astro-ph.EP] Archives

Planet occurrence rates as a function of stellar temperature for short-period (P = 1 − 40 days) super-Earths (green squares) and sub-Neptunes (blue circles). A power law was fit to the super-Earths, and a double broken power law was fit to the sub-Neptunes, showing two breaks: TBr,1 = 3750+153 −97 K and TBr,2 = 5758+94 −145 K. The short-period sub-Neptunes peak around a host type of M0.5 V, then decrease in planet occurrence toward cooler M dwarfs. G and K-type stars have comparable rates of short-period super-Earths and sub-Neptunes. Another noticeable decrease in sub-Neptunes happens for host stars hotter than the Sun. Short-period super-Earths increase in occurrence toward cooler stars, with no discernible peak in the host star temperatures for which we have data from Kepler and K2. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Status Report, Stellar Cartography

Scaling K2 VIII: Short-Period Sub-Neptune Occurrence Rates Peak Around Early-Type M Dwarfs

by Keith CowingAugust 13, 2025August 13, 2025

We uniformly combined data from the NASA Kepler and K2 missions to compute planet occurrence rates across the entire FGK and M dwarf stellar range.

Scientists think that under the icy surface of Jupiter's moon Europa a saltwater ocean exists that may contain more than twice as much liquid water as all of Earth's oceans combined. NASA/JPL-Caltech

Astrogeology, Enceladus, Europa, Icy Worlds, Status Report, Water/Hycean Worlds & Oceanography

Slantwise Convection And Heat Transport In The Icy Moon Oceans

by Keith CowingAugust 11, 2025August 11, 2025

Ocean heat transport on icy moons shapes the ice shell topography, a primary observable of these moons. Two key processes control the heat transport: baroclinic instability driven by surface buoyancy […]

Time series of atmospheric temperature and He column density for the observation day January 26, 2023. Blue and gray points represent the 20x binned and unbinned best-fit planetary parameters obtained from fitting the planetary absorption spectra as described in Sect. 3.3.2. The red line marks the weighted average of each retrieved parameter and the orange band represents the 1 σ region around this average. The black line shows the input values used in the simulation. We provide axes for the width in km/s and depth in % to facilitate the understanding of the analogy between temperature and width, and column density and depth. -- astro-ph.EP

Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Space Weather & Heliophysics, Status Report

Studying The Variability Of The He Triplet To Understand The Detection Limits Of Evaporating Exoplanet Atmospheres

by Keith CowingJuly 31, 2025July 31, 2025

With more than a dozen significant detections, the helium triplet has emerged as a key tracer of evaporating exoplanet atmospheres.

Near-UV to visible reflectance spectrum of 3I/ATLAS obtained with OSIRIS/GTC and normalized to unity at 5500 Å. Normalized reflectance of 1I/’Oumuamua (in brown) from Fitzsimmons et al. (2018) and 2I/Borisov (in green) from de León et al. (2020) are also shown for comparison, together with D-type spectral taxon from DeMeo et al. (2009). -- astro-ph.EP

Astrochemistry, Astrogeology, Astronomy & Telescopes, Biosignatures & Paleobiology, Icy Worlds, Imaging & Spectroscopy, Interstellar, Status Report

Assessing Interstellar Comet 3I/ATLAS With The 10.4 m Gran Telescopio Canarias And The Two-meter Twin Telescope

by Keith CowingJuly 25, 2025July 25, 2025

Context. Theories of the formation and evolution of small bodies in planetary systems predict that they may escape into interstellar space at any time.

Spectrum of C/2025 N1 (3I/ATLAS) showing the wavelength ranges where the emissions should appear above the noise level. -- astro-ph.EP

Astrochemistry, Astrogeology, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Comets and Asteroids, Icy Worlds, Imaging & Spectroscopy, Interstellar, Status Report

X-SHOOTER Spectrum Of Comet C/2025 N1 (3I/ATLAS): Insights Into A Distant Interstellar Visitor

by Keith CowingJuly 20, 2025

Comets are primitive remnants of the early Solar System whose composition offers fundamental clues to their formation and evolution. High-resolution, broad-wavelength spectroscopy is crucial for identifying volatile species and constraining […]

Family portrait of the five planets in the L 98-59 system showing their transit (or absence of transit) observed by TESS in the top panels and their Doppler signature from HARPS (red circles) and ESPRESSO (white/black circles for pre/post data) in the bottom panels. Only the error bars for ESPRESSO are shown to improve visibility. Black curves represent best-fit models from the transit analysis (top) and joint RV–TTV fit (bottom, using fixed orbital inclinations, see Sect. 4.5). For L 98- 59 e and f, 1000 predicted transit curves are shown in red using posterior samples from the RV–TTV fit and radii estimated from their minimum masses using spright (Parviainen et al. 2024). Planets e and f do not transit L 98-59. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report

Detailed Architecture Of The L 98-59 System And Confirmation Of A Fifth Planet In The Habitable Zone

by Keith CowingJuly 16, 2025July 16, 2025

The L 98-59 system, identified by TESS in 2019, features three transiting exoplanets in compact orbits of 2.253, 3.691, and 7.451 days around an M3V star, with an outer 12.83-day […]

