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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

The Gemini Planet Imager Exoplanet Survey: Dynamical Mass of the Exoplanet β Pictoris b from Combined Direct Imaging and Astrometry

Herein, we present new observations of the planet β Pictoris b from 2018 with the Gemini Planet Imager (GPI), the first GPI observations following conjunction. Based on these new measurements, we perform a joint orbit fit to the available relative astrometry from ground-based imaging, the Hipparcos Intermediate Astrometric Data (IAD), and the Gaia DR2 position, and demonstrate how to incorporate the IAD into direct imaging orbit fits. We find a mass consistent with predictions of hot-start evolutionary models and previous works following similar methods, though with larger uncertainties: $12.8^{+5.3}_{–3.2} M_{Jup}$. Our eccentricity determination of ${0.12}_{-0.03}^{+0.04}$ disfavors circular orbits. We consider orbit fits to several different imaging data sets, and find generally similar posteriors on the mass for each combination of imaging data. Our analysis underscores the importance of performing joint fits to the absolute and relative astrometry simultaneously, given the strong covariance between orbital elements. Time of conjunction is well-constrained within 2.8 days of 2017 September 13, with the star behind the planet's Hill sphere between 2017 April 11 and 2018 February 16 (±18 days). Following the recent radial velocity detection of a second planet in the system, β Pic c, we perform additional two-planet fits combining relative astrometry, absolute astrometry, and stellar radial velocities. These joint fits find a significantly smaller mass (8.0 ± 2.6 M Jup) for the imaged planet β Pic b, in a somewhat more circular orbit. We expect future ground-based observations to further constrain the visual orbit and mass of the planet in advance of the release of Gaia DR4.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Evidence for the Late Arrival of Hot Jupiters in Systems with High Host-star Obliquities

It has been shown that hot Jupiters systems with massive, hot stellar primaries exhibit a wide range of stellar obliquities. On the other hand, hot Jupiter systems with low-mass, cool primaries often have stellar obliquities close to zero. Efficient tidal interactions between hot Jupiters and the convective envelopes present in lower-mass main-sequence stars have been a popular explanation for these observations. If this explanation is accurate, then aligned systems should be older than misaligned systems. Likewise, the convective envelope mass of a hot Jupiter's host star should be an effective predictor of its obliquity. We derive homogeneous stellar parameters—including convective envelope masses—for hot Jupiter host stars with high-quality sky-projected obliquity inferences. Using a thin-disk stellar population's Galactic velocity dispersion as a relative age proxy, we find that hot Jupiter host stars with larger-than-median obliquities are older than hot Jupiter host stars with smaller-than-median obliquities. The relative age difference between the two populations is larger for hot Jupiter host stars with smaller-than-median fractional convective envelope masses and is significant at the 3.6σ level. We identify stellar mass, not convective envelope mass, as the best predictor of stellar obliquity in hot Jupiter systems. The best explanation for these observations is that many hot Jupiters in misaligned systems arrived in the close proximity of their host stars long after their parent protoplanetary disks dissipated. The dependence of observed age offset on convective envelope mass suggests that tidal realignment contributes to the population of aligned hot Jupiters orbiting stars with convective envelopes.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Hydrodynamics and Survivability during Post-main-sequence Planetary Engulfment

The engulfment of substellar bodies (SBs), such as brown dwarfs and planets, by giant stars is a possible explanation for rapidly rotating giants, lithium-rich giants, and the presence of SBs in close orbits around subdwarfs and white dwarfs. We perform three-dimensional hydrodynamical simulations of the flow in the vicinity of an engulfed SB. We model the SB as a rigid body with a reflective surface because it cannot accrete. This reflective boundary changes the flow morphology to resemble that of engulfed compact objects with outflows. We measure the drag coefficients for the ram-pressure and gravitational drag forces acting on the SB, and use them to integrate its trajectory inside the star. We find that engulfment can increase the luminosity of a 1 M ⊙ star by up to a few orders of magnitude. The time for the star to return to its original luminosity is up to a few thousand years when the star has evolved to ≈10 R ⊙ and up to a few decades at the tip of the red giant branch (RGB). No SBs can eject the envelope of a 1 M ⊙ star before it evolves to ≈10 R ⊙ if the orbit of the SB is the only energy source contributing to the ejection. In contrast, SBs as small as ≈10 MJup can eject the envelope at the tip of the RGB. The numerical framework we introduce here can be used to study planetary engulfment in a simplified setting that captures the physics of the flow at the scale of the SB.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2022

