共查询到20条相似文献，搜索用时 31 毫秒
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《Planetary and Space Science》2007,55(5):651-660
In this paper we estimate the likelihood to find habitable Earth-like planets on stable orbits for 86 selected extrasolar planetary systems, where luminosity, effective temperature and stellar age are known. For determining the habitable zone (HZ) an integrated system approach is used taking into account a variety of climatological, biogeochemical, and geodynamical processes. Habitability is linked to the photosynthetic activity on the planetary surface. We find that habitability strongly depends on the age of the stellar system and the characteristics of a virtual Earth-like planet. In particular, the portion of land/ocean coverages plays an important role. We approximated the conditions for orbital stability using a method based on the Hill radius. Almost 60% of the investigated systems could harbour habitable Earth-like planets on stable orbits. In 18 extrasolar systems we find even better prerequisites for dynamic habitability than in our own solar system. In general our results are comparable to those with an HZ determination based only on climatic constraints. However, there are remarkable differences for land worlds and for systems older than about 7 Gyr. 相似文献
3.
The TrES‐2 system harbors one planet which was discovered with the transit technique. In this work we investigate the dynamical behavior of possible additional, lower‐mass planets. We identify the regions where such planets can move on stable orbits and show how they depend on the initial eccentricity and inclination. We find, that there are stable regions inside and outside the orbit of TrES‐2b where additional, smaller planets can move. We also show that those planets can have a large orbital inclination which makes a detection with the transit technique very difficult (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
4.
A. M. S. Smith L. Hebb A. Collier Cameron D. R. Anderson T. A. Lister C. Hellier D. Pollacco D. Queloz I. Skillen R. G. West 《Monthly notices of the Royal Astronomical Society》2009,398(4):1827-1834
We present results from a search for additional transiting planets in 24 systems already known to contain a transiting planet. We model the transits due to the known planet in each system and subtract these models from light curves obtained with the SuperWASP (Wide Angle Search for Planets) survey instruments. These residual light curves are then searched for evidence of additional periodic transit events. Although we do not find any evidence for additional planets in any of the planetary systems studied, we are able to characterize our ability to find such planets by means of Monte Carlo simulations. Artificially generated transit signals corresponding to planets with a range of sizes and orbital periods were injected into the SuperWASP photometry and the resulting light curves searched for planets. As a result, the detection efficiency as a function of both the radius and orbital period of any second planet is calculated. We determine that there is a good (>50 per cent) chance of detecting additional, Saturn-sized planets in P ∼ 10 d orbits around planet-hosting stars that have several seasons of SuperWASP photometry. Additionally, we confirm previous evidence of the rotational stellar variability of WASP-10, and refine the period of rotation. We find that the period of the rotation is 11.91 ± 0.05 d, and the false alarm probability for this period is extremely low (∼10−13 ) . 相似文献
5.
St. Raetz M. Mugrauer T.O.B. Schmidt T. Roell T. Eisenbeiss M.M. Hohle N. Tetzlaff M. Va&#x;ko A. Seifahrt Ch. Broeg J. Koppenhoefer R. Neuhuser 《Astronomische Nachrichten》2009,330(5):475-481
We report on observations of transit events of the transiting planets XO‐1b and TrES‐1 with a 25 cm telescope of the University Observatory Jena. With the transit timings for XO‐1b from all 50 available XO, SuperWASP, Transit Light Curve (TLC)‐Project‐ and Exoplanet Transit Database (ETD)‐data, including our own I ‐band photometry obtained in March 2007, we find that the orbital period is P = (3.941501 ± 0.000001) d, a slight change by ∼3 s compared to the previously published period. We present new ephemeris for this transiting planet. Furthermore, we present new R ‐band photometry of two transits of TrES‐1. With the help of all available transit times from literature this allows us to refine the estimate of the orbital period: P = (3.0300722 ± 0.0000002) d. Our observations will be useful for future investigations of timing variations caused by additional perturbing planets and/or stellar spots and/or moons (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The tidal evolution of ten Kepler candidate two-planet systems is investigated by using the general secular perturbation theory, and then a general picture of tidal evolution for these systems is described. Taking the KOI 1239 system as an example, the tidal effect of the system is studied in detail, the results indicate that the dissipative term of the tidal effect causes the attenuation of planets’ orbital eccentricities, and it plays a dominant role in the process of orbital evolution, however, the conservative term of the tidal effect and the relativistic effect may damp the excitation of the eccentricity of the inner planet under the secular perturbation of the outer planet. In addition, the process of tidal evolution is also affected by both the initial eccentricity of the outer planet and the planet's tidal dissipation coeffcient. At the same time, the numerical simulation on the tidal evolution of the KOI 1239 system is also made, and the numerical results are consistent with those of general secular perturbation theory. 相似文献
8.
