SEARCH · Engineering Papers

Results for “planet”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 847 records · Page 47

All sources NASA NTRS DOE OSTI

DOE OSTI2015

NUMERICALLY PREDICTED INDIRECT SIGNATURES OF TERRESTRIAL PLANET FORMATION

The intermediate phases of planet formation are not directly observable due to lack of emission from planetesimals. Planet formation is, however, a dynamically active process resulting in collisions between the evolving planetesimals and the production of dust. Thus, indirect observation of planet formation may indeed be possible in the near future. In this paper we present synthetic observations based on numerical N-body simulations of the intermediate phase of planet formation including a state-of-the-art collision model, EDACM, which allows multiple collision outcomes, such as accretion, erosion, and bouncing events. We show that the formation of planetary embryos may be indirectly observable by a fully functioning ALMA telescope if the surface area involved in planetesimal evolution is sufficiently large and/or the amount of dust produced in the collisions is sufficiently high in mass.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2015

Confirmation and characterization of the protoplanet HD 100546 b—Direct evidence for gas giant planet formation at 50 AU

We present the first multi-wavelength, high-contrast imaging study confirming the protoplanet embedded in the disk around the Herbig Ae/Be star HD 100546. The object is detected at L′ (∼3.8 μm) and M′ (∼4.8 μm), but not at K{sub s} (∼2.1 μm), and the emission consists of a point source component surrounded by spatially resolved emission. For the point source component we derive apparent magnitudes of L′=13.92±0.10 mag, M′=13.33±0.16 mag, and K{sub s}>15.43±0.06 mag (3σ limit), and a separation and position angle of (0.457±0.014){sup ′′} and (8.4±1.4){sup ∘}, and (0.472±0.014){sup ′′} and (9.2±1.4){sup ∘} in L′ and M′, respectively. We demonstrate that the object is co-moving with HD 100546 and can reject any (sub-)stellar fore-/background object. Fitting a single-temperature blackbody to the observed fluxes of the point source component yields an effective temperature of T{sub eff}=932{sub −202}{sup +193} K and a radius for the emitting area of R=6.9{sub −2.9}{sup +2.7} R{sub Jupiter}. The best-fit luminosity is L=(2.3{sub −0.4}{sup +0.6})⋅10{sup −4} L{sub ⊙}. We quantitatively compare our findings with predictions from evolutionary and atmospheric models for young, gas giant planets, discuss the possible existence of a warm, circumplanetary disk, and note that the deprojected physical separation from the host star of (53±2) AU poses a challenge to standard planet formation theories. Considering the suspected existence of an additional planet orbiting at ∼13–14 AU, HD 100546 appears to be an unprecedented laboratory to study the formation of multiple gas giant planets empirically.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2015

THE STABILITY AND FATES OF HIERARCHICAL TWO-PLANET SYSTEMS

We study the dynamical stability and fates of hierarchical (in semimajor axis) two-planet systems with arbitrary eccentricities and mutual inclinations. We run a large number of long-term numerical integrations and use the Support Vector Machine algorithm to search for an empirical boundary that best separates stable systems from systems experiencing either ejections or collisions with the star. We propose the following new criterion for dynamical stability: a{sub out}(1−e{sub out})/[a{sub in} (1+e{sub in})]>2.4 [max(μ{sub in},μ{sub out})]{sup 1/3} (a{sub out}/a{sub in}){sup 1/2}+1.15, which should be applicable to planet-star mass ratios μ{sub in},μ{sub out}=10{sup −4}−10{sup −2}, integration times up to 10{sup 8} orbits of the inner planet, and mutual inclinations ≲40{sup ∘}. Systems that do not satisfy this condition by a margin of ≳0.5 are expected to be unstable, mostly leading to planet ejections if μ{sub in}>μ{sub out}, while slightly favoring collisions with the star for μ{sub in}<μ{sub out}. We use our numerical integrations to test other stability criteria that have been proposed in the literature and show that our stability criterion performs significantly better for the range of system parameters that we have explored.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2015

