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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Planetary populations in the mass-period diagram: A statistical treatment of exoplanet formation and the role of planet traps

The rapid growth of observed exoplanets has revealed the existence of several distinct planetary populations in the mass-period diagram. Two of the most surprising are (1) the concentration of gas giants around 1 AU and (2) the accumulation of a large number of low-mass planets with tight orbits, also known as super-Earths and hot Neptunes. We have recently shown that protoplanetary disks have multiple planet traps that are characterized by orbital radii in the disks and halt rapid type I planetary migration. By coupling planet traps with the standard core accretion scenario, we showed that one can account for the positions of planets in the mass-period diagram. In this paper, we demonstrate quantitatively that most gas giants formed at planet traps tend to end up around 1 AU, with most of these being contributed by dead zones and ice lines. We also show that a large fraction of super-Earths and hot Neptunes are formed as 'failed' cores of gas giants—this population being constituted by comparable contributions from dead zone and heat transition traps. Our results are based on the evolution of forming planets in an ensemble of disks where we vary only the lifetimes of disks and their mass accretion rates onto the host star. We show that a statistical treatment of the evolution of a large population of planetary cores caught in planet traps accounts for the existence of three distinct exoplanetary populations—the hot Jupiters, the more massive planets around r = 1 AU, and the short-period super-Earths and hot Neptunes. There are very few populations that feed into the large orbital radii characteristic of the imaged Jovian planet, which agrees with recent surveys. Finally, we find that low-mass planets in tight orbits become the dominant planetary population for low-mass stars (M {sub *} ≤ 0.7 M {sub ☉}).

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2002

Comparison of the Kepler and Eddington Missions

The Kepler and Eddington missions are spaceborne photometric missions with similar apertures. Both are capable of finding Earth-size extrasolar planets and both can detect p-mode oscillations in stars. The Kepler mission is optimized to find Earth-size planets in the habitability zone of Solar-like stars and does astroseismology only as incidental science. The Eddington mission appears to be optimized for astroseismology. The Kepler design provides a very large field of view, a low measurement cadence, a heliocentric orbit, and a long mission duration. The demand for a large field-of-view results in a Schmidt design with a massive corrector. However, the use of the corrector allows a 105 square degree FOV and thereby provides 15 times the number of stars at a given magnitude than does the optical design used in Eddington. Because Kepler stares at a single FOV throughout the mission, it does much less astroseismology than Eddington. Other comparisons are also discussed.

Borucki, William J.↗
DOE OSTI2014

Robotic laser adaptive optics imaging of 715 Kepler exoplanet candidates using Robo-AO

The Robo-AO Kepler Planetary Candidate Survey is observing every Kepler planet candidate host star with laser adaptive optics imaging to search for blended nearby stars, which may be physically associated companions and/or responsible for transit false positives. In this paper, we present the results from the 2012 observing season, searching for stars close to 715 Kepler planet candidate hosts. We find 53 companions, 43 of which are new discoveries. We detail the Robo-AO survey data reduction methods including a method of using the large ensemble of target observations as mutual point-spread-function references, along with a new automated companion-detection algorithm designed for large adaptive optics surveys. Our survey is sensitive to objects from ≈0.''15 to 2.''5 separation, with magnitude differences up to Δm ≈ 6. We measure an overall nearby-star probability for Kepler planet candidates of 7.4% ± 1.0%, and calculate the effects of each detected nearby star on the Kepler-measured planetary radius. We discuss several Kepler Objects of Interest (KOIs) of particular interest, including KOI-191 and KOI-1151, which are both multi-planet systems with detected stellar companions whose unusual planetary system architecture might be best explained if they are 'coincident multiple' systems, with several transiting planets shared between the two stars. Finally, we find 98% confidence evidence that short-period giant planets are two to three times more likely than longer-period planets to be found in wide stellar binaries.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