The extrasolar planets discovered to date possess unexpected orbital elements. Most orbit their host stars with larger eccentricities and smaller semi-major axes than similarly sized planets in our own Solar System do. It is generally agreed that the interaction between giant planets and circumstellar disks (Type II migration) drives these planets inward to small radii, but the effect of these same disks on orbital eccentricity, ?, is controversial. Several recent analytic calculations suggest that disk-planet interactions can excite eccentricity, while numerical studies generally produce eccentricity damping. This paper addresses this controversy using a quasi-analytic approach, drawing on several preceding analytic studies. This work refines the current treatment of eccentricity evolution by removing several approximations from the calculation of disk torques. We encounter neither uniform damping nor uniform excitation of orbital eccentricity, but rather a function d?/dt that varies in both sign and magnitude depending on eccentricity and other Solar System properties. Most significantly, we find that for every combination of disk and planet properties investigated herein, corotation torques produce negative values of d?/dt for some range in ? within the interval [0.1, 0.5]. If corotation torques are saturated, this region of eccentricity damping disappears, and excitation occurs on a short timescale of less than 0.08 Myr. Thus, our study does not produce eccentricity excitation on a timescale of a few Myr—we obtain either eccentricity excitation on a short time scale, or eccentricity damping on a longer time scale. Finally, we discuss the implications of this result for producing the observed range in extrasolar planet eccentricity. 相似文献
9.
A. V. Melnikov 《Astronomy Letters》2016,42(2):115-125
The chaotic orbital dynamics of the planet in the wide visual binary star system 16 Cyg is considered. The only planet in this system has a significant orbital eccentricity, e = 0.69. Previously, Holman et al. suggested the possibility of chaos in the orbital dynamics of the planet due to the proximity of 16 Cyg to the separatrix of the Lidov–Kozai resonance. We have calculated the Lyapunov characteristic exponents on the set of possible orbital parameters for the planet. In all cases, the dynamics of 16 Cyg is regular with a Lyapunov time of more than 30 000 yr. The dynamics is considered in detail for several possible models of the planetary orbit; the dependences of Lyapunov exponents on the time of their calculation and the time dependences of osculating orbital elements have been constructed. Phase space sections for the system dynamics near the Lidov–Kozai resonance have been constructed for all models. A chaotic behavior in the orbital motion of the planet in 16 Cyg is shown to be unlikely, because 16 Cyg in phase space is far from the separatrix of the Lidov–Kozai resonance at admissible orbital parameters, with the chaotic layer near the separatrix being very narrow. 相似文献
10.
Nelson Callegari Jr. Ádrian Rodríguez 《Celestial Mechanics and Dynamical Astronomy》2013,116(4):389-416
We numerically investigate the dynamics of rotation of several close-in terrestrial exoplanet candidates. In our model, the rotation of the planet is disturbed by the torque of the central star due to the asymmetric equilibrium figure of the planet. We model the shape of the planet by a Jeans spheroid. We use surfaces of section and spectral analysis to explore numerically the rotation phase space of the systems adopting different sets of parameters and initial conditions close to the main spin–orbit resonant states. One of the parameters, the orbital eccentricity, is critically discussed here within the domain of validity of orbital circularization timescales given by tidal models. We show that, depending on some parameters of the system like the radius and mass of the planet, eccentricity etc., the rotation can be strongly perturbed and a chaotic layer around the synchronous state may occupy a significant region of the phase space. 55 Cnc e is an example. 相似文献
11.
