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Journal articles on the topic 'Earth (planet), rotation'
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1
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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Bolmont, E., S. N. Breton, G. Tobie, C. Dumoulin, S. Mathis, and O. Grasset. "Solid tidal friction in multi-layer planets: Application to Earth, Venus, a Super Earth and the TRAPPIST-1 planets." Astronomy & Astrophysics 644 (December 2020): A165. http://dx.doi.org/10.1051/0004-6361/202038204.
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With the discovery of TRAPPIST-1 and its seven planets residing within 0.06 au, it is becoming increasingly necessary to carry out correct treatments of tidal interactions. The eccentricity, rotation, and obliquity of the planets of TRAPPIST-1 do indeed result from the tidal evolution over the lifetime of the system. Tidal interactions can also lead to tidal heating in the interior of the planets (as for Io), which may then be responsible for volcanism or surface deformation. In the majority of studies aimed at estimating the rotation of close-in planets or their tidal heating, the planets are considered as homogeneous bodies and their rheology is often taken to be a Maxwell rheology. Here, we investigate the impact of taking into account a multi-layer structure and an Andrade rheology in the way planets dissipate tidal energy as a function of the excitation frequency. We use an internal structure model, which provides the radial profile of structural and rheological quantities (such as density, shear modulus, and viscosity) to compute the tidal response of multi-layered bodies. We then compare the outcome to the dissipation of a homogeneous planet (which only take a uniform value for shear modulus and viscosity). We find that for purely rocky bodies, it is possible to approximate the response of a multi-layer planet by that of a homogeneous planet. However, using average profiles of shear modulus and viscosity to compute the homogeneous planet response leads to an overestimation of the averaged dissipation. We provide fitted values of shear modulus and viscosity that are capable of reproducing the response of various types of rocky planets. However, we find that if the planet has an icy layer, its tidal response can no longer be approximated by a homogeneous body because of the very different properties of the icy layers (in particular, their viscosity), which leads to a second dissipation peak at higher frequencies. We also compute the tidal heating profiles for the outer TRAPPIST-1 planets (e to h).
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Orlov, S. "Genesis of the Planet Earth." Journal of Advance Research in Applied Science (ISSN: 2208-2352) 3, no. 2 (February 29, 2016): 27–37. http://dx.doi.org/10.53555/nnas.v3i2.661.
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This article is based on the theory of vortex gravitation and physical abnormalities of the Earth slowing its rotation. Defined orbital acceleration, weight, approach to the Sun and the age of our planet. Offered to justify the creation of planetary material in the center of the Earth torsion, and not as the accumulation of cosmic dust and meteorites from outer space.
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Orlov, R. S. "Genesis of the Planet Earth." Evolving Trends in Engineering and Technology 5 (April 2015): 1–10. http://dx.doi.org/10.18052/www.scipress.com/etet.5.1.
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This article is based on the theory of vortex gravitation and physical abnormalities of the Earth - slowing its rotation. Defined orbital acceleration, weight, approach to the Sun and the age of our planet. Offered to justify the creation of planetary material in the center of the Earth torsion, and not as the accumulation of cosmic dust and meteorites from outer space.
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Orlov, Sergey. "Genesis of the Planet Earth." International Letters of Chemistry, Physics and Astronomy 54 (July 2015): 37–46. http://dx.doi.org/10.18052/www.scipress.com/ilcpa.54.37.
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This article is based on the theory of vortex gravitation and physical abnormalities of the Earth - slowing its rotation. Defined orbital acceleration, weight, approach to the Sun and the age of our planet. Offered to justify the creation of planetary material in the center of the Earth torsion, and not as the accumulation of cosmic dust and meteorites from outer space.
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Orlov, R. S. "Genesis of the Planet Earth." International Journal of Engineering and Technologies 5 (April 1, 2015): 1–10. http://dx.doi.org/10.56431/p-6fzs83.
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This article is based on the theory of vortex gravitation and physical abnormalities of the Earth - slowing its rotation. Defined orbital acceleration, weight, approach to the Sun and the age of our planet. Offered to justify the creation of planetary material in the center of the Earth torsion, and not as the accumulation of cosmic dust and meteorites from outer space.
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Orlov, Sergey. "Genesis of the Planet Earth." International Letters of Chemistry, Physics and Astronomy 54 (July 3, 2015): 37–46. http://dx.doi.org/10.56431/p-08pr4l.
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This article is based on the theory of vortex gravitation and physical abnormalities of the Earth - slowing its rotation. Defined orbital acceleration, weight, approach to the Sun and the age of our planet. Offered to justify the creation of planetary material in the center of the Earth torsion, and not as the accumulation of cosmic dust and meteorites from outer space.
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Su, W. j., A. M. Dziewonski, and R. Jeanloz. "Planet Within a Planet: Rotation of the Inner Core of Earth." Science 274, no. 5294 (December 13, 1996): 1883–87. http://dx.doi.org/10.1126/science.274.5294.1883.
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Rao, Suvrat, Georges Meynet, Patrick Eggenberger, Lionel Haemmerlé, Giovanni Privitera, Cyril Georgy, Sylvia Ekström, and Christoph Mordasini. "Star-planet interactions." Astronomy & Astrophysics 618 (October 2018): A18. http://dx.doi.org/10.1051/0004-6361/201833107.
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Context. When planets are formed from the protoplanetary disk and after the disk has dissipated, the evolution of their orbits is governed by tidal interactions, friction, and gravitational drag, and also by changes in the mass of the star and planet. These interactions may change the initial distribution of the distances between the planets and their host star by expanding the original orbit, by contracting it (which may cause an engulfment of the planet by the star), or by destroying the planet. Aims. We study the evolution of the orbit of a planet orbiting its host star under the effects of equilibrium tides, dynamical tides, drag (frictional and gravitational), and stellar mass loss. Methods. We used the Geneva stellar evolution code to compute the evolution of stars with initial masses of 1 and 1.5 M⊙ with different rotation rates at solar metallicity. The star is evolved from the pre-main-sequence (PMS) up to the tip of the red giant branch. We used these models as input for computing the evolution of the planetary orbits. We explored the effects of changing the planet masses (of 1 Earth mass up to 20 Jupiter masses), the distance between the planet and the star (of 0.015 and more than 3 au), the mass, and the spin of the star. We present results when only the equilibrium tide was accounted for and when both equilibrium and dynamical tides were accounted for. The expression for the dynamical tide is a frequency-averaged dissipation of tidally excited inertial waves, obtained from a piecewise homogeneous two-layer stellar model. Gravity wave damping was neglected. Results. Dynamical tides in convective zones have a significant effect on planetary orbits only during the PMS phase and only for fast-rotating stars. They have no significant effects during the PMS phase for initially slow-rotating stars and during the red giant branch phase, regardless of the initial rotation. In the plots of initial orbital distance versus planetary mass, we show the regions that lead to engulfment or any significant changes in the orbit. As a result of orbital evolution, a region near the star can become devoid of planets after the PMS phase. We call this zone the planet desert, and its extent depends sensitively on stellar rotation. An examination of the planet distribution as a function of distance to the host star and mass can provide constraints on current computations.
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Lyu, Xintong, Daniel D. B. Koll, Nicolas B. Cowan, Renyu Hu, Laura Kreidberg, and Brian E. J. Rose. "Super-Earth LHS3844b is Tidally Locked." Astrophysical Journal 964, no. 2 (March 28, 2024): 152. http://dx.doi.org/10.3847/1538-4357/ad2077.
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Abstract Short-period exoplanets on circular orbits are thought to be tidally locked into synchronous rotation. If tidally locked, these planets must possess permanent day- and night-sides, with extreme irradiation on the dayside and none on the nightside. However, so far the tidal locking hypothesis for exoplanets is supported by little to no empirical evidence. Previous work showed that the super-Earth LHS 3844b likely has no atmosphere, which makes it ideal for constraining the planet’s rotation. Here we revisit the Spitzer phase curve of LHS 3844b with a thermal model of an atmosphere-less planet and analyze the impact of nonsynchronous rotation, eccentricity, tidal dissipation, and surface composition. Based on the lack of observed strong tidal heating we rule out rapid nonsynchronous rotation (including a Mercury-like 3:2 spin–orbit resonance) and constrain the planet's eccentricity to less than ∼0.001 (more circular than Io's orbit). In addition, LHS 3844b’s phase curve implies that the planet either still experiences weak tidal heating via a small-but-nonzero eccentricity (requiring an undetected orbital companion), or that its surface has been darkened by space weathering; of these two scenarios we consider space weathering more likely. Our results thus support the hypothesis that short-period rocky exoplanets are tidally locked, and further show that space weathering can significantly modify the surfaces of atmosphere-less exoplanets.