THE K2-ESPRINT PROJECT. I. DISCOVERY OF THE DISINTEGRATING ROCKY PLANET K2-22b WITH A COMETARY HEAD AND LEADING TAIL

We present the discovery of a transiting exoplanet candidate in the K2 Field-1 with an orbital period of 9.1457 hr: K2-22b. The highly variable transit depths, ranging from ∼0% to 1.3%, are suggestive of a planet that is disintegrating via the emission of dusty effluents. We characterize the host star as an M-dwarf with T{sub eff} ≃ 3800 K. We have obtained ground-based transit measurements with several 1-m class telescopes and with the GTC. These observations (1) improve the transit ephemeris; (2) confirm the variable nature of the transit depths; (3) indicate variations in the transit shapes; and (4) demonstrate clearly that at least on one occasion the transit depths were significantly wavelength dependent. The latter three effects tend to indicate extinction of starlight by dust rather than by any combination of solid bodies. The K2 observations yield a folded light curve with lower time resolution but with substantially better statistical precision compared with the ground-based observations. We detect a significant “bump” just after the transit egress, and a less significant bump just prior to transit ingress. We interpret these bumps in the context of a planet that is not only likely streaming a dust tail behind it, but also has a more prominent leading dust trail that precedes it. This effect is modeled in terms of dust grains that can escape to beyond the planet's Hill sphere and effectively undergo “Roche lobe overflow,” even though the planet's surface is likely underfilling its Roche lobe by a factor of 2.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2015

Magellan adaptive optics first-light observations of the exoplanet β PIC b. II. 3–5 μm direct imaging with MagAO+Clio, and the empirical bolometric luminosity of a self-luminous giant planet

Young giant exoplanets are a unique laboratory for understanding cool, low-gravity atmospheres. A quintessential example is the massive extrasolar planet β Pic b, which is 9 AU from and embedded in the debris disk of the young nearby A6V star β Pictoris. We observed the system with first light of the Magellan Adaptive Optics (MagAO) system. In Paper I we presented the first CCD detection of this planet with MagAO+VisAO. Here we present four MagAO+Clio images of β Pic b at 3.1 μm, 3.3 μm, L′, and M{sup ′}, including the first observation in the fundamental CH{sub 4} band. To remove systematic errors from the spectral energy distribution (SED), we re-calibrate the literature photometry and combine it with our own data, for a total of 22 independent measurements at 16 passbands from 0.99 to 4.8 μm. Atmosphere models demonstrate the planet is cloudy but are degenerate in effective temperature and radius. The measured SED now covers >80% of the planet’s energy, so we approach the bolometric luminosity empirically. We calculate the luminosity by extending the measured SED with a blackbody and integrating to find log(L{sub bol}/L{sub ⊙}) = −3.78±0.03. From our bolometric luminosity and an age of 23 ± 3 Myr, hot-start evolutionary tracks give a mass of 12.7 ± 0.3 M{sub Jup}, radius of 1.45 ± 0.02 R{sub Jup}, and T{sub eff} of 1708 ± 23 K (model-dependent errors not included). Our empirically determined luminosity is in agreement with values from atmospheric models (typically −3.8 dex), but brighter than values from the field-dwarf bolometric correction (typically −3.9 dex), illustrating the limitations in comparing young exoplanets to old brown dwarfs.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2011

ARCHITECTURE AND DYNAMICS OF KEPLER'S CANDIDATE MULTIPLE TRANSITING PLANET SYSTEMS

About one-third of the {approx}1200 transiting planet candidates detected in the first four months of Kepler data are members of multiple candidate systems. There are 115 target stars with two candidate transiting planets, 45 with three, 8 with four, and 1 each with five and six. We characterize the dynamical properties of these candidate multi-planet systems. The distribution of observed period ratios shows that the vast majority of candidate pairs are neither in nor near low-order mean-motion resonances. Nonetheless, there are small but statistically significant excesses of candidate pairs both in resonance and spaced slightly too far apart to be in resonance, particularly near the 2:1 resonance. We find that virtually all candidate systems are stable, as tested by numerical integrations that assume a nominal mass-radius relationship. Several considerations strongly suggest that the vast majority of these multi-candidate systems are true planetary systems. Using the observed multiplicity frequencies, we find that a single population of planetary systems that matches the higher multiplicities underpredicts the number of singly transiting systems. We provide constraints on the true multiplicity and mutual inclination distribution of the multi-candidate systems, revealing a population of systems with multiple super-Earth-size and Neptune-size planets with low to moderate mutual inclinations.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2011

