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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Exoplanet Yield Sensitivity for the Hybrid Lyot Coronagraph from end-to-end modeling for LUVOIR-A

NASA's future direct imaging flagship mission will require telescope mirror segmentation to survey a statistically significant population of nearby stellar systems by increasing aperture size beyond that achieved by traditional space-borne monolithic apertures thus far. Segmentation is a path for the size expansion, but it entails a challenge due to the introduction of temporal pupil discontinuities in terms of both phase and amplitude. Modeling of the integrated performance of the coronagraph with the expected dynamical profile of the telescope is an important step toward realistic estimates of the mission's science yields. We present results of a study using the hybrid Lyot coronagraph with a 15-m on-axis, segmented optical telescope assembly (OTA), akin to that of the Large UV / Optical /Infrared (LUVOIR) mission. We have developed a high-fidelity, end-to-end model as part of the Segmented Coronagraph Design and Analysis (SCDA) study that includes diffractive optical propagations at the 1e-10 contrast level across the optical train including the OTA and intermediate re-imaging optics inside the coronagraph instrument. We perform a sensitivity analysis to assess the contrast sensitivity to wavefront perturbations for a set of key telescope terms including segment-level low-order and mid-spatial frequency aberrations and evaluate expected exoplanet yields obtained in the presence of these sets of aberrations. Industry-provided segment-level wavefront aberration datasets involving the following mechanisms are input to the end-to-end model: (1) thermal gradients and accelerations, and (2) telescope dynamics including line-of-sight and segment jitter. Dynamically averaged PSFs in the presence of aberrations are fed into AYO (Altruistic Yield Optimization), a mission design reference simulator, that then assesses the scientific yield sensitivities.

high-contrast imaging↗
DOE OSTI2026

Rotation‐Controlled Diurnal Evolution of Uranus' Asymmetric Bow Shock at Equinox

Uranus possesses the most extreme magnetic and rotational geometry in the solar system, resulting in a uniquely dynamic and asymmetric interaction between its magnetosphere and the solar wind. Here we investigate the diurnal evolution of the Uranian bow shock (BS) at equinox using global multifluid magnetohydrodynamic simulations constrained by Voyager 2 observations. The BS structure and variability are quantified using the stand‐off distance, terminator distance, flaring parameter, and BS parameter, enabling a systematic assessment of its global asymmetry over one planetary rotation. Our results show that the BS exhibits pronounced diurnal asymmetry that is primarily controlled by planetary rotation. Even under steady upstream solar wind conditions, the BS undergoes periodic expansion and contraction, reflecting rotation‐driven reconfiguration of the planetary magnetospheric topology. This diurnal modulation represents a remarkably large asymmetry in planetary BS geometry within the solar system. These results establish planetary rotation as the intrinsic primary driver of Uranus' BS dynamics at equinox and provide essential constraints for the design and formulation of future space missions to the ice giants. These findings also offer a unique framework for understanding shock physics in the abundant population of ice‐giant exoplanets.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRSDate not supplied

Following the αCen Ab Candidate Using the Roman Coronagraph Instrument

The Roman Space Telescope Coronagraph offers a unique opportunity to observe our nearest solar twin, Alpha Centauri A, and characterize the habitable-zone gas giant candidate, Alpha Cen Ab. The candidate uniquely stands out among all imaged exoplanets to date as the one most similar in temperature, age and location to the planets in our own Solar System. Roman CGI offers the tantalizing opportunity to observe the candidate—determining its radius, temperature, and albedo—and to constrain its orbit. Observing Alpha Cen Ab with Roman would make it the first exoplanet to be imaged in both thermal emission and reflected light and would motivate an exciting search for habitable exomoons with the upcoming ELTs and HWO. In addition, this candidate will inform the planet formation history and current dynamics of the Alpha Centauri AB system, including potentially habitable planets around both stars. In this talk, we describe our plan to observe this target using the Roman CGI, including the timing strategy to minimize contrast and avoid background objects. We also describe the key technical insights about coronagraph performance that we aim to gain, such as measuring companion leakage intensity, evaluating the impact of the large stellar diameter, and assessing CGI performance on very bright targets. In subsequent observations, we aim to demonstrate Multi-Star Wavefront Control (MSWC) on-sky, observing Alpha Cen A using the Wide FoV Shaped Pupil MSWC contributed mode in the Roman CGI. The insights from these technology demonstrations are crucial preparation for the planned HWO mission.

