Abstract In 1966, Iosif Shklovsky and Carl Sagan theorized that exospheric drag could explain Phobos’s rapid inspiral rate towards Mars if Phobos were hollow. Later observations revealed a slower orbital decay rate, and updated models can account for this rate via tidal friction. However, we demonstrate the validity of Shklovsky and Sagan’s method for distinguishing between natural and artificial solar system objects, using REBOUND simulations to compare the orbits of the actual Phobos and a hypothetical hollow Phobos subjected to drag in Mars’s exosphere. We find that Phobos would need to be reduced to 2.1 × 10 −5 times its actual mass to inspiral at the rate calculated by Shklovsky and Sagan. The change in its orbital period would be ∼2 × 10 −4 s yr −1 , detectable within a year of modern observations.

We present results from a systematic search for transiting short-period giant exoplanets around M dwarf stars (GEMS; P < 10 days, R _p ≳ 8 R _⊕ ) within a distance-limited 100 pc sample of 149,316 M dwarfs using TESS-Gaia Light Curve (or TGLC) data. We describe the development and application of the TESS-miner package and associated vetting procedures used in this analysis. To assess detection completeness, we conducted ∼72 million injection-recovery tests across ∼26,000 stars with an average of ∼3 sectors of data per star, subdivided into early-type (M0–M2.5), mid-type (M2.5–M4), and late-type (M4 or later) M dwarfs. Our pipeline demonstrates high sensitivity across all subtypes within the injection bounds. We estimate the occurrence rates of short-period GEMS as a function of stellar mass, and combine our measured rates with those derived for FGK stars, fitting an exponential trend with stellar mass, consistent with core-accretion theory predictions. We find GEMS occurrence rates of 0.118% ± 0.068% for early-type M dwarfs, 0.153% ± 0.069% for mid-type M dwarfs, and 0.036% ± 0.024% for late-type M dwarfs, with a mean rate of 0.068% ± 0.024% across the full sample. While our search spanned 1.0 day < P < 10.0 days, these rates were calculated using planets orbiting with 1.0 day < P < 5.0 days. This work establishes the basis for future occurrence-rate studies of transiting GEMS.

The Dyson Minds 2025 Workshop, held at the Center for Brains, Minds & Machines at Massachusetts Institute of Technology (MIT) and organized by Penn State, MIT, and The Ultraintelligence Foundation, brought together researchers in astrophysics, engineering, artificial intelligence, computer science, and philosophy to examine "Dyson Minds"-large-scale post-biological intelligences powered by energy harvested from supermassive black holes (SMBHs). Building on the ideas of Dyson and Good, participants explored the physical, engineering, behavioral, and observational consequences of civilizations embodied as machinery operating near the universe's most powerful energy sources. The workshop aimed to develop new observational strategies capable of detecting signatures of such systems. Despite the highly cross-disciplinary scope, discussions centered on how a Dyson Mind might be constructed, how it might behave, and how those factors would shape strategies for the search for extraterrestrial intelligence. Key themes included the thermodynamic, mechanical, and stability limits of Dyson swarms; the trade-offs between power availability and communication latency in distributed minds; and how observability changes depending on whether Dyson Minds act as coherent entities or as loosely coordinated collectives. Across these topics, the consensus was that details of architecture and behavior strongly influence observational signatures. A major recommendation was to apply anomaly-detection methods to archival datasets, including those from Wide-field Infrared Space Explorer, JWST, and the Event Horizon Telescope, to identify unusual sources potentially overlooked by standard reduction pipelines. By integrating insights from multiple disciplines, the meeting advanced concrete, observation-focused strategies for future technosignature searches around SMBHs.

