K-dwarfs Archives - Astrobiology

Planetary surface temperatures (°C) on M- and K-dwarf planets. Substellar point is plotted at the center, and black lines indicate the terminator. The top rows show aquaplanets (aq) and bottom rows show land planets (ld). -- astro-ph.EP

Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Habitable Zones, Status Report, Water/Hycean Worlds & Oceanography

Climate Regimes Across The Habitable Zone: A Comparison Of Synchronous Rocky M- And K-dwarf Planets

by Keith CowingAugust 15, 2024

M- and K-dwarf stars make up 86% of the stellar population and host many promising astronomical targets for detecting habitable climates in the near future. Of the two, M dwarfs […]

Extracted mid-infrared spectra for BD+60 1417B and W0047 with important molecular gas highlighted. -- astro-ph.SR

Astrochemistry, Atmospheres, Climate, Weather, Brown Dwarfs, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Retrieving Young Cloudy L-Dwarfs: A Nearby Planetary-Mass Companion BD+60 1417B and Its Isolated Red Twin W0047

by Keith CowingJuly 8, 2024July 6, 2024

We present an atmospheric retrieval analysis on a set of young, cloudy, red L-dwarfs — CWISER J124332.12+600126.2 and WISEP J004701.06+680352.1 — using the Brewster retrieval framework. We also present the […]

TESS target pixel files for TOI-260 for sector 3 (left), and for TOI-286 for sector 1 ( right). The remaining sectors are shown in Appendix A. The target star is labelled as 1 and marked by a white cross in each case. All sources from the Gaia DR3 catalogue down to a magnitude contrast of 8 are shown as red circles, with the size proportional to the contrast. The SPOC pipeline aperture is overplotted in shaded red squares. -- astro-ph.EP

Habitable Zones, Status Report, Water/Hycean Worlds & Oceanography

Three Super-Earths And A Possible Water World From TESS And ESPRESSO

by Keith CowingJune 12, 2024June 12, 2024

Since 2018, the ESPRESSO spectrograph at the VLT has been hunting for planets in the Southern skies via the RV method. One of its goals is to follow up candidate […]

Mass-Radius Diagram comparing the data from the PlanetS catalog and the data from NASA Exoplanet Archive to highlight the effects of our selection criteria and our detailed study of references. The grey dots represented the default parameters from NASA, the light blue triangles the same but filtered with our criteria on uncertainties and the blue dots correspond to the PlanetS catalog. The resulting M-R relationships from Sect.2.2 are in solid red lines with the confidence intervals represented by the shaded red areas. The transitions between the three populations are represented by the composition line of 20% water at 650 K from Luo et al. (2024) in dashed orange and the dotted black line at 138 M⊕. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Press Release, Stellar Cartography, Water/Hycean Worlds & Oceanography

From Super-Earths to Sub-Neptunes: Observational Constraints and Connections to Theoretical Models

by Keith CowingJune 7, 2024June 7, 2024

We update the PlanetS catalog of transiting planets with precise and robust mass and radius measurements and use this comprehensive catalog to explore Mass-Radius (M-R) diagrams.

Garden cress (Lepidium sativum) grown on a sand substrate with one hundred initial seeds under solar (effective temperature 5800 K), K dwarf (effective temperature 4300 K) and dark conditions. Here the visual results for selected days are shown. Garden cress under K dwarf radiation sprouts sooner relative to solar and dark conditions. -- astro-ph.EP

Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Life Support Systems, Microbiology & Virology, Plant Biology, Space Agriculture, Space Weather & Heliophysics, Status Report, Terraforming & Geoengineering, Water/Hycean Worlds & Oceanography

Observation of Significant Photosynthesis in Garden Cress and Cyanobacteria under Simulated Illumination from a K Dwarf Star

by Keith CowingMay 30, 2024

Stars with about 45 to 80% the mass of the Sun, so-called K dwarf stars, have previously been proposed as optimal host stars in the search for habitable extrasolar worlds.

