M-dwarf Archives

Three dimensional view of the extrapolated large-scale magnetic field of GJ 436. The colours at the surface of the star represent the radial magnetic field strength, while the blue/red colours along the magnetic field lines represent negative/positive polarities of the radial field. The rotation axis of the star is along the Z-axis and the source surface is set to 4 stellar radii, beyond which the field lines are fully open. -- astro-ph.SR

Astronomy & Telescopes, Exoplanets, -moons, -comets, Habitable Zones, Space Weather & Heliophysics, Status Report

The Space Weather Around The Exoplanet GJ 436b

by Keith CowingJune 28, 2023

The space environment in which planets are embedded depends mainly on the host star and impacts the evolution of the planetary atmosphere. The quiet M dwarf GJ 436 hosts a […]

TESS target pixel file images of TOI-2084 observed in Sector 16 (left panel) and TOI-4184 observed in Sector 1 (right panel), made by tpfplotter (Aller et al. 2020). Red dots show the location of Gaia DR3 sources, and the red shaded region shows the photometric apertures used to extract the photometric measurements. -- astro-ph.EP

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

TOI-2084 b and TOI-4184 b: Two New Sub-Neptunes Around M Dwarf Stars

by Keith CowingJune 28, 2023June 28, 2023

We present the discovery and validation of two TESS exoplanets orbiting nearby M dwarfs: TOI-2084b, and TOI-4184b. We characterized the host stars by combining spectra from Shane/Kast and Magellan/FIRE, SED […]

Artist impression showing the exoplanet LP 890-9c’s potential evolution from a hot Earth to a desiccated Venus. Carl Sagan Institute/R. Payne

Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Press Release, TRAPPIST-1, Venus, Water/Hycean Worlds & Oceanography

Exoplanet LP 890-9c May Reveal Secrets About The Edge Of Habitability

by Keith CowingJune 21, 2023June 21, 2023

How close can a rocky planet be to a star, and still sustain water and life? A recently discovered exoplanet may be key to solving that mystery.

Stellar irradiation comparison for the four inner planets of the Solar System (upper panel) and the LP 890-9 planetary system (lower panel), with scaled planetary radii. The Venus Zone (yellow shade) (Kane et al. 2014) and HZ (blue shade) transition gradually due to the complex climate feedback that may push planets into Earth-like or Venus-like states within the orbital range. HZ limit (solid blue) shown: inner empirical ‘Recent Venus’; and outer ‘Maximum Greenhouse’ limit. A ‘Runaway Greenhouse’ flux limit is also indicated following 1D (black dashed) (Kopparapu et al. 2014) and 3D (black dotted) climate modelling (Kopparapu et al. 2017).

Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Extinction events, Habitable Zones, Press Release, Venus

Venus Atmosphere In 3D Prepares Future Observations Of Rocky Exoplanets

by Keith CowingJune 15, 2023June 15, 2023

The Venus atmosphere may be used as a natural laboratory to understand the evolution of Earth-like planets, according to a study led by the Instituto de Astrofísica e Ciências do […]

The completeness of our survey, annotated with 95%-confidence upper limits on the occurrence rate of giant planets around low-mass M dwarfs as a function of planetary mass and period/instellation/zero-albedo equilibrium temperature under the assumption of circular orbits. In regions where we are highly sensitive (i.e., short periods and large masses), we constrain the occurrence rate to < 1.5% with 95% confidence. The colorbar indicates Neff , the effective number of stars around which we are sensitive to the hypothetical planet. The arrows in the righthand plot show instellations equivalent to that of the water snow line (Podolak & Zucker 2004) (white), Jupiter (brown), and Neptune (blue). We are sensitive to MPsini = 1MJ planets at the water snow line for 83% of stars (occurrence rate < 1.8% with 95% confidence) and at Jupiter-like instellations for 70% of stars (occurrence rate < 2.1%). We remain sensitive to MPsini = 1MJ planets at Neptune-like instellations around 19% of stars (occurrence rate < 7.7%). -- astro-ph.EP

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

Mid-to-Late M Dwarfs Lack Jupiter Analogs

by Keith CowingJune 14, 2023June 14, 2023

Cold Jovian planets play an important role in sculpting the dynamical environment in which inner terrestrial planets form. The core accretion model predicts that giant planets cannot form around low-mass […]

