Showing papers on "Planetary system published in 1998"
TL;DR: In this paper, the presence of the central cavity, approximately the size of Neptune's orbit, was detected in the emission from Fomalhaut, beta Pictoris and Vega, which may be the signature of Earth-like planets.
Abstract: Indirect detections of massive — presumably Jupiter-like — planets orbiting nearby Sun-like stars have recently been reported1,2. Rocky, Earth-like planets are much more difficult to detect, but clues to their possible existence can nevertheless be obtained from observations of the circumstellar debris disks of dust from which they form. The presence of such disks has been inferred3 from excess far-infrared emission but, with the exception of beta Pictoris4, it has proved difficult to image these structures directly as starlight dominates the faint light scattered by the dust5. A more promising approach is to attempt to image the thermal emission from the dust grains at submillimetre wavelengths6,7. Here we present images of such emission around Fomalhaut, beta Pictoris and Vega. For each star, dust emission is detected from regions comparable in size to the Sun's Kuiper belt of comets. The total dust mass surrounding each star is only a few lunar masses, so any Earth-like planets present must already have formed. The presence of the central cavity, approximately the size of Neptune's orbit, that we detect in the emission from Fomalhaut may indeed be the signature of such planets.
459 citations
TL;DR: In this article, the authors show that the probability of detecting planets of Jupiter mass or greater in the lensing zone is nearly 100%, with the probability remaining high down to Saturn masses and substantial even at 10 Earth masses.
Abstract: Hundreds of gravitational microlensing events have now been detected toward the Galactic bulge, with many more to come. The detection of fine structure in these events has been theorized as an excellent way to discover extrasolar planetary systems along the line of sight to the Galactic center. We show that by focusing on high-magnification events, the probability of detecting planets of Jupiter mass or greater in the lensing zone [(0.6-1.6)RE] is nearly 100%, with the probability remaining high down to Saturn masses and substantial even at 10 Earth masses. This high probability allows a nearly definitive statement to be made about the existence of lensing-zone planets in each such system that undergoes high magnification. One might expect light-curve deviations caused by the source passing near the small primary-lens caustic to be small because of the large distance of the perturbing planet, but this effect is overcome by the high magnification. High-magnification events are relatively rare (e.g., ~1/20 of events have peak magnifications greater than 20), but they occur regularly, and the peak can be predicted in advance, allowing extrasolar planet detection with a relatively small use of resources over a relatively small amount of time.
410 citations
TL;DR: In this article, a new submillimeter camera was used to image the nearby star epsilon Eridani, where a ring of dust is seen peaking at 60 AU from the star and with much lower emission inside 30 AU, and the total mass of the ring is at least ~0.01 M⊕ in dust.
Abstract: Dust emission around the nearby star epsilon Eridani has been imaged using a new submillimeter camera (the Submillimetre Common-User Bolometer Array at the James Clerk Maxwell Telescope). At an 850 μm wavelength, a ring of dust is seen peaking at 60 AU from the star and with much lower emission inside 30 AU. The mass of the ring is at least ~0.01 M⊕ in dust, while an upper limit of 0.4 M⊕ in molecular gas is imposed by CO observations. The total mass is comparable to the estimated amount of material, 0.04-0.3 M⊕, in comets orbiting the solar system. The most probable origin of the ring structure is that it is a young analog to the Kuiper Belt in our solar system and that the central region has been partially cleared by the formation of grains into planetesimals. Dust clearing around epsilon Eri is seen within the radius of Neptune's orbit, and the peak emission at 35-75 AU lies within the estimated Kuiper Belt zone of 30-100 AU radius. epsilon Eri is a main-sequence star of type K2 V (0.8 Modot) with an estimated age of 0.5-1.0 Gyr, so this interpretation is consistent with the early history of the solar system where heavy bombardment occurred up to ≈ 0.6 Gyr. An unexpected discovery is the substructure within the ring, and these asymmetries could be due to perturbations by planets.
338 citations
TL;DR: In this article, the authors present self-consistent numerical considerations of the problem of migrating giant planets and show that there is a wide range of possible fates for Jupiter-mass planets for both final heliocentric distance and final mass.