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Dolin, Sergei V., and Vadim F. Kanushin. "INFLUENCE OF ROTARY POST-EFFECT ON DISCHARGE IN THE CRUSTAL LAYER." Vestnik SSUGT (Siberian State University of Geosystems and Technologies) 26, no. 1 (2021): 16–24. http://dx.doi.org/10.33764/2411-1759-2021-26-1-16-24.
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This work represents experiments which have been performed in an attempt to establish a correla-tion between the constantly changing rotational regime of the planet and the discharge in the crustal layer. From the displacement of the TAI, UTC, and UT1 time scales taken from the site of the Interna-tional Earth Rotation Service (IERS), the average annual and monthly angular rotation rates were cal-culated for the period from 1962 to 2018, and a catalog of earthquakes with 1962 to 2018. The com-piled algorithm and the written program found partial derivatives of the total deforming potential and the distribution of annual number of earthquakes over the Earth's surface per one square kilometer. The article presents the results of analytical analysis and calculations for further investigation of the rotational regime of the Earth and other planets.
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Zhong, Wei, and Cong Yu. "In Situ Formation of Super-Earth/Sub-Neptune Driven by the Planetary Rotation." Astrophysical Journal 922, no. 2 (December 1, 2021): 215. http://dx.doi.org/10.3847/1538-4357/ac2cc5.
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Abstract Kepler’s observation shows that many of the detected planets are super-Earths. They are inside a range of critical masses overlapping the core masses (2–20 M ⊕), which would trigger the runaway accretion and develop the gas giants. Thus, super-Earths/sub-Neptunes can be formed by restraining runaway growth of gaseous envelopes. We assess the effect of planetary rotation in delaying the mass growth. The centrifugal force, induced by spin, will offset a part of the gravitational force and deform the planet. Tracking the change in structure, we find that the temperature at the radiative–convective boundary (RCB) is approximate to the boundary temperature. Since rotation reduces the radiation energy densities in the convective and radiative layers, RCB will penetrate deeper. The cooling luminosity would decrease. Under this condition, the evolutionary timescale can exceed the disk lifetime (10 Myr), and a super-Earth/sub-Neptune could be formed after undergoing additional mass-loss processes. In the dusty atmosphere, even a lower angular velocity can also promote a super-Earth/sub-Neptune forming. Therefore, we conclude that rotation can slow down the planet’s cooling and then promote a super-Earth/sub-Neptune forming.
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Raymond Hide, C. B. E. "Zenographic longitude systems and Jupiter's differential rotation." Notes and Records of the Royal Society of London 55, no. 1 (January 22, 2001): 69–79. http://dx.doi.org/10.1098/rsnr.2001.0126.
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More than ten times the Earth in diameter and 300 times as massive, Jupiter is by far the largest planet in the Solar System. Fifth in order of distance from the Sun, which it orbits in 11.8626 years, Jupiter spins more rapidly than any other planet, with a rotation period of just under 10 hours. Unlike the Earth and the other ‘terrestrial’ planets, Jupiter's principal chemical constituent is hydrogen, mainly in the molecular gaseous form at the visible cloud levels in the Jovian atmosphere, but liquid at the high pressures prevailing at much deeper levels within the planet. The electrical conductivity increases from negligible values near the cloud levels to metallic values at great depth. Differential rotation between equatorial and higher-latitude regions of the Jovian atmosphere is reflected in the two systems of zenographic longitude introduced by observers monitoring the motions of atmospheric cloud patterns. These are Systems I and II with rotation periods T 1 =35430.003s (9h 50min 30.003s) and T 2 =35740.632s (9h 55min 40.632s) respectively. The most striking feature of the cloud patterns is the durable (but longitudinally mobile) Great Red Spot, originally known as ’Hooke's Spot’, the first observations of which were recorded in the Philosophical Transactions of The Royal Society of London at the very beginning of its first issue, published in 1665. Differential rotation between the atmosphere and underlying electrically conducting regions is reflected in the need for radio astronomers to use yet another zenographic longitude system—System III, with rotation period T 3 =35729.771s (9h 55min 29.711s)––when monitoring powerful Jovian sources of non-thermal electromagnetic radiation at decimeter and decametre wavelengths. These are located in the plasma envelope of Jupiter, which is closely tied to the deep interior of the planet by lines of force of the zenomagnetic field.
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Li, Jiazheng, Jonathan H. Jiang, Huanzhou Yang, Dorian S. Abbot, Renyu Hu, Thaddeus D. Komacek, Stuart J. Bartlett, and Yuk L. Yung. "Rotation Period Detection for Earth-like Exoplanets." Astronomical Journal 163, no. 1 (December 21, 2021): 27. http://dx.doi.org/10.3847/1538-3881/ac36ce.
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Abstract A terrestrial planet’s rotation period is one of the key parameters that determines its climate and habitability. Current methods for detecting the rotation period of exoplanets are not suitable for terrestrial exoplanets. Here we demonstrate that, under certain conditions, the rotation period of an Earth-like exoplanet will be detectable using direct-imaging techniques. We use a global climate model that includes clouds to simulate reflected starlight from an Earth-like exoplanet and explore how different parameters (e.g., orbital geometry, wavelength, time resolution) influence the detectability of the planet’s rotation period. We show that the rotation period of an Earth-like exoplanet is detectable using visible-wavelength channels with time-series monitoring at a signal-to-noise ratio (S/N) >20 with ∼5–15 rotation periods of data, while the rotation period of a planet with full ocean coverage is unlikely to be detectable. To better detect the rotation period, one needs to plan the observation so that each individual integration would yield a S/N >10, while keeping the integration time shorter than 1/6 to 1/4 of the rotation period of the planet. Our results provide important guidance for rotation period detection of Earth-like exoplanets in reflected light using future space telescopes.
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Klindžić, D., D. M. Stam, F. Snik, C. U. Keller, H. J. Hoeijmakers, D. M. van Dam, M. Willebrands, et al. "LOUPE: observing Earth from the Moon to prepare for detecting life on Earth-like exoplanets." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 379, no. 2188 (November 23, 2020): 20190577. http://dx.doi.org/10.1098/rsta.2019.0577.
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LOUPE, the Lunar Observatory for Unresolved Polarimetry of the Earth, is a small, robust spectro-polarimeter for observing the Earth as an exoplanet. Detecting Earth-like planets in stellar habitable zones is one of the key challenges of modern exoplanetary science. Characterizing such planets and searching for traces of life requires the direct detection of their signals. LOUPE provides unique spectral flux and polarization data of sunlight reflected by Earth, the only planet known to harbour life. These data will be used to test numerical codes to predict signals of Earth-like exoplanets, to test algorithms that retrieve planet properties, and to fine-tune the design and observational strategies of future space observatories. From the Moon, LOUPE will continuously see the entire Earth, enabling it to monitor the signal changes due to the planet’s daily rotation, weather patterns and seasons, across all phase angles. Here, we present both the science case and the technology behind LOUPE’s instrumental and mission design. This article is part of a discussion meeting issue ‘Astronomy from the Moon: the next decades’.
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Podvigina, O. M. "Rotation of a Planet in a Three-body System: a Non-resonant Case." Nelineinaya Dinamika 18, no. 4 (2022): 0. http://dx.doi.org/10.20537/nd221001.
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We investigate the temporal evolution of the rotation axis of a planet in a system comprised of the planet (which we call an exo-Earth), a star (an exo-Sun) and a satellite (an exo-Moon). The planet is assumed to be rigid and almost spherical, the difference between the largest and the smallest principal moments of inertia being a small parameter of the problem. The orbit of the planet around the star is a Keplerian ellipse. The orbit of the satellite is a Keplerian ellipse with a constant inclination to the ecliptic, involved in two types of slow precessional motion, nodal and apsidal. Applying time averaging over the fast variables associated with the frequencies of the motion of exo-Earth and exo-Moon, we obtain Hamilton’s equations for the evolution of the angular momentum axis of the exo-Earth. Using a canonical change of variables, we show that the equations are integrable. Assuming that the exo-Earth is axially symmetric and its symmetry and rotation axes coincide, we identify possible types of motions of the vector of angular momentum on the celestial sphere. Also, we calculate the range of the nutation angle as a function of the initial conditions. (By the range of the nutation angle we mean the difference between its maximal and minimal values.)