AN INCREASE IN THE MASS OF PLANETARY SYSTEMS AROUND LOWER-MASS STARS

Trends in the planet population with host star mass provide an avenue to constrain planet formation theories. We derive the planet radius distribution function for Kepler stars of different spectral types, sampling a range in host star masses. We find that M dwarf stars have 3.5 times more small planets (1.0–2.8 R{sub ⨁}) than main-sequence FGK stars, but two times fewer Neptune-sized and larger (>2.8 R{sub ⨁}) planets. We find no systematic trend in the planet size distribution between spectral types F, G, and K to explain the increasing occurrence rates. Taking into account the mass–radius relationship and heavy-element mass of observed exoplanets, and assuming those are independent of spectral type, we derive the inventory of the heavy-element mass locked up in exoplanets at short orbits. The overall higher planet occurrence rates around M stars are not consistent with the redistribution of the same mass into more, smaller planets. At the orbital periods and planet radii where Kepler observations are complete for all spectral types, the average heavy-element mass locked up in exoplanets increases roughly inversely with stellar mass from 4 M{sub ⨁} in F stars to 5 M{sub ⨁} in G and K stars to 7 M{sub ⨁} in M stars. This trend stands in stark contrast with observed protoplanetary disk masses that decrease toward lower mass stars, and provides a challenge for current planet formation models. Neither models of in situ formation nor migration of fully formed planets are consistent with these results. Instead, these results are indicative of large-scale inward migration of planetary building blocks—either through type-I migration or radial drift of dust grains—that is more efficient for lower mass stars, but does not result in significantly larger or smaller planets.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Very low density planets around Kepler-51 revealed with transit timing variations and an anomaly similar to a planet-planet eclipse event

We present an analysis of the transit timing variations (TTVs) in the multi-transiting planetary system around Kepler-51 (KOI-620). This system consists of two confirmed transiting planets, Kepler-51b (P {sub b} = 45.2 days) and Kepler-51c (P {sub c} = 85.3 days), and one transiting planet candidate KOI-620.02 (P {sub 02} = 130.2 days), which lie close to a 1: 2: 3 resonance chain. Our analysis shows that their TTVs are consistently explained by the three-planet model, and constrains their masses as M{sub b}=2.1{sub −0.8}{sup +1.5} M{sub ⊕} (Kepler-51b), M {sub c} = 4.0 ± 0.4 M {sub ⊕} (Kepler-51c), and M {sub 02} = 7.6 ± 1.1 M {sub ⊕} (KOI-620.02), thus confirming KOI-620.02 as a planet in this system. The masses inferred from the TTVs are rather small compared to the planetary radii based on the stellar density and planet-to-star radius ratios determined from the transit light curves. Combining these estimates, we find that all three planets in this system have densities among the lowest determined, ρ {sub p} ≲ 0.05 g cm{sup –3}. With this feature, the Kepler-51 system serves as another example of low-density compact multi-transiting planetary systems. We also identify a curious feature in the archived Kepler light curve during the double transit of Kepler-51b and KOI-620.02, which could be explained by their overlapping on the stellar disk (a planet-planet eclipse). If this is really the case, the sky-plane inclination of KOI-620.02's orbit relative to that of Kepler-51b is given by ΔΩ=−25.3{sub −6.8}{sup +6.2} deg, implying significant misalignment of their orbital planes. This interpretation, however, seems unlikely because such an event that is consistent with all of the observations is found to be exceedingly rare.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

High resolution transmission spectroscopy as a diagnostic for Jovian exoplanet atmospheres: constraints from theoretical models

We present high resolution transmission spectra of giant planet atmospheres from a coupled three-dimensional (3D) atmospheric dynamics and transmission spectrum model that includes Doppler shifts which arise from winds and planetary motion. We model Jovian planets covering more than two orders of magnitude in incident flux, corresponding to planets with 0.9-55 day orbital periods around solar-type stars. The results of our 3D dynamical models reveal certain aspects of high resolution transmission spectra that are not present in simple one-dimensional (1D) models. We find that the hottest planets experience strong substellar to anti-stellar (SSAS) winds, resulting in transmission spectra with net blueshifts of up to 3 km s{sup –1}, whereas less irradiated planets show almost no net Doppler shifts. We find only minor differences between transmission spectra for atmospheres with temperature inversions and those without. Compared to 1D models, peak line strengths are significantly reduced for the hottest atmospheres owing to Doppler broadening from a combination of rotation (which is faster for close-in planets under the assumption of tidal locking) and atmospheric winds. Finally, high resolution transmission spectra may be useful in studying the atmospheres of exoplanets with optically thick clouds since line cores for very strong transitions should remain optically thick to very high altitude. High resolution transmission spectra are an excellent observational test for the validity of 3D atmospheric dynamics models, because they provide a direct probe of wind structures and heat circulation. Ground-based exoplanet spectroscopy is currently on the verge of being able to verify some of our modeling predictions, most notably the dependence of SSAS winds on insolation. We caution that interpretation of high resolution transmission spectra based on 1D atmospheric models may be inadequate, as 3D atmospheric motions can produce a noticeable effect on the absorption signatures.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Indirect detection of forming protoplanets via chemical asymmetries in disks