Abstract: Giant planets in circumstellar disks can migrate inward from their initial (formation) positions. Radial migration is caused by inward torques between the planet and the disk, by outward torques between the planet and the spinning star, and by outward torques due to Roche lobe overflow and consequent mass loss from the planet. We present self-consistent numerical considerations of the problem of migrating giant planets. Summing torques on planets for various physical parameters, we find that Jupiter-mass planets can stably arrive and survive at small heliocentric distances, thus reproducing observed properties of some of the recently discovered extrasolar planets. Inward migration timescales can be approximately equal to or less than disk lifetimes and star spindown timescales. Therefore, the range of fates of massive planets is broad and generally comprises three classes: (I) planets that migrate inward too rapidly and lose all their mass; (II) planets that migrate inward, lose some but not all of their mass, and survive in very small orbits; and (III) planets that do not lose any mass. Some planets in class III do not migrate very far from their formation locations. Our results show that there is a wide range of possible fates for Jupiter-mass planets for both final heliocentric distance and final mass.
284 citations
TL;DR: Doppler measurements of the M4 dwarf star Gliese 876 taken at both Lick and Keck Observatories reveal periodic, Keplerian velocity variations with a period of 61 days.
Abstract: Doppler measurements of the M4 dwarf star Gliese 876 taken at both Lick and Keck Observatories reveal periodic, Keplerian velocity variations with a period of 61 days. The orbital fit implies that the companion has a mass of M=2.1 MJUP${r JUP}$ -->$t SUBgt {r JUP}t/SUBgt $ -->/sin${r sin}$ -->${r sin}$ -->i, an orbital eccentricity of e=0.27 ± 0.03, and a semimajor axis of a=0.21 AU. The planet is the first found around an M dwarf and was drawn from a survey of 24 such stars at Lick Observatory. It is the closest extrasolar planet yet found, providing opportunities for follow-up detection. The presence of a giant planet on a noncircular orbit, 0.2 AU from a 0.32 M☉ star, presents a challenge to planet formation theory. This planet detection around an M dwarf suggests that giant planets are numerous in the Galaxy.
242 citations
TL;DR: Russell and Boss as discussed by the authors discuss the latest results on extrasolar planetary systems presented at a recent conference in Santa Barbara, and discuss the characteristics and origins of these planetary bodies, as well as their properties and origins.
Abstract: In recent years, astronomers have begun to discover an increasing number of planets orbiting stars outside our solar system The characteristics and origins of these planetary bodies are the subject of intense interest and debate In their Perspective, Russell and Boss discuss the latest results on extrasolar planetary systems presented at a recent conference in Santa Barbara
218 citations
TL;DR: In this article, the core of the star-forming region L1551 has been studied at a linear resolution of seven astronomical units (less than the diameter of Jupiter's orbit).
Abstract: Planet formation is believed to occur in the disks of gas and dust that surround young solar-type stars1. Most stars, however, form in multiple systems2,3,4,5, where the presence of a close companion could affect the structure of the disk6,7,8 and perhaps interfere with planet formation. It has been difficult to investigate this because of the resolution needed. Here we report interferometric observations (at a wavelength of 7 mm) of the core of the star-forming region L1551. We have achieved a linear resolution of seven astronomical units (less than the diameter of Jupiter's orbit). The core of L1551 contains two distinct disks, with a separation of 45 AU; these appear to be associated with a binary system. Both disks are spatially resolved, with semi-major axes of about 10 AU, which is about a factor of ten smaller than disks around isolated stars9,10,11,12. The disk masses are of order 0.05 solar masses, which could be enough to form planetary systems like our own.
196 citations
TL;DR: In this article, the influence of planetary systems on the location of stars on the Hertzsprung-Russel diagram is examined, and it is shown that the presence of a planetary system can explain some anomalies in horizontal branch morphologies.
