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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.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

A high-resolution planetary boundary layer height seasonal climatology from GNSS radio occultations

We present a new seasonal planetary boundary layer height (PBLH) climatology product derived from 14 years of Global Navigation Satellite System radio occultation (GNSS-RO) data from multiple missions including COSMIC, TerraSAR-X, KOMPSAT-5, and PAZ. PBLH estimates are derived from the minimum gradients of retrieved refractivity profiles, with a vertical resolution of ~200 m. The climatology is obtained from occultations observed between June 2006 and December 2019, and is divided into land and ocean regimes on a 2-degree grid. We provide seasonal climatologies at 2-degree resolution as well as climatologies of diurnal cycle amplitude and phase at 5-degree resolution. The new GNSS PBLH climatology is compared to radiosonde data from the ship-based Marine ARM GPCI Investigation of Clouds (MAGIC) campaign in the subtropical northeast Pacific ocean and to previous GNSS PBLH climatology estimates. The higher spatial resolution reveals new details such as seasonal PBLH modulation due to sea ice off the coast of Antarctica. The PBLH product is the first publicly available at 2-degree resolution.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Variations in the Geomagnetic Cutoff Rigidity during the Magnetic Storm in March 2015

Variations in the planetary system of the geomagnetic cutoff rigidity during the moderate geomagnetic storm in March 2015 are calculated on the basis of data from cosmic-ray measurements at the world network of stations. The distance to the subsolar point and the radius of the ring current are calculated on the basis of the axisymmetric restricted Earth’smagnetosphere model that takes into account currents at the magnetopause and the ring current. The contribution of the ring current to variations in the geomagnetic cutoff rigidity and to the disturbance storm time (Dst) index is also determined within this model.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

MOA-2012-BLG-505Lb: A Super-Earth-mass Planet That Probably Resides in the Galactic Bulge

We report the discovery of a super-Earth-mass planet in the microlensing event MOA-2012-BLG-505. This event has the second shortest event timescale of t {sub E} = 10 ± 1 days where the observed data show evidence of a planetary companion. Our 15 minute high cadence survey observation schedule revealed the short subtle planetary signature. The system shows the well known close/wide degeneracy. The planet/host-star mass ratio is q = 2.1 × 10{sup −4} and the projected separation normalized by the Einstein radius is s = 1.1 or 0.9 for the wide and close solutions, respectively. We estimate the physical parameters of the system by using a Bayesian analysis and find that the lens consists of a super-Earth with a mass of 6.7{sub −3.6}{sup +10.7} M{sub ⊕} orbiting around a brown dwarf or late-M-dwarf host with a mass of 0.10{sub −0.05}{sup +0.16} M{sub ⊙} with a projected star–planet separation of 0.9{sub −0.2}{sup +0.3} au. The system is at a distance of 7.2 ± 1.1 kpc, i.e., it is likely to be in the Galactic bulge. The small angular Einstein radius (θ {sub E} = 0.12 ± 0.02 mas) and short event timescale are typical for a low-mass lens in the Galactic bulge. Such low-mass planetary systems in the Bulge are rare because the detection efficiency of planets in short microlensing events is relatively low. This discovery may suggest that such low-mass planetary systems are abundant in the Bulge and currently on-going high cadence survey programs will detect more such events and may reveal an abundance of such planetary systems.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

The dedicated monitor of exotransits (DEMONEX): Seven transits of XO-4b

The DEdicated MONitor of EXotransits (DEMONEX) was a 20-inch robotic and automated telescope to monitor bright stars hosting transiting exoplanets to discover new planets and improve constraints on the properties of known transiting planetary systems. We present results for the misaligned hot Jupiter XO-4b containing seven new transits from the DEMONEX telescope, including three full and four partial transits. We combine these data with archival light curves and archival radial velocity measurements to derive the host star mass M{sub ∗}=1.293{sub −0.029}{sup +0.030} M{sub ⊙} and radius R{sub ∗}=1.554{sub −0.030}{sup +0.042} R{sub ⊙}, the planet mass M{sub P}=1.615{sub −0.099}{sup +0.10} M{sub J} and radius R{sub P}=1.317{sub −0.029}{sup +0.040} R{sub J}, and a refined ephemeris of P=4.1250687±0.0000024 days and T{sub 0}=2,4547,58.18978±0.00024 BJD{sub TDB}. We include archival Rossiter–McLaughlin measurements of XO-4 to infer the stellar spin–planetary orbit alignment of λ=−40.0{sub −7.5}{sup +8.8} degrees. We test the effects of including various detrend parameters, theoretical and empirical mass–radius relations, and Rossiter–McLaughlin models. We infer that detrending against CCD position and time or airmass can improve data quality but can have significant effects on the inferred values of many parameters—most significantly R{sub P}/R{sub ∗} and the observed central transit times T{sub C}. In the case of R{sub P}/R{sub ∗} we find that the systematic uncertainty due to detrending can be three times that of the quoted statistical uncertainties. The choice of mass–radius relation has little effect on our inferred values of the system parameters. The choice of Rossiter–McLaughlin models can have significant effects on the inferred values of vsinI{sub ∗} and the stellar spin–planet orbit angle λ.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Orbital Refinement and Stellar Properties for the HD 9446, HD 43691, and HD 179079 Planetary Systems