TOI-712 A System of Adolescent Mini-Neptunes Extending to the Habitable Zone

As an all-sky survey, NASA’s Transiting Exoplanet Survey Satellite (TESS) mission is able to detect the brightest and rarest types of transiting planetary systems, including young planets that enable study of the evolutionary processes that occur within the first billion years. Here we report the discovery of a young, multiplanet system orbiting the bright K4.5V star, TOI-712 ( V = 10.838, M * = 0.733 +0.026 -0.025 M ⨀ , R * = 0.674 ± 0.016 R ⨀ , T eff = 4622 +61 -60 K). From the TESS light curve, we measure a rotation period of 12.48 days and derive an age between about 500 Myr and 1.1 Gyr. The photometric observations reveal three transiting mini-Neptunes ( R b = 2.049 +0.120 -0.080 R ⊕ , R c = 2.701 +0.092 -0.082 R ⊕ , R d = 2.474 +0.090 -0.082 R ⊕ ), with orbital periods of P b = 9.531 days, P c = 51.699 days, and P d = 84.839 days. After modeling the three-planet system, an additional Earth-sized candidate is identified, TOI-712.05 ( P = 4.32 days, R P = 0.81 ± 0.11 R ⊕ ). We calculate that the habitable zone falls between 0.339 and 0.844 au (82.7 and 325.3 days), placing TOI-712 d near its inner edge. Among planetary systems harboring temperate planets, TOI-712 ( T = 9.9) stands out as a relatively young star bright enough to motivate further characterization.

Exoplanets↗
NASA NTRS2022

The Warm Neptune GJ 3470b Has a Polar Orbit

The warm Neptune GJ 3470b transits a nearby (d = 29 pc) bright slowly rotating M1.5-dwarf star. Using spectroscopic observations during two transits with the newly commissioned NEID spectrometer on the WIYN 3.5 m Telescope at Kitt Peak Observatory, we model the classical Rossiter–McLaughlin effect, yielding a sky-projected obliquity of λ=98 +15 −12 ˚and a v sin i = 0.85 +0.27 −0.33 kms -1 . Leveraging information about the rotation period and size of the host star, our analysis yields a true obliquity of ψ=95 +9 −8 ◦ , revealing that GJ 3470b is on a polar orbit. Using radial velocities from HIRES, HARPS, and the Habitable-zone Planet Finder, we show that the data are compatible with a long-term radial velocity (RV) slope of 𝛾̀=-0.0022±0.0011 ms -1 day -1 over a baseline of 12.9 yr. If the RV slope is due to acceleration from another companion in the system, we show that such a companion is capable of explaining the polar and mildly eccentric orbit of GJ 3470b using two different secular excitation models. The existence of an outer companion can be further constrained with additional RV observations, Gaia astrometry, and future high-contrast imaging observations. Lastly, we show that tidal heating from GJ 3470b’s mild eccentricity has most likely inflated the radius of GJ 3470b by a factor of ∼1.5–1.7, which could help account for its evaporating atmosphere.

Exoplanet astronomy↗
NASA NTRS2018

Transiting Exoplanet Survey Satellite (TESS) Flight Dynamics Commissioning Results and Experiences

The Transiting Exoplanet Survey Satellite (TESS) will perform the first-ever spaceborne all-sky exoplanet transit survey and is the first primary-mission application of a lunar-resonant orbit. Launched on April 18, 2018, TESS completed a two-month commissioning phase consisting of three phasing loops followed by a lunar flyby and a final maneuver to achieve resonance. During the mission orbit, no further station-keeping maneuvers are planned or required. NASA Goddard Space Flight Center is performing flight dynamics operations for the mission. This paper covers the design, implementation, and results from TESS commissioning, including the projected performance of the final mission orbit.

Satellite↗
NASA NTRS2018

Transiting Exoplanet Survey Satellite (TESS) Flight Dynamics Commissioning Results and Experiences

The Transiting Exoplanet Survey Satellite (TESS) will perform the first-ever spaceborne all-sky exoplanet transit survey and is the first primary-mission application of a lunar-resonant orbit. Launched on April 18, 2018, TESS completed a two-month commissioning phase consisting of three phasing loops followed by a lunar flyby and a final maneuver to achieve resonance. During the mission orbit, no further station-keeping maneuvers are planned or required. NASA Goddard Space Flight Center is performing flight dynamics operations for the mission. This paper covers the design, implementation, and results from TESS commissioning, including the projected performance of the final mission orbit.

