mini-Neptunes Archives

Time series of RV and activity indicators.

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

The RoPES Project With HARPS and HARPS-N II. A Third Planet In The Multi-planet System HD 176986

by Keith CowingJanuary 29, 2026January 29, 2026

Context. Earth-like planets orbiting in the habitable zone of K- to G-type stars create an RV effect in amplitude of less than 1 m s−1 and have orbital periods of […]

Stability analysis of the TOI-5788 planetary system. For fixed initial conditions (Table 4), the parameter space of the system is explored by varying the orbital period and the eccentricity of planet c (left panel) and the eccentricities of both planets (right panel). The step size is 0.0025 in the eccentricities, 0.001 d in the orbital period of planet b, and 0.003 d in the orbital period of planet c. For each initial condition, the system is integrated over 5000 yr and, from a frequency analysis of the mean longitude of the outer planet, a stability indicator is calculated. The colours in the plot represent the chaotic diffusion, measured by the variation in the frequency (see text). Red points correspond to highly unstable orbits, whilst blue points correspond to orbits which are likely to be stable on Gyr timescales. The black dots show the values of the best fit solution (Table 4). -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report, Stellar Cartography, Water/Hycean Worlds & Oceanography

Discovery and Characterisation of Two Exoplanets Orbiting the Metal-poor, Solar-type Star TOI-5788 with TESS, CHEOPS, and HARPS-N

by Keith CowingJanuary 28, 2026January 28, 2026

We present the discovery and characterisation of two transiting exoplanets orbiting the metal-poor, solar-type star TOI-5788.

Seasonal variations of circulation patterns during the eastward phase (the top two rows) and the westward phase (the bottom two rows) under nonsynchronous rotation. Each row, from left to right, corresponds to the snapshot at vernal equinox, summer solstice, fall equinox, and winter solstice. For each phase: the top panels show horizontal temperature maps (K) near the photosphere (∼0.2 bar) with horizontal winds as arrows as functions of longitude and latitude. The intersection of the horizontal and vertical black lines (marked by red filled circles) denotes the substellar point. The bottom panels display zonal-mean zonal wind (colors, m s−1 ) and temperature (contours, K) as functions of latitude and pressure. -- astro-ph.EP

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

Atmospheric Circulation Of High-Obliquity Mini-Neptunes

by Keith CowingJanuary 27, 2026January 27, 2026

With the operation of JWST, atmospheric characterization has now extended to low-mass exoplanets.

Artist’s impression of four orbiting exoplanets. Intense radiation from the host star may be heating their puffy atmospheres, causing atmospheric escape into space. (Credit: Astrobiology Center)

Astronomy & Telescopes, Exoplanets, -moons, -comets, Ice Giant, Icy Worlds, Imaging & Spectroscopy, Press Release, Stellar Cartography, Water/Hycean Worlds & Oceanography

Astronomers Find Missing Link To Our Galaxy’s Most Common Planets

by Keith CowingJanuary 8, 2026January 8, 2026

One of the biggest recent surprises in astronomy is the discovery that most stars like the Sun harbor a planet between the size of Earth and Neptune within the orbit […]

TESS target pixel file images of TOI-2094 (LEFT) and TOI-7166 (RIGHT). The red circles are sources identified by Gaia DR3 catalogue (Gaia Collaboration et al. 2016, 2023), labelled with numbers sorted by angular distance to the target source. The size of the circles indicates the magnitude contrast to the target source. The mosaic of orange pixels shows the aperture of TESS photometry, where the pixel scale is 20′′. The plots were produced using tpfplotter (Aller et al. 2020).

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

Multicolour Validation Of Two Temperate Mini-Neptunes Around M-dwarf Habitable Zones

by Keith CowingDecember 26, 2025December 26, 2025

For small planets orbiting within the habitable zones of their host stars, multicolour validation via photometric transit observations offers an efficient alternative to prioritize targets before intensive radial-velocity follow-up, thereby […]

TESS PDC-SAP flux measurements extracted from the 2-min cadence data of TOI-7166. The target was observed in sector 82. The blue points show the 2-min data, and the red points show the 20-min binned data. The transit locations of TOI-7166 b are shown with black arrows and zoom boxes. -- astro-ph.EP

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

TOI-7166 b: A Habitable Zone Mini-Neptune Planet Around A Nearby Low-mass Star

by Keith CowingDecember 9, 2025January 15, 2026

We present the discovery and validation of TOI-7166b, a 2.01+/-0.05R_Earth planet orbiting a nearby low-mass star.

