Megaconstellations of thousands to tens of thousands of artificial satellites (satcons) are rapidly being developed and launched. These satcons will have negative consequences for observational astronomy research, and are poised to drastically interfere with naked-eye stargazing worldwide should mitigation efforts be unsuccessful. Here we provide predictions for the optical brightnesses and on-sky distributions of several satcons, including Starlink, OneWeb, Kuiper, and StarNet/GW, for a total of 65,000 satellites on their filed or predicted orbits. We develop a simple model of satellite reflectivity, which is calibrated using published Starlink observations. We use this model to estimate the visible magnitudes and on-sky distributions for these satellites as seen from different places on Earth, in different seasons, and different times of night. For latitudes near 50° north and south, satcon satellites make up a few percent of all visible point sources all night long near the summer solstice, as well as near sunrise and sunset on the equinoxes. Altering the satellites' altitudes only changes the specific impacts of the problem. Without drastic reduction of the reflectivities, or significantly fewer total satellites in orbit, satcons will greatly change the night sky worldwide.
The American Astronomical Society (AAS), established in 1899 and based in Washington, DC, is the major organization of professional astronomers in North America. Its membership of about 7,000 individuals also includes physicists, mathematicians, geologists, engineers, and others whose research and educational interests lie within the broad spectrum of subjects comprising contemporary astronomy. The mission of the AAS is to enhance and share humanity's scientific understanding of the universe.
The Institute of Physics (IOP) is a leading scientific society promoting physics and bringing physicists together for the benefit of all. It has a worldwide membership of around 50 000 comprising physicists from all sectors, as well as those with an interest in physics. It works to advance physics research, application and education; and engages with policy makers and the public to develop awareness and understanding of physics. Its publishing company, IOP Publishing, is a world leader in professional scientific communications.
The Astronomical Journal is an open access journal publishing original astronomical research, with an emphasis on significant scientific results derived from observations. Publications in AJ include descriptions of data capture, surveys, analysis techniques, astronomical interpretation, instrumentation, and software and computing.
Remembering former AJ editor, Paul W. Hodge (1934–2019)
GOLD OPEN ACCESS FROM 1 JANUARY 2022
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Samantha M. Lawler et al 2022 AJ 163 21
Camryn Mullin et al 2024 AJ 167 183
As part of the James Webb Space Telescope (JWST) Guaranteed Time Observation program "Direct Imaging of YSOs" (program ID 1179), we use JWST NIRCam's direct imaging mode in F187N, F200W, F405N, and F410M to perform high-contrast observations of the circumstellar structures surrounding the protostar HL Tau. The data reveal the known stellar envelope, outflow cavity, and streamers, but do not detect any companion candidates. We detect scattered light from an inflowing spiral streamer previously detected in HCO+ by the Atacama Large Millimeter/submillimeter Array, and part of the structure connected to the c-shaped outflow cavity. For detection limits in planet mass we use BEX evolutionary tracks when Mp < 2 MJ and AMES-COND evolutionary tracks otherwise, assuming a planet age of 1 Myr (youngest available age). Inside the disk region, due to extended envelope emission, our point-source sensitivities are ∼5 mJy (37 MJ) at 40 au in F187N and ∼0.37 mJy (5.2 MJ) at 140 au in F405N. Outside the disk region, the deepest limits we can reach are ∼0.01 mJy (0.75 MJ) at a projected separation ∼ 525 au.