The Transit Ephemeris Refinement and Monitoring Survey is a project that aims to detect transits of intermediate-long period planets by refining orbital parameters of the known radial velocity planets using additional data from ground-based telescopes, calculating a revised transit ephemeris for the planet, then monitoring the planet host star during the predicted transit window. Here we present the results from three systems that had high probabilities of transiting planets: HD 9446 b and c, HD 43691 b, and HD 179079 b. We provide new radial velocity (RV) measurements that are then used to improve the orbital solution for the known planets. We search the RV data for indications of additional planets in orbit and find that HD 9446 shows a strong linear trend of 4.8σ. Using the newly refined planet orbital solutions, which include a new best-fit solution for the orbital period of HD 9446 c, and an improved transit ephemerides, we found no evidence of transiting planets in the photometry for each system. Transits of HD 9446 b can be ruled out completely and transits HD 9446 c and HD 43691 b can be ruled out for impact parameters up to b = 0.5778 and b = 0.898, respectively, due to gaps in the photometry. A transit of HD 179079 b cannot be ruled out, however, due to the relatively small size of this planet compared to the large star and thus low signal to noise. We determine properties of the three host stars through spectroscopic analysis and find through photometric analysis that HD 9446 exhibits periodic variability.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Understanding the Transport Properties of Methane–Hydrogen Mixtures under the Interior Conditions of Ice Giants

Inaccuracy in our knowledge of the transport properties of relevant mixtures under planetary interior conditions is a roadblock in predicting the observable properties of planets in our solar system and beyond. In this work, we investigate methane–hydrogen mixtures using data sets obtained from density functional theory calculations for the electronic structure, combined with molecular dynamics simulations for the ions for a wide range of pressure and temperature. Hydrogen concentration significantly affects the equation of state (EOS) but has little influence on transport properties. We provide an analytical expression to model thermal EOS and transport properties as a function of hydrogen content, with the maximum deviation observed at low P–T conditions. These insights are particularly relevant to improve the planetary models and enhance our ability to predict the properties of “ice” giants and beyond.

Methane↗
DOE OSTI2017

Determining Empirical Stellar Masses and Radii from Transits and Gaia Parallaxes as Illustrated by Spitzer Observations of KELT-11b

Using the Spitzer Space Telescope, we observed a transit at 3.6 μm of KELT-11b. We also observed three partial planetary transits from the ground. We simultaneously fit these observations, ground-based photometry from Pepper et al., radial velocity data from Pepper et al., and a spectral energy distribution (SED) model using catalog magnitudes and the Hipparcos parallax to the system. The only significant difference between our results and those of Pepper et al. is that we find the orbital period to be shorter by 37 s, 4.73610 ± 0.00003 versus 4.73653 ± 0.00006 days, and we measure a transit center time of BJD{sub TDB} 2457483.4310 ± 0.0007, which is 42 minutes earlier than predicted. Using our new photometry, we precisely measure the density of the star KELT-11 to 4%. By combining the parallax and catalog magnitudes of the system, we are able to measure the radius of KELT-11b essentially empirically. Coupled with the stellar density, this gives a parallactic mass and radius of 1.8 M{sub ⊙} and 2.9 R{sub ⊙}, which are each approximately 1σ higher than the adopted model-estimated mass and radius. If we conduct the same fit using the expected parallax uncertainty from the final Gaia data release, this difference increases to 4σ. The differences between the model and parallactic masses and radii for KELT-11 demonstrate the role that precise Gaia parallaxes, coupled with simultaneous photometric, radial velocity, and SED fitting, can play in determining stellar and planetary parameters. With high-precision photometry of transiting planets and high-precision Gaia parallaxes, the parallactic mass and radius uncertainties of stars become 1% and 3%, respectively. TESS is expected to discover 60–80 systems where these measurements will be possible. These parallactic mass and radius measurements have uncertainties small enough that they may provide observational input into the stellar models themselves.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Machine learning and serving of discrete field theories

