.org/10.1017/s1743921308026380.
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AbstractSo far radial velocity measurements have discovered ~25 stars to host multiple planets. The statistics imply that many of the known hosts of transiting planets should have additional planets, yet none have been solidly detected. They will be soon, via complementary search methods of RV, transit-time variations of the known planet, and transits of the additional planet. When they are found, what can transit measurements add to studies of multiplanet dynamical evolution? First, mutual inclinations become measurable, for comparison to the solar system's disk-like configuration. Such measurements will give important constraints to planet-planet scattering models, just as the radial velocity measurements of eccentricity have done. Second, the Rossiter-McLaughlin effect measures stellar obliquity, which can be modified by two-planet dynamics with a tidally evolving inner planet. Third, transit-time variations are exquisitely sensitive to planets in mean motion resonance. Two planets differentially migrating in the disk can establish such resonances, and tidal evolution of the planets can break them, so the configuration and frequency of these resonances as a function of planetary parameters will constrain these processes.
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Nixon, Matthew C., and Nikku Madhusudhan. "How deep is the ocean? Exploring the phase structure of water-rich sub-Neptunes." Monthly Notices of the Royal Astronomical Society 505, no. 3 (June 17, 2021): 3414–32. http://dx.doi.org/10.1093/mnras/stab1500.
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ABSTRACT Understanding the internal structures of planets with a large H2O component is important for the characterization of sub-Neptune planets. The finding that the mini-Neptune K2-18b could host a liquid water ocean beneath a mostly hydrogen envelope motivates a detailed examination of the phase structures of water-rich planets. To this end, we present new internal structure models for super-Earths and mini-Neptunes that enable detailed characterization of a planet’s water component. We use our models to explore the possible phase structures of water worlds and find that a diverse range of interiors are possible, from oceans sandwiched between two layers of ice to supercritical interiors beneath steam atmospheres. We determine how the bulk properties and surface conditions of a water world affect its ocean depth, finding that oceans can be up to hundreds of times deeper than on Earth. For example, a planet with a 300 K surface can possess H2O oceans with depths from 30–500 km, depending on its mass and composition. We also constrain the region of mass–radius space in which planets with H/He envelopes could host liquid H2O, noting that the liquid phase can persist at temperatures up to 647 K at high pressures of 218–$7\times 10^4$ bar. Such H/He envelopes could contribute significantly to the planet radius while retaining liquid water at the surface, depending on the planet mass and temperature profile. Our findings highlight the exciting possibility that habitable conditions may be present on planets much larger than Earth.
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Rosenthal, Lee J., Heather A. Knutson, Yayaati Chachan, Fei Dai, Andrew W. Howard, Benjamin J. Fulton, Ashley Chontos, et al. "The California Legacy Survey. III. On the Shoulders of (Some) Giants: The Relationship between Inner Small Planets and Outer Massive Planets." Astrophysical Journal Supplement Series 262, no. 1 (August 17, 2022): 1. http://dx.doi.org/10.3847/1538-4365/ac7230.
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Abstract We use a high-precision radial velocity survey of FGKM stars to study the conditional occurrence of two classes of planets: close-in small planets (0.023–1 au, 2–30 M ⊕) and distant giant planets (0.23–10 au, 30–6000 M ⊕). We find that 41 − 13 + 15 % of systems with a close-in, small planet also host an outer giant, compared to 17.6 − 1.9 + 2.4 % for stars irrespective of small planet presence. This implies that small planet hosts may be enhanced in outer giant occurrences compared to all stars with 1.7σ significance. Conversely, we estimate that 42 − 13 + 17 % of cold giant hosts also host an inner small planet, compared to 27.6 − 4.8 + 5.8 % of stars irrespective of cold giant presence. We also find that more massive and close-in giant planets are not associated with small inner planets. Specifically, our sample indicates that small planets are less likely to have outer giant companions more massive than approximately 120 M ⊕ and within 0.3–3 au, than to have less massive or more distant giant companions, with ∼2.2σ confidence. This implies that massive gas giants within 0.3–3 au may suppress inner small planet formation. Additionally, we compare the host-star metallicity distributions for systems with only small planets and those with both small planets and cold giants. In agreement with previous studies, we find that stars in our survey that only host small planets have a metallicity distribution that is consistent with the broader solar-metallicity-median sample, while stars that host both small planets and gas giants are distinctly metal rich with ∼2.3σ confidence.