Abstract: I examine the influence of planets on the location of stars on the Hertzsprung-Russel diagram as the stars turn to the horizontal branch. As stars that have planetary systems evolve along the red giant branch and expand, they interact with the close planets, with orbital separations of 5 AU. The planets deposit angular momentum and energy into the red giant stars' envelopes, both of which are likely to enhance mass loss on the red giant branch. The enhanced mass loss causes the star to become bluer as it turns to the horizontal branch. I propose that the presence of planetary systems, through this mechanism, can explain some anomalies in horizontal branch morphologies. In particular, planetary systems may be related to the second parameter, which determines the distribution of horizontal branch stars on the Hertzsprung-Russel diagram. The presence of planets, though, cannot be the only factor that influences the second parameter. The distribution of planets' properties (e.g., mass, orbital separation, prevalence) in a specific globular cluster depends on several properties of the globular cluster itself (e.g., shape, density). This dependence may explain some of the anomalies and variations in the horizontal branch morphologies between different globular clusters. The proposed scenario predicts that surviving massive planets or brown dwarfs orbit some of the extreme blue horizontal branch stars, at orbital periods of ~10 days.
194 citations
TL;DR: In this article, the dynamical tides raised on a non-rotating solar-type star by a close stellar or planetary companion are calculated and compared to the results obtained by assuming that a very small frequency limit can be taken in order to calculate the tidal response (equilibrium tide).
Abstract: We calculate the dynamical tides raised on a nonrotating solar-type star by a close stellar or planetary companion. Dissipation arising from a turbulent viscosity operating in the convection zone and radiative damping in the radiative core are considered. We compute the torque exerted on the star by a companion in circular orbit and determine the potentially observable magnitude of the tidally induced velocity at the stellar photosphere. These calculations are compared to the results obtained by assuming that a very small frequency limit can be taken in order to calculate the tidal response (equilibrium tide). For a standard solar model the latter is found to give a relatively poor approximation at the periods of interest of several days, even when the system is far from resonance with a normal mode. This behavior is caused by the small value of the Brunt-Vaisala frequency in the interior regions of the convection zone. It is shown that although the companion may go through a succession of resonances as it spirals in under the action of the tides, for a fixed spectrum of normal modes its migration is controlled essentially by the nonresonant interaction. We find that the turbulent viscosity that is required to provide the observed circularization rates of main-sequence solar-type binaries is about 50 times larger than that simply estimated from mixing-length theory for nonrotating stars. We discuss the means by which this enhanced viscosity might be realized. These calculations are applied to 51 Pegasi. We show that the perturbed velocity induced by the tides at the stellar surface is too small to be observed. This result is insensitive to the magnitude of the turbulent viscosity assumed and is not affected by the possibility of resonance. For this system the stellar rotation and the orbital motion are expected to be synchronized if the mass of the companion is as much as 1/10 M☉.
181 citations
TL;DR: In this paper, the authors reported the discovery of a circumstellar disk around the young AO star, HR 4796, in thermal infrared imaging carried out at the W.M. Keck Observatory.
Abstract: We report the discovery of a circumstellar disk around the young AO star, HR 4796, in thermal infrared imaging carried out at the W.M. Keck Observatory.
181 citations
TL;DR: In this paper, the irradiation of extrasolar giant planets (EGPs) was investigated by treating the radiative transfer in detail, so that the flux from the parent star interacted with all relevant depths of the planetary atmosphere with no need for a preassumed albedo.
Abstract: We investigate irradiation of extrasolar giant planets (EGPs) by treating the radiative transfer in detail, so that the flux from the parent star interacts with all relevant depths of the planetary atmosphere with no need for a preassumed albedo. Rayleigh scattering (in dust-free models) increases the EGP's flux by orders of magnitude shortward of the Ca II H and K doublet (3930 A), and the spectral features of the parent star are exactly reflected. The inclusion of dust increases the reflected flux in the blue. In the optical and near-IR, the thermal absorption of the planet takes over, but the absorption features are changed by the irradiation.
TL;DR: In this paper, a set of bottom-up numerical simulations designed to generate plausible giant planet systems from a large number of planetary embryos is presented, which are stable for at least a billion years and exhibit a wide range of characteristics.