We examine changes in the molecular abundances resulting from increased heating due to a self-luminous planetary companion embedded within a narrow circumstellar disk gap. Using 3D models that include stellar and planetary irradiation, we find that luminous young planets locally heat up the parent circumstellar disk by many tens of Kelvin, resulting in efficient thermal desorption of molecular species that are otherwise locally frozen out. Furthermore, the heating is deposited over large regions of the disk, ±5 AU radially and spanning ≲60{sup ∘} azimuthally. From the 3D chemical models, we compute rotational line emission models and full Atacama Large Millimeter Array simulations, and find that the chemical signatures of the young planet are detectable as chemical asymmetries in ∼10h observations. HCN and its isotopologues are particularly clear tracers of planetary heating for the models considered here, and emission from multiple transitions of the same species is detectable, which encodes temperature information in addition to possible velocity information from the spectra itself. We find submillimeter molecular emission will be a useful tool to study gas giant planet formation in situ, especially beyond R≳10 AU.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Interior phase transformations and mass-radius relationships of silicon-carbon planets

Planets such as 55 Cancri e orbiting stars with a high carbon-to-oxygen ratio may consist primarily of silicon and carbon, with successive layers of carbon, silicon carbide, and iron. The behavior of silicon-carbon materials at the extreme pressures prevalent in planetary interiors, however, has not yet been sufficiently understood. In this work, we use simulations based on density functional theory to determine high-pressure phase transitions in the silicon-carbon system, including the prediction of new stable compounds with Si{sub 2}C and SiC{sub 2} stoichiometry at high pressures. We compute equations of state for these silicon-carbon compounds as a function of pressure, and hence derive interior structural models and mass-radius relationships for planets composed of silicon and carbon. Notably, we predict a substantially smaller radius for SiC planets than in previous models, and find that mass radius relationships for SiC planets are indistinguishable from those of silicate planets. We also compute a new equation of state for iron. We rederive interior models for 55 Cancri e and are able to place more stringent restrictions on its composition.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Effects of the Planetary Temperature on the Circumplanetary Disk and on the Gap

Circumplanetary disks (CPDs) regulate the late accretion to the giant planet and serve as the birthplace for satellites. Understanding their characteristics via simulations also helps to prepare for their observations. Here we study disks around 1, 3, 5, and 10 M {sub Jup} planets with 3D global radiative hydrodynamic simulations with sub-planet peak resolution and various planetary temperatures. We found that as the 1 M {sub Jup} planet radiates away its formation heat, the circumplanetary envelope transitions to a disk between T{sub p}=6000 and 4000 K. In the case of 3–10 M {sub Jup} planets, a disk always forms. The temperature profile of the CPDs is very steep, the inner 1/6th is higher than the silicate condensation temperature, and the entire disk is higher than the water freezing point, making satellite formation impossible in this early stage (<1 Myr). Satellites might form much later and first in the outer parts of the disk, migrating inwards later on. Our disk masses are 1, 7, and 20 40×10{sup −3} M{sub Jup} for the 1, 3, 5, and 10 M {sub Jup} gas giants, respectively, and we provide an empirical formula to estimate the subdisk masses based on the planet- and circumstellar disk (CSD) mass. Our finding is that the cooler the planet, the lower the temperature of the subdisk, and the higher the vertical influx velocities. The planetary gap is also both deeper and wider. We also show that the gaps in 2D and 3D are different. The subdisk eccentricity increases with M{sub p} and violently interacts with the CSD, making satellite-formation less likely when M{sub p}≳5M{sub Jup}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Kinematic Evidence for an Embedded Planet in the IM Lupi Disk