Pavol Pástor Jozef Klačka Ladislav Kómar 《Celestial Mechanics and Dynamical Astronomy》2009,103(4):343-364
Effect of stellar electromagnetic radiation on the motion of spherical dust particle in mean motion orbital resonances with
a planet is investigated. Planar circular restricted three-body problem with the Poynting–Robertson (P–R) effect yields monotonic
secular evolution of eccentricity when the particle is trapped in the resonance. Planar elliptic restricted three-body problem
with the P–R effect enables nonmonotonous secular evolution of eccentricity and the evolution of eccentricity is qualitatively
consistent with the published results for the complicated case of interaction of electromagnetic radiation with nonspherical
dust grain. Thus, it is sufficient to allow either nonzero eccentricity of the planet or nonsphericity of the grain and the
orbital evolutions in the resonances are qualitatively equal for the two cases. This holds both for exterior and interior
mean motion orbital resonances. Evolutions of argument of perihelion in the planar circular and elliptical restricted three-body
problems are shown. Numerical integrations show that an analytic expression for the secular time derivative of the particle’s
argument of perihelion does not exist, if only dependence on semimajor axis, eccentricity and argument of perihelion is admitted.
Connection between the shift of perihelion and oscillations in secular eccentricity is presented for the planar elliptic restricted
three-body problem with the P–R effect. Period of the oscillations corresponds to the period of one revolution of perihelion.
Change of optical properties of the spherical grain with the heliocentric distance is also considered. The change of the optical
properties: (i) does not have any significant influence on the secular evolution of eccentricity, (ii) causes that the shift
of perihelion is mainly in the same direction/orientation as the particle motion around the Sun. The statements hold both
for circular and noncircular planetary orbits. 相似文献
12.
自1995年第一颗类太阳恒星周围的系外行星发现以来,随着已发现的系外行星数目的增多,对系外行星性质的统计分析变得重要和有意义。截至2011年6月9日,共发现系外行星555颗。以这些系外行星的轨道参数为依据,对系外行星的性质进行统计分析,得出了一些有意义的结论。同时简要介绍现有的行星形成与演化模型并依据得出的行星统计性质对其进行检验,这对于系外行星的进一步探测具有一定的指导作用。 相似文献
13.
E. N. Sokov I. A. Vereshchagina Yu. N. Gnedin A. V. Devyatkin D. L. Gorshanov V. Yu. Slesarenko A. V. Ivanov K. N. Naumov S. V. Zinov’ev A. S. Bekhteva E. S. Romas S. V. Karashevich V. V. Kupriyanov 《Astronomy Letters》2012,38(3):180-190
Exoplanet observations have been performed on the automated Pulkovo Observatory telescopes. We have obtained 33 transit light curves for 16 known exoplanets and six transit observations for three exoplanet candidates discovered by the Kepler telescope. Based on our observations, we have reliably confirmed the existence of an exoplanet with an extremely large radius, R pl = 1.83 ± 0.16R Jup, in the system KOI 256 and detected a strong deviation of its orbital revolution from the theoretically predicted one. During the transit of the exoplanet WASP-12b across the stellar disk, we detected bursts that could be caused by the planet transit across spots on the star or by the presence of a satellite around this exoplanet. We detected possible periodic variations in the duration of the exoplanet transit across the stellar disk with time for HAT-P-12b that could be caused by variations in orbital inclination. The transit duration and depth, the central transit time, and the radius and orbital inclination of the planet have been estimated. The equilibrium temperature and albedo have been estimated for several exoplanets. 相似文献
14.