Abstract: In order to better understand the range of dynamically long-lived giant planet systems, we present the results of a set of bottom-up numerical simulations designed to generate plausible giant planet systems from a large number of planetary embryos. Our simulations produced systems that are stable for at least a billion years and that exhibit a wide range of characteristics. Some of these systems are reminiscent of the outer solar system. The number of planets ranged from one to seven. Many systems contained only Uranus-mass objects. We constructed systems that were more compact than the outer solar system and systems that were much sparser, with planets on very eccentric orbits. Perhaps most surprisingly, some of the systems that we constructed were stable for at least a billion years despite undergoing macroscopic orbital changes on much shorter timescales.
TL;DR: The Probing Lensing Anomalies NETwork (PLANET) as discussed by the authors monitors microlensing events densely and precisely in order to detect and study anomalies that contain information about Galactic lenses and sources that would otherwise be unobtainable.
Abstract: PLANET (the Probing Lensing Anomalies NETwork) is a worldwide collaboration of astronomers whose primary goal is to monitor microlensing events densely and precisely in order to detect and study anomalies that contain information about Galactic lenses and sources that would otherwise be unobtainable. The results of PLANET's highly successful first year of operation are presented here. Details of the observational setup, observing procedures, and data-reduction procedures used to track the progress in real time at the three participating observing sites in 1995 are discussed. The ability to follow several events simultaneously with a median sampling interval of 1.6 hr and a photometric precision of better than 0.10 mag even at I = 19 has been clearly demonstrated. During PLANET's 1995 pilot campaign, ten microlensing events were monitored, resulting in the most precise and densely-sampled light curves to date; the binary nature of one of these, MACHO 95-BLG-12, was recognized by PLANET on the mountain. Another event, OGLE 95-BLG-04, displayed chromaticity that may betray the presence of blending with unresolved stars projected onto the same resolution element. Although lasting only about a month, the campaign may allow constraints to be placed on the number of planets with mass ratios to the parent star of 0.01 or greater.
TL;DR: In this paper, an approximate power-law correlation between the time elapsed until a pair of planetary orbits cross and the solar-to-planetary-mass ratio was found for systems based on the giant planets.
TL;DR: In this article, the authors derive analytic expressions for binary-source events in the extreme flux-ratio limit and use these to demonstrate the basic degeneracy between binary source and planet perturbations.
Abstract: A planetary microlensing event is characterized by a short-lived perturbation to the standard microlensing curve. Planetary perturbations typically last from a few hours to a day, have maximum amplitudes, ?max, of ?5%-20% of the standard curve, and come in two classes: major and minor image perturbations. There exist a subset of binary-source events that can reproduce the main features of major image perturbations, which are likely to represent more than half of all planetary events, and thus masquerade as planetary events. These events require a binary source with a small flux ratio, ~ 10-2 to 10-4, and a small impact parameter for the fainter source, ?2 /?max. The detection probability of events of this type is ~?2, and can be as high as ~30%; this is comparable to planetary detection rates. Thus a sample of planetary-like perturbations could be seriously contaminated by binary-source events, and there exists the possibility that completely meaningless physical parameters would be derived for any given major image perturbation. Here I derive analytic expressions for a binary-source event in the extreme flux-ratio limit and use these to demonstrate the basic degeneracy between binary-source and planet perturbations. I describe how the degeneracy can be broken by dense and accurate sampling of the perturbation, optical/infrared photometry, or spectroscopic measurements.
TL;DR: In this paper, the results of the first molecular spectral line survey toward a typical dark cloud, TMC-1 (Taurus Molecular Cloud-1) have been reported, and the observations were completed in the frequency range 8800-50000 MHz.
Abstract: Interstellar dark clouds are known as the source of star and planetary system formation, and the study of chemical composition in dark clouds is important for understanding the process of evolution of matter in the universe toward the planets and to life. The results of the first molecular spectral line survey toward a typical dark cloud, TMC-1 (Taurus Molecular Cloud-1) have been reported. The observations were completed in the frequency range 8800–50000 MHz, and the results of detailed data analysis are presented. This is the first complete spectral line survey toward a cold, dark cloud ever made. We used the 45 m mm-wave telescope and a very large acousto-optical radiospectrometer with 32000 output channels of the Nobeyama Radio Observatory, NAOJ. We detected 404 lines from 38 molecules including 11 new molecules such as C6H, CCO, CCCO, CCS, CCCS, HNCCC, HCCNC, HCCCNH+, HCCCHO, CH2CN and cyclic C3H, all of them are short-lived organic compounds unknown before our detection. We also detected three new isotopomers, CC34S, CCC34S and HDCS. These results provide the basic general composition of cold, dark clouds for the first time. We also discuss chemical and physical evolution of dark clouds.