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Cuntz, Manfred, Scott G. Engle, and Edward F. Guinan. "The Once-canceled Habitable-zone Super-Earth Gliese 581d Might Indeed Exist!" Research Notes of the AAS 8, no. 1 (January 16, 2024): 20. http://dx.doi.org/10.3847/2515-5172/ad1de4.
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Abstract Recent studies indicate that Gliese 581d, a proposed habitable zone (HZ) super-Earth planet, does not exist, as the respective data denote that the planet is an artifact of stellar activity. Here we report evidence to the contrary considering that those studies were based on inaccurate spectroscopic measurements of the stellar rotation period regarding the planet’s inactive host star (dM3). Gliese 581d, if real, is of particular interest as it constitutes the first planet identified to be in a stellar HZ outside of the solar system based on studies in 2007. If confirmed as a true planet, at 20.5 lt-yr, it would also be one of the nearest potentially habitable super-Earths.
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Brumberg, Victor A., and Tamara V. Ivanova. "A supplementary note on constructing the general Earth's rotation theory." Proceedings of the International Astronomical Union 9, S310 (July 2014): 13–16. http://dx.doi.org/10.1017/s1743921314007716.
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AbstractRepresenting a post-scriptum supplementary to a previous paper of the authors Brumberg & Ivanova (2011) this note aims to simplify the practical development of the Earth's rotation theory, in the framework of the general planetary theory, avoiding the non–physical secular terms and involving the separation of the fast and slow angular variables, both for planetary–lunar motion and Earth's rotation. In this combined treatment of motion and rotation, the fast angular terms are related to the mean orbital longitudes of the bodies, the diurnal and Euler rotations of the Earth. The slow angular terms are due to the motions of pericenters and nodes, as well as the precession of the Earth. The combined system of the equations of motion for the principal planets and the Moon and the equations of the Earth's rotation is reduced to the autonomous secular system with theoretically possible solution in a trigonometric form. In the above–mentioned paper, the Earth's rotation has been treated in Euler parameters. The trivial change of the Euler parameters to their small declinations from some nominal values may improve the practical efficiency of the normalization of the Earth's rotation equations. This technique may be applied to any three-axial rigid planet. The initial terms of the corresponding expansions are given in the Appendix.
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Dreizler, S., S. V. Jeffers, E. Rodríguez, M. Zechmeister, J. R. Barnes, C. A. Haswell, G. A. L. Coleman, et al. "RedDots: a temperate 1.5 Earth-mass planet candidate in a compact multiterrestrial planet system around GJ 1061." Monthly Notices of the Royal Astronomical Society 493, no. 1 (January 29, 2020): 536–50. http://dx.doi.org/10.1093/mnras/staa248.
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ABSTRACT Small low-mass stars are favourable targets for the detection of rocky habitable planets. In particular, planetary systems in the solar neighbourhood are interesting and suitable for precise characterization. The RedDots campaigns seek to discover rocky planets orbiting nearby low-mass stars. The 2018 campaign targeted GJ 1061, which is the 20th nearest star to the Sun. For three consecutive months we obtained nightly, high-precision radial velocity measurements with the HARPS spectrograph. We analysed these data together with archival HARPS data. We report the detection of three planet candidates with periods of 3.204 ± 0.001, 6.689 ± 0.005, and 13.03 ± 0.03 d, which are close to 1:2:4 period commensurability. After several considerations related to the properties of the noise and sampling, we conclude that a fourth signal is most likely explained by stellar rotation, although it may be due to a planet. The proposed three-planet system (and the potential four-planet solution) is long-term dynamically stable. Planet–planet gravitational interactions are below our current detection threshold. The minimum masses of the three planets range from 1.4 ± 0.2 to 1.8 ± 0.3 M⊕. Planet d, with msin i = 1.64 ± 0.24 M⊕, receives a similar amount of energy as Earth receives from the Sun. Consequently it lies within the liquid-water habitable zone of the star and has a similar equilibrium temperature to Earth. GJ 1061 has very similar properties to Proxima Centauri but activity indices point to lower levels of stellar activity.
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Tarasenko, G. V. "MECHANISM OF ROTATION OF GEOSPHERES OF THE PLANET EARTH." Globus 7, no. 3(60) (May 4, 2021): 21–23. http://dx.doi.org/10.52013/2658-5197-60-3-3.
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In recent decades, a fundamentally new direction of scientific work has appeared in the field of natural sciences, associated with the study of the effect on matter of such physical factors as radiation, electromagnetic radiation, ultrasound, plasma, high pressure, space vacuum, gravity, etc., where the general criterion of extremeness exposure can be the emergence of intermediate highly active states of particles of matter, which ultimately leads to a qualitative change in the micro- and macro characteristics of the processed object, the emergence of new properties. One of the types of complex extreme exposure is the effect of a high-voltage electric discharge, which combines the simultaneous action on a substance of strong mechanical compression, powerful ultrasound, hard X-ray, UV and IR radiation. The electromagnetic fields generated in the course of the discharge also have a strong effect on both the discharge itself and the ionic processes occurring in the surrounding liquid. Under their influence, various physical changes and chemical reactions occur in the processed material.
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Brady, Madison, Jacob L. Bean, Andreas Seifahrt, David Kasper, Rafael Luque, Guđmundur Stefánsson, Julian Stürmer, et al. "Early Results from the HUMDRUM Survey: A Small, Earth-mass Planet Orbits TOI-1450A." Astronomical Journal 168, no. 2 (July 10, 2024): 67. http://dx.doi.org/10.3847/1538-3881/ad500a.
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Abstract M-dwarf stars provide us with an ideal opportunity to study nearby small planets. The HUnting for M Dwarf Rocky planets Using MAROON-X (HUMDRUM) survey uses the MAROON-X spectrograph, which is ideally suited to studying these stars, to measure precise masses of a volume-limited (<30 pc) sample of transiting M-dwarf planets. TOI-1450 is a nearby (22.5 pc) binary system containing a M3 dwarf with a roughly 3000 K companion. Its primary star, TOI-1450A, was identified by the Transiting Exoplanet Survey Satellite (TESS) to have a 2.04 days transit signal, and is included in the HUMDRUM sample. In this paper, we present MAROON-X radial velocities (RVs) which confirm the planetary nature of this signal and measure its mass at nearly 10% precision. The 2.04 days planet, TOI-1450A b, has R b = 1.13 ± 0.04 R ⊕ and M b = 1.26 ± 0.13 M ⊕. It is the second-lowest-mass transiting planet with a high-precision RV mass measurement. With this mass and radius, the planet’s mean density is compatible with an Earth-like composition. Given its short orbital period and slightly sub-Earth density, it may be amenable to JWST follow-up to test whether the planet has retained an atmosphere despite extreme heating from the nearby star. We also discover a nontransiting planet in the system with a period of 5.07 days and a M sin i c = 1.53 ± 0.18 M ⊕ . We also find a 2.01 days signal present in the systems’s TESS photometry that likely corresponds to the rotation period of TOI-1450A’s binary companion, TOI-1450B. TOI-1450A, meanwhile, appears to have a rotation period of approximately 40 days, which is in line with our expectations for a mid-M dwarf.
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Rodríguez Martínez, Romy, David V. Martin, B. Scott Gaudi, Joseph G. Schulze, Anusha Pai Asnodkar, Kiersten M. Boley, and Sarah Ballard. "A Comparison of the Composition of Planets in Single-planet and Multiplanet Systems Orbiting M dwarfs." Astronomical Journal 166, no. 4 (September 1, 2023): 137. http://dx.doi.org/10.3847/1538-3881/aced9a.