The peak temperature achieved by all tracer particles in simulations of a 1 km diameter comet impacting at 10 km s−1 (left) and 40 km s−1 (right) in a provenance plot, where the tracers are shown at their initial locations prior to the impact. A solid black line is shown between the two halves of the figure to delineate the difference between the two simulations. The 10 km s−1 impact on the left shows a peak temperature of ∼ 8900 K, whereas the 40 km s−1 impact on the right achieves a peak temperature of ∼ 74 000 K. Although the range of temperatures achieved during the two impacts is vastly different, the distribution of temperatures is similar, with a sharp increase in temperatures at the leading edge and raised temperatures towards the centre of the body. -- astro-ph.EP

Astrochemistry, Astrogeology, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Comets and Asteroids, Impact events, Status Report

Constraining The Survival Of HCN During Cometary Impacts

by Keith CowingJuly 14, 2025July 14, 2025

Cometary impacts have been invoked as an atmosphere-independent method of stockpiling hydrogen cyanide (HCN), a key prebiotic feedstock molecule, into environments favourable for the onset of prebiotic chemistry on the […]

Potential interior structures of Uranus, Neptune, K2-18 b and TOI-270 d if they have undergone hydrogen-water demixing. We note that alternatives models are also possible (see Secs. 3 and 4). For Uranus and Neptune, the sketches correspond to the cases with Toffset = 1100 K, in which both planets are fully demixed. However, we can’t exclude scenarios in which demixing is still ongoing or does not occur at all. The sketch for K2-18 b shows a mini-Neptune scenario with ongoing demixing, while the one for TOI-270 d corresponds to a case of full demixing. -- astro-ph.EP

Ariel Mission, Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Ice Giant, Icy Worlds, Neptune, Status Report, Uranus

The Possibility of Hydrogen-Water Demixing in Uranus, Neptune, K2-18b and TOI-270d

by Keith CowingJuly 13, 2025July 13, 2025

The internal structures of Uranus and Neptune remain unknown. In addition, sub-Neptunes are now thought to be the most common type of exoplanets.

Radial velocity timeseries from MAROON-X with the median Rossiter-McLaughlin and 1σ confidence shown as the black line and blue shaded region. Black points are the binned radial velocities. The inset shows the geometry of the system with the black arrow indicating the orbital angular momentum vector and the gray shaded area representing the uncertainty. The bottom panel shows the residuals with an RMS of ∼ 1 m s−1. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

An Aligned Sub-Neptune Revealed with MAROON-X and a Tendency Towards Alignment for Small Planets

by Keith CowingJuly 9, 2025July 9, 2025

We present the Rossiter-McLaughlin measurement of the sub-Neptune TOI-1759A b with MAROON-X. A joint analysis with MuSCAT3 photometry and nine additional TESS transits produces a sky-projected obliquity of |λ|= 4∘±18∘.

Modelled planetary bulk-density over time. The initial hydrogen inventory of each bulk-density evolution track is shown by the line colour. Blue/green shaded regions are reference densities for a planet of this mass (Zeng et al., 2019). Black dashed/dotted lines demarcate edges of the radius valley (at this planet mass) for low mass stars (Ho et al., 2024). The region ±1σ compatible with the estimated bulk-density of this planet is indicated by the blue errorbar (Rajpaul et al., 2024; Demangeon et al., 2021). Top panel: evolution of surface temperature (coloured) and stellar XUV energy flux (black). For visual clarity, this figure only shows cases with S/H=8. -- astro-ph.EP

Exoplanets, -moons, -comets, Status Report

Volatile-rich Evolution Of Molten Super-Earth L 98-59 d

by Keith CowingJuly 7, 2025September 18, 2025

Small low-density exoplanets are sculpted by strong stellar irradiation but their origin is unknown.

astro-ph.EP]

Scaling K2 VIII: Short-Period Sub-Neptune Occurrence Rates Peak Around Early-Type M Dwarfs

Slantwise Convection And Heat Transport In The Icy Moon Oceans

Studying The Variability Of The He Triplet To Understand The Detection Limits Of Evaporating Exoplanet Atmospheres

Assessing Interstellar Comet 3I/ATLAS With The 10.4 m Gran Telescopio Canarias And The Two-meter Twin Telescope

X-SHOOTER Spectrum Of Comet C/2025 N1 (3I/ATLAS): Insights Into A Distant Interstellar Visitor

Detailed Architecture Of The L 98-59 System And Confirmation Of A Fifth Planet In The Habitable Zone

Constraining The Survival Of HCN During Cometary Impacts

The Possibility of Hydrogen-Water Demixing in Uranus, Neptune, K2-18b and TOI-270d

An Aligned Sub-Neptune Revealed with MAROON-X and a Tendency Towards Alignment for Small Planets

Volatile-rich Evolution Of Molten Super-Earth L 98-59 d

Astrobiologist Dale Andersen’s Antarctic Field Report: 11 November 2026: Weather Update And Forecast

Astrobiologist Dale Andersen’s Antarctic Field Report: 10 November 2026: Weather Update Forecast

Dispersal of Bacterial Spores Away From Spacecraft on the Martian Surface is Unlikely to Contaminate Subsequent Life-detection Samples

From Exo-Earth Detection to Atmospheric Characterization: Enabling Phase-Dependent Molecular Detection SNR in EXOSIMS

Ancient Rocks Reveal When Earth’s Tectonic Engine Switched On