TL;DR: In this paper, a Monte Carlo approach was used to estimate the effective cross section for severe orbital disruption of Jovian planets in the birth cluster of binary stars, and it was shown that a typical interaction rate of Γ =nσv ≈ 0.13 disruptive encounters per star per 100 million years.
Abstract: We show that Jovian planets will frequently experience orbital disruption due to interactions with binary stars in their birth clusters. We attack the problem using a Monte Carlo approach and estimate the effective cross section for severe orbital disruption: σ=(230 AU)2. Combining the numerically determined cross section with typical cluster densities n and velocity dispersions v, we find a typical interaction rate of Γ=nσv ≈ 0.13 disruptive encounters per star per 100 million years. This scattering mechanism naturally accounts for extrasolar systems such as 14 Her or 16 Cyg B, in which a Jovian planet is found in an eccentric and reasonably close orbit. This mechanism can also produce systems with extremely small orbits, such as 51 Peg. However, the efficiency is too low to account for the observed frequency of such close systems, and hence some other mechanism for orbital migration is almost certainly at work. Because of mass segregation within the birth cluster, we predict that higher mass stars will have a larger fraction of planets with eccentric orbits than the low-mass stars that comprise the bulk of the stellar population.
TL;DR: In this paper, the authors consider the range of parameters appropriate for magneto-centrifugally driven stellar and disk outflow models and find that, if the proto-Jovian planet or accretion disk had a magnetic field of 10 G and moderate mass-inflow accretion rates through the disk of less than ~10-7MJ yr-1, it is possible to drive an outflow.
Abstract: We discuss the possibility that gaseous giant planets drive strong outflows during early phases of their formation. We consider the range of parameters appropriate for magneto-centrifugally driven stellar and disk outflow models and find that, if the proto-Jovian planet or accretion disk had a magnetic field of 10 G and moderate mass-inflow accretion rates through the disk of less than ~10-7MJ yr-1, it is possible to drive an outflow. Estimates based both on scaling from empirical laws observed in protostellar outflows and the magneto-centrifugal disk and stellar plus disk wind models suggest that winds with mass-outflow rates of order 10-8MJ yr-1 and velocities of order ~20 km s-1 could be driven from proto-Jovian planets. Prospects for detection and some implications for the formation of the solar system are briefly discussed.
TL;DR: In this article, it was shown that, regardless of orientation, all Jovian-mass planets with separations near 6-16RE dramatically affect the central region of the magnification pattern and thus have a significant probability of being detected (or ruled out) in high-magnification events.
Abstract: Microlensing is increasingly gaining recognition as a powerful method for the detection and characterization of extrasolar planetary systems Naively, one might expect that the probability of detecting the influence of more than one planet on any single microlensing light curve would be small Recently, however, Griest & Safizadeh have shown that, for a subset of events, those with minimum-impact parameter umin 01 (high-magnification events), the detection probability is nearly 100% for Jovian-mass planets with projected separations in the range 06-16 of the primary Einstein ring radius RE and remains substantial outside this zone In this Letter, we point out that this result implies that, regardless of orientation, all Jovian-mass planets with separations near 06-16RE dramatically affect the central region of the magnification pattern and thus have a significant probability of being detected (or ruled out) in high-magnification events The joint probability, averaged over all inclinations and phases, of two planets having projected separations within 06-16RE is substantial: 1%-15% for two planets with the intrinsic separations of Jupiter and Saturn orbiting around 03-10 M parent stars We illustrate by example the complicated magnification patterns and light curves that can result when two planets are present, and we discuss the possible implications of our result on detection efficiencies and the ability to discriminate between multiple and single planets in high-magnification events
TL;DR: Doppler measurements from the Keck/HIRES spectrometer of the G3 V star HD 187123 reveal Keplerian variations with a period of 3097 days and a semiamplitude of 72 m s−1.