A method for machine learning and serving of discrete field theories in physics is developed. The learning algorithm trains a discrete field theory from a set of observational data on a spacetime lattice, and the serving algorithm uses the learned discrete field theory to predict new observations of the field for new boundary and initial conditions. The approach of learning discrete field theories overcomes the difficulties associated with learning continuous theories by artificial intelligence. The serving algorithm of discrete field theories belongs to the family of structure-preserving geometric algorithms, which have been proven to be superior to the conventional algorithms based on discretization of differential equations. The effectiveness of the method and algorithms developed is demonstrated using the examples of nonlinear oscillations and the Kepler problem. In particular, the learning algorithm learns a discrete field theory from a set of data of planetary orbits similar to what Kepler inherited from Tycho Brahe in 1601, and the serving algorithm correctly predicts other planetary orbits, including parabolic and hyperbolic escaping orbits, of the solar system without learning or knowing Newton’s laws of motion and universal gravitation. The proposed algorithms are expected to be applicable when the effects of special relativity and general relativity are important.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2015

THE PAN-PACIFIC PLANET SEARCH. II. CONFIRMATION OF A TWO-PLANET SYSTEM AROUND HD 121056

Precise radial velocities from the Anglo-Australian Telescope (AAT) confirm the presence of a rare short-period planet around the K0 giant HD 121056. An independent two-planet solution using the AAT data shows that the inner planet has P = 89.1 ± 0.1 days, and m sin i = 1.35 ± 0.17 M{sub Jup}. These data also confirm the planetary nature of the outer companion, with m sin i = 3.9 ± 0.6 M{sub Jup} and a = 2.96 ± 0.16 AU. HD 121056 is the most-evolved star to host a confirmed multiple-planet system, and is a valuable example of a giant star hosting both a short-period and a long-period planet.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Robo-AO Kepler Survey. IV. The Effect of Nearby Stars on 3857 Planetary Candidate Systems

We present the overall statistical results from the Robo-AO Kepler planetary candidate survey, comprising of 3857 high-angular resolution observations of planetary candidate systems with Robo-AO, an automated laser adaptive optics system. These observations reveal previously unknown nearby stars blended with the planetary candidate host stars that alter the derived planetary radii or may be the source of an astrophysical false positive transit signal. In the first three papers in the survey, we detected 440 nearby stars around 3313 planetary candidate host stars. In this paper, we present observations of 532 planetary candidate host stars, detecting 94 companions around 88 stars; 84 of these companions have not previously been observed in high resolution. We also report 50 more-widely separated companions near 715 targets previously observed by Robo-AO. We derive corrected planetary radius estimates for the 814 planetary candidates in systems with a detected nearby star. If planetary candidates are equally likely to orbit the primary or secondary star, the radius estimates for planetary candidates in systems with likely bound nearby stars increase by a factor of 1.54, on average. We find that 35 previously believed rocky planet candidates are likely not rocky due to the presence of nearby stars. From the combined data sets from the complete Robo-AO KOI survey, we find that 14.5 ± 0.5% of planetary candidate hosts have a nearby star with 4″, while 1.2% have two nearby stars, and 0.08% have three. We find that 16% of Earth-sized, 13% of Neptune-sized, 14% of Saturn-sized, and 19% of Jupiter-sized planet candidates have detected nearby stars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Stellar rotation-planetary orbit period commensurability in the HAT-P-11 system

A number of planet host stars have been observed to rotate with a period equal to an integer multiple of the orbital period of their close planet. We expand this list by analyzing Kepler data of HAT-P-11 and finding a period ratio of 6:1. In particular, we present evidence for a long-lived spot on the stellar surface that is eclipsed by the planet in the same position four times, every sixth transit. We also identify minima in the out-of-transit light curve and confirm that their phase with respect to the stellar rotation is mostly stationary for the 48 month time frame of the observations, confirming the proposed rotation period. For comparison, we apply our methods to Kepler-17 and confirm the findings of Bonomo and Lanza that the period ratio is not exactly 8:1 in that system. Finally, we provide a hypothesis on how interactions between a star and its planet could possibly result in an observed commensurability for systems where the stellar differential rotation profile happens to include a period at some latitude that is commensurable to the planetary orbit.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Greigite (Fe 3 S 4 ) is thermodynamically stable: Implications for its terrestrial and planetary occurrence