Abstract We test the hypothesis that an embedded giant planet in the IM Lupi protostellar disk can produce velocity kinks seen in CO line observations as well as the spiral arms seen in scattered light and continuum emission. We inject planets into 3D hydrodynamics simulations of IM Lupi, generating synthetic observations using Monte Carlo radiative transfer. We find that an embedded planet of 2–3 M Jup can reproduce non-Keplerian velocity perturbations, or “kinks”, in the 12 CO J = 2–1 channel maps. Such a planet can also explain the spiral arms seen in 1.25 mm dust continuum emission and 1.6 μ m scattered-light images. We show that the wake of the planet can be traced in the observed peak velocity map, which appears to closely follow the morphology expected from our simulations and from analytic models of planet–disk interaction.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

HABITABILITY OF EXOMOONS AT THE HILL OR TIDAL LOCKING RADIUS

Moons orbiting extrasolar planets are the next class of object to be observed and characterized for possible habitability. Like the host-planets to their host-star, exomoons have a limiting radius at which they may be gravitationally bound, or the Hill radius. In addition, they also have a distance at which they will become tidally locked and therefore in synchronous rotation with the planet. We have examined the flux phase profile of a simulated, hypothetical moon orbiting at a distant radius around the confirmed exoplanets {mu} Ara b, HD 28185 b, BD +14 4559 b, and HD 73534 b. The irradiated flux on a moon at its furthest, stable distance from the planet achieves its largest flux gradient, which places a limit on the flux ranges expected for subsequent (observed) moons closer in orbit to the planet. We have also analyzed the effect of planetary eccentricity on the flux on the moon, examining planets that traverse the habitable zone either fully or partially during their orbit. Looking solely at the stellar contributions, we find that moons around planets that are totally within the habitable zone experience thermal equilibrium temperatures above the runaway greenhouse limit, requiring a small heat redistribution efficiency. In contrast, exomoons orbiting planets that only spend a fraction of their time within the habitable zone require a heat redistribution efficiency near 100% in order to achieve temperatures suitable for habitability. This means that a planet does not need to spend its entire orbit within the habitable zone in order for the exomoon to be habitable. Because the applied systems comprise giant planets around bright stars, we believe that the transit detection method is most likely to yield an exomoon discovery.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Tycho: Realistically Simulating Exoplanets within Stellar Clusters. I. Improving the Monte Carlo Approach

To fully understand the diverse population of exoplanets, we must study their early lives within open clusters, the birthplace of most stars with masses >0.5M {sub ⊙} (including those currently in the field). Indeed, when we observe planets within clustered environments, we notice highly eccentric and odd systems that suggest the importance of dynamical pathways created by interactions with additional bodies (as in the case of HD 285507b). However, it has proven difficult to investigate these effects, as many current numerical solvers for the multi-scale N-body problem are simplified and limited in scope. To remedy this, we aim to create a physically complete computational solution to explore the role of stellar close encounters and interplanetary interactions in producing the observed exoplanet populations for both open cluster stars and field stars. We present a new code, Tycho, which employs a variety of different computational techniques, including multiple N-body integration methods, close encounter handling, modified Monte Carlo scattering experiments, and a variety of empirically informed initial conditions. We discuss the methodology in detail, and its implementation within the AMUSE software framework. Approximately 1% of our systems are promptly disrupted by star-star encounters contributing to the rogue planets occurrence rate. Additionally, we find that close encounters which that perturb long-period planets lead to 38.3% of solar-system-like planetary systems becoming long-term unstable.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

How bright are planet-induced spiral arms in scattered light?