Abstract: Doppler measurements from the Keck/HIRES spectrometer of the G3 V star HD 187123 reveal Keplerian variations with a period of 3097 days and a semiamplitude of 72 m s–1 An orbital fit yields a companion mass of M = 052 MJUP/ sin i}, a semimajor axis of a = 0042 AU, and an eccentricity of e = 003 (consistent with zero) HD 187123 appears similar to the Sun in mass, age, chromosphere, and rotation rate Although unlikely, non-Keplerian explanations for the Doppler variations, such as spots and pulsation, cannot be ruled out and require future photometry and spectroscopy
TL;DR: In this paper, the authors present a review of the present understanding of the β Pictoris circumstellar environment, which still appears unique in the solar neighborhood and is probably the missing link between young stellar objects presenting proto-planetary disks and much more evolved systems in which planets (at least giant ones) are already formed.
TL;DR: In this paper, the authors present high-resolution imaging of the young binary T T Tauri in continuum emission at 3 mm and estimate its properties by fitting a flat-disk model to visibilities at? = 1 and 3 mm, and to the flux density at 7 mm.
Abstract: We present high-resolution imaging of the young binary T Tauri in continuum emission at ? = 3 mm. Compact dust emission with integrated flux density 50 ? 6 mJy is resolved in an aperture synthesis map at 05 resolution and is centered at the position of the optically visible component, T Tau N. No emission above a 3 ? level of 9 mJy is detected 07 south of T Tau N at the position of the infrared companion, T Tau S. We interpret the continuum detection as arising from a circumstellar disk around T Tau N, and estimate its properties by fitting a flat-disk model to visibilities at ? = 1 and 3 mm, and to the flux density at ? = 7 mm. Given the data, probability distributions are calculated for values of the free parameters, including the temperature, density, dust opacity, and disk outer radius. The radial variation in temperature and density is not narrowly constrained by the data. The most likely value of the frequency dependence of the dust opacity, ?=0.53 -->?0.17+0.27, is consistent with that of disks around other single T Tauri stars in which grain growth is believed to have taken place. The outer radius, R=41 -->?14+26 AU, is smaller than the projected separation between T Tau N and T Tau S, and may indicate tidal or resonance truncation of the disk by T Tau S. The total mass estimated for the disk, log (MD/M?) = -2.4 -->?0.6+0.7, is similar to masses observed around many single pre-main-sequence sources and, within the uncertainties, is similar to the minimum nebular mass required to form a planetary system like our own. This observation strongly suggests that the presence of a binary companion does not rule out the possibility of formation of a sizable planetary system.
TL;DR: In this paper, the authors present high-resolution imaging of the young binary T T Tauri in 3 mm continuum emission and estimate its properties by fitting a flat disk model to visibilities at wavelengths of 1 and 3 mm and to the flux density at 7 mm.
Abstract: We present high-resolution imaging of the young binary T Tauri in 3 mm continuum emission. Compact dust emission with integrated flux density 50 +/- 6 mJy is resolved in an aperture synthesis map at 0.5" resolution and is centered at the position of the optically visible component, T Tau N. No emission above a 3 sigma level of 9 mJy is detected 0.7" south of T Tau N at the position of the infrared companion, T Tau S. We interpret the continuum detection as arising from a circumstellar disk around T Tau N and estimate its properties by fitting a flat-disk model to visibilities at wavelengths of 1 and 3 mm and to the flux density at 7 mm. Given the data, probability distributions are calculated for values of the free parameters, including the temperature, density, dust opacity, and the disk outer radius. The radial variation in temperature and density is not narrowly constrained by the data. The most likely value of the frequency dependence of the dust opacity, beta = 0.53^{+0.27}_{-0.17}, is consistent with that of disks around other T Tauri stars in which grain growth is believed to have taken place. The outer radius, R = 41^{+26}_{-14} AU, is smaller than the projected binary separation, and may indicate truncation of the disk. The total mass estimated for the disk, log(M/M_sun) = {-2.4}^{+0.7}_{-0.6}, is similar to masses observed around many young single sources and to the minimum nebular mass required to form a planetary system like our own. This observation strongly suggests that the presence of a binary companion does not rule out the formation of a sizeable planetary system.