Significance The new experimental thermodynamic studies of bulk, nanophase, and monoclinic high-pressure forms of greigite (Fe 3 S 4 ) confirm its stability in the Fe–S system and explain its common occurrence in sediments, magnetotactic bacteria, and other ambient temperature environments under anoxic conditions. The data disprove the commonly held hypothesis that greigite is a metastable phase. The low surface energy of greigite provides insight not only into the stability of greigite nanoparticles but also into their role in prebiotic, biological, and planetary processes. Our experimental data for the stability of the three forms of Fe 3 S 4 confirm that it could be stable on Mercury, thus contributing to Mercury’s weak magnetic field.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Investigating flow patterns and related dynamics in multi-instability turbulent plasmas using a three-point cross-phase time delay estimation velocimetry scheme

Complexities of flow patterns in the azimuthal cross-section of a cylindrical magnetized helicon plasma and the corresponding plasma dynamics are investigated by means of a novel scheme for time delay estimation velocimetry. The advantage of this introduced method is the capability of calculating the time-averaged 2D velocity fields of propagating wave-like structures and patterns in complex spatiotemporal data. It is able to distinguish and visualize the details of simultaneously present superimposed entangled dynamics and it can be applied to fluid-like systems exhibiting frequently repeating patterns (e.g., waves in plasmas, waves in fluids, dynamics in planetary atmospheres, etc.). The velocity calculations are based on time delay estimation obtained from cross-phase analysis of time series. Each velocity vector is unambiguously calculated from three time series measured at three different non-collinear spatial points. This method, when applied to fast imaging, has been crucial to understand the rich plasma dynamics in the azimuthal cross-section of a cylindrical linear magnetized helicon plasma. The capabilities and the limitations of this velocimetry method are discussed and demonstrated for two completely different plasma regimes, i.e., for quasi-coherent wave dynamics and for complex broadband wave dynamics involving simultaneously present multiple instabilities.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Architecture of TOI-561 planetary system

ABSTRACT We present new observations from CHEOPS (CHaracterising ExOPlanet Satellite) and TESS (Transiting Exoplanet Survey Satellite) to clarify the architecture of the planetary system hosted by the old Galactic thick disc star TOI-561. Our global analysis, which also includes previously published photometric and radial velocity data, incontrovertibly proves that TOI-561 is hosting at least four transiting planets with periods of 0.44 d (TOI-561 b), 10.8 d (TOI-561 c), 25.7 d (TOI-561 d), and 77.1 d (TOI-561 e) and a fifth non-transiting candidate, TOI-561f with a period of 433 d. The precise characterization of TOI-561’s orbital architecture is interesting since old and metal-poor thick disc stars are less likely to host ultrashort-period super-Earths like TOI-561 b. The new period of planet -e is consistent with the value obtained using radial velocity alone and is now known to be $77.14399\pm 0.00025$ d, thanks to the new CHEOPS and TESS transits. The new data allowed us to improve its radius ($R_p = 2.517 \pm 0.045\,\mathrm{ R}_{\rm{\oplus }}$ from 5 per cent to 2 per cent precision) and mass ($M_p = 12.4 \pm 1.4\, \mathrm{ M}_{\rm{\oplus }}$) estimates, implying a density of $\rho _p = 0.778 \pm 0.097\, \rho _{\rm{\oplus }}$. Thanks to recent TESS observations and the focused CHEOPS visit of the transit of TOI-561 e, a good candidate for exomoon searches, the planet’s period is finally constrained, allowing us to predict transit times through 2030 with 20-min accuracy. We present an updated version of the internal structure of the four transiting planets. We finally performed a detailed stability analysis, which confirmed the long-term stability of the outer planet TOI-561 f.

Piotto, G. (ORCID:0000000299376387)↗
DOE OSTI2013

A SYSTEMATIC SEARCH FOR TROJAN PLANETS IN THE KEPLER DATA

Trojans are circumstellar bodies that reside in characteristic 1:1 orbital resonances with planets. While all the trojans in our solar system are small ({approx}<100 km), stable planet-size trojans may exist in extrasolar planetary systems, and the Kepler telescope constitutes a formidable tool to search for them. Here we report on a systematic search for extrasolar trojan companions to 2244 known Kepler Objects of Interest (KOIs), with epicyclic orbital characteristics similar to those of the Jovian trojan families. No convincing trojan candidates are found, despite a typical sensitivity down to Earth-size objects. This fact, however, cannot be used to stringently exclude the existence of trojans in this size range, since stable trojans need not necessarily share the same orbital plane as the planet, and thus may not transit. Following this reasoning, we note that if Earth-sized trojans exist at all, they are almost certainly both present and in principle detectable in the full set of Kepler data, although a very substantial computational effort would be required to detect them. Additionally, we also note that some of the existing KOIs could in principle be trojans themselves, with a primary planet orbiting outside of the transiting plane. A few examples are given for which this is a readily testable scenario.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