Parker, Joel J. K.↗
NASA NTRS2018

Transiting Exoplanet Survey Satellite (TESS) Flight Dynamics Commissioning Results and Experiences

The Transiting Exoplanet Survey Satellite (TESS) will perform the first-ever spaceborne all-sky exoplanet transit survey and is the first primary-mission application of a lunar-resonant orbit. Launched on April 18, 2018, TESS completed a two-month commissioning phase consisting of three phasing loops followed by a lunar flyby and a final maneuver to achieve resonance. During the mission orbit, no further station-keeping maneuvers are planned or required. NASA Goddard Space Flight Center is performing flight dynamics operations for the mission. This paper covers the design, implementation, and results from TESS commissioning, including the projected performance of the final mission orbit.

Parker, Joel J. K.↗
NASA NTRS2022

Alma Images the Eccentric HD 53143 Debris Disk

We present ALMA 1.3 mm observations of the HD 53143 debris disk—the first infrared or millimeter image produced of this ∼1 Gyr old solar analog. Previous HST STIS coronagraphic imaging did not detect flux along the minor axis of the disk, which could suggest a face-on geometry with two clumps of dust. These ALMA observations reveal a disk with a strikingly different structure. In order to fit models to the millimeter visibilities and constrain the uncertainties on the disk parameters, we adopt a Markov Chain Monte Carlo approach. This is the most eccentric debris disk observed to date with a forced eccentricity of 0.21 ± 0.02, nearly twice that of the Fomalhaut debris disk, and also displays an apocenter glow. Although this eccentric model fits the outer debris disk well, significant interior residuals remain, which may suggest a possible edge-on inner disk, which remains unresolved in these observations. Combined with the observed structure difference between HST and ALMA, these results suggest a potential previous scattering event or dynamical instability in this system. We also note that the stellar flux changes considerably over the course of our observations, suggesting flaring at millimeter wavelengths. Using simultaneous TESS observations, we determine the stellar rotation period to be 9.6 ± 0.1 days.

Radio astronomy↗
NASA NTRS2023

A High-Eccentricity Warm Jupiter Orbiting TOI-4127

We report the discovery of TOI-4127 b, which is a transiting, Jupiter-sized exoplanet on a long period (P=56.39879 +0.00010 -0.00010 days) and a high-eccentricity orbit around a late F-type dwarf star. This warm Jupiter was first detected and identified as a promising candidate from a search for single-transit signals in TESS Sector 20 data and was later characterized as a planet following two subsequent transits (TESS Sectors 26 and 53) and follow-up ground-based RV observations with the NEID and SOPHIE spectrographs. We jointly fit the transit and RV data to constrain the physical (R p =1.096 +0.039 -0.032 R J , M p =2.30 +0.11 -0.11 M J ) and orbital parameters of the exoplanet. Given its high orbital eccentricity (𝓮=0.7471 +0.0078 -0.0086 ), TOI-4127 b is a compelling candidate for studies of warm Jupiter populations and of hot Jupiter formation pathways. We show that the present periastron separation of TOI-4127 b is too large for high-eccentricity tidal migration to circularize its orbit, and that TOI-4127 b is unlikely to be a hot Jupiter progenitor unless it is undergoing angular momentum exchange with an undetected outer companion. Although we find no evidence for an external companion, the available observational data are insufficient to rule out the presence of a perturber that can excite eccentricity oscillations and facilitate tidal migration.

Exoplanet astronomy↗
NASA NTRS2023

Exploring Climate With Obliquity in A Variable-Eccentricity Earth-Like World

Exploring planetary systems similar to our solar system can provide a means to explore a large range of possibly temperate climates on Earth-like worlds. Rather than run hundreds of simulations with different eccentricities at fixed obliquities, our variable-eccentricity approach provides a means to cover an incredibly large parameter space. Herein Jupiter's orbital radius is moved substantially inward in two different scenarios, causing a forcing on Earth's eccentricity. In one case, the eccentricity of Earth varies from 0 to 0.27 over ∼7000 yr for three different fixed obliquities (0°, 23°, and 45°). In another case, the eccentricity varies from 0 to 0.53 over ∼9400 yr in a single case with zero obliquity. In all cases, we find that the climate remains stable, but regional habitability changes through time in unique ways. At the same time, the moist greenhouse state is approached but only when at the highest eccentricities.

Exoplanet astronomy↗
NASA NTRS2019

Dynamic Analyses of the Proposed Habitable Exoplanet Astrophysics Facility

The proposed Habitable Exoplanet (HabEx) astrophysics facility is one of four large such facilities being proposed to the 2020 decadal. It is a large telescope that is sensitive to ultraviolet, optical, and near-infrared photons. The proposed design’s overall length is on the order of 17.2 m and its maximum cross section is on the order of 5.25 X 5.25 m. The primary mirror is 4 m in diameter. A transient dynamic analysis was performed to estimate the order of magnitude of ring down time after moving the telescope and pointing at a new target for science planning purposes. Without uncertainty factors, results from a simple re-pointing maneuver indicate that primary to secondary mirror LOS errors are on the order of 10-4 pico-m after 5 minutes. Also, a frequency response analysis was performed to predict the impact of planned micro-thruster vibrations on required stability. Based on provided noise level associated with the micro-thrusters and loading assumptions and without uncertainty factors, the assessed vibrations do not impact predicted performance requirements.