Coronagraph↗
DOE OSTI2021

Implications of the iron oxide phase transition on the interiors of rocky exoplanets

The discovery of an extraordinary number of extrasolar planets, characterized by an unexpected variety of sizes, masses and orbits, challenges our understanding of the formation and evolution of the planets in the Solar System and the perception of the Earth as the prototypical habitable world. Many exoplanets appear to be rocky and yet more massive than the Earth, with expected pressures and temperatures of hundreds of gigapascal and thousands of Kelvin in their deep interiors. At these conditions, the properties of bridgmanite and ferropericlase, expected to dominate their mantles, are largely unconstrained, limiting our knowledge of their interior structure. Here we used nano-second X-ray diffraction and dynamic compression to experimentally investigate the atomic structure and density of iron oxide (FeO), one of the end-members of the (Mg,Fe)O ferropericlase solid solution, up to 700 GPa, a pressure exceeding the core–mantle boundary of a 5 Earth masses planet. Our data document the stability of the high-pressure cesium-chloride B2 structure above 300 GPa, well below the pressure required for magnesium oxide (MgO) to adopt the same phase. These observations, complemented by the calculation of the binary MgO–FeO phase diagram, reveal complex stratification and rheology inside large terrestrial exoplanets.

58 GEOSCIENCES↗
NASA NTRS2012

Gas Debris Disks: A New Way to Produce Dust Patterns

Debris disks like those around Fomalhaut and Beta Pictoris show striking dust patterns often attributed to planets. But adding a bit of gas to our models of these disks--too little to detect-could alter this interpretation. Small amounts of gas lead to new dynamical instabilities that may mimic the narrow eccentric rings and other structures planets would create in a gas-free disk. rll discuss these phenomena and whether or not we can still use dust patterns as indicators of hidden exoplanets.

Kuchner, Marc J.↗
NASA NTRS2018

The Impact of Stellar Variability on the Detection of Transiting Earth-Like Planets

Stellar variability represents a key limitation on the detectability of weak transit signatures of small, Earth-size planets with space-based missions such as NASA's Kepler Mission or ESA's PLATO Mission. The expectations for the performance of the Kepler Mission in the face of solar-like variability were predicated on observations of the Sun with the Variability of Solar Irradiance and Gravity Oscillations (VIRGO) instrument aboard NASA and ESA's joint Solar and Heliospheric Observatory (SOHO) mission, which was launched in December 1995. Analyses of SOHO data indicated that solar-like variability would contribute ~10 ppm to Kepler's noise budget at 6.5 ours, a typical grazing transit timescale. This proved to be optimistic as the typical 12th mag G2V star in the Kepler field of view exhibited 20 ppm of stellar variability-related noise at 6.5 hours, making the detection of true Earth-Sun analogs more difficult. While the consequent increase in the total noise at 6.5 hours from 20 ppm to 30 ppm could have been overcome by extending the mission to a total duration of 7 to 8 years. Unfortunately, a second reaction wheel failed in May 2013, ending the Kepler primary mission. Nevertheless, Kepler proved to be a veritable cornucopia of science results, both for exoplanets and for astrophysics. The phenomenal photometric precision and continuous observations required in order to identify small, rocky transiting planets enables the study of a large range of phenomena contributing to stellar variability for many thousands of solar-like stars in Kepler's field of view in exquisite detail. These effects range from <1 ppm acoustic oscillations on timescales from a few minutes and longward, to flares on timescales of hours, to spot-induced modulation on timescales of days to weeks to activity cycles on timescales of months to years. Kepler discovered over 2600 validated and confirmed exoplanets, and measured the pressure-mode oscillations of over 15000 stars over the course of its mission and the reconstituted K2 mission. We present the adaptive, wavelet-based matched filter used for both the Kepler and the TESS missions, and discuss the connections between this detection algorithm and fundamental detection theory, which allows the detector to function as a noise characterization engine. This provides a dynamical measurement of the photometric noise at transit timescales and thus, a key performance metric for missions like PLATO and Kepler. We give an overview of the stellar variability we see across the full range of spectral types observed by Kepler, from the cool, small red M stars to the hot, large late A stars, both in terms of amplitude as well as timescale.

exoplanets↗
NASA NTRS2018

The Impact of Stellar Variability on the Detection of Transiting Earth-like Planets

