On 2024 April 8, tens of millions of people across North America will be able to view a total solar eclipse. Such astronomical events have been important throughout history, but with nearly 10,000 satellites in orbit, we question whether total eclipses will now reveal a sky full of satellites, fundamentally changing this experience for humanity. Using the current population of Starlink satellites, we find that the brightest satellites would be naked-eye visible in dark skies, but the high sky brightness during totality will make them undetectable to the unaided eye. Our model does not take into account the effects of chance reflections from large, flat surfaces like solar panels, which we expect will cause glints and flares that could be visible from large satellites and abandoned rocket bodies. Time-lapse all-sky imaging might reveal satellites during the eclipse.

We report the detection of a significant sudden ionospheric disturbance in the D-region of Earth's ionosphere (∼60–100 km), which was associated with the massive γ-ray burst GRB 221009A that occurred on 2022 October 9. We identified the disturbance over northern Europe—a result of the increased ionization by X- and γ-ray emission from the GRB-using very low frequency radio waves as a probe of the D-region. These observations demonstrate that an extra-galactic GRB (z ∼ 0.151) can have a significant impact on the terrestrial atmosphere and illustrates that the Earth's ionosphere can be used as a giant X- and γ-ray detector. Indeed, these observations may provide an insight into the impacts of GRBs on the ionospheres of planets in our solar system and beyond.

We report the recovery of returning Halley-type comet 12P/Pons-Brooks using the 4.3 m Lowell Discovery Telescope, at a heliocentric distance of 11.89 au. Comparative analysis with a dust model suggests that the comet may have been active since ∼30 au from the Sun. We derive a nuclear radius of 17 ± 6 km from the nucleus photometry, though this number is likely an overestimate due to the contamination from dust and gas. Continuing monitoring is encouraged in anticipation of the comet's forthcoming perihelion in 2024 April.

We have conducted an extensive towed-magnetic-sled survey during the period 2023 June 14–28, over the seafloor about 85 km north of Manus Island, Papua New Guinea, centered around the calculated path of the bolide CNEOS 2014 January 8 (IM1). We found about 850 spherules of diameter 0.05–1.3 mm in our samples. They were analyzed by microXRF, Electron Probe Microanalyzer and ICP Mass spectrometry. We identified 22% of the spherules as the product of planetary igneous differentiation and labeled them as D-type spherules. A small portion of the D-spherules show an excess of Be, La and U, by up to three orders of magnitude relative to the solar system standard of CI chondrites, and a composition pattern that is distinctly different from coal fly ash.

Caballero identified the star 2MASS 19281982-2640123 as a potential Sun-like star from which the WOW! signal could have originated. We conducted a search for artificial narrowband (2.79 Hz/1.91 Hz), drifting (±4 Hz s⁻¹) technosignatures from this source using the turboSETI pipeline, from 1–2 GHz, using simultaneous multi-telescope observations with both the Robert C. Byrd Green Bank Telescope and the newly refurbished Allen Telescope Array on 2022 May 21. Both telescope observations had an overlap of 580 s. While blind searches using radio telescopes have been conducted in the general field of view in which the WOW! signal was first detected, this is the first time a targeted search has been done. No technosignature candidates were detected.

This paper employs machine learning to estimate stellar temperatures using photometric data, focusing on the GAIA ESA Archive Data Release 3 data set. The study underscores the effectiveness of neural networks in deciphering intricate relationships within the data. Notably, the addition of metallicity improves model accuracy in characterizing stellar properties. The study also investigates outlier removal techniques, specifically favoring the Isolation Forest method, showcasing its efficacy in refining model performance. Automated machine learning, facilitated by PyCaret Regressor, emerges as a valuable tool, identifying top-performing models and highlighting feature importance. The implications of this research extend beyond the specifics of stellar temperature estimation. In contemplating future directions, this study suggests the exploration of diverse data sources to ensure balanced distributions of stellar temperatures and the potential incorporation of deep learning architectures for heightened accuracy in addressing astrophysical inquiries.

The broadband solar K-corona is linearly polarized due to Thomson scattering. Various strategies have been used to represent coronal polarization. Here, we present a new way to visualize the polarized corona, using observations from the 2023 April 20 total solar eclipse in Australia in support of the Citizen CATE 2024 project. We convert observations in the common four-polarizer orthogonal basis (0°, 45°, 90°, & 135°) to −60°, 0°, and +60° (MZP) polarization, which is homologous to R, G, B color channels. The unique image generated provides some sense of how humans might visualize polarization if we could perceive it in the same way we perceive color.

We analyzed the inactive nucleus of the main-belt comet 2010 LH15 at a true anomaly of 262°. Observations using the Gemini North Telescope in 2023 July yielded an absolute R-band magnitude of (18.4 ± 0.2) mag. Assuming a C-type geometric albedo and phase function, we estimated the nucleus radius to be (0.5 ± 0.1) km. The examination of the lightcurve profile did not yield clear evidence for a rotational period shorter than 2 hr.