RETIRED A STARS AND THEIR COMPANIONS. VII. 18 NEW JOVIAN PLANETS

We report the detection of 18 Jovian planets discovered as part of our Doppler survey of subgiant stars at Keck Observatory, with follow-up Doppler and photometric observations made at McDonald and Fairborn Observatories, respectively. The host stars have masses 0.927 {<=} M{sub *}/M{sub Sun} {<=} 1.95, radii 2.5 {<=} R{sub *}/R{sub Sun} {<=} 8.7, and metallicities -0.46 {<=} [Fe/H] {<=}+0.30. The planets have minimum masses 0.9 M{sub Jup} {<=} M{sub P} sin i {approx}< 13 M{sub Jup} and semimajor axes a {>=} 0.76 AU. These detections represent a 50% increase in the number of planets known to orbit stars more massive than 1.5 M{sub Sun} and provide valuable additional information about the properties of planets around stars more massive than the Sun.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

SHORT-DURATION LENSING EVENTS. I. WIDE-ORBIT PLANETS? FREE-FLOATING LOW-MASS OBJECTS? OR HIGH-VELOCITY STARS?

Short-duration lensing events tend to be generated by low-mass lenses or by lenses with high transverse velocities. Furthermore, for any given lens mass and speed, events of short duration are preferentially caused by nearby lenses (mesolenses) that can be studied in detail, or else by lenses so close to the source star that finite-source-size effects may be detected, yielding information about both the Einstein ring radius and the surface of the lensed star. Planets causing short-duration events may be in orbits with any orientation, and may have semimajor axes smaller than 1 AU, or they may reach the outer limits of their planetary systems, in the region corresponding to the solar system's Oort Cloud. They can have masses larger than Jupiter's or smaller than Pluto's. Lensing therefore has a unique potential to expand our understanding of planetary systems. A particular advantage of lensing is that it can provide precision measurements of system parameters, including the masses of and projected separation between star and planet. We demonstrate how the parameters can be extracted and show that a great deal can be learned. For example, it is remarkable that the gravitational mass of nearby free-floating planet-mass lenses can be measured by complementing observations of a photometric event with deep images that detect the planet itself. A fraction of short events may be caused by high-velocity stars located within a kiloparsec. Many high-velocity lenses are likely to be neutron stars that received large natal kicks. Other high-speed stars may be members of the halo population. Still others may be hypervelocity stars that have been ejected from the Galactic center, or runaway stars escaped from close binaries, possibly including the progenitor binaries of Type Ia supernovae.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2011

A 5 {mu}m IMAGE OF {beta} PICTORIS b AT A SUB-JUPITER PROJECTED SEPARATION: EVIDENCE FOR A MISALIGNMENT BETWEEN THE PLANET AND THE INNER, WARPED DISK

We present and analyze a new M' detection of the young exoplanet {beta} Pictoris b from 2008 VLT/NaCo data at a separation of {approx}4 AU and a high signal-to-noise rereduction of L' data taken in 2009 December. Based on our orbital analysis, the planet's orbit is viewed almost perfectly edge-on (i {approx} 89 deg) and has a Saturn-like semimajor axis of 9.50 AU{sup +3.93} {sup AU}{sub -1.7AU}. Intriguingly, the planet's orbit is aligned with the major axis of the outer disk ({Omega} {approx} 31 deg.) but is probably misaligned with the warp/inclined disk at 80 AU, often cited as a signpost for the planet's existence. Our results motivate new studies to clarify how {beta} Pic b sculpts debris disk structures and whether a second planet is required to explain the warp/inclined disk.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2011

USING STAR SPOTS TO MEASURE THE SPIN-ORBIT ALIGNMENT OF TRANSITING PLANETS

Spectroscopic follow-up of dozens of transiting planets has revealed the degree of alignment between the equators of stars and the orbits of the planets they host. Here we determine a method, applicable to spotted stars, that can reveal the same information from the photometric discovery data, with no need for follow-up. A spot model fit to the global light curve, parameterized by the spin orientation of the star, predicts when the planet will transit the spots. Observing several spot crossings during different transits then leads to constraints on the spin-orbit alignment. In cases where stellar spots are small, the stellar inclination, i{sub s} , and hence the true alignment, rather than just the sky projection, can be obtained. This method has become possible with the advent of space telescopes such as CoRoT and Kepler, which photometrically monitor transiting planets over a nearly continuous, long time baseline. We apply our method to CoRoT-2 and find the projected spin-orbit alignment angle, {lambda} = 4.{sup 0}7 {+-} 12.{sup 0}3, in excellent agreement with a previous determination that employed the Rossiter-McLaughlin effect. The large spots of the parent star, CoRoT-2, limit our precision on i{sub s} : 84{sup 0} {+-} 36{sup 0}, where i{sub s} < 90{sup 0}(> 90{sup 0}) indicates that the rotation axis is tilted toward (away from) the line of sight.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