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Abstract We investigate and compare the composition of M-dwarf planets in systems with only one known planet (“singles”) to those residing in multiplanet systems (“multis”) and the fundamental properties of their host stars. We restrict our analysis to planets with directly measured masses and radii, which comprise a total of 70 planets: 30 singles and 40 multis in 19 systems. We compare the bulk densities for the full sample, which includes planets ranging in size from 0.52 R ⊕ to 12.8 R ⊕, and find that single planets have significantly lower densities on average than multis, which we cannot attribute to selection biases. We compare the bulk densities normalized by an Earth model for planets with R p < 6 R ⊕ and find that multis are also denser with 99% confidence. We calculate and compare the core/water mass fractions (CMF/WMF) of low-mass planets (M p < 10 M ⊕) and find that the likely rocky multis (with R p < 1.6 R ⊕) have lower CMFs than singles. We also compare the [Fe/H] metallicity and rotation period of all single-planet versus multiplanet host stars with such measurements in the literature and find that multiplanet hosts are significantly more metal-poor than those hosting a single planet. Moreover, we find that the host star metallicity decreases with increasing planet multiplicity. In contrast, we find only a modest difference in the rotation period. The significant differences in planetary composition and metallicity of the host stars point to different physical processes governing the formation of single-planet and multiplanet systems in M dwarfs.
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Canup, Robin M. "Accretion of the Earth." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 366, no. 1883 (September 30, 2008): 4061–75. http://dx.doi.org/10.1098/rsta.2008.0101.
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The origin of the Earth and its Moon has been the focus of an enormous body of research. In this paper I review some of the current models of terrestrial planet accretion, and discuss assumptions common to most works that may require re-examination. Density-wave interactions between growing planets and the gas nebula may help to explain the current near-circular orbits of the Earth and Venus, and may result in large-scale radial migration of proto-planetary embryos. Migration would weaken the link between the present locations of the planets and the original provenance of the material that formed them. Fragmentation can potentially lead to faster accretion and could also damp final planet orbital eccentricities. The Moon-forming impact is believed to be the final major event in the Earth's accretion. Successful simulations of lunar-forming impacts involve a differentiated impactor containing between 0.1 and 0.2 Earth masses, an impact angle near 45° and an impact speed within 10 per cent of the Earth's escape velocity. All successful impacts—with or without pre-impact rotation—imply that the Moon formed primarily from material originating from the impactor rather than from the proto-Earth. This must ultimately be reconciled with compositional similarities between the Earth and the Moon.
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Bjelić, Slobodan, and Nenad Marković. "A more advanced theoretical model of the sphere earth's EM in a foreign homogeneous EM field." Vojnotehnicki glasnik 71, no. 2 (2023): 362–91. http://dx.doi.org/10.5937/vojtehg71-42923.
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Introduction/purpose: The paper describes a more advanced theoretical model of the Earth's EM field based on two-component hypotheses. A defined mathematical model that shows the rotation of the magnetically conducting sphere of Tthe magnetization M in a foreign magnetic field and the components of the magnetic field that may arise due to the rotation of the Earth around its axis. According to the established model, in relation to the reference values of the planet Earth, the values of the components of the other planets in the solar system were calculated and the results were tabulated. Methods: The solution to the problem highlighted in the title of the paper was determined using the combined, for that purpose, formalized methods of physics and mathematical analysis, in order to develop a new, more advanced mathematical model. For this purpose, the method of analogy was used, related to the application of similar structural forms and systems for researching electromagnetic processes and planetary rotation. The method of analogy was applied for two interrelated reasons. The first one is that all values that characterize the function of any natural system are subject to change, and the second one is that the applied solutions do not determine the conditions of the structure's function in each specific case. Results: The solutions in the form of original analytical formulas and numerical values arranged in Table 2, referring to the influence of the rotation of the planets and especially the Earth, will be applied to research the effects of the EM field emitted by the Sun towards the planets, especially the role that the process plays in protecting the planet Earth. The results given in Table 2 are particularly important. Conclusion: The paper discusses the appearance and effect of the Earth's EM field in a way that is understandable at the current level of scientific development. Scientific findings in science and measurements in geoand astrophysics indicate the Sun as a possible source of the EM field that extends through interplanetary space and the component of the Earth's magnetic field is only a response to the influence of that source. Natural phenomena and processes on the Earth can be defined in system theory by a model that contains changes in the parameters of the state of the planet.
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Haqq-Misra, Jacob, and Benjamin P. C. Hayworth. "An Energy Balance Model for Rapidly and Synchronously Rotating Terrestrial Planets." Planetary Science Journal 3, no. 2 (February 1, 2022): 32. http://dx.doi.org/10.3847/psj/ac49eb.
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Abstract This paper describes the habitable energy balance model for exoplanet observations (HEXTOR), which is a model for calculating latitudinal temperature profiles on Earth and other rapidly rotating planets. HEXTOR includes a lookup table method for calculating the outgoing infrared radiative flux and the planetary albedo, which provides improvements over other approaches to parameterizing radiative transfer in an energy balance model (EBM). Validation cases are presented for present-day Earth and other Earth-sized planets with aquaplanet and land planet conditions from 0° to 45° obliquity. A tidally locked coordinate system is also implemented in the EBM, which enables calculation of the horizontal temperature profile for planets in synchronous rotation around low-mass stars. This coordinate-transformed model is applied to cases for TRAPPIST-1e as defined by the TRAPPIST Habitable Atmosphere Intercomparison protocol, which demonstrates better agreement with general circulation models than with the latitudinal EBM. Advances in applying EBMs to exoplanets can be made by using general circulation models as a benchmark for tuning as well as by conducting intercomparisons between EBMs with different physical parameterizations.
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Brinkman, Casey L., James Cadman, Lauren Weiss, Eric Gaidos, Ken Rice, Daniel Huber, Zachary R. Claytor, et al. "Kepler-102: Masses and Compositions for a Super-Earth and Sub-Neptune Orbiting an Active Star." Astronomical Journal 165, no. 2 (January 27, 2023): 74. http://dx.doi.org/10.3847/1538-3881/aca64d.
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Abstract Radial velocity (RV) measurements of transiting multiplanet systems allow us to understand the densities and compositions of planets unlike those in the solar system. Kepler-102, which consists of five tightly packed transiting planets, is a particularly interesting system since it includes a super-Earth (Kepler-102d) and a sub-Neptune-sized planet (Kepler-102e) for which masses can be measured using RVs. Previous work found a high density for Kepler-102d, suggesting a composition similar to that of Mercury, while Kepler-102e was found to have a density typical of sub-Neptune size planets; however, Kepler-102 is an active star, which can interfere with RV mass measurements. To better measure the mass of these two planets, we obtained 111 new RVs using Keck/HIRES and Telescopio Nazionale Galileo/HARPS-N and modeled Kepler-102's activity using quasiperiodic Gaussian process regression. For Kepler-102d, we report a mass upper limit M d < 5.3 M ⊕ (95% confidence), a best-fit mass M d = 2.5 ± 1.4 M ⊕, and a density ρ d = 5.6 ± 3.2 g cm−3, which is consistent with a rocky composition similar in density to the Earth. For Kepler-102e we report a mass M e = 4.7 ± 1.7 M ⊕ and a density ρ e = 1.8 ± 0.7 g cm−3. These measurements suggest that Kepler-102e has a rocky core with a thick gaseous envelope comprising 2%–4% of the planet mass and 16%–50% of its radius. Our study is yet another demonstration that accounting for stellar activity in stars with clear rotation signals can yield more accurate planet masses, enabling a more realistic interpretation of planet interiors.
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Amelkin, N. I. "Evolution of Rotational Motion of the Planet Earth under the Influence of Internal Dissipative Forces." Космические исследования 61, no. 6 (November 1, 2023): 486–97. http://dx.doi.org/10.31857/s0023420623600162.
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The influence of internal dissipation on the rotational motion of the Earth in the gravitational field of the Sun and Moon is studied within the model of M.A. Lavrentiev. The averaged equations of second approximation describing the evolution of the Earth’s rotation axis and the magnitude of its angular velocity are obtained. The dependence of the rate of evolution on the values of the model parameters is studied. Phase trajectories of the evolutionary process are constructed for different parameter values. It is shown that the observed drift of the Earth’s magnetic poles can be explained within the framework of a mechanical model by the angular acceleration of the Earth.