Identification of molecular carriers for diffuse interstellar bands (DIBs) may stem in part from the determination of interrelated lines using the Apache Point Observatory Catalog of DIBs. However, Pearson correlations may be impacted by the number of interstellar clouds along the sightlines. The trend of extinction with distance was constrained using Bayestar19 and Gaia DR3, and clouds were identified via step-functions and extended increasing linear progressions may be indicative of traversal through dense spiral arms. Thirteen sightlines are likely observed through more than one cloud. The hypergiants HD168625 and VI Cyg 12 are contaminated by local nebulosity and circumstellar disks. New findings presented here support the reddenings cited within the Apache Point Observatory catalog of DIBs.

Turbulent radiative mixing layers (TRMLs) occur ubiquitously in astrophysical environments; e.g., TRMLs are prevalent within galactic outflows at the intersections between hot supernovae ejecta and cold molecular clouds. A velocity shear between the rapidly outflowing hot gas and cold clouds drives the Kelvin–Helmholtz instability producing TRMLs, with radiative cooling dominating the heat transfer between the gas phases. Using hydrodynamic simulations, we have modeled TRMLs for a range of overdensities (100, 1000, 3000) applied to cold phase temperatures of 400, 10³, and 10⁴ K. The production of an intermediate gas phase at the interface between the hot and cold phases is consistently observed at ∼10⁴ K for molecular clouds, in agreement with larger-scale wind-tunnel simulations.

This talk reviewed key developments leading to the establishment of the AAS Division on Dynamical Astronomy. In the 1890s, Simon Newcomb calculated astronomical constants and ephemerides for solar system bodies that were internationally adopted and used for 80 yr. The introduction of punch card equipment in the 1940s and computers in the 50s allowed much faster computations. Launches of Sputnik, Explorer, Vanguard, and Mercury satellites led to computing the orbits of satellites around the Earth and the field of astrodynamics. Dirk Brouwer's death in 1966 resulted in the celestial mechanics faculty at Yale spreading across the country. The space program, radar observations, and faster computers propelled advances in celestial mechanics. Teams at the Jet Propulsion Laboratory and Massachusetts Institute of Technology developed solar system ephemerides using numerical integrations fit to optical observations and radar ranging measurements. It was time for the AAS Division on Dynamical Astronomy.

We present mass estimates and companion demographics on stellar multiples within 25 pc, using a survey of stars of all spectral types done by Robo-AO and supplemented by Gaia. The survey combined direct imaging by Robo-AO, a robotic adaptive optics instrument for 2 m class telescopes, to detect tight companions (<4'' separation) and with Gaia astrometry to detect wider co-moving companions. We estimated the masses for 267 companions using empirical relations and, for a subset of 97, dynamical mass estimates. We utilized previous mass–magnitude models using contrasts measured from Gaia and Robo-AO to estimate the mass and also used the orvara python package, a Markov Chain Monte Carlo orbit fitter using the companion astrometry and Hipparcos-Gaia proper motion accelerations, to estimate dynamical masses. We compare agreements and discrepancies in mass estimates from these two methods.

Solar/stellar flares which release large energies occur less frequently than those with small energies. Flare energies on a given star have not (yet) been observed to exceed E_fm. Similarly, coronal mass ejections (CME's) with large kinetic energies (KE) on a given star also occur less frequently than those with small energies. The KE's of CME's on a given star have not (yet) been observed to exceed KE_m. Interestingly, in any given star, E_fm is found to be comparable in magnitude to KE_m. This is puzzling since a one-to-one correlation between flares and CME's does not exist: some flares occur without any accompanying CME, and some CME's have no accompanying flare. Moreover, different types of MHD instabilities are believed to give rise to flares and CME's. The result E_fm ≈ KE_m could indicate support for Bemporad's conclusion: magnetic energy in the corona is in global equipartition with gravitational potential energy.

A complete understanding of methane in the atmosphere of Mars requires information on putative sources. Organic carbon derived from meteoritic sources, such as interplanetary dust particles (IDPs), over geologic time is the best-defined source of organic carbon on the surface of Mars. Here we examine two different mechanisms for degrading this material to produce methane (1) Ultraviolet photolysis and (2) thermal decomposition. Neither of these mechanisms can produce sufficient methane under realistic assumptions to explain observed methane at Gale Crater, suggesting that IDPs are not the primary source material producing methane on Mars.

SN 2023ixf is a Type II-L supernova that occurred in M101 in 2023 May. The European VLBI Network (EVN) observed SN 2023ixf at 5 GHz approximately one month later, on June 28. We calibrated the EVN data using AIPS and CASA, reporting non-detection of a radio source with 5σ flux upper limits of 113 μJy and 135 μJy for both pipelines, respectively.