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Chen, Cheng, Rebecca G. Martin, and C. J. Nixon. "Can a binary star host three giant circumbinary planets?" Monthly Notices of the Royal Astronomical Society 525, no. 3 (September 1, 2023): 3781–89. http://dx.doi.org/10.1093/mnras/stad2543.
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ABSTRACT We investigate the orbital stability of a tilted circumbinary planetary system with three giant planets. The planets are spaced by a constant number (Δ) of mutual Hill radii in the range Δ = 3.4–12.0 such that the period ratio of the inner pair is the same as that of the outer pair. A tilted circumbinary planetary system can be unstable even if the same system around a coplanar binary is stable. For an equal-mass binary, we find that the stability of a three-planet system is qualitatively similar to that of a two-planet system, but the three-planet system is more unstable in mean motion resonance regions. For an unequal-mass binary, there is significantly more instability in the three-planet system as the inner planets can undergo von Zeipel–Kozai–Lidov oscillations. Generally in unstable systems, the inner planets are more likely to be ejected than the outer planets. The most likely unstable outcome for closely spaced systems, with Δ ≲ 8, is a single remaining stable planet. For more widely separated systems, Δ ≳ 8, the most likely unstable outcome is two stable planets, only one being ejected. An observed circumbinary planet with significant eccentricity may suggest that it was formed from an unstable system. Consequently, a binary can host three tilted giant planets if the binary stars are close to equal mass and provided that the planets are well spaced and not close to a mean motion resonance.
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Chametla, Raúl O., Frédéric S. Masset, Clément Baruteau, and Bertram Bitsch. "How the planetary eccentricity influences the pebble isolation mass." Monthly Notices of the Royal Astronomical Society 510, no. 3 (December 24, 2021): 3867–75. http://dx.doi.org/10.1093/mnras/stab3753.
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ABSTRACT We investigate the pebble isolation mass (PIM) for a planet on a fixed eccentric orbit in its protoplanetary disc by conducting a set of two-dimensional (2D) hydrodynamical simulations, including dust turbulent diffusion. A range of planet eccentricities up to e = 0.2 is adopted. Our simulations also cover a range of α-turbulent viscosities, and for each pair {α, e} the PIM is estimated as the minimum planet mass in our simulations such that solids with a Stokes number ≳0.05 do not flow across the planet orbit and remain trapped around a pressure bump outside the planet gap. For α < 10−3, we find that eccentric planets reach a well-defined PIM, which can be smaller than for planets on circular orbits when the eccentricity remains smaller than the disc’s aspect ratio. We provide a fitting formula for how the PIM depends on the planet's eccentricity. However, for α > 10−3, eccentric planets cannot fully stall the pebbles flow and, thus, do not reach a well-defined PIM. Our results suggest that the maximum mass reached by rocky cores should exhibit a dichotomy depending on the disc's turbulent viscosity. While being limited to ${\cal O}(10\, M_\oplus)$ in low-viscosity discs, this maximum mass could reach much larger values in discs with a high turbulent viscosity in the planet vicinity. Our results further highlight that pebble filtering by growing planets might not be as effective as previously thought, especially in high-viscosity discs, with important implications to protoplanetary discs observations.
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Shin, In-Gu, Jennifer C. Yee, Weicheng Zang, Cheongho Han, Hongjing Yang, Andrew Gould, Chung-Uk Lee, et al. "Systematic KMTNet Planetary Anomaly Search. XI. Complete Sample of 2016 Subprime Field Planets." Astronomical Journal 167, no. 6 (May 16, 2024): 269. http://dx.doi.org/10.3847/1538-3881/ad3ba3.