Stellar variability represents a key limitation on the detectability of weak transit signatures of small, Earth-size planets with space-based missions such as NASA's Kepler Mission or ESA's PLATO Mission. The expectations for the performance of the Kepler Mission in the face of solar-like variability were predicated on observations of the Sun with the Variability of Solar Irradiance and Gravity Oscillations (VIRGO) instrument aboard NASA and ESA's joint Solar and Heliospheric Observatory (SOHO) mission, which was launched in December 1995. Analyses of SOHO data indicated that solar-like variability would contribute approx.10 ppm to Kepler's noise budget at 6.5 ours, a typical grazing transit timescale. This proved to be optimistic as the typical 12th mag G2V star in the Kepler field of view exhibited 20 ppm of stellar variability-related noise at 6.5 hours, making the detection of true Earth-Sun analogs more difficult. While the consequent increase in the total noise at 6.5 hours from 20 ppm to 30 ppm could have been overcome by extending the mission to a total duration of 7 to 8 years. Unfortunately, a second reaction wheel failed in May 2013, ending the Kepler primary mission. Nevertheless, Kepler proved to be a veritable cornucopia of science results, both for exoplanets and for astrophysics. The phenomenal photometric precision and continuous observations required in order to identify small, rocky transiting planets enables the study of a large range of phenomena contributing to stellar variability for many thousands of solar-like stars in Kepler's field of view in exquisite detail. These effects range from less than 1 ppm acoustic oscillations on timescales from a few minutes and longward, to flares on timescales of hours, to spot-induced modulation on timescales of days to weeks to activity cycles on timescales of months to years. Kepler discovered over 2600 validated and confirmed exoplanets, and measured the pressure-mode oscillations of over 15000 stars over the course of its mission and the reconstituted K2 mission. We present the adaptive, wavelet-based matched filter used for both the Kepler and the TESS missions, and discuss the connections between this detection algorithm and fundamental detection theory, which allows the detector to function as a noise characterization engine. This provides a dynamical measurement of the photometric noise at transit timescales and thus, a key performance metric for missions like PLATO and Kepler. We give an overview of the stellar variability we see across the full range of spectral types observed by Kepler, from the cool, small red M stars to the hot, large late A stars, both in terms of amplitude as well as timescale.

transit surveys↗
NASA NTRS2022

Planet Hunters TESS IV: A Massive, Compact Hierarchical Triple Star System TIC 470710327

We report the discovery and analysis of a massive, compact, hierarchical triple system (TIC 470710327) initially identified by citizen scientists in data obtained by NASA’s Transiting Exoplanet Survey Satellite (TESS). Spectroscopic follow-up observations obtained with the HERMES spectrograph, combined with eclipse-timing variations (ETVs), confirm that the system is comprised of three OB stars, with a compact 1.10 d eclipsing binary and a non-eclipsing tertiary on a 52.04 d orbit. Dynamical modelling of the system (from radial velocity and ETVs) reveal a rare configuration wherein the tertiary star (O9.5-B0.5V; 14–17 M ꙩ ) is more massive than the combined mass of the inner binary (10.9–13.2 M ꙩ ). Given the high mass of the tertiary, we predict that this system will undergo multiple phases of mass transfer in the future, and likely end up as a double neutron star gravitational wave progenitor or an exotic Thorne–Żytkow object. Further observational characterization of this system promises constraints on both formation scenarios of massive stars as well as their exotic evolutionary end-products.

NASA's Transiting Exoplanet Survey Satellite (TESS↗
NASA NTRS2008

Optical Images of an Exosolar Planet 25 Light-Years from Earth

Fomalhaut is a bright star 7.7 parsec (25 light year) from Earth that harbors a belt of cold dust with a structure consistent with gravitational sculpting by an orbiting planet. Here, we present optical observations of an exoplanet candidate. Fomalhaut b. In the plane of the belt, Fomalhaut b lies approximately 119 astronomical units (AU) from the star, and within 18 All of the dust belt. We detect counterclockwise orbital motion using Hubble Space Telescope observations separated by 1.73 years. Dynamical models of the interaction between the planet and the belt indicate that the planet's mass is at most three times that of Jupiter for the belt to avoid gravitational disruption. The flux detected at 0.8 micron flux is also consistent with that of a planet with mass a few limes that of Jupiter. The brightness at 0.6 microns and the lack of detection at longer wavelengths suggest that the detected flux may include starlight reflected off a circumplanetary disk, with dimension comparable to the orbits of the Galilean satellites. We also observed variability of unknown origin at 0.6 microns.