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Luque, R., E. Pallé, D. Kossakowski, S. Dreizler, J. Kemmer, N. Espinoza, J. Burt, et al. "Planetary system around the nearby M dwarf GJ 357 including a transiting, hot, Earth-sized planet optimal for atmospheric characterization." Astronomy & Astrophysics 628 (August 2019): A39. http://dx.doi.org/10.1051/0004-6361/201935801.
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We report the detection of a transiting Earth-size planet around GJ 357, a nearby M2.5 V star, using data from the Transiting Exoplanet Survey Satellite (TESS). GJ 357 b (TOI-562.01) is a transiting, hot, Earth-sized planet (Teq = 525 ± 11 K) with a radius of Rb = 1.217 ± 0.084 R⊕ and an orbital period of Pb = 3.93 d. Precise stellar radial velocities from CARMENES and PFS, as well as archival data from HIRES, UVES, and HARPS also display a 3.93-day periodicity, confirming the planetary nature and leading to a planetary mass of Mb = 1.84 ± 0.31 M⊕. In addition to the radial velocity signal for GJ 357 b, more periodicities are present in the data indicating the presence of two further planets in the system: GJ 357 c, with a minimum mass of Mc = 3.40 ± 0.46 M⊕ in a 9.12 d orbit, and GJ 357 d, with a minimum mass of Md = 6.1 ± 1.0 M⊕ in a 55.7 d orbit inside the habitable zone. The host is relatively inactive and exhibits a photometric rotation period of Prot = 78 ± 2 d. GJ 357 b isto date the second closest transiting planet to the Sun, making it a prime target for further investigations such as transmission spectroscopy. Therefore, GJ 357 b represents one of the best terrestrial planets suitable for atmospheric characterization with the upcoming JWST and ground-based ELTs.
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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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May, E. M., Ryan J. MacDonald, Katherine A. Bennett, Sarah E. Moran, Hannah R. Wakeford, Sarah Peacock, Jacob Lustig-Yaeger, et al. "Double Trouble: Two Transits of the Super-Earth GJ 1132 b Observed with JWST NIRSpec G395H." Astrophysical Journal Letters 959, no. 1 (December 1, 2023): L9. http://dx.doi.org/10.3847/2041-8213/ad054f.
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Abstract The search for rocky planet atmospheres with JWST has focused on planets transiting M dwarfs. Such planets have favorable planet-to-star size ratios, enhancing the amplitude of atmospheric features. Since the expected signal strength of atmospheric features is similar to the single-transit performance of JWST, multiple observations are required to confirm any detection. Here, we present two transit observations of the rocky planet GJ 1132 b with JWST NIRSpec G395H, covering 2.8–5.2 μm. Previous Hubble Space Telescope WFC3 observations of GJ 1132 b were inconclusive, with evidence reported for either an atmosphere or a featureless spectrum based on analyses of the same data set. Our JWST data exhibit substantial differences between the two visits. One transit is consistent with either an H2O-dominated atmosphere containing ∼1% CH4 and trace N2O ( χ ν 2 = 1.13 ) or stellar contamination from unocculted starspots ( χ ν 2 = 1.36 ). However, the second transit is consistent with a featureless spectrum. Neither visit is consistent with a previous report of HCN. Atmospheric variability is unlikely to explain the scale of the observed differences between the visits. Similarly, our out-of-transit stellar spectra show no evidence of changing stellar inhomogeneity between the two visits—observed 8 days apart, only 6.5% of the stellar rotation rate. We further find no evidence of differing instrumental systematic effects between visits. The most plausible explanation is an unlucky random noise draw leading to two significantly discrepant transmission spectra. Our results highlight the importance of multivisit repeatability with JWST prior to claiming atmospheric detections for these small, enigmatic planets.
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Khalid, M., Mariam Sultana, and Faheem Zaidi. "Delta T: Polynomial Approximation of Time Period 1620–2013." Journal of Astrophysics 2014 (July 9, 2014): 1–4. http://dx.doi.org/10.1155/2014/480964.
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The difference between the Uniform Dynamical Time and Universal Time is referred to as ΔT (delta T). Delta T is used in numerous astronomical calculations, that is, eclipses,and length of day. It is additionally required to reduce quantified positions of minor planets to a uniform timescale for the purpose of orbital determination. Since Universal Time is established on the basis of the variable rotation of planet Earth, the quantity ΔT mirrors the unevenness of that rotation, and so it changes slowly, but rather irregularly, as time passes. We have worked on empirical formulae for estimating ΔT and have discovered a set of polynomials of the 4th order with nine intervals which is accurate within the range of ±0.6 seconds for the duration of years 1620–2013.
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Makarov, Valeri V., and Alexey Goldin. "Secular Orbital Dynamics of the Possibly Habitable Planet K2-18 b with and without the Proposed Inner Companion." Universe 9, no. 11 (October 28, 2023): 463. http://dx.doi.org/10.3390/universe9110463.
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The transiting planet K2-18 b is one of the best candidates for a relatively nearby world harboring biological life. The long-term orbital evolution of this planet is investigated using theoretical and purely numerical techniques for two possible configurations: A single planet orbiting the host star, and a two-planet system including the proposed inner planet close to the 4:1 mean motion rationalization. The emphasis is made on the secular changes of eccentricity and orbital inclination, which are important for the climate stability of the planet. It is demonstrated that the secular orbital dynamics of planet K2-18 b with an internal companion are accurately represented by the periodic eccentricity and inclination exchange on the time scales of a few Kyr. A single planet is not expected to experience fast orbital changes, with the much weaker tidal and rotation-driven perturbations mostly reflecting in a slow periastron and nodal precession. The tidal decay of the orbit is too insignificant on the time scale of the stellar age. However, the conditions for the habitability of a single K2-18 b planet are much improved if, like the Earth, it rotates faster than the mean motion and its rotation angle is tilted by a hypothetical moon. Milanković’s cycles of the habitable planet’s climate are discussed for both configurations.
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Louden, Emma M., Songhu Wang, Joshua N. Winn, Erik A. Petigura, Howard Isaacson, Luke Handley, Samuel W. Yee, Corey Beard, Joseph M. Akana Murphy, and Gregory Laughlin. "A Larger Sample Confirms Small Planets around Hot Stars Are Misaligned ∗." Astrophysical Journal Letters 968, no. 1 (June 1, 2024): L2. http://dx.doi.org/10.3847/2041-8213/ad4b1b.
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Abstract The distribution of stellar obliquities provides critical insight into the formation and evolution pathways of exoplanets. In the past decade, it was found that hot stars hosting hot Jupiters are more likely to have high obliquities than cool stars, but it is not clear whether this trend exists only for hot Jupiters or holds for other types of planets. In this work, we extend the study of the obliquities of hot (6250–7000 K) stars with transiting super-Earth-sized and sub-Neptune-sized planets. We constrain the obliquity distribution based on measurements of the stars’ projected rotation velocities. Our sample consists of 170 TESS and Kepler planet-hosting stars and 180 control stars chosen to have indistinguishable spectroscopic characteristics. In our analysis, we find evidence suggesting that the planet hosts have a systematically higher 〈 sin i 〉 compared to the control sample. This result implies that the planet hosts tend to have lower obliquities. However, the observed difference in 〈 sin i 〉 is not significant enough to confirm spin–orbit alignment as it is 3.8σ away from perfect alignment. We also find evidence that within the planet-hosting stars there is a trend of higher obliquity (lower 〈 sin i 〉 ) for the hotter stars (T eff > 6250 K) than for the cooler stars in the sample. This suggests that hot stars hosting smaller planets exhibit a broader obliquity distribution ( 〈 sin i 〉 = 0.79 ± 0.053 ) than cooler planet-hosting stars, indicating that high obliquities are not exclusive to hot Jupiters and instead are more broadly tied to hot stars.
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Pezzotti, C., P. Eggenberger, G. Buldgen, G. Meynet, V. Bourrier, and C. Mordasini. "Revisiting Kepler-444." Astronomy & Astrophysics 650 (June 2021): A108. http://dx.doi.org/10.1051/0004-6361/202039652.