A TWO-DIMENSIONAL INFRARED MAP OF THE EXTRASOLAR PLANET HD 189733b

We derive the first secondary eclipse map of an exoplanet, HD 189733b, based on Spitzer IRAC 8 {mu}m data. We develop two complementary techniques for deriving the two-dimensional planet intensity: regularized slice mapping and spherical harmonic mapping. Both techniques give similar derived intensity maps for the infrared dayside flux of the planet, while the spherical harmonic method can be extended to include phase variation data which better constrain the map. The longitudinal offset of the dayside hot spot is consistent with that found in prior studies, strengthening the claim of super-rotating winds, and eliminating the possibility of phase variations being caused by stellar variability. The latitude of the hot spot is within 12.{sup 0}5 (68% confidence) of the planet's equator, confirming the predictions of general circulation models for hot Jupiters and indicative of a small planet obliquity.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2013

BUILDING TATOOINE: SUPPRESSION OF THE DIRECT SECULAR EXCITATION IN KEPLER CIRCUMBINARY PLANET FORMATION

Circumbinary planetary systems recently discovered by Kepler represent an important testbed for planet formation theories. Planetesimal growth in disks around binaries has been expected to be inhibited interior to {approx}10 AU by secular excitation of high relative velocities between planetesimals, leading to their collisional destruction (rather than agglomeration). Here we show that gravity of an axisymmetric gaseous circumbinary disk in which planets form drives fast precession of both the planetesimal and binary orbits, resulting in strong suppression of planetesimal eccentricities beyond 2-3 AU and making possible the growth of 1-10{sup 2} km objects in this region. The precise location of the boundary of the accretion-friendly region depends on the size of the inner disk cavity cleared by the binary torques and on the disk mass (even 0.01 M{sub Sun} disk strongly suppresses planetesimal excitation), among other things, but this zone does not extend to present orbits of Kepler circumbinary planets. The precession of the orbit of the central binary, enhanced by the mass concentration that is naturally present at the inner edge of a circumbinary disk, plays a key role in this suppression, which is a feature specific to the circumbinary planet formation.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2013

CONFIRMATION OF THE PLANET AROUND HD 95086 BY DIRECT IMAGING

VLT/NaCo angular differential imaging at L' (3.8 μm) revealed a probable giant planet comoving with the young and early-type HD 95086, also known to harbor an extended debris disk. The discovery was based on the proper motion analysis of two datasets spanning 15 months. However, the second dataset suffered from bad atmospheric conditions, which limited the significance of the re-detection at the 3σ level. In this Letter, we report new VLT/NaCo observations of HD 95086 obtained on 2013 June 26 and 27 at L' to recover the planet candidate. We unambiguously re-detect the companion HD 95086 b with multiple independent pipelines at a signal-to-noise ratio greater than or equal to 5. Combined with previously reported measurements, our astrometry decisively shows that the planet is comoving with HD 95086 and inconsistent with a background object. With a revised mass of 5 ± 2 Jupiter masses, estimated from its L' photometry and ''hot-start'' models at 17 ± 4 Myr, HD 95086 b becomes a new benchmark for further physical and orbital characterization of young giant planets.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

FORMING CIRCUMBINARY PLANETS: N-BODY SIMULATIONS OF KEPLER-34

Observations of circumbinary planets orbiting very close to the central stars have shown that planet formation may occur in a very hostile environment, where the gravitational pull from the binary should be very strong on the primordial protoplanetary disk. Elevated impact velocities and orbit crossings from eccentricity oscillations are the primary contributors to high energy, potentially destructive collisions that inhibit the growth of aspiring planets. In this work, we conduct high-resolution, inter-particle gravity enabled N-body simulations to investigate the feasibility of planetesimal growth in the Kepler-34 system. We improve upon previous work by including planetesimal disk self-gravity and an extensive collision model to accurately handle inter-planetesimal interactions. We find that super-catastrophic erosion events are the dominant mechanism up to and including the orbital radius of Kepler-34(AB)b, making in situ growth unlikely. It is more plausible that Kepler-34(AB)b migrated from a region beyond 1.5 AU. Based on the conclusions that we have made for Kepler-34, it seems likely that all of the currently known circumbinary planets have also migrated significantly from their formation location with the possible exception of Kepler-47(AB)c.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