Previous studies have shown that extrasolar Earth-like planets in close-in habitable zones around M-stars are weakly protected against galactic cosmic rays (GCRs), leading to a strongly increased particle flux to the top of the planetary atmosphere. Two main effects were held responsible for the weak shielding of such an exoplanet: (a) For a close-in planet, the planetary magnetic moment is strongly reduced by tidal locking. Therefore, such a close-in extrasolar planet is not protected by an extended magnetosphere. (b) The small orbital distance of the planet exposes it to a much denser stellar wind than that prevailing at larger orbital distances. This dense stellar wind leads to additional compression of the magnetosphere, which can further reduce the shielding efficiency against GCRs. In this work, we analyse and compare the effect of (a) and (b), showing that the stellar wind variation with orbital distance has little influence on the cosmic ray shielding. Instead, the weak shielding of M star planets can be attributed to their small magnetic moment. We further analyse how the planetary mass and composition influence the planetary magnetic moment, and thus modify the cosmic ray shielding efficiency. We show that more massive planets are not necessarily better protected against galactic cosmic rays, but that the planetary bulk composition can play an important role. 相似文献
15.
S. R. Kane W. I. Clarkson R. G. West D. M. Wilson D. J. Christian A. Collier Cameron B. Enoch T. A. Lister R. A. Street A. Evans A. Fitzsimmons C. A. Haswell C. Hellier S. T. Hodgkin K. Horne J. Irwin F. P. Keenan A. J. Norton J. Osborne N. R. Parley D. L. Pollacco R. Ryans I. Skillen P. J. Wheatley 《Monthly notices of the Royal Astronomical Society》2008,384(3):1097-1108
The Wide Angle Search for Planets (WASP) survey currently operates two installations, designated SuperWASP-N and SuperWASP-S, located in the Northern and Southern hemispheres, respectively. These installations are designed to provide high time-resolution photometry for the purpose of detecting transiting extrasolar planets, asteroids, and transient events. Here, we present results from a transit-hunting observing campaign using SuperWASP-N covering a right ascension (RA) range of 06h < RA < 16h . This paper represents the fifth and final in the series of transit candidates released from the 2004 observing season. In total, 729 335 stars from 33 fields were monitored with 130 566 having sufficient precision to be scanned for transit signatures. Using a robust transit detection algorithm and selection criteria, six stars were found to have events consistent with the signature of a transiting extrasolar planet based on the photometry, including the known transiting planet XO-1b. These transit candidates are presented here along with discussion of follow-up observations and the expected number of candidates in relation to the overall observing strategy. 相似文献
16.
Nader Haghighipour Stephanie Capen Tobias C. Hinse 《Celestial Mechanics and Dynamical Astronomy》2013,117(1):75-89
We have carried out an extensive study of the possibility of the detection of Earth-mass and super-Earth Trojan planets using transit timing variation method with the Kepler space telescope. We have considered a system consisting of a transiting Jovian-type planet in a short period orbit, and determined the induced variations in its transit timing due to an Earth-mass/super-Earth Trojan planet. We mapped a large section of the phase space around the 1:1 mean-motion resonance and identified regions corresponding to several other mean-motion resonances where the orbit of the planet would be stable. We calculated transit timing variations (TTVs) for different values of the mass and orbital elements of the transiting and perturbing bodies as well as the mass of central star, and identified orbital configurations of these objects (ranges of their orbital elements and masses) for which the resulted TTVs would be within the range of the variations of the transit timing of Kepler’s planetary candidates. Results of our study indicate that in general, the amplitudes of the TTVs fall within the detectable range of timing precision obtained from the Kepler’s long-cadence data, and depending on the parameters of the system, their magnitudes may become as large as a few hours. The probability of detection is higher for super-Earth Trojans with slightly eccentric orbits around short-period Jovian-type planets with masses slightly smaller than Jupiter. We present the details of our study and discuss the implications of its results. 相似文献
17.