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Context. Kepler-444 is one of the oldest planetary systems known thus far. Its peculiar configuration consisting of five sub-Earth-sized planets orbiting the companion to a binary stellar system makes its early history puzzling. Moreover, observations of HI-Lyα variations raise many questions about the potential presence of escaping atmospheres today. Aims. We aim to study the orbital evolution of Kepler-444-d and Kepler-444-e and the impact of atmospheric evaporation on Kepler-444-e. Methods. Rotating stellar models of Kepler-444-A were computed with the Geneva stellar evolution code and coupled to an orbital evolution code, accounting for the effects of dynamical, equilibrium tides and atmospheric evaporation. The impacts of multiple stellar rotational histories and X-ray and extreme ultraviolet (XUV) luminosity evolutionary tracks are explored. Results. Using detailed rotating stellar models able to reproduce the rotation rate of Kepler-444-A, we find that its observed rotation rate is perfectly in line with what is expected for this old K0-type star, indicating that there is no reason for it to be exceptionally active as would be required to explain the observed HI-Lyα variations from a stellar origin. We show that given the low planetary mass (~0.03 M⊕) and relatively large orbital distance (~0.06 AU) of Kepler-444-d and e, dynamical tides negligibly affect their orbits, regardless of the stellar rotational history considered. We point out instead how remarkable the impact is of the stellar rotational history on the estimation of the lifetime mass loss for Kepler-444-e. We show that, even in the case of an extremely slow rotating star, it seems unlikely that such a planet could retain a fraction of the initial water-ice content if we assume that it formed with a Ganymede-like composition.
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Tarassenko, G. V., and M. G. Tarassenko. "COLD FUSION ON THE BASIS OF THE MODEL OF THE PLANET EARTH." Globus 7, no. 3(60) (May 4, 2021): 12–20. http://dx.doi.org/10.52013/2658-5197-60-3-2.
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Cold fusion is not possible in atmospheric conditions but it is possible underground. Synthesis formation is connected with electricity in the entrails of the earth. Electricity is produced with the help of friction and geospheres speed differential from the core (20-40 m/s to the surface), the speed of which according to GPS data is 2-16 cm per year. Faraday has determined planet electric capacity with 1 farad. Continent drift takes place at the expense of geospheres rotation, leading to subduction of ocean and continental plates, abduction, spreading, rifting and collision. An example of planet formation is ball concretions.
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Osborn, Ares, David J. Armstrong, Bryson Cale, Rafael Brahm, Robert A. Wittenmyer, Fei Dai, Ian J. M. Crossfield, et al. "TOI-431/HIP 26013: a super-Earth and a sub-Neptune transiting a bright, early K dwarf, with a third RV planet." Monthly Notices of the Royal Astronomical Society 507, no. 2 (August 11, 2021): 2782–803. http://dx.doi.org/10.1093/mnras/stab2313.
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ABSTRACT We present the bright (Vmag = 9.12), multiplanet system TOI-431, characterized with photometry and radial velocities (RVs). We estimate the stellar rotation period to be 30.5 ± 0.7 d using archival photometry and RVs. Transiting Exoplanet Survey Satellite (TESS) objects of Interest (TOI)-431 b is a super-Earth with a period of 0.49 d, a radius of 1.28 ± 0.04 R⊕, a mass of 3.07 ± 0.35 M⊕, and a density of 8.0 ± 1.0 g cm−3; TOI-431 d is a sub-Neptune with a period of 12.46 d, a radius of 3.29 ± 0.09 R⊕, a mass of $9.90^{+1.53}_{-1.49}$ M⊕, and a density of 1.36 ± 0.25 g cm−3. We find a third planet, TOI-431 c, in the High Accuracy Radial velocity Planet Searcher RV data, but it is not seen to transit in the TESS light curves. It has an Msin i of $2.83^{+0.41}_{-0.34}$ M⊕, and a period of 4.85 d. TOI-431 d likely has an extended atmosphere and is one of the most well-suited TESS discoveries for atmospheric characterization, while the super-Earth TOI-431 b may be a stripped core. These planets straddle the radius gap, presenting an interesting case-study for atmospheric evolution, and TOI-431 b is a prime TESS discovery for the study of rocky planet phase curves.
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Maurin, Anne-Sophie, Franck Selsis, Franck Hersant, and Marco Delbò. "Characterization of rocky exoplanets from their infrared phase curve." Proceedings of the International Astronomical Union 6, S276 (October 2010): 485–86. http://dx.doi.org/10.1017/s1743921311020904.
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AbstractDuring the last few years, observations have yielded an abundant population of short-period planets under 15 Earth masses. Among those, hot terrestrial exoplanets represent a key population to study the survival of dense atmospheres close to their parent star. Thermal emission from exoplanets orbiting low-mass stars will be observable with the next generation of infrared telescopes, in particular the JWST. In order to constrain planetary and atmospheric properties, we have developed models to simulate the variation of the infrared emission along the path of the orbit (IR phase curve) for both airless planets and planets with dense atmospheres. Here, we focus on airless planets and present preliminary results on the influence of orbital elements, planet rotation, surface properties and observation geometry. Then, using simulated noisy phase curves, we test the retrieval of planets' properties and identify the degeneracies.
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Barbiero*, Flavio. "Earth an Unstable Planet Why and How the Poles can Shift." Current Trends in Engineering Science (CTES) 3, no. 1 (January 28, 2023): 1–4. http://dx.doi.org/10.54026/ctes/1019.
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bstract There is compelling evidence that the poles have shifted in the past, but this idea is dismissed as impossible by the scientific community on the assumption that the stabilizing effect of the equatorial bulge is so great that no conceivable force could make the Earth shifting on its axis, except for the collision with a planet-size body. In theory, however, a wide shift of the poles could be obtained simply by reshaping the equatorial bulge, a ring of matter that from about 15km at the equator decreases down to zero at the poles. At least 20% of this matter is made by water, which covers 2/3d of the whole Earth. A well-known physical law assures that free liquid surfaces create instability, thus Earth is an inherently unstable planet. Every displacement of water provokes a wobbling of the axis of rotation. An ocean wide tide or tsunami of hundreds of meters would displace the axis of some degrees, therefore the polar icecaps would rotate off-center developing a toppling torque. The shift would increasingly grow to the point of provoking the sudden rebound of the Earth’s mantle and in the end a reshaping of the equatorial bulge around a different axis of rotation. We can imagine more than one reason that in theory could provoke a tide of the required magnitude, but the most probable culprit should be the impact of a large asteroid. The analysis of the behaviour of a gyroscope subject to a disturbing torque provides a clear explanation of why and how the impulsive torque produced by the impact of an asteroid could trigger a process which in the end results in a shift of the poles.
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Levin, B. W., E. V. Sasorova, V. B. Gurianov, and V. V. Yarmolyuk. "The relationship between global volcanic activity and variations in the velocity of Earth's rotation." Доклады Академии наук 484, no. 6 (May 23, 2019): 729–33. http://dx.doi.org/10.31857/s0869-56524846729-733.
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Analysis of observations of the Earth's rotational velocity and volcanic activity of the planet from 1720 until 2015 suggests that higher volcanic activity temporally coincided with periods of decreased angular velocity of Earth's rotation (deceleration), and, vice versa, lower volcanic activity coincided with the periods of increased velocity of the Earth's rotation (acceleration). Our analysis employed the data from the catalog by the Smithsonian Institute, United States, in which each volcanic explosion had its own determined value of the Volcanic Explosivity Index (VEI). The total number of selected intensive eruptions with VEI > 4 was 160, including 25 eruptions with VEI > 5. At present (beginning from 2006), the Earth was entry in a deceleration phase and series of catastrophic eruptions reveals the tendency toward intensifying volcanic activity.
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Laliotis, Katherine, Jennifer A. Burt, Eric E. Mamajek, Zhexing Li, Volker Perdelwitz, Jinglin Zhao, R. Paul Butler, et al. "Doppler Constraints on Planetary Companions to Nearby Sun-like Stars: An Archival Radial Velocity Survey of Southern Targets for Proposed NASA Direct Imaging Missions*." Astronomical Journal 165, no. 4 (March 27, 2023): 176. http://dx.doi.org/10.3847/1538-3881/acc067.