Konstantin Batygin and Michael E. Brown 2016 AJ 151 22
Recent analyses have shown that distant orbits within the scattered disk population of the Kuiper Belt exhibit an unexpected clustering in their respective arguments of perihelion. While several hypotheses have been put forward to explain this alignment, to date, a theoretical model that can successfully account for the observations remains elusive. In this work we show that the orbits of distant Kuiper Belt objects (KBOs) cluster not only in argument of perihelion, but also in physical space. We demonstrate that the perihelion positions and orbital planes of the objects are tightly confined and that such a clustering has only a probability of 0.007% to be due to chance, thus requiring a dynamical origin. We find that the observed orbital alignment can be maintained by a distant eccentric planet with mass ≳10 m⊕ whose orbit lies in approximately the same plane as those of the distant KBOs, but whose perihelion is 180° away from the perihelia of the minor bodies. In addition to accounting for the observed orbital alignment, the existence of such a planet naturally explains the presence of high-perihelion Sedna-like objects, as well as the known collection of high semimajor axis objects with inclinations between 60° and 150° whose origin was previously unclear. Continued analysis of both distant and highly inclined outer solar system objects provides the opportunity for testing our hypothesis as well as further constraining the orbital elements and mass of the distant planet.
Michael E. Brown et al 2024 AJ 167 146
We present a search for Planet Nine using the second data release of the Pan-STARRS1 survey. We rule out the existence of a Planet Nine with the characteristics of that predicted in Brown & Batygin to a 50% completion depth of V = 21.5. This survey, along with previous analyses of the Zwicky Transient Facility and Dark Energy Survey data, rules out 78% of the Brown & Batygin parameter space. Much of the remaining parameter space is at V > 21 in regions near and in the area where the northern galactic plane crosses the ecliptic.
Colin Orion Chandler et al 2024 AJ 167 156
We present the Citizen Science program Active Asteroids and describe discoveries stemming from our ongoing project. Our NASA Partner program is hosted on the Zooniverse online platform and launched on 2021 August 31, with the goal of engaging the community in the search for active asteroids—asteroids with comet-like tails or comae. We also set out to identify other unusual active solar system objects, such as active Centaurs, active quasi-Hilda asteroids (QHAs), and Jupiter-family comets (JFCs). Active objects are rare in large part because they are difficult to identify, so we ask volunteers to assist us in searching for active bodies in our collection of millions of images of known minor planets. We produced these cutout images with our project pipeline that makes use of publicly available Dark Energy Camera data. Since the project launch, roughly 8300 volunteers have scrutinized some 430,000 images to great effect, which we describe in this work. In total, we have identified previously unknown activity on 15 asteroids, plus one Centaur, that were thought to be asteroidal (i.e., inactive). Of the asteroids, we classify four as active QHAs, seven as JFCs, and four as active asteroids, consisting of one main-belt comet (MBC) and three MBC candidates. We also include our findings concerning known active objects that our program facilitated, an unanticipated avenue of scientific discovery. These include discovering activity occurring during an orbital epoch for which objects were not known to be active, and the reclassification of objects based on our dynamical analyses.
Kevin Wagner et al 2024 AJ 167 181
MWC 758 is a young star hosting a spiral protoplanetary disk. The spirals are likely companion-driven, and two previously identified candidate companions have been identified—one at the end the Southern spiral arm at ∼06, and one interior to the gap at ∼01. With JWST/NIRCam, we provide new images of the disk and constraints on planets exterior to ∼1''. We detect the two-armed spiral disk, a known background star, and a spatially resolved background galaxy, but no clear companions. The candidates that have been reported are at separations that are not probed by our data with sensitivity sufficient to detect them−nevertheless, these observations place new limits on companions down to ∼2 MJup at ∼150 au and ∼0.5 MJup at ≳600 au. Owing to the unprecedented sensitivity of JWST and youth of the target, these are among the deepest mass-detection limits yet obtained through direct imaging observations, and provide new insights into the system's dynamical nature.