The most puzzling property of the extrasolar planets discovered by recent radial velocity surveys is their high orbital eccentricities, which are very difficult to explain within our current theoretical paradigm for planet formation. Current data reveal that at least 25% of these planets, including some with particularly high eccentricities, are orbiting a component of a binary star system. The presence of a distant companion can cause significant secular perturbations in the orbit of a planet. At high relative inclinations, large-amplitude, periodic eccentricity perturbations can occur. These are known as “Kozai cycles” and their amplitude is purely dependent on the relative orbital inclination. Assuming that every planet host star also has a (possibly unseen, e.g., substellar) distant companion, with reasonable distributions of orbital parameters and masses, we determine the resulting eccentricity distribution of planets and compare it to observations? We find that perturbations from a binary companion always appear to produce an excess of planets with both very high (?0.6) and very low (e ? 0.1) eccentricities. The paucity of near-circular orbits in the observed sample implies that at least one additional mechanism must be increasing eccentricities. On the other hand, the overproduction of very high eccentricities observed in our models could be combined with plausible circularization mechanisms (e.g., friction from residual gas) to create more planets with intermediate eccentricities (e? 0.1–0.6). 相似文献
18.
Alice C. Quillen Peter Faber 《Monthly notices of the Royal Astronomical Society》2006,373(3):1245-1250
We consider particles with low free or proper eccentricity that are orbiting near planets on eccentric orbits. Through collisionless particle integration, we numerically find the location of the boundary of the chaotic zone in the planet's corotation region. We find that the distance in semimajor axis between the planet and boundary depends on the planet mass to the 2/7 power and is independent of the planet eccentricity, at least for planet eccentricities below 0.3. Our integrations reveal a similarity between the dynamics of particles at zero eccentricity near a planet in a circular orbit and with zero free eccentricity particles near an eccentric planet. The 2/7th law has been previously explained by estimating the semimajor at which the first-order mean motion resonances are large enough to overlap. Orbital dynamics near an eccentric planet could differ due to first-order corotation resonances that have strength proportional to the planet's eccentricity. However, we find that the corotation resonance width at low free eccentricity is small; also the first-order resonance width at zero free eccentricity is the same as that for a zero-eccentricity particle near a planet in a circular orbit. This accounts for insensitivity of the chaotic zone width to planet eccentricity. Particles at zero free eccentricity near an eccentric planet have similar dynamics to those at zero eccentricity near a planet in a circular orbit. 相似文献
19.
Erik Høg 《Astrophysics and Space Science》2002,280(1-2):139-142
The transit of exoplanets across a stellar disk will often occur in GAIA observations. A safe detection of the slight dimming
of the star can be made many hundred times, i.e. in cases where the star is sufficiently constant in intensity, and the photometry
is very precise. When combined with the simultaneous GAIA astrometry or ground-based radial velocities the scientific harvest
is orbit, mass and mass density for hundreds of exoplanets. We have typically considered Jupiter-size planets at Earth-like
distances from the stars.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
We present high-precision K -band photometry of the transit and secondary eclipse of extrasolar planet OGLE-TR-113, using the SOFI near-infrared instrument on European Southern Observatory's New Technology Telescope. Data were taken in 5-s exposures over two periods of 3–4 h, using random jitter position offsets. In this way, a relative photometric precision of ∼1 per cent per frame was achieved, avoiding systematic effects that seem to become dominant at precisions exceeding this level, and resulting in an overall accuracy of 0.1 per cent per ∼10 min. The observations of the transit show a flat-bottomed light-curve indicative of a significantly lower stellar limb darkening at near-infrared than at optical wavelengths. The observations of the secondary eclipse result in a 3σ detection of emission from the exoplanet at 0.17 ± 0.05 per cent. However, residual systematic errors make this detection rather tentative. 相似文献