Clampin, Mark↗
NASA NTRS2008

Optical Images of an Exosolar Planet 25 Light Years from Earth

Fomalhaut is a bright star 7.7 parsecs (25 light years) from Earth that harbors a belt of cold dust with a structure consistent with gravitational sculpting by an orbiting planet. Here, we present optical observations of an exoplanet candidate, Fomalhaut b. In the plane of the belt, Fomalhaut b lies approximately 119 astronomical units (AU) from the star and 18 AU from the dust belt, matching predictions. We detect counterclockwise orbital motion using Hubble Space Telescope observations separated by 1.73 years. Dynamical models of the interaction between the planet and the belt indicate that the planet's mass is at most three times that of Jupiter for the belt to avoid gravitational disruption. The flux detected at 0.8 m is also consistent with that of a planet with mass no greater than a few times that of Jupiter. The brightness at 0.6 micron and the lack of detection at longer wavelengths suggest that the detected flux may include starlight reflected off a circumplanetary disk, with dimension comparable to the orbits of the Galilean satellites. We also observed variability of unknown origin at 0.6 micron.

Kalas, Paul↗
NASA NTRS2017

Design Trade Study for a 4-Meter Off-Axis Primary Mirror Substrate and Mount for the Habitable-Zone Exoplanet Direct Imaging Mission

An extensive trade study was conducted to evaluate primary mirror substrate design architectures for the HabEx mission baseline 4-meter off-axis telescope. The study’s purpose is not to produce a final design, but rather to established a design methodology for matching the mirror’s properties (mass and stiffness) with the mission’s optical performance specifications (static dynamic wavefront error, WFE). The study systematically compares the effect of proven design elements (closed-back vs. open-back vs. partial-back; meniscus vs. flat back vs. shaped back; etc.), which can be implemented with proven space mirror materials (ULE and Zerodur), on static and dynamic WFE. Additionally, the study compares static and dynamic WFE of each substrate point design integrated onto three and six point mounts.

space↗
DOE OSTI2024

The Radiative Magneto-Hydrodynamics of Colliding Flow: Instabilities, Reconnection and Exoplanet Atmosphere Connections

Hypersonic flows of magnetized plasmas naturally produce strong shocks when obstructions or self‐interactions (flow collisions) occur. Such complex flows occur in a wide variety of HEDP settings such as Z‐pinches and laser driven implosion experiments that include magnetic fields via explosive Helmholtz coils (MIFEDS) When thermal energy behind the shocks can be lost to optically thin radiation, the flow dynamics becomes even more complex, admitting a range of new instabilities such as the Nonlinear Thin Shell Instability (NTSI). Because of their inherent non‐ linearity, multi‐dimensionality and time‐dependence (i.e. turbulence), the ability to articulate the underlying physics of colliding hypersonic magnetized flows represents a significant frontier in HEDP studies. The addition of radiative cooling to these flows propels the study even further into the domain of extreme plasma physics. Exploration of these forms of HED plasmas is of interest to basic plasma physics as well as of interest for their application to Inertial Confinement Fusion.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRSDate not supplied

Possible climate histories of Venus type worlds

There are two well-known scenarios for Venus’ climate evolution. In one Venus had a long-lived magma ocean phase in its first 100Myr with a steam and CO2dominated atmosphere[1]. The faint young sun with its high XUV flux would cause photo-dissociation of the steam atmosphere and hydrodynamic escape would cause most of the hydrogen to escape and the left over oxygen would be absorbed by the magma ocean. Hence Venus would have started out hot and dry and the high D/H ratio measured by Pioneer Venus [2] would be from this period of water loss. The other scenario is that Venus’ magma ocean lifetime would have been roughly the same length of time as Earth’s (~1Myr) and water would have condensed on its surface in its early history. As long as Venus remained in the slowly rotating climate dynamics regime [3,4] its cloud albedo feedback would have kept it temperate for possibly billions of years. The only way to confirm which one of these scenarios occurred for Venus is to visit it and make the necessary measurements of noble and volatile gases [5].But exoplanet observations of young exo-Venus type worlds around young F,G,K dwarf stars may constrain whether both scenarios are equally probable for a population of such planets. We present a vision of Venus’ climate history that places it and its exo-Venus cousins in an ‘Optimistic Venus Zone’ within the conventionally named ‘Venus Zone’ [6] and hence encourage the exoplanet community to seek out these worlds as possible habitable environments.