B. Ralph Chou et al 2021 AJ 162 103
We investigated the compliance of 43 commercially available solar filters (eclipse glasses) with the ISO 12312-2:2015 standard by measuring their spectral transmittances (280–2000 nm) and calculating their luminous, solar ultraviolet A, ultraviolet B, and infrared (IR) transmittances. We also evaluated the filters for usability by observing the full midday Sun and rating the view on a seven-point balanced scale, from "far too dark, details seen only with great difficulty" to "far too light, uncomfortable to view the Sun." The mean ratings of two observers, one experienced and one inexperienced in solar observing, differed by 0.28 (95% confidence interval of the mean = 0.26). The inexperienced observer tended to be less accepting of high transmittances. All 43 solar filters complied with the UV and IR requirements. Eighteen filters passed the luminous transmittance requirements, and 24 were borderline too light or too dark. Seven of the 15 solar filters with a luminous transmittance darker than the requirement were rated as acceptable. One filter that passed and another that was borderline too light were rated as too light or far too light. The ISO 12312-2 limits derive from welding filter standards and do not represent an appropriate evidence base for direct solar viewing. This work provides the evidence base for a maximum 0.0012% and a minimum 0.00004% luminous transmittance for solar filters. The results of this study also support the use of welding filters between shades 12 and 16. Lighter welding filters are more acceptable than solar filters of the same luminous transmittance.
Ryan S. Park et al 2021 AJ 161 105
The planetary and lunar ephemerides called DE440 and DE441 have been generated by fitting numerically integrated orbits to ground-based and space-based observations. Compared to the previous general-purpose ephemerides DE430, seven years of new data have been added to compute DE440 and DE441, with improved dynamical models and data calibration. The orbit of Jupiter has improved substantially by fitting to the Juno radio range and Very Long Baseline Array (VLBA) data of the Juno spacecraft. The orbit of Saturn has been improved by radio range and VLBA data of the Cassini spacecraft, with improved estimation of the spacecraft orbit. The orbit of Pluto has been improved from use of stellar occultation data reduced against the Gaia star catalog. The ephemerides DE440 and DE441 are fit to the same data set, but DE441 assumes no damping between the lunar liquid core and the solid mantle, which avoids a divergence when integrated backward in time. Therefore, DE441 is less accurate than DE440 for the current century, but covers a much longer duration of years −13,200 to +17,191, compared to DE440 covering years 1550–2650.
Gabriele Cugno et al 2024 AJ 167 182
We present JWST/NIRCam F187N, F200W, F405N, and F410M direct imaging data of the disk surrounding SAO 206462. Previous images show a very structured disk, with a pair of spiral arms thought to be launched by one or more external perturbers. The spiral features are visible in three of the four filters, with the nondetection in F410M due to the large detector saturation radius. We detect with a signal-to-noise ratio of 4.4 a companion candidate that, if on a coplanar circular orbit, would orbit SAO 206462 at a separation of ∼300 au, 2.25σ away from the predicted separation for the driver of the eastern spiral. No other companion candidates were detected. At the location predicted by simulations of both spirals generated by a single massive companion, the NIRCam data exclude objects more massive than ∼2.2 MJ assuming the BEX evolutionary models. In terms of temperatures, the data are sensitive to objects with Teff ∼ 650–850 K, when assuming planets emit like blackbodies (Rp between 1 and 3RJ). From these results, we conclude that if the spirals are driven by gas giants, these must be either cold or embedded in circumplanetary material. In addition, the NIRCam data provide tight constraints on ongoing accretion processes. In the low extinction scenario we are sensitive to mass accretion rates of the order yr−1. Thanks to the longer wavelengths used to search for emission lines, we reach unprecedented sensitivities to processes with yr−1 even toward highly extincted environments (AV ≈ 50 mag).