Knight, J. Brent↗
DOE OSTI2020

An Updated Visual Orbit of the Directly Imaged Exoplanet 51 Eridani b and Prospects for a Dynamical Mass Measurement with Gaia

We present a revision to the visual orbit of the young, directly imaged exoplanet 51 Eridani b using four years of observations with the Gemini Planet Imager. The relative astrometry is consistent with an eccentric (e=0.53{sub -0.13}{sup +0.09}) orbit at an intermediate inclination (i=136{sub -11}{sup +10} °), although circular orbits cannot be excluded due to the complex shape of the multidimensional posterior distribution. We find a semimajor axis of 11.1{sub -1.3}{sup +4.2} au and a period of 28.1{sub -4.9}{sup +17.2} yr, assuming a mass of 1.75 M{sub ⊙} for the host star. We find consistent values with a recent analysis of VLT/SPHERE data covering a similar baseline. We investigate the potential of using the absolute astrometry of the host star to obtain a dynamical mass constraint for the planet. The astrometric acceleration of 51 Eri derived from a comparison of the Hipparcos and Gaia catalogs was found to be inconsistent at the 2σ–3σ level with the predicted reflex motion induced by the orbiting planet. Potential sources of this inconsistency include a combination of random and systematic errors between the two astrometric catalogs and the signature of an additional companion within the system interior to current detection limits. We also explored the potential of using Gaia astrometry alone for a dynamical mass measurement of the planet by simulating Gaia measurements of the motion of the photocenter of the system over the course of the extended 8 yr mission. We find that such a measurement is only possible (>98% probability) given the most optimistic predictions for the Gaia scan astrometric uncertainties for bright stars and a high mass for the planet (≳3.6 M {sub Jup}).

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2019

Habitable Climate Scenarios for Proxima Centauri B with a Dynamic Ocean

The nearby exoplanet Proxima Centauri b will be a prime future target for characterization, despite questions about its retention of water. Climate models with static oceans suggest that Proxima b could harbor a small dayside surface ocean despite its weak instellation. We present the first climate simulations of Proxima b with a dynamic ocean. We find that an ocean-covered Proxima b could have a much broader area of surface liquid water but at much colder temperatures than previously suggested, due to ocean heat transport and/or depression of the freezing point by salinity. Elevated greenhouse gas concentrations do not necessarily produce more open ocean because of dynamic regime transitions between a state with an equatorial Rossby-Kelvin wave pattern and a state with a day-night circulation. For an evolutionary path leading to a highly saline ocean, Proxima b could be an inhabited, mostly open ocean planet with halophilic life. A fresh water ocean produces a smaller liquid region than does an Earth salinity ocean. An ocean planet in 3:2 spin-orbit resonance has a permanent tropical waterbelt for moderate eccentricity. A larger vs. smaller area of surface liquid water for similar equilibrium temperature may be distinguishable using the amplitude of the thermal phase curve. Simulations of Proxima Centauri b may be a model for the habitability of weakly irradiated planets orbiting slightly cooler or warmer stars, e.g., in the TRAPPIST-1, LHS 1140, GJ 273, and GJ 3293 systems.

Aquaplanet↗
NASA NTRS2012

The Exozodiacal Dust Problem for Direct Observations of ExoEarths

Debris dust in the habitable zones of stars otherwise known as exozodiacal dust comes from extrasolar asteroids and comets and is thus an expected part of a planetary system. Background flux from the Solar Systems zodiacal dust and the exozodiacal dust in the target system is likely to be the largest source of astrophysical noise in direct observations of terrestrial planets in the habitable zones of nearby stars. Furthermore, dust structures like clumps, thought to be produced by dynamical interactions with exoplanets, are a possible source of confusion. In this paper, we qualitatively assess the primary impact of exozodical dust on high-contrast direct imaging at optical wavelengths, such as would be performed with a coronagraph. Then we present the sensitivity of previous, current, and near-term facilities to thermal emission from debris dust at all distances from nearby solar-type stars, as well as our current knowledge of dust levels from recent surveys. Finally, we address the other method of detecting debris dust, through high-contrast imaging in scattered light. This method is currently far less sensitive than thermal emission observations, but provides high spatial resolution for studying dust structures. This paper represents the first report of NASA's Exoplanet Exploration Program Analysis Group (ExoPAG).

Roberge, Aki↗