Recently, high angular resolution imaging instruments such as SPHERE and GPI have discovered many spiral-arm-like features in near-infrared scattered-light images of protoplanetary disks. Theory and simulations have suggested that these arms are most likely excited by planets forming in the disks; however, a quantitative relation between the arm-to-disk brightness contrast and planet mass is still missing. Using 3D hydrodynamics and radiative transfer simulations, we examine the morphology and contrast of planet-induced arms in disks. We find a power-law relation for the face-on arm contrast (δ{sub max}) as a function of planet mass (M{sub p}) and disk aspect ratio (h/r): δ{sub max}≈((M{sub p}/M{sub J})/(h/r){sup 1.38}){sup 0.22}. With current observational capabilities, at a 30 au separation, the minimum planet mass for driving detectable arms in a disk around a 1 Myr, 1 M{sub ⊙} star at 140 pc at low inclinations is around Saturn mass. For planets more massive than Neptune masses, they typically drive multiple arms. Therefore, in observed disks with spirals, it is unlikely that each spiral arm originates from a different planet. We also find that only massive perturbers with at least multi-Jupiter masses are capable of driving bright arms with δ{sub max}≳2 as found in SAO 206462, MWC 758, and LkHα 330, and these arms do not follow linear wave propagation theory. Additionally, we find that the morphology and contrast of the primary and secondary arms are largely unaffected by a modest level of viscosity with α≲0.01. Finally, the contrast of the arms in the SAO 206462 disk suggests that the perturber SAO 206462 b at ∼100 au is about 5--10 M{sub J} in mass.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

OPTICAL-TO-NEAR-INFRARED SIMULTANEOUS OBSERVATIONS FOR THE HOT URANUS GJ3470b: A HINT OF A CLOUD-FREE ATMOSPHERE

We present optical (g', R{sub c}, and I{sub c}) to near-infrared (J) simultaneous photometric observations for a primary transit of GJ3470b, a Uranus-mass transiting planet around a nearby M dwarf, by using the 50 cm MITSuME telescope and the 188 cm telescope, both at the Okayama Astrophysical Observatory. From these data, we derive the planetary mass, radius, and density as 14.1 {+-} 1.3 M{sub Circled-Plus }, 4.32{sup +0.21}{sub -0.10} R{sub Circled-Plus }, and 0.94 {+-} 0.12 g cm{sup -3}, respectively, thus confirming the low density that was reported by Demory et al. based on the Spitzer/IRAC 4.5 {mu}m photometry (0.72{sup +0.13}{sub -0.12} g cm{sup -3}). Although the planetary radius is about 10% smaller than that reported by Demory et al., this difference does not alter their conclusion that the planet possesses a hydrogen-rich envelope whose mass is approximately 10% of the planetary total mass. On the other hand, we find that the planet-to-star radius ratio (R{sub p} /R{sub s} ) in the J band (0.07577{sup +0.00072}{sub -0.00075}) is smaller than that in the I{sub c} (0.0802 {+-} 0.0013) and 4.5 {mu}m (0.07806{sup +0.00052}{sub -0.00054}) bands by 5.8% {+-} 2.0% and 2.9% {+-} 1.1%, respectively. A plausible explanation for the differences is that the planetary atmospheric opacity varies with wavelength due to absorption and/or scattering by atmospheric molecules. Although the significance of the observed R{sub p} /R{sub s} variations is low, if confirmed, this fact would suggest that GJ3470b does not have a thick cloud layer in the atmosphere. This property would offer a wealth of opportunity for future transmission-spectroscopic observations of this planet to search for certain molecular features, such as H{sub 2}O, CH{sub 4}, and CO, without being prevented by clouds.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2020

The Resilience of Habitable Climates Around Circumbinary Stars

Here we use a 3‐D climate system model to study the habitability of Earth‐like planets orbiting in circumbinary systems. In the most extreme cases, Earth‐like planets in circumbinary systems could experience variations in the incident stellar flux of up to ~50% on ~100‐day timescales. However, we find that Earth‐like planets, having abundant surface liquid water, are generally effective at buffering against these time‐dependent changes in the stellar irradiation due to the high thermal inertia of oceans compared with the relatively short periods of circumbinary‐driven variations in the received stellar flux. Ocean surface temperatures exhibit little to no variation in time; however, land surfaces can experience modest changes in temperature, thus exhibiting an additional mode of climate variability driven by the circumbinary variations. Still, meaningful oscillations in surface temperatures are only found for circumbinary system architectures featuring the largest physically possible amplitudes in the stellar flux variation. In the most extreme cases, an Earth‐like planet could experience circumbinary‐driven variations in the global mean land surface temperature of up to ~5 K, and variations of local daytime maximum temperatures of up to ~12 K on seasonal timescales, while the global mean ocean temperatures vary by less than ~2 K. Such seasonal temperature swings over land areas could potentially pose adaptability challenges for extant life. Still, habitable planets in circumbinary systems appear to be remarkably resilient against circumbinary‐driven climate variations and can avoid any true climate catastrophes.