Naman S. Bajaj et al 2024 AJ 167 127
Understanding when and how circumstellar disks disperse is crucial to constrain planet formation and migration. Thermal winds powered by high-energy stellar photons have long been theorized to drive disk dispersal. However, evidence for these winds is currently based only on small (∼3–6 km s−1) blueshifts in [Ne ii] 12.81 μm lines, which does not exclude MHD winds. We report JWST MIRI MRS spectro-imaging of T Cha, a disk with a large dust gap (∼30 au in radius) and blueshifted [Ne ii] emission. We detect four forbidden noble gas lines, [Ar ii], [Ar iii], [Ne ii], and [Ne iii], of which [Ar iii] is the first detection in any protoplanetary disk. We use line flux ratios to constrain the energy of the ionizing photons and find that argon is ionized by extreme ultraviolet, whereas neon is most likely ionized by X-rays. After performing continuum and point-spread function subtraction on the integral field unit cube, we discover a spatial extension in the [Ne ii] emission off the disk continuum emission. This is the first spatially resolved [Ne ii] disk wind emission. The mostly ionic spectrum of T Cha, in combination with the extended [Ne ii] emission, points to an evolved stage for any inner MHD wind and is consistent with the existence of an outer thermal wind ionized and driven by high-energy stellar photons. This work acts as a pathfinder for future observations aiming at investigating disk dispersal using JWST.
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Abigail Burrows et al 2024 AJ 167 243
We revisit the long-studied radial velocity (RV) target HD 26965 using recent observations from the NASA-NSF "NEID" precision Doppler facility. Leveraging a suite of classical activity indicators, combined with line-by-line RV analyses, we demonstrate that the claimed 45-day signal previously identified as a planet candidate is most likely an activity-induced signal. Correlating the bulk (spectrally averaged) RV with canonical line activity indicators confirms a multiday "lag" between the observed activity indicator time series and the measured RV. When accounting for this lag, we show that much of the observed RV signal can be removed by a linear detrending of the data. Investigating activity at the line-by-line level, we find a depth-dependent correlation between individual line RVs and the bulk RVs, further indicative of periodic suppression of convective blueshift causing the observed RV variability, rather than an orbiting planet. We conclude that the combined evidence of the activity correlations and depth dependence is consistent with an RV signature dominated by a rotationally modulated activity signal at a period of ∼42 days. We hypothesize that this activity signature is due to a combination of spots and convective blueshift suppression. The tools applied in our analysis are broadly applicable to other stars and could help paint a more comprehensive picture of the manifestations of stellar activity in future Doppler RV surveys.
Alberto Rodríguez-Ardila et al 2024 AJ 167 244
We use near-infrared spectroscopy covering simultaneously the zJHK bands to look for outflowing gas from the nuclear environment of 1H 0707−495 taking advantage that this region is dominated by low-ionization broad-line region lines, most of them isolated. We detect broad components in H i, Fe ii, and O i, at rest to the systemic velocity, displaying FWHM values of ∼500 km s−1, consistent with its classification as a narrow-line Seyfert 1 active galactic nucleus. Moreover, most lines display a conspicuous blue-asymmetric profile, modeled using a blueshifted component, whose velocity shift reaches up to ∼826 km s−1. This last feature can be interpreted in terms of outflowing gas already observed in X-ray and UV lines in 1H 0707−495 but not detected before in the low-ionization lines. We discuss the relevance of our findings within the framework of the wind scenario already proposed for this source and suggest that the wind extends well into the narrow-line region owing to the observation of a blueshifted component in the forbidden line of [S iii] λ9531.
Sadhana Singh et al 2024 AJ 167 242
Using starlight polarization, we present the properties of foreground dust toward cluster NGC 7380 embedded in H ii region Sh 2-142. Observations of starlight polarization are carried out in four filters using an imaging polarimeter equipped with a 104 cm ARIES telescope. Polarization vectors of stars are aligned along the Galactic magnetic field. Toward the east and southeast regions, the dust structure appears much denser than in other regions (inferred from extinction contours and a color composite image) and is also reflected in polarization distribution. We find that the polarization degree and extinction tend to increase with distance and indication for the presence of a dust layer at a distance of around 1.2 kpc. We have identified eight potential candidates exhibiting intrinsic polarization by employing three distinct criteria to distinguish between stars of intrinsic polarization and interstellar polarized stars. For interstellar polarized stars, we find that the maximum polarization degree increases with the color excess and has a strong scatter, with the mean value of 1.71% ± 0.57%. The peak wavelength spans 0.40–0.88 μm, with a mean value of 0.56 ± 0.07 μm, suggesting similar grain sizes in the region to those in the average diffuse interstellar medium. The polarization efficiency is also found to decrease with visual extinction as . Our observational results are found to be consistent with the predictions by the radiative torque alignment theory.