Detection of a binary companion around HD 148352. (a) The left panel illustrates the point spread function of the host star (red cross) from a median collapsed spectral cube of a 30-second single exposure reduced by the OSIRIS data reduction pipeline. (b) The right panel shows the combined detection map from ≈ 30 minutes of OSIRIS-Kn5 observations. The signal of the host star has been modeled out and the signal of the companion is highlighted by the blue dot. The S/N ≈ 34 detection at ∆y = ∆x = −0.08” from the host star is likely a previously undetected M dwarf binary companion. -- astro-ph.EP

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

Detecting Exoplanets Closer to Stars with Moderate Spectral Resolution Integral-Field Spectroscopy

by Keith CowingMay 17, 2023May 17, 2023

While radial velocity surveys have demonstrated that the population of gas giants peaks around 3 au, the most recent high-contrast imaging surveys have only been sensitive to planets beyond ∼ […]

CME mass estimated through different ways plotted against flaring bolometric energy. KIC 8093473 is marked by the two red open stars connected by a dashed line. The two points correspond the CME masses estimated by different CME dynamical length scales (see the main text for the details). The four M-dwarf flares studied in Wang et al. (2021) and Wang et al. (2022) are denoted by the magenta open squares. The stellar CME candidates complied in Moschou et al. (2019) and one studied in Argiroffi et al. (2019) are shown by the solid blue points. The solar flare-CME events studied in Yashiro & Gopalswamy (2009) are denoted by the cyan circles. The best fit to these solar events obtained in Drake et al. (2013) is presented by the dashed line. -- astro-ph.SR

Astronomy & Telescopes, Exoplanets, -moons, -comets, Habitable Zones, Space Weather & Heliophysics, Status Report

Possible Detection of A Flare-associated Coronal Mass Ejection on A M-dwarf

by Keith CowingMay 17, 2023May 17, 2023

We here report a probable detection of a stellar coronal mass ejection (CME) in active M dwarf KIC 8093473 by performing an analysis on its time resolved X-ray spectra observed […]

Mass-radius diagram for all the confirmed transiting exoplanets with mass determination (from RV or transit time variations), colour-coded by effective temperature of the host star, along with the planets of the Solar System. The dashed coloured curved are theoretical composition models by Zeng et al. (2019) described in the legend, and the dashed grey line represents the limiting mass for the deuterium burning (13MJup). Figure adapted from Caballero et al. (2022). -- astro-ph.EP

Astronomy & Telescopes, Brown Dwarfs, Exoplanets, -moons, -comets, Press Release

Astrophysical Parameters Of M Dwarfs With Exoplanets

by Keith CowingMay 17, 2023May 17, 2023

M dwarfs are the most abundant stars in the Universe and are hosts of a rich diversity of planetary companions.

Astronauts on the International Space Station are ready to sample their harvest of a crop of "Outredgeous" red romaine lettuce from the Veggie plant growth system that tests hardware for growing vegetables and other plants in space. Credits: NASA

Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Plant Biology, Space Agriculture, Status Report

Photosynthesis Under a Red Sun: Predicting The Absorption Characteristics Of An Extraterrestrial light-harvesting Antenna

by Keith CowingMay 3, 2023May 3, 2023

Here we discuss the feasibility of photosynthesis on Earth-like rocky planets in close orbit around ultra-cool red dwarf stars.

Eureka! spectroscopic and white light curves from two transits of GJ 486b. The top two rows contain the spectroscopic light curves (left), our best-fit models (center), and subsequent residuals (right) for each transit. Most evident in the data are wavelength-dependent ramps near 3.2 µm that we readily remove. The bottom row depicts the white light curves from each detector (NRS1 and NRS2) before removing their systematic trends. Correlated noise is evident in the residuals and is likely due to thermal cycling (Rigby et al. 2022). The standard deviation of the normalized residuals is 140 ppm for NRS1 and 165 ppm for NRS2. The complete figure set (3 images, one for each reduction) is available in the online journal. -- astro-ph.EP

Astrochemistry, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report

A Water-Rich Atmosphere or Stellar Contamination for the Warm Super-Earth GJ~486b from JWST Observations

by Keith CowingMay 1, 2023May 1, 2023

Planets orbiting M-dwarf stars are prime targets in the search for rocky exoplanet atmospheres. The small size of M dwarfs renders their planets exceptional targets for transmission spectroscopy, facilitating atmospheric […]