TL;DR: In this article, the evolution of a giant planet within the stellar envelope of a main-sequence star is investigated as a possible mechanism for enhancing the stellar metallicities of the parent stars of extrasolar planetary systems.
Abstract: The evolution of a giant planet within the stellar envelope of a main-sequence star is investigated as a possible mechanism for enhancing the stellar metallicities of the parent stars of extrasolar planetary systems. Three-dimensional hydrodynamical simulations of a planet subject to impacting stellar matter indicate that the envelope of a Jupiter-like giant planet can be completely stripped in the outer stellar convection zone of a 1 M☉ star. In contrast, Jupiter-like and less massive Saturn-like giant planets are able to survive through the base of the convection zone of a 1.22 M☉ star. Although strongly dependent on details of planetary interior models, partial or total dissolution of giant planets can result in significant enhancements in the metallicity of host stars with masses in the range 1.0 MM1.3 M. The implications of these results with regard to planetary orbital migration are briefly discussed.
TL;DR: In this article, the authors compare the Bode's law with the fit of a simple planetary system generated by a random distribution of planetary orbital radii in log r between 0.2 and 50 AU, with masses and order identical to ours.
01 Jan 1998
TL;DR: In this article, the authors constructed synthetic systems of giant planets and integrated their orbits to determine the dynamical lifetimes and thus the viability of these systems, and the results showed that these systems were stable for at least a billion years despite undergoing macroscopic orbital changes.
Abstract: The process of planetary growth is extremely complicated, involving a myriad of physical and chemical processes, many of which are poorly understood. The ultimate configuration that a planetary system attains depends upon the properties of the disk out of which it grew, of the star at the center of the disk and, at least in some cases, of the interstellar environment. In an effort to numerically survey the possible diversity of planetary systems, we have constructed synthetic systems of giant planets and integrated their orbits to determine the dynamical lifetimes and thus the viability of these systems. Our construction algorithm begins with 110 -- 180 planetesimals located between 4 and 40 AU from a one solar mass star; most initial planetesimals have masses several tenths that of Earth. We integrate the orbits of these bodies subject to mutual gravitational perturbations and -as drag for 10(exp 6) - 10(exp 7) years, merging any pair of planetesimals which pass within one-tenth of a Hill Sphere of one another and adding "gas" to embryos larger than 10 Earth masses. Use of such large planetesimal radii provided sufficient damping to prevent the system from excessive dynamical heating. Subsequently, systems were evolved without gas drag, either with the enlarged radii or with more realistic radii. Systems took from a few million years to greater than ten billion years to become stable (10(exp 9) years without mergers of ejections). Some of the systems produced with the enlarged radii closely resemble our outer Solar System. Many systems contained only Uranus-mass objects. Encounters in simulations using realistic radii resulted in ejections, typically leaving only a few planets per system, most of which were on very eccentric orbits. Some of the systems that we constructed were stable for at least a billion years despite undergoing macroscopic orbital changes on much shorter timescales.
TL;DR: In this paper, a planetary core in orbit around a white dwarf may reveal its presence through its interaction with the magnetosphere of the white dwarf through electrical currents, which will heat the atmosphere of the WD near its magnetic poles.
Abstract: The fate of a planetary system like our own, as the parent star expands through the red giant phase and becomes a white dwarf (WD), has been a topic of some discussion. For an Earth-like inner planet, the conducting core may remain intact, even though severe ablation occurs of the outer layers. We argue that a planetary core in orbit around a WD may reveal its presence through its interaction with the magnetosphere of the WD. As the planet moves through the magnetosphere, electrical currents will be generated, which will heat the atmosphere of the WD near its magnetic poles. The results of such a heating may be detected in the optical as Hα emission. Ohmic dissipation will result in the slow decay of the planetary orbit, and such a planet will merge with the WD in less than a Hubble time, unless the initial orbital separation is greater than about 10 solar radii. We propose that the peculiar emission-line WD GD 356 may be a system in the process of such a merger.