Charlotte Fairman et al 2024 AJ 167 240
Exoplanet transmission spectra provide rich information about the chemical composition, clouds, and temperature structure of exoplanet atmospheres. Most exoplanet transmission spectra only span infrared wavelengths (≳1 μm), which can preclude crucial atmospheric information from shorter wavelengths. Here, we explore how retrieved atmospheric parameters from exoplanet transmission spectra change with the addition of optical data. From a sample of 14 giant planets with transit spectra from 0.3–4.5 μm, primarily from the Hubble and Spitzer space telescopes, we apply a free chemistry retrieval to planetary spectra for wavelength ranges of 0.3–4.5 μm, 0.6–4.5 μm, and 1.1–4.5 μm. We analyze the posterior distributions of these retrievals and perform an information content analysis, finding wavelengths below 0.6 μm are necessary to constrain cloud scattering slope parameters ( and γ) and alkali species Na and K. There is limited improvement in the constraints on the remaining atmospheric parameters. Across the population, we find that limb temperatures are retrieved colder than planetary equilibrium temperatures but have an overall good agreement with Global Circulation Models. As the JWST extends to a minimum wavelength of 0.6 μm, we demonstrate that exploration into complementing JWST observations with optical HST data is important to further our understanding of aerosol properties and alkali abundances in exoplanet atmospheres.
Stephen R. Kane et al 2024 AJ 167 239
The discovery of planetary systems beyond the solar system has revealed a diversity of architectures, most of which differ significantly from our system. The initial detection of an exoplanet is often followed by subsequent discoveries within the same system as observations continue, measurement precision is improved, or additional techniques are employed. The HD 104067 system is known to consist of a bright K-dwarf host star and a giant planet in a ∼55 days period eccentric orbit. Here we report the discovery of an additional planet within the HD 104067 system, detected through the combined analysis of radial velocity (RV) data from the High Resolution Echelle Spectrometer and High Accuracy Radial velocity Planet Searcher instruments. The new planet has a mass similar to Uranus and is in an eccentric ∼14 days orbit. Our injection-recovery analysis of the RV data exclude Saturn-mass and Jupiter-mass planets out to 3 au and 8 au, respectively. We further present Transiting Exoplanet Survey Satellite observations that reveal a terrestrial planet candidate (Rp = 1.30 ± 0.12 R⊕) in a ∼2.2 days period orbit. Our dynamical analysis of the three planet model shows that the two outer planets produce significant eccentricity excitation of the inner planet, resulting in tidally induced surface temperatures as high as ∼2600 K for an emissivity of unity. The terrestrial planet candidate may therefore be caught in a tidal storm, potentially resulting in its surface radiating at optical wavelengths.
Open all abstracts, in this tab
Abigail Burrows et al 2024 AJ 167 243
We revisit the long-studied radial velocity (RV) target HD 26965 using recent observations from the NASA-NSF "NEID" precision Doppler facility. Leveraging a suite of classical activity indicators, combined with line-by-line RV analyses, we demonstrate that the claimed 45-day signal previously identified as a planet candidate is most likely an activity-induced signal. Correlating the bulk (spectrally averaged) RV with canonical line activity indicators confirms a multiday "lag" between the observed activity indicator time series and the measured RV. When accounting for this lag, we show that much of the observed RV signal can be removed by a linear detrending of the data. Investigating activity at the line-by-line level, we find a depth-dependent correlation between individual line RVs and the bulk RVs, further indicative of periodic suppression of convective blueshift causing the observed RV variability, rather than an orbiting planet. We conclude that the combined evidence of the activity correlations and depth dependence is consistent with an RV signature dominated by a rotationally modulated activity signal at a period of ∼42 days. We hypothesize that this activity signature is due to a combination of spots and convective blueshift suppression. The tools applied in our analysis are broadly applicable to other stars and could help paint a more comprehensive picture of the manifestations of stellar activity in future Doppler RV surveys.