We report on JWST/MIRI imaging and spectroscopy of two M-dwarf stars previously singled out by project Hephaistos as potential Dyson-sphere candidates (their candidates D and E) due to the presence of excess flux at mid-infrared wavelengths. We find that the infrared excess does not originate from Dysonian megastructures, or other radiation mechanisms close to these stars, but from background galaxies projected within ∼ 1 arcsec of the M dwarfs, thereby confusing previous mid-infrared photometry obtained with the WISE telescope. The candidate D background galaxy lies at redshift z≈ 0.9, appears point-source dominated in imaging and has a mid-infrared spectrum consistent with being a Hot Dust Obscured Galaxy (Hot DOG). The candidate E background galaxy lies at z≈ 0.4, displays an extended morphology with bright knots and a spectrum consistent with a dusty starburst.

Measurements of physical parameters for stars and (exo)planets are often quoted in units normalized to the Sun and/or Earth. The nominal total solar irradiance, S^ N_⊙, while based on a current best estimate with uncertainties, was adopted to be an exact reference value of 1361 W m^-2 by IAU 2015 Resolution B3, corresponding to “the mean total electromagnetic energy from the Sun, integrated over all wavelengths, incident per unit area per unit time at distance 1 au”. In the planetary and exoplanetary science literature, the units employed for “flux”, “insolation”, “instellation”, etc., are often cumbersome or inconsistent. To simplify the quoting of irradiance units for astronomical applications, we introduce the portmanteau solirad, short for solar irradiance, as an abbreviated version of the longer IAU term “nominal total solar irradiance”. The solirad (So) is a unit of irradiance, where 1 solirad = 1 So = 1361 W m^-2, equivalent to the IAU nominal total solar irradiance, and to an apparent bolometric magnitude of m_bol = -26.832 mag (per IAU 2015 Resolution B2).

We present the most robust stellar population synthesis (SPS)-based search for galaxy-spanning technological waste heat to date, applied to 129 nearby galaxies spanning a wide range of spectral energy distribution (SED) types, including ultraluminous IR galaxies and MIR-luminous active galactic nuclei (AGN). We incorporate the AGENT Dyson sphere formalism into the Flexible Stellar Population Synthesis code at the stellar population level, so nebular and dust emission respond self-consistently to Dyson sphere reprocessing. With , we perform a suite of 1,419 injection recovery tests across a range of covering fractions, α, where we successfully recover the injected covering fractions (best-fit slope m = 0.92) and detect them through Bayesian model selection down to α∼ 4–5% in quiescent galaxies. None of our 129 galaxies prefer a Dyson sphere component, and we place the first per-galaxy 95% upper limits on warm (T_ BB≳ 100K) swarms, reaching a median α< 0.3% across quiescent hosts without a dominant AGN. Our injection-calibrated detection rates convert these zero detections into a population bound of <2.6% of galaxies hosting α= 25% swarms (95% confidence). Because survey colors cannot separate waste heat from starbursts and AGN, we develop a scaffold for future searches, running from inexpensive archival screens such as the Balmer decrement and the stellar-to-dynamical-mass offset a swarm leaves behind, through resolved fitting with nuclear excision, to PRIMA FIR photometry that makes targeted JWST imaging decisive. We find that the outskirts of quiescent galaxies are the best hunting grounds for future technosignature searches.

The study of warm Jupiters is crucial to understanding the processes that govern giant-planet formation and migration. These planets sit at the boundary between cold giant planets and hot Jupiters, and studying their orbital properties, including period, eccentricity, and spin–orbit alignment, can offer insights into their past evolution and migration histories. We report the discovery and confirmation of a transiting warm Jupiter, HD 278555 b, which was first detected as a single transit event in a light curve from the Transiting Exoplanet Survey Satellite (TESS). We confirm the planetary nature of the signal using additional TESS data and ground based radial velocity (RV) follow-up observations from the NEID spectrograph, and we characterize the planet via a joint fit to the transit and RV signals. HD 278555 b has a mass of $0.8{4}_{-0.10}^{+0.10}\,{M}_{{\rm{J}}}$ and a radius of $0.98{0}_{-0.035}^{+0.036}\,{R}_{{\rm{J}}}$ , and orbits an F8-type star with a period of $28.8{4}_{-0.000046}^{+0.000045}$ days and a very low eccentricity of $0.08{5}_{-0.049}^{+0.047}$ . These orbital parameters suggest the planet had a quiescent formation history, and either formed in situ or formed beyond the ice line and underwent a smooth inward migration process such as disk-driven migration. This discovery adds to the growing population of well characterized warm Jupiters that will inform planet migration theory.