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Abstract Directly imaging temperate rocky planets orbiting nearby, Sun-like stars with a 6 m class IR/O/UV space telescope, recently dubbed the Habitable Worlds Observatory, is a high-priority goal of the Astro2020 Decadal Survey. To prepare for future direct imaging (DI) surveys, the list of potential targets should be thoroughly vetted to maximize efficiency and scientific yield. We present an analysis of archival radial velocity data for southern stars from the NASA/NSF Extreme Precision Radial Velocity (EPRV) Working Group’s list of high-priority target stars for future DI missions (drawn from the HabEx, LUVOIR, and Starshade Rendezvous studies). For each star, we constrain the region of companion mass and period parameter space we are already sensitive to based on the observational baseline, sampling, and precision of the archival radial velocity (RV) data. Additionally, for some of the targets, we report new estimates of magnetic activity cycle periods, rotation periods, improved orbital parameters for previously known exoplanets, and new candidate planet signals that require further vetting or observations to confirm. Our results show that for many of these stars we are not yet sensitive to even Saturn-mass planets in the habitable zone, let alone smaller planets, highlighting the need for future EPRV vetting efforts before the launch of a DI mission. We present evidence that the candidate temperate super-Earth exoplanet HD 85512b is most likely due to the star’s rotation, and report an RV acceleration for δ Pav that supports the existence of a distant giant planet previously inferred from astrometry.
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Bonfils, X., J. M. Almenara, R. Cloutier, A. Wünsche, N. Astudillo-Defru, Z. Berta-Thompson, F. Bouchy, et al. "Radial velocity follow-up of GJ1132 with HARPS." Astronomy & Astrophysics 618 (October 2018): A142. http://dx.doi.org/10.1051/0004-6361/201731884.
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The source GJ1132 is a nearby red dwarf known to host a transiting Earth-size planet. After its initial detection, we pursued an intense follow-up with the HARPS velocimeter. We now confirm the detection of GJ1132b with radial velocities alone. We refined its orbital parameters, and in particular, its mass (mb = 1.66 ± 0.23 M⊕), density (ρb = 6.3 ± 1.3 g cm−3), and eccentricity (eb < 0.22; 95%). We also detected at least one more planet in the system. GJ1132c is a super-Earth with period Pc = 8.93 ± 0.01 days and minimum mass mc sinic = 2.64 ± 0.44 M⊕. Receiving about 1.9 times more flux than Earth in our solar system, its equilibrium temperature is that of a temperate planet (Teq = 230−300 K for albedos A = 0.75 − 0.00), which places GJ1132c near the inner edge of the so-called habitable zone. Despite an a priori favorable orientation for the system, Spitzer observations reject most transit configurations, leaving a posterior probability <1% that GJ1132c transits. GJ1132(d) is a third signal with period Pd = 177 ± 5 days attributed to either a planet candidate with minimum mass md sin id = 8.4−2.5+1.7 M⊕ or stellar activity. Its Doppler signal is the most powerful in our HARPS time series but appears on a timescale where either the stellar rotation or a magnetic cycle are viable alternatives to the planet hypothesis. On the one hand, the period is different than that measured for the stellar rotation (~125 days), and a Bayesian statistical analysis we performed with a Markov chain Monte Carlo and Gaussian processes demonstrates that the signal is better described by a Keplerian function than by correlated noise. On the other hand, periodograms of spectral indices sensitive to stellar activity show power excess at similar periods to that of this third signal, and radial velocity shifts induced by stellar activity can also match a Keplerian function. We, therefore, prefer to leave the status of GJ1132(d) undecided.
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Shaikh*, Md Sadique. "Modelling Insight to Ball Eyes for Higher Dimensional Hyperspace Vision." Journal of Biomedical Research & Environmental Sciences 2, no. 7 (July 31, 2021): 599–601. http://dx.doi.org/10.37871/jbres1283.
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To understand this complicated conceptual idea let me begin first with the definition of VISION and then after DIMENSIONS. The Vision is ability to acquire surrounding with input light, shapes, places, color to brain to create animated CONSCIOUSNESS in the help of Brain call Observable Life, Planet, Universe and Multiverse. Equally Vision also important to grow Brain Intelligence and Control to enhance, develop and shape planet earth and at present observable Universe. Now I would like to define term Dimensions as the ability of Eyes to scan surrounding available Vision with Left, Right, Top, Bottom, Reflection, Rotation, Transformation, Spinning and Diagonal with all possible angles and geometry and provide data to Brain to create high definition Consciousness of environment, planet, universe and multiverse....
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Ciulin, Dan. "Contributions to a Future Inertial Motor and More." International Journal of Strategic Information Technology and Applications 4, no. 1 (January 2013): 63–97. http://dx.doi.org/10.4018/jsita.2013010105.
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For a future interplanetary trip, a space ship must be able to take off and/or land on a planet and travel at a convenient speed, insure convenient life conditions for the embarked crew, and keep contact with Earth. Chemical jet-engines used for the space ships must throw masses with enough speed to insure a convenient lifting force. Ion jet-engines, which have a much bigger jet-speed than chemical, may work for a longer time but the resulting force is small and cannot insure the take off and/or landing on a planet. A future inertial motor does not need to throw masses but needs only energy to produce the necessary lifting force. The paper presents contributions to build such a motor. As on a given vehicle, mainly rotations may be done to insure its propulsion, we start by presenting generally the rotations, at first for the electronic devices and then for mechanical one Methods that may convert the rotation into translation are after presented. Observing that the mathematical models used for rotations are extended from trigonometric functions to elliptical and ultra-elliptical ones, the author presents the differential equations that define such functions. Finally, using the modified Euler equations, a mathematical model for the gravitational waves is deduced. By using this type of waves, a permanent contact between an interplanetary ship and the earth can be kept. The presented tools may be used for modeling the fields and insure also a more comprehensive understanding.
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Sulis, S., D. Dragomir, M. Lendl, V. Bourrier, B. O. Demory, L. Fossati, P. E. Cubillos, et al. "Multi-season optical modulation phased with the orbit of the super-Earth 55 Cancri e." Astronomy & Astrophysics 631 (November 2019): A129. http://dx.doi.org/10.1051/0004-6361/201936066.
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Context. 55 Cnc e is a transiting super-Earth orbiting a solar-like star with an orbital period of ~17.7 h. In 2011, using the Microvariability and Oscillations in Stars (MOST) space telescope, a quasi-sinusoidal modulation in flux was detected with the same period as the planetary orbit. The amplitude of this modulation was too large to be explained as the change in light reflected or emitted by the planet. Aims. The MOST telescope continued to observe 55 Cnc e for a few weeks per year over five years (from 2011 to 2015), covering 143 individual transits. This paper presents the analysis of the observed phase modulation throughout these observations and a search for the secondary eclipse of the planet. Methods. The most important source of systematic noise in MOST data is due to stray-light reflected from the Earth, which is modulated with both the orbital period of the satellite (101.4 min) and the Earth’s rotation period. We present a new technique to deal with this source of noise, which we combined with standard detrending procedures for MOST data. We then performed Markov chain Monte Carlo analyses of the detrended light curves, modeling the planetary transit and phase modulation. Results. We find phase modulations similar to those seen in 2011 in most of the subsequent years; however, the amplitude and phase of maximum light are seen to vary, from year to year, from 113 to 28 ppm and from 0.1 to 3.8 rad. The secondary eclipse is not detected, but we constrain the geometric albedo of the planet to less than 0.47 (2σ). Conclusions. While we cannot identify a single origin of the observed optical modulation, we propose a few possible scenarios. Those include star-planet interaction, such as coronal rains and spots rotating with the motion of the planet along its orbit, or the presence of a transiting circumstellar torus of dust. However, a detailed interpretation of these observations is limited by their photometric precision. Additional observations at optical wavelengths could measure the variations at higher precision, contribute to uncovering the underlying physical processes, and measure or improve the upper limit on the albedo of the planet.
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Sloane, Stephen A., Edward F. Guinan, and Scott G. Engle. "Super-Earth GJ 667Cc: Age and XUV Irradiances of the Temperate-zone Planet with Potential for Advanced Life." Research Notes of the AAS 7, no. 6 (June 28, 2023): 135. http://dx.doi.org/10.3847/2515-5172/ace189.