Alberto Rodríguez-Ardila et al 2024 AJ 167 244
We use near-infrared spectroscopy covering simultaneously the zJHK bands to look for outflowing gas from the nuclear environment of 1H 0707−495 taking advantage that this region is dominated by low-ionization broad-line region lines, most of them isolated. We detect broad components in H i, Fe ii, and O i, at rest to the systemic velocity, displaying FWHM values of ∼500 km s−1, consistent with its classification as a narrow-line Seyfert 1 active galactic nucleus. Moreover, most lines display a conspicuous blue-asymmetric profile, modeled using a blueshifted component, whose velocity shift reaches up to ∼826 km s−1. This last feature can be interpreted in terms of outflowing gas already observed in X-ray and UV lines in 1H 0707−495 but not detected before in the low-ionization lines. We discuss the relevance of our findings within the framework of the wind scenario already proposed for this source and suggest that the wind extends well into the narrow-line region owing to the observation of a blueshifted component in the forbidden line of [S iii] λ9531.
Sadhana Singh et al 2024 AJ 167 242
Using starlight polarization, we present the properties of foreground dust toward cluster NGC 7380 embedded in H ii region Sh 2-142. Observations of starlight polarization are carried out in four filters using an imaging polarimeter equipped with a 104 cm ARIES telescope. Polarization vectors of stars are aligned along the Galactic magnetic field. Toward the east and southeast regions, the dust structure appears much denser than in other regions (inferred from extinction contours and a color composite image) and is also reflected in polarization distribution. We find that the polarization degree and extinction tend to increase with distance and indication for the presence of a dust layer at a distance of around 1.2 kpc. We have identified eight potential candidates exhibiting intrinsic polarization by employing three distinct criteria to distinguish between stars of intrinsic polarization and interstellar polarized stars. For interstellar polarized stars, we find that the maximum polarization degree increases with the color excess and has a strong scatter, with the mean value of 1.71% ± 0.57%. The peak wavelength spans 0.40–0.88 μm, with a mean value of 0.56 ± 0.07 μm, suggesting similar grain sizes in the region to those in the average diffuse interstellar medium. The polarization efficiency is also found to decrease with visual extinction as . Our observational results are found to be consistent with the predictions by the radiative torque alignment theory.
Charlotte Fairman et al 2024 AJ 167 240
Exoplanet transmission spectra provide rich information about the chemical composition, clouds, and temperature structure of exoplanet atmospheres. Most exoplanet transmission spectra only span infrared wavelengths (≳1 μm), which can preclude crucial atmospheric information from shorter wavelengths. Here, we explore how retrieved atmospheric parameters from exoplanet transmission spectra change with the addition of optical data. From a sample of 14 giant planets with transit spectra from 0.3–4.5 μm, primarily from the Hubble and Spitzer space telescopes, we apply a free chemistry retrieval to planetary spectra for wavelength ranges of 0.3–4.5 μm, 0.6–4.5 μm, and 1.1–4.5 μm. We analyze the posterior distributions of these retrievals and perform an information content analysis, finding wavelengths below 0.6 μm are necessary to constrain cloud scattering slope parameters ( and γ) and alkali species Na and K. There is limited improvement in the constraints on the remaining atmospheric parameters. Across the population, we find that limb temperatures are retrieved colder than planetary equilibrium temperatures but have an overall good agreement with Global Circulation Models. As the JWST extends to a minimum wavelength of 0.6 μm, we demonstrate that exploration into complementing JWST observations with optical HST data is important to further our understanding of aerosol properties and alkali abundances in exoplanet atmospheres.