The three-layer diagram of the outcome of our model.

Atmospheres, Climate, Weather, Brown Dwarfs, Exoplanets, -moons, -comets, Gas Giants, Press Release

Efficiency of Hydrodynamic Atmospheric Escape in Hot Jupiters and Super Earths

by Keith CowingNovember 27, 2025November 27, 2025

We develop a flexible one-dimensional code to model the escape of hydrogen and helium from a hot Jupiter as a result of photoionization from extreme-ultraviolet (EUV) radiation.

A new study finds that many “mini-Neptunes”—perhaps the most common planets in the galaxy—are under so much pressure from their heavy atmospheres that the surface is likely compressed solid. Illustration courtesy NASA/JPL-Caltech/R. Hurt (IPAC)

Astrogeology, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Lava / magma ocean / Volcanic Worlds, Press Release

Revising Our Understanding Of The Most Common Planets In Our Galaxy

by Keith CowingNovember 6, 2025November 6, 2025

As telescopes have become more powerful, it’s turned out our solar system is not the only game in town: There are millions of other planets out there in the galaxy.

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

TOI-7166 b: A Habitable Zone Mini-Neptune Planet Around A Nearby Low-mass Star

by Keith CowingOctober 27, 2025October 27, 2025

We present the discovery and validation of TOI-7166 b, a 2.01 ± 0.05 R⊕ planet orbiting a nearby low-mass star.

Mass-radius diagram for TOI-283 b (red star) and known transiting planets with mass determinations with a precision better than 30 % (parameters taken from the TEPCat database; Southworth 2011). Planets orbiting K-type stars (4000 ≤ Teff ≤ 5300 K) are marked with orange circles. The lines in the mass-radius diagram represent the composition models of Zeng et al. (2016, 2019) for planets with pure iron cores (100 % Fe, brown line), Earth-like rocky compositions (32.5 % Fe plus 67.5 % MgSiO3, dashed green line), Earth-like compositions with a 0.1% H2 envelope (dotted purple line), and a water world with a 0.1 % H2 gas envelope (dash-dotted blue line). We show some Solar System planets for reference (Venus, Earth, Uranus, and Neptune). -- astro-ph.EP

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

TOI-283 b: A Transiting Mini-Neptune In A 17.6-day Orbit Discovered With TESS And ESPRESSO

by Keith CowingOctober 23, 2025October 22, 2025

Super-Earths and mini-Neptunes are missing from our Solar System, yet they appear to be the most abundant planetary types in our Galaxy.

mini-Neptunes

The RoPES Project With HARPS and HARPS-N II. A Third Planet In The Multi-planet System HD 176986

Discovery and Characterisation of Two Exoplanets Orbiting the Metal-poor, Solar-type Star TOI-5788 with TESS, CHEOPS, and HARPS-N

Atmospheric Circulation Of High-Obliquity Mini-Neptunes

Astronomers Find Missing Link To Our Galaxy’s Most Common Planets

Multicolour Validation Of Two Temperate Mini-Neptunes Around M-dwarf Habitable Zones

TOI-7166 b: A Habitable Zone Mini-Neptune Planet Around A Nearby Low-mass Star

Efficiency of Hydrodynamic Atmospheric Escape in Hot Jupiters and Super Earths

Revising Our Understanding Of The Most Common Planets In Our Galaxy

TOI-7166 b: A Habitable Zone Mini-Neptune Planet Around A Nearby Low-mass Star

TOI-283 b: A Transiting Mini-Neptune In A 17.6-day Orbit Discovered With TESS And ESPRESSO

Roman Space Telescope: Enabling Images Of Distant Worlds

NASA Solar System Exploration Research Virtual Institute (SSERVI) Cooperative Agreement Notice (NNH26ZDA016C) Final Text And Due Dates

Interstellar Aromatic Infrared Bands: IR Absorption Spectroscopy Of The Lowest Triplet State Of Naphthalene

The Highly Unusual Behavior And Chemical Composition Of Interstellar Comet 2I/Borisov

Volatile Depletion In Rocky Planets As A Chemical Fingerprint Of Hybrid Accretion