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Abstract Following Shin et al. (2023b), which is a part of the “Systematic KMTNet Planetary Anomaly Search” series (i.e., a search for planets in the 2016 KMTNet prime fields), we conduct a systematic search of the 2016 KMTNet subprime fields using a semi-machine-based algorithm to identify hidden anomalous events missed by the conventional by-eye search. We find four new planets and seven planet candidates that were buried in the KMTNet archive. The new planets are OGLE-2016-BLG-1598Lb, OGLE-2016-BLG-1800Lb, MOA-2016-BLG-526Lb, and KMT-2016-BLG-2321Lb, which show typical properties of microlensing planets, i.e., giant planets orbit M-dwarf host stars beyond their snow lines. For the planet candidates, we find planet/binary or 2L1S/1L2S degeneracies, which are an obstacle to firmly claiming planet detections. By combining the results of Shin et al. (2023b) and this work, we find a total of nine hidden planets, which is about half the number of planets discovered by eye in 2016. With this work, we have met the goal of the systematic search series for 2016, which is to build a complete microlensing planet sample. We also show that our systematic searches significantly contribute to completing the planet sample, especially for planet/host mass ratios smaller than 10−3, which were incomplete in previous by-eye searches of the KMTNet archive.
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Taylor, Stuart F. "Flow of Planets Raises Short Period Fall-Off." Proceedings of the International Astronomical Union 8, S293 (August 2012): 241–43. http://dx.doi.org/10.1017/s174392131301291x.
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AbstractAfter finding more planets than expected at the shortest period, there has been an effort to explain their numbers by weak tidal friction. However, we find that the strength of tidal dissipation that would produce the occurence distribution found from Kepler planet candidates is different for giant versus medium radii planets. This discrepancy can be resolved if there is a “flow” of the largest planets regularly arriving such that they go through a “hot Jupiter” stage. We also show a correlation of higher stellar Fe/H with higher eccentricity of giant planets that may be from smaller planets having been sent into the star by the migration of the larger planet. This disruption of the orbits of medium and smaller planets could account for the lower occurrence of “hot Neptune” medium radius planets.
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Ford, Eric B., and Knicole D. Colón. "Characterizing the Eccentricities of Transiting Extrasolar Planets with Kepler and CoRoT." Proceedings of the International Astronomical Union 4, S253 (May 2008): 111–19. http://dx.doi.org/10.1017/s1743921308026306.
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AbstractRadial velocity planet searches have revealed that many giant planets have large eccentricities, in striking contrast with the giant planets in the solar system and prior theories of planet formation. The realization that many giant planets have large eccentricities raises a fundamental question: Do terrestrial-size planets of other stars typically have significantly eccentric orbits or nearly circular orbits like the Earth? While space-based missions such as CoRoT and Kepler will be capable of detecting nearly Earth-sized planets, it will be extremely challenging to measure their eccentricities using radial velocity observations. We review several ways that photometric measurements of transit light curves can constrain the eccentricity of transiting planets. In particular, photometric observations of transit durations can be used to characterize the distribution of orbital eccentricities for various populations of transiting planets (e.g., nearly Earth-sized planets in the habitable zone) without relying on radial velocity measurements. Applying this technique to rocky planets to be found by CoRoT and Kepler will enable constraints on theories for the excitation of eccentricities and tidal dissipation. We also remind observers that several short-period transiting planets are known to have significant eccentricities and caution that assuming they are on a circular orbit can reduce the probability of detecting transits, impact planning for follow-up observations, and adversely affect measurements of the physical parameters of the star and planet.
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Pu, Bonan, and Dong Lai. "Low-eccentricity migration of ultra-short-period planets in multiplanet systems." Monthly Notices of the Royal Astronomical Society 488, no. 3 (July 25, 2019): 3568–87. http://dx.doi.org/10.1093/mnras/stz1817.
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ABSTRACT Recent studies suggest that ultra-short-period planets (USPs), Earth-sized planets with sub-day periods, constitute a statistically distinct sub-sample of Kepler planets: USPs have smaller radii (1–1.4R⊕) and larger mutual inclinations with neighbouring planets than nominal Kepler planets, and their period distribution is steeper than longer period planets. We study a ‘low-eccentricity’ migration scenario for the formation of USPs, in which a low-mass planet with initial period of a few days maintains a small but finite eccentricity due to secular forcings from exterior companion planets, and experiences orbital decay due to tidal dissipation. USP formation in this scenario requires that the initial multiplanet system have modest eccentricities (≳0.1) or angular momentum deficit. During the orbital decay of the innermost planet, the system can encounter several apsidal and nodal precession resonances that significantly enhance eccentricity excitation and increase the mutual inclination between the inner planets. We develop an approximate method based on eccentricity and inclination eigenmodes to efficiently evolve a large number of multiplanet systems over Gyr time-scales in the presence of rapid (as short as ∼100 yr) secular planet–planet interactions and other short-range forces. Through a population synthesis calculation, we demonstrate that the ‘low-e migration’ mechanism can naturally produce USPs from the large population of Kepler multis under a variety of conditions, with little fine-tuning of parameters. This mechanism favours smaller inner planets with more massive and eccentric companion planets, and the resulting USPs have properties that are consistent with observations.