Stephen R. Kane et al 2024 AJ 167 239
The discovery of planetary systems beyond the solar system has revealed a diversity of architectures, most of which differ significantly from our system. The initial detection of an exoplanet is often followed by subsequent discoveries within the same system as observations continue, measurement precision is improved, or additional techniques are employed. The HD 104067 system is known to consist of a bright K-dwarf host star and a giant planet in a ∼55 days period eccentric orbit. Here we report the discovery of an additional planet within the HD 104067 system, detected through the combined analysis of radial velocity (RV) data from the High Resolution Echelle Spectrometer and High Accuracy Radial velocity Planet Searcher instruments. The new planet has a mass similar to Uranus and is in an eccentric ∼14 days orbit. Our injection-recovery analysis of the RV data exclude Saturn-mass and Jupiter-mass planets out to 3 au and 8 au, respectively. We further present Transiting Exoplanet Survey Satellite observations that reveal a terrestrial planet candidate (Rp = 1.30 ± 0.12 R⊕) in a ∼2.2 days period orbit. Our dynamical analysis of the three planet model shows that the two outer planets produce significant eccentricity excitation of the inner planet, resulting in tidally induced surface temperatures as high as ∼2600 K for an emissivity of unity. The terrestrial planet candidate may therefore be caught in a tidal storm, potentially resulting in its surface radiating at optical wavelengths.
Olcay Ates Goksu et al 2024 AJ 167 236
Metal pollution onto white dwarfs is a widespread phenomenon that remains puzzling. Some of these white dwarfs also harbor gaseous debris disks. Emission lines from these disks open a unique window to the physical properties of the polluting material, lending insights into their origin. We model the emission line kinematics for the gas disk around SDSS J1228+1040, a system that has been monitored for over two decades. We show that the disk mass is strongly peaked at 1 R⊙ (modulo the unknown inclination), and the disk eccentricity decreases from a value of 0.44 at the inner edge, to nearly zero at the outer edge. This eccentricity profile is exactly what one expects if the disk is in a global eccentric mode, precessing rigidly under general relativity and gas pressure. The precession period is about two decades. We infer that the mass of the gas disk is roughly equivalent to that of a 50 km rocky body, while the mass of the accompanying dust disk is likely insignificant. The disk eccentricity confirms an origin in tidal disruption, while the short disk diffusion time suggests that the disruption event happened a few centuries ago. Moreover, we argue that the initial orbit for the disrupted body, and that of its putative planetary perturber, fall within an astronomical unit around the white dwarf. The total mass of the source population is likely orders of magnitude more massive than our own Asteroid belt and does not seem to exist around main-sequence stars.
Sean M. O'Brien et al 2024 AJ 167 238
We present the results from the first two years of the Planet Hunters Next Generation Transit Survey (NGTS) citizen science project, which searches for transiting planet candidates in data from the NGTS by enlisting the help of members of the general public. Over 8000 registered volunteers reviewed 138,198 light curves from the NGTS Public Data Releases 1 and 2. We utilize a user weighting scheme to combine the classifications of multiple users to identify the most promising planet candidates not initially discovered by the NGTS team. We highlight the five most interesting planet candidates detected through this search, which are all candidate short-period giant planets. This includes the TIC-165227846 system that, if confirmed, would be the lowest-mass star to host a close-in giant planet. We assess the detection efficiency of the project by determining the number of confirmed planets from the NASA Exoplanet Archive and TESS Objects of Interest (TOIs) successfully recovered by this search and find that 74% of confirmed planets and 63% of TOIs detected by NGTS are recovered by the Planet Hunters NGTS project. The identification of new planet candidates shows that the citizen science approach can provide a complementary method to the detection of exoplanets with ground-based surveys such as NGTS.