Independent analysis of individual spectral lines, or line-by-line (LBL) analyses, can improve upon standard cross-correlation function (CCF) methods for measuring radial velocities (RVs) because they preserve critical information about individual line shape changes that can be caused by stellar activity. In this work, we measure LBL RVs of 3,830 spectral lines across 383 days of NEID solar observations. Our LBL approach achieves an RV RMS of 2.012 m s^-1, which is slightly lower than the 2.129 m s^-1 achieved by a CCF approach using a shared line list. Then, we describe and benchmark several methods for selecting line lists based on line properties such as depth and intrinsic RV scatter. We find that these subsets have a lower RV RMS compared to either the full line list or random subsets of equal size. Motivated by these results, we present FLARES (Filtering Lines for Accurate Radial-velocity Exoplanet Search), an iterative line-selection algorithm. FLARES selects candidate spectral lines with extreme values of multiple line metrics and properties such as depth, signal-to-noise ratio, and detector position, and preferentially rejects lines whose removal produces the largest decrease in the weighted RV scatter. FLARES achieves an RV RMS of 1.122 m s^-1 using just 24 lines and performs better than the benchmark methods. We perform Monte Carlo simulations and show FLARES is robust and reproducible. Comparisons to alternative line lists chosen to have properties similar to the best FLARES-selected lines demonstrate that FLARES is successfully identifying line properties that lead to effective line lists for future extreme-precision RV measurements.

We present the confirmation of HD 190360 d, a warm ( P=88.690-0.049+0.051days ), low-mass ( msini=10.23-0.80+0.81M circle plus ) planet orbiting the nearby (d = 16.0 pc), Sun-like (G7) star HD 190360. We detect HD 190360 d at high statistical significance even though its radial velocity (RV) semiamplitude is only K = 1.48 +/- 0.11 m s-1. Such low-amplitude signals are often challenging to confirm due to potential confusion with low-amplitude stellar signals. The HD 190360 system previously had two known planets: the 1.7 MJ (true mass) HD 190360 b on a 7.9 yr orbit and the 21 M circle plus(minimum mass) HD 190360 c on a 17.1 days orbit. Here, we present an in-depth analysis of the HD 190360 planetary system that comprises more than 30 yr of RV measurements and absolute astrometry from the Hipparcos and Gaia spacecraft. Our analysis uses more than 1400 RVs, including nearly 100 from NEID. The proper motion anomaly as measured by these two astrometric missions solves for the dynamical mass of HD 190360 b and contributes to our understanding of the overall system architecture, while the long baseline of RVs enables the robust characterization of HD 190360 c and confirms the discovery of HD 190360 d.

We report on the diagnostic inspection of nine Project Hephaistos Dyson Sphere candidate M-dwarfs based on archival data. By comparing the Gaia positions, propagated to the AllWISE epoch, with the mid-infrared centroids measured from the AllWISE images, together with deep archival optical/near-infrared imaging, we identified significant background contamination in candidates B and C. Candidate B is coincident with a radio counterpart with spectral index alpha = 0.63 +/- 0.11, while candidate C has a near-infrared companion at an offset of 3.75 arcsec. Candidate A provides suggestive evidence through a radio counterpart with spectral index alpha = 0.40 +/- 0.35, while candidates E, F, H and J show marginal evidence. These systems exhibit either significant astrometric offsets or visible interlopers, indicating that the mid-infrared excess likely arises from line-of-sight contamination by hot, dust-obscured galaxies. However, candidates D and I still lack obvious signs of contamination. Dedicated observations are therefore essential to characterise these potential interlopers, eliminate false positives, and ensure that technosignature searches focus on the most robust Dyson Sphere candidates.