THE OCCURRENCE OF WIDE-ORBIT PLANETS IN BINARY STAR SYSTEMS

The occurrence of planets in binary star systems has been investigated via a variety of techniques that sample a wide range of semi-major axes, but with a preponderance of such results applicable to planets with semi-major axes less than a few astronomical units. We utilize a new method—the presence or absence of heavy elements in the atmospheres of white dwarf stars—to elucidate the frequency in main sequence binary star systems of planets with semi-major axes greater than a few astronomical units. We consider only binaries where a putative planetary system orbits one member (no circumbinary planets). For main sequence binaries where the primary star is of spectral type A or F, data in the published literature suggests that the existence of a secondary star with a semi-major axis less than about 1000 AU suppresses the formation and/or long-term stability of an extended planetary system around the primary. For these spectral types and initial semi-major axis ≥1000 AU, extended planetary systems appear to be as common around stars in binary systems as they are around single stars.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

DISENTANGLING PLANETS AND STELLAR ACTIVITY FOR GLIESE 667C

Gliese 667C is an M1.5V star with a multi-planet system, including planet candidates in the habitable zone. The exact number of planets in the system is unclear, because the existing radial velocity (RV) measurements are known to contain contributions from stellar magnetic activity. Following our analysis of Gliese 581, we have analyzed the effect of stellar activity on the HARPS/HARPS-TERRA RVs of GJ 667C, finding a significant RV-activity correlation when using the width (FWHM) of the HARPS cross-correlation function to trace the magnetic activity. When we correct for this correlation, we confirm the detections of the previously observed planets b and c in the system, while simultaneously ascribing the RV signal near 90 days ({sup p}lanet d{sup )} to an artifact of the stellar rotation. We are unable to confirm the existence of the additional RV periodicities described in Anglada-Escudé et al. in our activity-corrected data.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

WATER TRAPPING ON TIDALLY LOCKED TERRESTRIAL PLANETS REQUIRES SPECIAL CONDITIONS

Surface liquid water is essential for standard planetary habitability. Calculations of atmospheric circulation on tidally locked planets around M stars suggest that this peculiar orbital configuration lends itself to the trapping of large amounts of water in kilometers-thick ice on the night side, potentially removing all liquid water from the day side where photosynthesis is possible. We study this problem using a global climate model including coupled atmosphere, ocean, land, and sea ice components as well as a continental ice sheet model driven by the climate model output. For a waterworld, we find that surface winds transport sea ice toward the day side and the ocean carries heat toward the night side. As a result, nightside sea ice remains O(10 m) thick and nightside water trapping is insignificant. If a planet has large continents on its night side, they can grow ice sheets O(1000 m) thick if the geothermal heat flux is similar to Earth's or smaller. Planets with a water complement similar to Earth's would therefore experience a large decrease in sea level when plate tectonics drives their continents onto the night side, but would not experience complete dayside dessiccation. Only planets with a geothermal heat flux lower than Earth's, much of their surface covered by continents, and a surface water reservoir O(10%) of Earth's would be susceptible to complete water trapping.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2015

CHARACTERIZING THE ATMOSPHERES OF THE HR8799 PLANETS WITH HST/WFC3

We present results from a Hubble Space Telescope (HST) program characterizing the atmospheres of the outer two planets in the HR8799 system. The images were taken over 15 orbits in three near-infrared (near-IR) medium-band filters—F098M, F127M, and F139M—using the Wide Field Camera 3. One of the three filters is sensitive to a water absorption band inaccessible from ground-based observations, providing a unique probe of the thermal emission from the atmospheres of these young giant planets. The observations were taken at 30 different spacecraft rolls to enable angular differential imaging (ADI), and the full data set was analyzed with the Karhunen–Loéve Image Projection routine, an advanced image processing algorithm adapted to work with HST data. To achieve the required high contrast at subarcsecond resolution, we utilized the pointing accuracy of HST in combination with an improved pipeline designed to combine the dithered ADI data with an algorithm designed to both improve the image resolution and accurately measure the photometry. The results include F127M (J) detections of the outer planets, HR8799b and c, and the first detection of HR8799b in the water-band (F139M) filter. The F127M photometry for HR8799c agrees well with fitted atmospheric models, resolving the longstanding difficulty in consistently modeling the near-IR flux of the planet.

79 ASTRONOMY AND ASTROPHYSICS↗