The Statistics of Extended Debris Disks Measured with Gaia and Planck

Thermal emission from debris disks around stars has been measured using targeted and resolved observations. We present an alternative likelihood-based approach in which temperature maps from the Planck cosmic microwave background (CMB) survey at 857 and 545 GHz are analyzed in conjunction with stellar positions from Gaia to estimate the fraction of stars hosting disks and the thermal emission from the disks. The debris disks are not resolved (or even necessarily detected individually), but their statistical properties and the correlations with stellar properties are measured for several thousand stars. We compare our findings with higher sensitivity surveys of smaller samples of stars. For dimmer stars, in particular K and M dwarfs, we find that about 10% of stars within 80 pc have emission consistent with debris disks. We also report on 80 candidate disks, the majority of which are not previously identified. We have previously constrained the properties of Exo-Oort clouds using Planck data—with future CMB surveys, both components can be measured for different stellar types, providing a new avenue to study the outer parts of planetary systems.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Toward a Climate OSSE Framework for Satellite Mission Design

The rich history of observing system simulation experiments (OSSEs) does not yet include a well-established framework for using climate models. The need for a climate OSSE is triggered by the need to quantify the value of a particular measurement for reducing the uncertainty in climate predictions, which differ from numerical weather predictions in that they depend on future atmospheric composition rather than the current state of the weather. However, both weather and climate modeling communities share a need for motivating major observing system investments. Here, we outline a new framework for climate OSSEs that leverages the use of machine learning to calibrate climate model physics against existing satellite data. We demonstrate its application using NASA’s GISS-E3 model to objectively quantify the value of potential future improvements in spaceborne measurements of Earth’s planetary boundary layer. A mature climate OSSE framework should be able to quantitatively compare the ability of proposed observing system architectures to answer a climate-related question, thus offering added value throughout the mission design process, which is subject to increasingly rapid advances in instrument and satellite technology. Technical considerations include selection of observational benchmarks and climate projection metrics, approaches to pinpoint the sources of model physics uncertainty that dominate uncertainty in projections, and the use of instrument simulators. Community and policy-making considerations include the potential to interface with an established culture of model intercomparison projects and a growing need to economically assess the value-driven efficiency of social spending on Earth observations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Disentangling the Planet from the Star in Late-Type M Dwarfs: A Case Study of TRAPPIST-1g

The atmospheres of late M stars represent a significant challenge in the characterization of any transiting exoplanets because of the presence of strong molecular features in the stellar atmosphere. TRAPPIST-1 is an ultracool dwarf, host to seven transiting planets, and contains its own molecular signatures that can potentially be imprinted on planetary transit lightcurves as a result of inhomogeneities in the occulted stellar photosphere. We present a case study on TRAPPIST-1g, the largest planet in the system, using a new observation together with previous data, to disentangle the atmospheric transmission of the planet from that of the star. We use the out-of-transit stellar spectra to reconstruct the stellar flux on the basis of one, two, and three temperature components. We find that TRAPPIST-1 is a 0.08 M {sub *}, 0.117 R {sub *}, M8V star with a photospheric effective temperature of 2400 K, with ∼35% 3000 K spot coverage and a very small fraction, <3%, of ∼5800 K hot spot. We calculate a planetary radius for TRAPPIST-1g to be R {sub p} = 1.124 R {sub ⊕}with a planetary density of ρ {sub p} = 0.8214 ρ {sub ⊕}. On the basis of the stellar reconstruction, there are 11 plausible scenarios for the combined stellar photosphere and planet transit geometry; in our analysis, we are able to rule out eight of the 11 scenarios. Using planetary models, we evaluate the remaining scenarios with respect to the transmission spectrum of TRAPPIST-1g. We conclude that the planetary transmission spectrum is likely not contaminated by any stellar spectral features and are able to rule out a clear solar H{sub 2}/He-dominated atmosphere at greater than 3σ.

79 ASTRONOMY AND ASTROPHYSICS↗