Eric T Wolf↗
NASA NTRS2004

Terrestrial Planet Finder Coronagraph overview of technology development & system design

Astronomers have discovered over 150 planets orbiting other stars. NASA mission; Find and characterize terrestrial (or rocky) exo-planets that might harbor life (like Earth)liquid water on the planet (habitable zone). An atmosphere that indicates the presence of life water, oxygen, ozone, carbon dioxide, chlorophyll, and methane. Two missions under development: A coronagraph and an interferometer.

Balasubramanian, Kunjuthapatham↗
NASA NTRS2019

Architecture and Dynamics of Kepler's Multi-Transiting Planet Systems.III. Comprehensive Investigation Using All Four Years of Kepler Mission Data

We study the orbital architectures of planetary systems orbiting within ∼1 AU of their stars by analyzing the ensemble of Kepler systems having two or more planet candidates. We use data from the entire Kepler mission, and in many cases we apply improved analysis techniques (e.g., replacing histograms by top-hat Kernel Density Estimators that avoid the loss of information resulting from choosing a particular phase for the bin boundaries) to extend and enhance the studies of Lissauer et al. (2011, ApJS 197, 8) and Fabrycky et al. (2014, ApJ 790, 146).These data show ~ 1700 transiting planet candidates in > 600 multiple-planet systems, far more than were available for our previous two studies. The increased numbers and better information about planetary radii and the properties of stellar hosts made possible by Gaia DR2 allow more statistically-robust analyses of the entire ensemble of Kepler multis as well as independent analyses of subsets of the population. We are thus able to contrast the dynamical configurations of small and large planets, short-period and longer-period planets, and planets orbiting various types of host stars. We reinforce our previous findings that most pairs of planets within the same system are neither in nor near low-order mean motion resonances and that there is a substantial excess of planets having period ratios slightly larger than those of first-order mean-motion resonances. However, neglecting three systems whose planets are locked in 3- body resonances and summing over all first-order mean motion resonances, the deficit of planet pairs with period ratios just narrow of resonance is as large as the excess of planets wide of resonance (within statistical uncertainties), suggesting that overall there is no overall excess of planet pairs in the vicinity of resonance. Other aspects of our study, including estimates of the typical relative inclinations of planetary orbits and their variations as functions of orbital period, planet sizes and stellar properties, are in progress, with results expected to be available for presentation by the time of the conference.

Lissauer, Jack↗
NASA NTRS2022

TESS Hunt for Young and Maturing Exoplanets (THYME). VI. An 11 Myr Giant Planet Transiting a Very-low-mass Star in Lower Centaurus Crux

Mature super-Earths and sub-Neptunes are predicted to be ≃ Jovian radius when younger than 10 Myr. Thus, we expect to find 5-15 R ⊕ planets around young stars even if their older counterparts harbor none. We report the discovery and validation of TOI 1227b, a 0.85 ± 0.05 R J (9.5 R ⊕) planet transiting a very-low-mass star (0.170 ± 0.015 M ⊙) every 27.4 days. TOI 1227's kinematics and strong lithium absorption confirm that it is a member of a previously discovered subgroup in the Lower Centaurus Crux OB association, which we designate the Musca group. We derive an age of 11 ± 2 Myr for Musca, based on lithium, rotation, and the color-magnitude diagram of Musca members. The TESS data and ground-based follow-up show a deep (2.5%) transit. We use multiwavelength transit observations and radial velocities from the IGRINS spectrograph to validate the signal as planetary in nature, and we obtain an upper limit on the planet mass of ≃0.5 M J. Because such large planets are exceptionally rare around mature low-mass stars, we suggest that TOI 1227b is still contracting and will eventually turn into one of the more common <5 R ⊕ planets.

5–15 R⊕ planets↗