Venus’ climate evolution↗
NASA NTRS2014

Imaging Transitional Disks with TMT: Lessons Learned from the SEEDS Survey

TMT studies of the early phases of giant planet formation will build on studies carried out in this decade using 8-meter class telescopes. One such study is the Strategic Exploration of Exoplanets and Disks with Subaru transitional disk survey. We have found a wealth of indirect signatures of giant planet presence, including spiral arms, pericenter offsets of the outer disk from the star, and changes in disk color at the inner edge of the outer disk in intermediate-mass PMS star disks. T Tauri star transitional disks are less flamboyant, but are also dynamically colder: any spiral arms in these diskswill be more tightly wound. Imaging such features at the distance of the nearest star-forming regions requires higher angular resolution than achieved with HiCIAO+ AO188. Imaging such disks with extreme AO systems requires use of laser guide stars, and are infeasible with the extreme AO systems currently commissioning on 8-meter class telescopes. Similarly, the JWST and AFTAWFIRST coronagraphs being considered have inner working angles 0.2, and will occult the inner 28 atomic units of systems at d140pc, a region where both high-contrast imagery and ALMA data indicate that giant planets are located in transitional disks. However, studies of transitional disks associated with solar-mass stars and their planet complement are feasible with TMT using NFIRAOS.

star-forming regions↗
NASA NTRS2015

NIAC Phase II Orbiting Rainbows Granular Imager

In this paper, we present some ideas regarding the optics and imaging aspects of granular spacecraft. Granular spacecraft are complex systems composed of a spatially disordered distribution of a large number of elements, for instance a cloud of grains in orbit. An example of application is a spaceborne observatory for exoplanet imaging, where the primary aperture is a cloud instead of a monolithic aperture.

dynamics↗
DOE OSTI2021

Exosphere Modeling of Proxima b: A Case Study of Photochemical Escape with a Venus-like Atmosphere

Exoplanets orbiting M dwarfs within habitable zones are exposed to stellar environments more extreme than that terrestrial planets experience in our solar system, which can significantly impact the atmospheres of the exoplanets and affect their habitability and sustainability. This study provides the first prediction of hot oxygen corona structure and the associated photochemical loss from a 1 bar CO 2 -dominated atmosphere of a Venus-like rocky exoplanet, where dissociative recombination of O 2 + ions is assumed to be the major source reaction for the escape of neutral O atoms and formation of the hot O corona (or exospheres) as on Mars and Venus. We employ a 3D Monte Carlo code to simulate the exosphere of Proxima Centauri b (PCb) based on the ionosphere simulated by a 3D magnetohydrodynamic model. Our simulation results show that variability of the stellar wind dynamic pressure over one orbital period of PCb does not affect the overall spatial structure of the hot O corona but contributes to the change in the global hot O escape rate that varies by an order of magnitude. The escape increases dramatically when the planet possesses its intrinsic magnetic fields as the ionosphere becomes more extended with the presence of a global magnetic field. Furthermore, the extended hot O corona may lead to a more extended H exosphere through collisions between thermal H and hot O, which exemplifies the importance of considering nonthermal populations in exospheres to interpret future observations.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRSDate not supplied

Looking Local: Milky Way Science with JWST

The James Webb Space Telescope has only been operating for a short time, but has already revolutionized multiple areas of astrophysics, including our understanding of our home Galaxy. With a 6.6 meter primary mirror and four infrared science instruments, JWST’s science mission includes measurements of exoplanet atmospheres, observations of the chemistry of molecular clouds, tracing the lifecycle of dust in the interstellar medium (ISM), investigations of galaxy mergers and probing the first galaxies and the cosmological history of the universe. By investigating the Milky Way with JWST astronomers can not only better understand the physics, chemistry and dynamics of our own backyard, but these results can be used to more accurately inform the interpretation of observations of the distant universe. This presentation will detail JWST’s capabilities for conducting observations and surveys in the Milky Way, as well as highlight some early results from the observatory.

Erin C. Smith↗
NASA NTRS2013

Thermal Testing of a Stacked Core Mirror for UV Applications

The ASTRO2010 Decadal Survey stated that an advanced large-aperture ultraviolet, optical, near-infrared (UVOIR) telescope is required to enable the next generation of compelling astrophysics and exoplanet science; and, that present technology is not mature enough to affordably build and launch any potential UVOIR mission concept. Under Science and Technology funding, NASA's Marshall Space Flight Center and ITT Exelis have developed a more cost effective process to make 4m monolithic spaceflight UV quality, low areal density, thermally and dynamically stable primary mirrors. A proof of concept mirror was built and tested down to 250K which would allow imaging out to 2.5 microns. This mirror was thermally tested at the Marshall Spaceflight Center to understand the thermal changes between the processing temperature of 293K and the potential low end of the operational temperature of 250K. Isothermal testing results and front plate gradient results have been evaluated and compared to analysis predictions. Measurement of gravity effects on surface figure will be compared to analytical predictions. Future testing of a larger Pathfinder mirror will also be discussed.

Matthews, Gary↗