Stellar Flares from the First TESS Data Release: Exploring a New Sample of M Dwarfs

We perform a study of stellar flares for the 24,809 stars observed with 2 minute cadence during the first two months of the TESS mission. Flares may erode exoplanets' atmospheres and impact their habitability, but might also trigger the genesis of life around small stars. TESS provides a new sample of bright dwarf stars in our galactic neighborhood, collecting data for thousands of M dwarfs that might host habitable exoplanets. Here, we use an automated search for flares accompanied by visual inspection. Then, our public allesfitter code robustly selects the appropriate model for potentially complex flares via Bayesian evidence. We identify 1228 flaring stars, 673 of which are M dwarfs. Among 8695 flares in total, the largest superflare increased the stellar brightness by a factor of 16.1. Bolometric flare energies range from 10<SUP>31.0</SUP> to 10<SUP>36.9</SUP> erg, with a median of 10<SUP>33.1</SUP> erg. Furthermore, we study the flare rate and energy as a function of stellar type and rotation period. We solidify past findings that fast rotating M dwarfs are the most likely to flare and that their flare amplitude is independent of the rotation period. Finally, we link our results to criteria for prebiotic chemistry, atmospheric loss through coronal mass ejections, and ozone sterilization. Four of our flaring M dwarfs host exoplanet candidates alerted on by TESS, for which we discuss how these effects can impact life. With upcoming TESS data releases, our flare analysis can be expanded to almost all bright small stars, aiding in defining criteria for exoplanet habitability.

Carbon-bearing Molecules in a Possible Hycean Atmosphere

The search for habitable environments and biomarkers in exoplanetary atmospheres is the holy grail of exoplanet science. The detection of atmospheric signatures of habitable Earth-like exoplanets is challenging owing to their small planet–star size contrast and thin atmospheres with high mean molecular weight. Recently, a new class of habitable exoplanets, called Hycean worlds, has been proposed, defined as temperate ocean-covered worlds with H<SUB>2</SUB>-rich atmospheres. Their large sizes and extended atmospheres, compared to rocky planets of the same mass, make Hycean worlds significantly more accessible to atmospheric spectroscopy with JWST. Here we report a transmission spectrum of the candidate Hycean world K2-18 b, observed with the JWST NIRISS and NIRSpec instruments in the 0.9–5.2 μm range. The spectrum reveals strong detections of methane (CH<SUB>4</SUB>) and carbon dioxide (CO<SUB>2</SUB>) at 5σ and 3σ confidence, respectively, with high volume mixing ratios of ∼1% each in a H<SUB>2</SUB>-rich atmosphere. The abundant CH<SUB>4</SUB> and CO<SUB>2</SUB>, along with the nondetection of ammonia (NH<SUB>3</SUB>), are consistent with chemical predictions for an ocean under a temperate H<SUB>2</SUB>-rich atmosphere on K2-18 b. The spectrum also suggests potential signs of dimethyl sulfide (DMS), which has been predicted to be an observable biomarker in Hycean worlds, motivating considerations of possible biological activity on the planet. The detection of CH<SUB>4</SUB> resolves the long-standing missing methane problem for temperate exoplanets and the degeneracy in the atmospheric composition of K2-18 b from previous observations. We discuss possible implications of the findings, open questions, and future observations to explore this new regime in the search for life elsewhere.

Scientists Have Discovered a Planet That Is Better than Earth!

Scientists Have Discovered a Planet That Is Better than Earth! Credit to : TheSimplySpace

Information on Service 'CARMENES DR1: Spectra'

Information on Service 'Carmenes DR1 Radial Velocity Time Series'

Nothing is as we thought - Harvard-Smithsonian Astrophysics Center reveals that super-Earths are more common and diverse in the Milky Way than previously thought, according to study OGLE-2016-BLG-0007

Do we know everything about the Milky Way? A team of astronomers has arrived to change everything we know about our universe, and they have found strong

NASA Climate Modeling Suggests Venus May Have Been Habitable - NASA

Venus may have had a shallow liquid-water ocean and habitable surface temperatures for up to 2 billion years of its early history, according to computer