M-dwarf Archives

Stellar flares observed in JWST/NIRISS time-series spectroscopy of TRAPPIST-1. Each column shows one flare event during transits of the TRAPPIST-1c or TRAPPIST-1f planets. Tow row: Light curves with the total flux (integrated over the full spectral range and normalized to the mean out-of-transit flux). Colored points indicate pre-flare (green), flare (orange), maximum flare light (red), and post-flare (blue) phases. Green and blue dashed lines mark the average pre- and post-flare flux levels. Middle row: Light curves of the normalized Hα flux. Bottom row: Time-resolved spectrograms (wavelength vs. time) normalized to the pre-flare spectrum. The shaded blue region shows the drop in flux caused by the planetary transit. For comparison, the time axis in all panels are aligned such that t = 0 corresponds to the beginning of the maximum flare light phase. In all four events, the total flux in the post-flare phase is systematically elevated relative to the pre-flare level. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Magnetic Fields, Electromagnetism, bioelectricity,, Press Release, Radiation, Space Weather & Heliophysics, TRAPPIST-1

Flares On TRAPPIST-1 Reveal The Spectrum Of Magnetic Features On Its Surface

by Keith CowingAugust 8, 2025August 8, 2025

TRAPPIST-1 is an M8 dwarf hosting seven known exoplanets and is currently one of the most frequently observed targets of the James Webb Space Telescope (JWST).

Streamlined schematic of the experimental setup, simulated atmospheric compositions and conditions, UV bombardment process, measurements, and experimental outcomes. Two laboratory hazes were produced (the initial conditions varying only in the minor carbon source) in the PHAZER chamber (He et al. 2017) by exposing the gas mixture at room temperature to an AC plasma source. After the hazes were produced, each half of the films were exposed to UV radiation under two different filters. The transmittance and reflectance spectra pre– and post–UV irradiation of both samples were measured using a FTIR spectrometer to quantify molecular changes and destruction during the irradiation process. -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Radiation, Space Weather & Heliophysics, Status Report

Effects of Ultraviolet Radiation on Sub-Neptune Exoplanet Hazes Through Laboratory Experiments

by Keith CowingJuly 30, 2025July 30, 2025

Temperate sub-Neptune exoplanets could contain large inventories of water in various phases, such as water-worlds with water-rich atmospheres or even oceans.

Multicolor simultaneous light curves in g-, r-, i-, and zs-bands, obtained by MuSCAT2 on 2021 March 19 (Top) and MuSCAT3 on 2021 January 28 (Bottom) (Section 2.2 and 2.3). The data are jointly fitted with the transit model (blue, green, orange, and red) and baseline model, and the data are subtracted with the baseline models (gray). Alt text: Time-series flux for the transits of the MuSCAT2 and MuSCAT3 data in g-, r-, i-, and zs-bands, and the optimum models for each. -- astro-ph.EP

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

The Mass Of TOI-654 b: A Short-period Sub-Neptune Transiting A Mid-M Dwarf

by Keith CowingJuly 23, 2025July 23, 2025

Sub-Neptunes are small planets between the size of the Earth and Neptune. The orbital and bulk properties of transiting sub-Neptunes can provide clues for their formation and evolution of small […]

Logarithm of exomoon lifetime (log10 (𝑡max ); color coded) from stability simulations that vary a host planet’s mass, tidal constant time-lag, 𝜏p, and initial eccentricity while using Earth-like parameters for the 𝑘2 Love number and moment of inertia constant, 𝐶. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report, Water/Hycean Worlds & Oceanography

Can Moons Exist Around The Habitable-zone Planet K2-18 b?

by Keith CowingJuly 18, 2025July 18, 2025

K2-18 b closely orbits a nearby M3 dwarf within its habitable zone, where this planet could be either a super-Earth or a mini-Neptune.

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 instantaneous Vtid on Proxima b at periastron (a) and at apastron (b), and the orbital-mean amplitude of tidal potential (Vtid) on Proxima b (c) and on Earth (d). -- astro-ph.EP

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

Ocean Tides On Asynchronously Rotating Planets Orbiting Low-mass Stars

by Keith CowingJuly 12, 2025July 12, 2025

Planets in the liquid-water habitable zone of low-mass stars experience large tidal forces, 103 to 104 times those on Earth, due to the small distance between the habitable zone and […]

Phase-folded radial velocities of the planets in the L 98-59 system. (a): L 98-59.06. (b): L 98-59 b. (c): L 98-59 c. (d)t: L 98-59 d. (e): L 98-59 e. (f): L 98-59 f. -- astro-ph.EP

Exoplanets, -moons, -comets, Status Report

Confirmation Of A Non-transiting Planet In The Habitable Zone Of The Nearby M dwarf L 98-59

by Keith CowingJuly 11, 2025

Only 40 exoplanetary systems with five or more planets are currently known. These systems are crucial for our understanding of planet formation and planet-planet interaction.

Left: Eccentricity posterior generated by fitting the first nine chronological transits of TOI 555.01. Right: Eccentricity posterior generated by fitting the first nine chronological long-cadence transits of KOI 247.01. -- astro-ph.EP

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

The Orbital Eccentricity-Radius Relation For Planets Orbiting M Dwarfs

by Keith CowingJuly 11, 2025

The orbital eccentricity-radius relation for small planets is indicative of the predominant dynamical sculpting processes during late-stage orbital evolution.

GMM fits to the unbinned radius data, along with corresponding histograms, are presented for the entire low-mass star sample and for M, K, and G stellar types. The Super-Earth and Mini-Neptune peaks, as well as the radius valley, are indicated in each plot. -- astro-ph.EP

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

Radius Valley Scaling Among Low Mass Stars With TESS

by Keith CowingJuly 11, 2025July 11, 2025

The Transiting Exoplanet Survey Satellite (TESS) has been highly successful in detecting planets in close orbits around low-mass stars, particularly M dwarfs.

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

Rocky Worlds DDT Updates: New Targets, Upcoming Observations, and More

by Keith CowingJuly 9, 2025July 9, 2025

The Rocky worlds DDT Core Implementation Team (CIT) at STScI, along with the external Science Advisory Council (SAC), have been hard at work to make progress on this exciting program, […]