Ben W. P. Lew et al 2024 AJ 167 237
The launch of the James Webb Space Telescope (JWST) marks a pivotal moment for precise atmospheric characterization of Y dwarfs, the coldest brown dwarf spectral type. In this study, we leverage moderate spectral resolution observations (R ∼ 2700) with the G395H grating of the Near-Infrared Spectrograph (NIRSpec) on board JWST to characterize the nearby (9.9 pc) Y dwarf WISEPA J182831.08+265037.8. With the NIRSpec G395H 2.88–5.12 μm spectrum, we measure the abundances of CO, CO2, CH4, H2S, NH3, and H2O, which are the major carbon-, nitrogen-, oxygen-, and sulfur-bearing species in the atmosphere. Based on the retrieved volume mixing ratios with the atmospheric retrieval framework CHIMERA, we report that the C/O ratio is 0.45 ± 0.01, close to the solar C/O value of 0.458, and the metallicity is +0.30 ± 0.02 dex. Comparison between the retrieval results and the forward modeling results suggests that the model bias for C/O and metallicity could be as high as 0.03 and 0.97 dex, respectively. We also report a lower limit of the 12CO/13CO ratio of >40, being consistent with the nominal solar value of 90. Our results highlight the potential for JWST to measure the C/O ratios down to percent-level precision and characterize isotopologues of cold planetary atmospheres similar to WISE 1828.
Satoshi Itoh et al 2024 AJ 167 235
Potentially habitable planets around nearby stars less massive than solar-type stars could join targets of the spectroscopy of the planetary reflected light with future space telescopes. However, the orbits of most of these planets occur near the diffraction limit for 6 m diameter telescopes. Thus, while securing contrast-mitigation ability under a broad spectral bandwidth and a finite stellar angular diameter, we must maintain planetary throughput even at the diffraction-limited angles to be able to reduce the effect of the photon noise within a reasonable observation time. A one-dimensional diffraction-limited coronagraph (1DDLC) observes planets near the diffraction limit with undistorted point spread functions but has a finite-stellar diameter problem in wideband use. This study presents a method for wide-spectral-band nulling insensitive to stellar-angular-diameter by adding a fiber nulling with a Lyot-plane phase mask to the 1DDLC. Designing the pattern of the Lyot-plane mask function focuses on the parity of the amplitude spread function of light. Our numerical simulation shows that the planetary throughput (including the fiber-coupling efficiency) can reach about 11% for about 1.35-λ/D planetary separation almost independently of the spectral bandwidth. The simulation also shows the raw contrast of about 4 × 10−8 (the spectral bandwidth of 25%) and 5 × 10−10 (the spectral bandwidth of 10%) for 3 × 10−2λ/D stellar angular diameter. The planetary throughput depends on the planetary azimuthal angle, which may degrade the exploration efficiency compared to an isotropic throughput but is partially offset the wide spectral band.
Xiumin Huang and Hanlun Lei 2024 AJ 167 234
Secular dynamics have been extensively studied in both the inner and outer restricted hierarchical three-body systems. In the inner restricted problem, the quadrupole-order resonance (i.e., the well-known Kozai resonance) causes large coupled oscillations of eccentricity and inclination when the maximum inclination is higher than 39.2°, and the octupole-order resonance leads to the behavior of orbital flips. In the outer restricted problem, the behavior of orbital flips is due to the quadrupole-order resonance. Secular dynamics under the inner and outer restricted systems are distinctly different. The mass ratio of inner and outer bodies could change the ratio of circular orbital angular momenta β, which significantly influences dynamical structures of the system. But this influence is still unclear. In this paper, we focus on nonrestricted hierarchical planetary systems where β > 1 and investigate the secular dynamics by changing mass ratios. Dynamical structures are systematically explored from four aspects: periodic orbits, secular resonances, orbital flips, and chaos detection. We find that (a) it tends to lead to more bifurcations in the host family of prograde periodic orbits associated with Kozai resonance with smaller β; (b) with the decrease of β, fewer orbits inside the octupole-order resonance can realize flip; (c) for given initial conditions, the forbidden region appears in the retrograde region and becomes larger as β decreases, meaning that the mutual inclination cannot reach a very high value if β is small; and (d) chaotic orbits are distributed in the low-eccentricity, high-inclination region when β > 1.