Mass-radius relationship of the TOI-178 planets (final posterior), compared with the super-Earth to Mini-Neptune populations for which the mass was derived through RV (Otegi et al. 2020) and TTVs (Hadden & Lithwick 2017; Leleu et al. 2023). The composition lines ‘terrestrial Earth-like’, in solid brown, and pure MgSiO3 ‘rocky’, in dashed brown, are taken from Zeng et al. (2016). -- astro-ph.EP

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

Photo-dynamical Characterisation Of The TOI-178 Resonant Chain

by Keith CowingMay 24, 2024May 24, 2024

The TOI-178 system consists of a nearby late K-dwarf transited by six planets in the super-Earth to mini-Neptune regime, with radii ranging from 1.2 to 2.9 earth radius and orbital […]

Mass-radius diagram of transiting exoplanets with well established mass and radius from the NASA Exoplanet archive along with some theoretical composition curves (Zeng et al. 2019). The purple squares highlight the transiting planets orbiting K-dwarfs. The green blobs show the mass and radius posteriors (1- and 2-σ contours) of TOI–238 b and c. The planets of the solar system are included as reference. -- astro-ph.EP

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

TESS and ESPRESSO Discover A Super-Earth And A Mini-Neptune Orbiting The K-dwarf TOI-238

by Keith CowingFebruary 7, 2024February 7, 2024

The number of super-Earth and mini-Neptune planet discoveries has increased significantly in the last two decades thanks to transit and radial velocity surveys. When it is possible to apply both […]

Future radii of planets b, c, d at an age of 5 Gyr. The current radii of planets c, d and b are shown as dashed lines, together with the current and final radii for a range of planetary masses for the outer two planets d and b; the core is represented by a black circle, while the envelope is shown as a colored circle around the core. The core size increases with increasing mass. Note that the size scaling of the envelope compared to the core is arbitrary. It is chosen such that one can easily compare present and final planetary radii and immediately see, which configuration can hold on to some fraction of the envelope and remain above the gap. While the outermost planet b will retain enough envelope to remain well above the radius gap around 1.8 R⊕ for all masses considered, we find that for planet d there is an intermediate mass range between ∼7 to 18 M⊕, for which planets can retain an envelope and survive above the gap. Lower mass planets will experience enough mass loss to completely lose their envelope, while higher mass planets only have very thin envelopes at present age to match the observed radius due to their larger core size, that their thin envelope is easily lost, in spite of their large mass. Planet c is assumed to be rocky at present and will not change its size significantly. The current radius of planet c matches well with the radii predicted for Earth-like rocky cores in the mass regime of 3-5 M⊕. -- astro-ph.HE

Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Habitable Zones, Status Report

Three Young Planets Around The K-dwarf K2-198: High-energy Environment, Evaporation History And Expected Future

by Keith CowingNovember 15, 2023November 15, 2023

Planets orbiting young stars are thought to experience atmospheric evaporation as a result of the host stars’ high magnetic activity. We study the evaporation history and expected future of the […]

Dynamical evolution of planets in one of the typical systems that underwent several late dynamical instabilities after the gas dispersal. The plots show the temporal evolution (20 Myr) of planetary bodies, specifically their semimajor axes, masses, eccentricities, and orbital inclinations. Each line color represents an individual object; however, the color is random in each plot. The dashed black line shows the estimated time of the gas dissipation at ∼ 8 Myr. For better visualization, the panels on the left (semimajor axes and masses) show the evolution of all bodies with masses > 0.1 M⊕, and the panels on the right (eccentricities and orbital inclinations) show only bodies with masses > 0.5 M⊕. -- astro-ph.EP

Astrogeology, Exoplanets, -moons, -comets, Status Report

Forming Rocky Exoplanets Around K-dwarf Stars

by Keith CowingAugust 14, 2023August 14, 2023

How multiple close-in super-Earths form around stars with masses lower than that of the Sun is still an open issue.

TheKOBE

Astronomy & Telescopes, Exoplanets, -moons, -comets, Habitable Zones, Press Release

The KOBE experiment: K-dwarfs Orbited By habitable Exoplanets. Project goals, target selection and stellar characterization

by Keith CowingSeptember 12, 2022September 12, 2022

The detection of habitable worlds is one of humanity’s greatest endeavors. So far, astrobiological studies show that one of the most critical components for life development is liquid water. Its […]