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Yang, Biao, Yu Jiang, Hengnian Li, Chunsheng Jiang, Yongjie Liu, Chaojin Zhan, Hongbao Jing, and Yake Dong. "Semi-Analytical Search for Sun-Synchronous and Planet Synchronous Orbits around Jupiter, Saturn, Uranus and Neptune." Mathematics 10, no. 15 (July 29, 2022): 2684. http://dx.doi.org/10.3390/math10152684.
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With the development of aerospace science and technology, more and more probes are expected to be deployed around extraterrestrial planets. In this paper, some special orbits around Jupiter, Saturn, Uranus, and Neptune are discussed and analyzed. The design methods of some special orbits are sorted out, considering the actual motion parameters and main perturbation forces of these four planets. The characteristics of sun-synchronous orbits, repeating ground track orbits, and synchronous planet orbits surrounding these plants are analyzed and compared. The analysis results show that Uranus does not have sun-synchronous orbits in the general sense. This paper also preliminarily calculates the orbital parameters of some special orbits around these planets, including the relationship between the semi-major axis, the eccentricity and the orbital inclination of the sun-synchronous orbits, the range of the regression coefficient of the sun-synchronous repeating ground track orbits, and the orbital parameters of synchronous planet orbits, laying a foundation for more accurate orbit design of future planetary probes.
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Rogers, Leslie A. "Glimpsing the Compositions of Sub-Neptune-Size Exoplanets." Proceedings of the International Astronomical Union 8, S299 (June 2013): 247–51. http://dx.doi.org/10.1017/s1743921313008491.
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AbstractThe growing number of transiting planets with mass constraints opens the possibility of applying a statistical approach to learn about the underlying population of planet compositions. We focus on the intriguing transition between rocky exoplanets and planets with voluminous gas layers, and explore how the current census of sub-Neptune-size exoplanets constrains the maximum radii of rocky planets. We outline a hierarchical Bayesian model approach to infer the fraction of planets that are dense enough to be rocky (as a function of planet radius). A preliminary analysis of the current sample of planets with mass and radius constraints reveals that most planets larger than 1.9 R⊕ are too low density to be comprised of Fe and silicates alone.
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Pearce, Tim D., Ralf Launhardt, Robert Ostermann, Grant M. Kennedy, Mario Gennaro, Mark Booth, Alexander V. Krivov, et al. "Planet populations inferred from debris discs." Astronomy & Astrophysics 659 (March 2022): A135. http://dx.doi.org/10.1051/0004-6361/202142720.
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We know little about the outermost exoplanets in planetary systems because our detection methods are insensitive to moderate-mass planets on wide orbits. However, debris discs can probe the outer-planet population because dynamical modelling of observed discs can reveal properties of perturbing planets. We use four sculpting and stirring arguments to infer planet properties in 178 debris-disc systems from the ISPY, LEECH, and LIStEN planet-hunting surveys. Similar analyses are often conducted for individual discs, but we consider a large sample in a consistent manner. We aim to predict the population of wide-separation planets, gain insight into the formation and evolution histories of planetary systems, and determine the feasibility of detecting these planets in the near future. We show that a ‘typical’ cold debris disc likely requires a Neptune- to Saturn-mass planet at 10–100 au, with some needing Jupiter-mass perturbers. Our predicted planets are currently undetectable, but modest detection-limit improvements (e.g. from JWST) should reveal many such perturbers. We find that planets thought to be perturbing debris discs at late times are similar to those inferred to be forming in protoplanetary discs, so these could be the same population if newly formed planets do not migrate as far as currently thought. Alternatively, young planets could rapidly sculpt debris before migrating inwards, meaning that the responsible planets are more massive (and located farther inwards) than debris-disc studies assume. We combine self-stirring and size-distribution modelling to show that many debris discs cannot be self-stirred without having unreasonably high masses; planet- or companion-stirring may therefore be the dominant mechanism in many (perhaps all) debris discs. Finally, we provide catalogues of planet predictions and identify promising targets for future planet searches.
