K-dwarf Archives - Astrobiology

Activity-age relationship for solar-type stars from Pezzotti et al. (2026). HD 219134 is denoted by the green square. Kepler LEGACY data from Pezzotti et al. (2026) are shown as cyan dots, Booth et al. (2017) data are indicated by salmon pentagons, and the Sun is shown by a black circled dot. The black lines indicate the linear fit from Booth et al. (2017) (dashed line) and Pezzotti et al. (2026) (dotted line). -- [astro-ph.EP]

Stellar Cartography

Detailed Study of HD 219134: A Benchmark K-dwarf With A Compact Planetary System

by Keith CowingOctober 14, 2026October 14, 2026

[astro-ph.EP] Space missions such as CoRoT, Kepler, and TESS have transformed asteroseismology and its synergies with exoplanet science.

Panel (a): HR diagram of the OC members with detections. The blue solid line is the fitting results of MS. green dashed lines represent the upper and lower bounds of the MS fitted with a ±0.5 offset, and the red dashed line is the same sequence shifted upwards by 2. The color bars represent the stellar ages. Panel (b): HR diagram of the field stars with detections. Panel (c): The Galactic distribution of the selected sources from the detected OC members. Panel (d): The Galactic distribution of the selected sources from the detected field stars. -- [astro-ph.SR]

Habitable Zones

Evolution of Stellar Activity and Habitable Zone (EATEN): III. X-ray Activity of Dwarfs in Open Clusters and Field Stars

by Keith CowingSeptember 10, 2026September 10, 2026

[astro-ph.SR] Stellar X-ray emission serves as a direct diagnostic of coronal activity, which is fundamentally linked to coronal heating processes. It also strongly influences the atmospheres and long-term habitability of […]

Fits and residuals of stage 3 F1550C data subtracted using the results of PyMultiNest single- and double-PSF fitting.

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

Direct Imaging Constraints on Binary Planets and Exomoons around Epsilon Indi A b

by Keith CowingApril 29, 2026April 29, 2026

Epsilon Indi A b is a directly imaged ∼6MJup exoplanet orbiting a nearby (3.6 pc) K-dwarf at ∼30 AU.

Planetary system of GJ 1137 relative to the conservative habitable zone (cHZ; green) and the optimistic habitable zone (oHZ; yellow), respectively. Black orbital bands come from our 1σ posteriors of the orbital parameters of GJ 1137 b and GJ 1137 c.-- astro-ph.EP

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

Long-period Magnetic Activity In The K Dwarf GJ 1137 And A New Super-Earth On A 9-day Orbit

by Keith CowingMarch 9, 2026March 9, 2026

Aims: We investigate long-term radial velocity (RV) variability in the K-dwarf star GJ 1137 (HD 93083, HIP52521), a known Saturn-mass exoplanet host, and assess the role of stellar activity in […]

HD 137010 b in context. We plot known transiting planets smaller than

Exoplanets, -moons, -comets, Status Report

A Cool Earth-sized Planet Candidate Transiting a Tenth Magnitude K-dwarf From K2

by Keith CowingJanuary 28, 2026January 28, 2026

The transit method is currently one of our best means for the detection of potentially habitable “Earth-like” exoplanets.

Phase folded transits of TOI-2345 b (purple) and TOI-2345 c (green) with the best-fit model from the joint fit in juliet in the top panel. The bottom panel shows the residuals. Left: TESS data. Right: CHEOPS data. -- astro-ph.EP

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

An Ultra-Short Period Super-Earth and Sub-Neptune Spanning the Radius Valley Orbiting the Kinematic Thick Disk Star TOI-2345

by Keith CowingOctober 16, 2025October 16, 2025

A crucial chemical link between stars and their orbiting exoplanets is thought to exist. If universal, this connection could affect the formation and evolution of all planets. Therefore, this potential […]

TESS light curve of TOI-1453 (29 sectors comprised between sector 14 and sector 76) together with the transit model in black. (a) Full TESS light curve. The zone highlighted in purple illustrates the timespan of the HARPS-N observations. The three deeper transit features in the model correspond to simultaneous transits of planets b and c. (b) TESS light curve phase-folded on the transits of TOI-1453 b (TOI-1453.02). The orange dots are binned TESS data for better visibility. (c) Same for TOI-1453 c (TOI-1453.01), where the green dots are binned TESS data. -- astro-ph.EP

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

TESS and HARPS-N Unveil Two Planets Transiting TOI-1453. A Super-Earth and One of the Lowest Mass sub-Neptunes

by Keith CowingMarch 11, 2025September 18, 2025

We report on the validation and characterisation of two transiting planets around TOI-1453, a K-dwarf star in the TESS northern continuous viewing zone. In addition to the TESS data, we […]

This infographic compares the characteristics of three classes of stars in our galaxy: Sunlike stars are classified as G stars; stars less massive and cooler than our Sun are K dwarfs; and even fainter and cooler stars are the reddish M dwarfs. The graphic compares the stars in terms of several important variables. The habitable zones, potentially capable of hosting life-bearing planets, are wider for hotter stars. The longevity for red dwarf M stars can exceed 100 billion years. K dwarf ages can range from 15 to 45 billion years. And, our Sun only lasts for 10 billion years. The relative amount of harmful radiation (to life as we know it) that stars emit can be 80 to 500 times more intense for M dwarfs relative to our Sun, but only 5 to 25 times more intense for the orange K dwarfs. Red dwarfs make up the bulk of the Milky Way's population, about 73%. Sunlike stars are merely 6% of the population, and K dwarfs are at 13%. When these four variables are balanced, the most suitable stars for potentially hosting advanced life forms are K dwarfs. Credits: NASA, ESA and Z. Levy (STScI) Larger image

Alpha Centauri, Biosignatures & Paleobiology, Brown Dwarfs, Epsilon Eridani, Exoplanets, -moons, -comets, Habitable Zones, Press Release, Proxima Centauri, tau Ceti, TRAPPIST-1

Goldilocks Stars Are Best Places to Look for Life

by Keith CowingJanuary 8, 2020August 13, 2025

In the search for life beyond Earth, astronomers look for planets in a star’s “habitable zone” — sometimes nicknamed the “Goldilocks zone” — where temperatures are just right for liquid […]