TL;DR: In this paper, a one-meter aperture photometer with a twelve-degree field of view and a focal plane of 21 CCDs was used to detect earth-class planets for a wide variety of spectral types of stars.
Abstract: With the detection of giant extrasolar planets and the quest for life on Mars, there is heightened interest in finding earth-class planets, those that are less than ten earth masses and might be life supporting. A space-based photometer has the ability to detect the periodic transits of earth-class planets for a wide variety of spectral types of stars. From the data and known type of host star, the orbital semi-major axis, size and characteristic temperature of each planet can be calculated. The frequency of planet formation with respect to spectral type and occurrence for both singular and multiple-stellar systems can be determined. A description is presented of a one-meter aperture photometer with a twelve-degree field of view and a focal plane of 21 CCDs. The photometer would continuously and simultaneously monitor 160,000 stars of visual magnitude <14. Its onesigma system sensitivity for a transit of a twelfth magnitude solar-like star by a planet of one-earth radius would be one part in 50,000. It is anticipated that about 480 earth-class planets (0.5
TL;DR: In this paper, the authors studied the detection of planets in wide orbits via microlensing surveys and found that, if all planetary systems are similar to our own Solar System, reasonable extensions of the present observing strategies would allow us to detect 3-6 repeating events per year along the direction to the Bulge.
Abstract: In the companion paper we began the task of systematically studying the detection of planets in wide orbits ($a > 1.5 R_E$) via microlensing surveys. In this paper we continue, focusing on repeating events. We find that, if all planetary systems are similar to our own Solar System, reasonable extensions of the present observing strategies would allow us to detect 3-6 repeating events per year along the direction to the Bulge. Indeed, if planetary systems with multiple planets are common, then future monitoring programs which lead to the discovery of thousands of stellar-lens events will likely discover events in which several different planets within a single system serve as lenses, with light curves exhibiting multiple repetitions. In this paper we discuss observing strategies to maximize the discovery of all wide-orbit planet-lens events. We also compare the likely detection rates of planets in wide orbits to those of planets located in the zone for resonant lensing. We find that, depending on the values of the planet masses and stellar radii of the lensed sources (which determine whether or not finite source size is important), and also on the sensitivity of the photometry used by observers, the detection of planets in wide orbits may be the primary route to the discovery of planets via microlensing. We also discuss how the combination of resonant and wide-orbit events can help us to learn about the distribution of planetary system properties (S 6.1). In addition, by determining the fraction of short-duration events due to planets, we indirectly derive information about the fraction of all short-duration events that may be due to low-mass MACHOs (S 6.2).
TL;DR: In this article, the authors reported infrared coronagraphic observations of 55 Cancri in which the light from the primary star is blocked, allowing them to image a circumstellar dust disk.
Abstract: A planet with a minimum mass of 0.84 Jupiter masses (MJ) has been indirectly detected1 in a close orbit (radius 0.11 astronomical units, period 14.65 days) around the star 55 Cancri, which is of spectral type G8 and about 3 billion years old. The detection of excess infrared emission from this system also suggests2 the presence of circumstellar dust. Our Solar System has a disk of dust (and larger bodies) that is roughly coplanar with the planets—the so-called Kuiper Belt3. Here we report infrared coronagraphic observations of 55 Cancri in which the light from the primary star is blocked, allowing us to image a circumstellar dust disk. We find that the dust lies in a disk that extends to at least 40 AU, comparable to the expected extent for our Kuiper Belt3, whereas the inferred mass of the disk is approximately ten times that estimated for our Kuiper Belt. The disk around 55 Cancri is relatively dark at a wavelength of 2.3µm, which is consistent with absorption of light by methane ice on the dust particles. Assuming that the disk is coplanar with the planet, we determine the planet's mass to be 1.9−0.4+1.1 Jupiter masses. All the available evidence is suggestive of a mature planetary system around 55 Cancri.