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Abstract GJ 667Cc is a nearby (23.6 lt-yr) super-Earth that orbits within the habitable zone (HZ) of its ∼M2V host star and has Earth-like properties: (M- sin ( i ) ∼ 4.1 M ⊕ ; R ∼ 1.7 R ⊕; T eq (A = 0.3) ∼ 277 K). The age of the star/planet is poorly constrained at 2 ≳ Gyr. Age is crucial in evaluating the potential for complex life. We determine an age of ∼6.10 ± 2.2 Gyr from our recent Age-Rotation relations. This is compatible with its low metallicity ([Fe/H] ∼ −0.59 ± 0.1 dex), weak coronal/chromospheric X-ray/FUV emissions, and space motions. We also determine the photodissociating/photoionizing X-ray-UV irradiances from Chandra and ROSAT X-ray and HST/FUV observations. Like most HZ-planets hosted by M-dwarfs, these irradiances are much higher than Earth's and are detrimental to the planet's atmosphere retention, water inventories, and habitability. A strong geomagnetic field could mitigate atmospheric erosion, permitting life to develop.
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Kemmer, J., S. Dreizler, D. Kossakowski, S. Stock, A. Quirrenbach, J. A. Caballero, P. J. Amado, et al. "Discovery and mass measurement of the hot, transiting, Earth-sized planet, GJ 3929 b." Astronomy & Astrophysics 659 (March 2022): A17. http://dx.doi.org/10.1051/0004-6361/202142653.
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We report the discovery of GJ 3929 b, a hot Earth-sized planet orbiting the nearby M3.5 V dwarf star, GJ 3929 (G 180-18, TOI-2013). Joint modelling of photometric observations from TESS sectors 24 and 25 together with 73 spectroscopic observations from CARMENES and follow-up transit observations from SAINT-EX, LCOGT, and OSN yields a planet radius of Rb = 1.150 ± 0.040 R⊕, a mass of Mb = 1.21 ± 0.42 M⊕, and an orbital period of Pb = 2.6162745 ± 0.0000030 d. The resulting density of ρb = 4.4 ± 1.6 g cm−3 is compatible with the Earth’s mean density of about 5.5 g cm−3. Due to the apparent brightness of the host star (J = 8.7 mag) and its small size, GJ 3929 b is a promising target for atmospheric characterisation with the JWST. Additionally, the radial velocity data show evidence for another planet candidate with P[c] = 14.303 ± 0.035 d, which is likely unrelated to the stellar rotation period, Prot = 122 ± 13 d, which we determined from archival HATNet and ASAS-SN photometry combined with newly obtained TJO data.
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Gunaydin, Gizem, Gamze Duvan, and Eren Ozceylan. "An Integrated Approach of Multi-Criteria Decision Making to Determine the Most Habitable Planet." HighTech and Innovation Journal 3, no. 2 (February 19, 2022): 151–61. http://dx.doi.org/10.28991/hij-2022-03-02-04.
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Every planet in the universe has its own characteristics. These features make the planets different among themselves. For this reason, all the different properties of the planets must be evaluated at the same time when determining habitable planets. This situation requires a multi-criteria decision making (MCDM) approach. In this study, a list of habitable planets (nine planets and the Moon) has been considered. Seventeen different criteria such as mass, gravity, diameter, density, escape velocity, rotation time, day of length, distance from the sun, perihelion, aphelion, orbital period, orbital velocity, orbital inclination, orbital eccentricity, obliquity to orbit, mean temperature, and number of satellites are taken into account. The weights of criteria are determined with DEMATEL (The Decision Making Trial and Evaluation Laboratory) by analyzing the interactions among criteria. Orbital inclination is the criterion with the highest weight, and the criterion with the lowest weight is the number of satellites. After weighting the criteria with DEMATEL, VIKOR (VIseKriterijumska Optimizacija I Kompromisno Resenje) and TOPSIS (Technique for Order Preference to Similarity to Ideal Solution) approaches are used to rank the planets. According to the TOPSIS, Earth is ranked first, Venus ranked second and Mercury ranked third in the order of the most habitable planets. According to the VIKOR method, Earth is ranked first, Mars is ranked second, and Mercury is ranked third in the order of the most habitable planets. Finally, the same calculations are considered with equal weights and the results are discussed. Doi: 10.28991/HIJ-2022-03-02-04 Full Text: PDF
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Kawahara, Hajime, and Yuka Fujii. "Image Retrieval of Earth-like Planets from Light Curves." Proceedings of the International Astronomical Union 8, S293 (August 2012): 71–73. http://dx.doi.org/10.1017/s1743921313012568.
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AbstractSurface environment of habitable exoplanets will be important for astrobiologists on exoplanets in near future. Diverse surface environments on the Earth including continents, ocean, and meteorological condition (clouds and rains) serve as the backbone of biodiversity. One of the promising approaches to know the landscape of the terrestrial exoplanets is to use scattered light of the planet through direct imaging.Since spin rotation and orbital revolution change illuminating area on planetary surface and cause time variation to disk-integrated brightness, light curves carry spatial information on the planetary surface. We propose an inversion technique of annual reflected light curves to sketch a two-dimensional albedo map of exoplanets, named the spin-orbit tomography (SOT). Applying the SOT to realistic simulations of the reflected light of an Earth-twin, we demonstrate how the SOT works. The mean cloud and continental distributions can be roughly obtained with single band photometry and difference of two-bands photometry, respectively. The SOT retrieves the planetary image without actually resolving the planet, which can be used to know the habitat of the exoplanets in near future.
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Moraes, R. A., G. Borderes-Motta, O. C. Winter, and J. Monteiro. "On the stability of additional moons orbiting Kepler-1625 b." Monthly Notices of the Royal Astronomical Society 510, no. 2 (January 5, 2022): 2583–96. http://dx.doi.org/10.1093/mnras/stab3576.
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ABSTRACT Since it was proposed, the exomoon candidate Kepler-1625 b-I has changed the way we see satellite systems. Because of its unusual physical characteristics, many questions about the stability and origin of this candidate have been raised. Currently, we have enough theoretical studies to show that if Kepler-1625 b-I is indeed confirmed, it will be stable. Regarding its origin, previous works indicated that the most likely scenario is capture, although conditions for in situ formation have also been investigated. In this work, we assume that Kepler-1625 b-I is an exomoon and study the possibility of an additional, massive exomoon being stable in the same system. To model this scenario, we perform N-body simulations of a system including the planet, Kepler-1625 b-I, and one extra Earth-like satellite. Based on previous results, the satellites in our system will be exposed to tidal interactions with the planet and to gravitational effects owing to the rotation of the planet. We find that the satellite system around Kepler-1625 b is capable of harbouring two massive satellites. The extra Earth-like satellite can be stable in various locations between the planet and Kepler-1625 b-I, with a preference for regions inside $25\, R_{\rm p}$. Our results suggest that the strong tidal interaction between the planet and the satellites is an important mechanism to ensure the stability of satellites in circular orbits closer to the planet, while the 2:1 mean motion resonance between the Earth-like satellite and Kepler-1625 b-I would provide stability for satellites in wider orbits.
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Bryant, Edward M., and Daniel Bayliss. "Revisiting WASP-47 with ESPRESSO and TESS." Astronomical Journal 163, no. 5 (April 6, 2022): 197. http://dx.doi.org/10.3847/1538-3881/ac58ff.
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Abstract WASP-47 hosts a remarkable planetary system containing a hot Jupiter (WASP-47 b; P = 4.159 days) with an inner super-Earth (WASP-47 e; P = 0.7896 days), a close-orbiting outer Neptune (WASP-47 d; P = 9.031 days), and a long-period giant planet (WASP-47 c; P = 588.4 days). We use the new Transiting Exoplanet Survey Satellite (TESS) photometry to refine the orbital ephemerides of the transiting planets in the system, particularly the hot Jupiter WASP-47 b, for which we find an update equating to a 17.4 minute shift in the transit time. We report new radial-velocity measurements from the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) spectrograph for WASP-47, which we use to refine the masses of WASP-47 d and WASP-47 e, with a high-cadence observing strategy aimed to focus on the super-Earth WASP-47 e. We detect a periodic modulation in the K2 photometry that corresponds to a 32.5 ± 3.9 day stellar rotation, and find further stellar activity signals in our ESPRESSO data consistent with this rotation period. For WASP-47 e we measure a mass of 6.77 ± 0.57 M ⊕ and a bulk density of 6.29 ± 0.60 g cm−3, giving WASP-47 e the second most precisely measured density to date of any super-Earth. The mass and radius of WASP-47 e, combined with the exotic configuration of the planetary system, suggest the WASP-47 system formed through a mechanism different to systems with multiple small planets or more typical isolated hot Jupiters.