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Fromont, Emeline F., John P. Ahlers, Laura N. R. do Amaral, Rory Barnes, Emily A. Gilbert, Elisa V. Quintana, Sarah Peacock, Thomas Barclay, and Allison Youngblood. "Atmospheric Escape From Three Terrestrial Planets in the L 98-59 System." Astrophysical Journal 961, no. 1 (January 1, 2024): 115. http://dx.doi.org/10.3847/1538-4357/ad0e0e.
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Abstract A critically important process affecting the climate evolution and potential habitability of an exoplanet is atmospheric escape, in which high-energy radiation from a star drives the escape of hydrogen atoms and other light elements from a planet’s atmosphere. L 98-59 is a benchmark system for studying such atmospheric processes, with three transiting terrestrial-sized planets receiving Venus-like instellations (4–25 S ⊕) from their M3 host star. We use the VPLanet model to simulate the evolution of the L 98-59 system and the atmospheric escape of its inner three small planets, given different assumed initial water quantities. We find that, regardless of their initial water content, all three planets accumulate significant quantities of oxygen due to efficient water photolysis and hydrogen loss. All three planets also receive enough strong X-ray and extreme-ultraviolet flux to drive rapid water loss, which considerably affects their developing climates and atmospheres. Even in scenarios of low initial water content, our results suggest that the JWST will be sensitive to observations of retained oxygen on the L 98-59 planets in its future scheduled observations, with planets b and c being the most likely targets to possess an extended atmosphere. Our results constrain the atmospheric evolution of these small rocky planets, and they provide context for current and future observations of the L 98-59 system to generalize our understanding of multiterrestrial planet systems.
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Azevedo Silva, T., O. D. S. Demangeon, S. C. C. Barros, D. J. Armstrong, J. F. Otegi, D. Bossini, E. Delgado Mena, et al. "The HD 137496 system: A dense, hot super-Mercury and a cold Jupiter." Astronomy & Astrophysics 657 (January 2022): A68. http://dx.doi.org/10.1051/0004-6361/202141520.
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Context. Most of the currently known planets are small worlds with radii between that of the Earth and that of Neptune. The characterization of planets in this regime shows a large diversity in compositions and system architectures, with distributions hinting at a multitude of formation and evolution scenarios. However, many planetary populations, such as high-density planets, are significantly under-sampled, limiting our understanding of planet formation and evolution. Aims. NCORES is a large observing program conducted on the HARPS high-resolution spectrograph that aims to confirm the planetary status and to measure the masses of small transiting planetary candidates detected by transit photometry surveys in order to constrain their internal composition. Methods. Using photometry from the K2 satellite and radial velocities measured with the HARPS and CORALIE spectrographs, we searched for planets around the bright (Vmag = 10) and slightly evolved Sun-like star HD 137496. Results. We precisely estimated the stellar parameters, M* = 1.035 ± 0.022 M⊙, R* = 1.587 ± 0.028 R⊙, Teff = 5799 ± 61 K, together with the chemical composition (e.g. [Fe/H] = −0.027 ± 0.040 dex) of the slightly evolved star. We detect two planets orbiting HD 137496. The inner planet, HD 137496 b, is a super-Mercury (an Earth-sized planet with the density of Mercury) with a mass of Mb = 4.04 ± 0.55 M⊕, a radius of Rb = 1.31−0.05+0.06 R⊕, and a density of ρb = 10.49−1.82+2.08 g cm-3. With an interior modeling analysis, we find that the planet is composed mainly of iron, with the core representing over 70% of the planet’s mass (Mcore / Mtotal = 0.73−0.12+0.11). The outer planet, HD 137496 c, is an eccentric (e = 0.477 ± 0.004), long period (P = 479.9−1.1+1.0 days) giant planet (Mc sinic = 7.66 ± 0.11 MJup) for which we do not detect a transit. Conclusions. HD 137496 b is one of the few super-Mercuries detected to date. The accurate characterization reported here enhances its role as a key target to better understand the formation and evolution of planetary systems. The detection of an eccentric long period giant companion also reinforces the link between the presence of small transiting inner planets and long period gas giants.