Exomoon Archives

Analytical predictions for the astrometric effect of a moon with varying mass and distance to HD 206893 B. GRAVITY could in principle detect moons lower than a Neptune mass at larger periods. The fit of the GRAVITY data is shown as a green point assuming the mass and period as upper limits in our tentative detection. The orange area shows the plausible parameter space where a moon could be located, and still be potentially detectable with GRAVITY assuming an astrometric accuracy of 10 µas (see section 3.3). -- astro-ph.EP

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

Exomoon Search With VLTI/GRAVITY Around The Substellar Companion HD 206893 B

by Keith CowingNovember 26, 2025June 10, 2026

Direct astrometric detection of exomoons remains unexplored. This study presents the first application of high-precision astrometry to search for exomoons around substellar companions.

Astronomy & Telescopes, Exoplanets, -moons, -comets, Gas Giants, Ice Giant, Imaging & Spectroscopy, Status Report

A JWST Transit Of A Jupiter Analog: II. A Search For Exomoons

by Keith CowingNovember 22, 2025June 10, 2026

We present a search for exomoons around the Jupiter-like exoplanet Kepler-167e using a NIRSpec JWST transit.

Self-consistent obliquity and spin rate evolution for several realizations of exoplanet Kepler-79 d. Trajectories go from right to left. The planet is initalized with a spin rate of 7.5 hours (i.e. ω/np ≈ 170) and different obliquities equispaced in cos θ. A moon with mass mm/mp = 10−6 is initialized at a distance am = 4 Rp. Integrations are stopped when the moon’s pericenter goes below the Roche limit. The three largest resonances reacheable by Kepler-79 d appear in red, blue, and green. The hatched blue zone is the E1 region. For definitiveness, the resonances and E1 region in the background are drawn assuming that the moon is on a circular orbit at am = 4 Rp; for moons that do not cross the E1 region, this remains approximatively true during the whole simulation. -- astro-ph.EP

Astrogeology, Exoplanets, -moons, -comets, Gas Giants, Ice Giant, Status Report, Stellar Cartography

The Coupled Tidal Evolution of the Moons and Spins of Warm Exoplanets

by Keith CowingNovember 10, 2025

Context: The Solar System giant planets harbour a wide variety of moons. Moons around exoplanets are plausibly similarly abundant, even though most of them are likely too small to be […]

The time-series spectra with the full wavelength range (in microns) of the observations shown on the x-axis, observation time (in hours) on the y-axis, and a color bar representing the amplitude variability for any given flux value as a percent deviation from the mean. The 2 wavelength regions used to construct the light curves are shown where each has a distinct variability pattern. Region 1: negative, positive, negative positive amplitude; Region 2: negative, positive amplitude. The picket fence pattern (narrow striping) visible in region 2 is due to CO absorption. -- astro-ph.SR

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

A Deep Search For Exomoons Around WISE 0855 With JWST

by Keith CowingNovember 7, 2025November 7, 2025

JWST is collecting time-series observations of many free-floating planets (FFPs) to study their weather, but these light curves are the ideal datasets to search for exomoons that transit the FFP […]

An artistic rendering of a dust and gas disk encircling the young exoplanet, CT Cha b, 625 light-years from Earth. Spectroscopic data from NASA’s James Webb Space Telescope suggests the disk contains the raw materials for moon formation: diacetylene, hydrogen cyanide, propyne, acetylene, ethane, carbon dioxide, and benzene. The planet appears at lower right, while its host star and surrounding circumstellar disk are visible in the background. Illustration: NASA, ESA, CSA, STScI, Gabriele Cugno (University of Zürich, NCCR PlanetS), Sierra Grant (Carnegie Institution for Science), Joseph Olmsted (STScI), Leah Hustak (STScI)

Astrochemistry, Astrogeology, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Callisto, Exoplanets, -moons, -comets, Ganymede, Icy Worlds, Imaging & Spectroscopy, Press Release

Webb Studies A Carbon-rich Moon-Forming Disk Around A Massive Planet

by Keith CowingSeptember 30, 2025September 30, 2025

NASA’s James Webb Space Telescope has provided the first direct measurements of the chemical and physical properties of a potential moon-forming disk encircling a large exoplanet. The carbon-rich disk surrounding […]

Signal amplitudes in the vicinity of the putative exomoon around β Pic b suggested by Poon et al. (2024) as a function of moon mass and semi-major axis for RV studies on the left and astrometric searches on the right. The grey shaded region is the parameter space where a P24- moon is likely to reside if it is indeed real. The dashed lines indicate contours delineating the provided signal strengths. -- astro-ph.EP

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

Astrometric Exomoon Detection By Means Of Optical Interferometry

by Keith CowingSeptember 27, 2025September 27, 2025

Context: With no conclusive detection to date, the search for exomoons, satellites of planets orbiting other stars, remains a formidable challenge. Detecting these objects, compiling a population-level sample and constraining […]

Physical parameters of the simulated events with and without detected moons. In each panel, the grey points show the events our simulation where a moon was not detected, i.e., these are the distributions of the physical parameters of the planets and moons we simulated. The stars show events where the moon was detected. The blue markers indicate the locations of the light curves shown in Figure 6 in these parameter spaces. Each panel shows (a) the planet/star mass ratio versus planet projected separation in units of the Einstein ring radius of the system. The lines indicate the boundaries of the resonant caustic region that we exclude from our sample; (b) the planet mass versus the planet semimajor axis; (c) moon/planet mass ratio versus the moon-planet separation in units of the Einstein ring radius of the planet; (d) moon mass versus semimajor axis of the moon in units of the Hill radius. -- astro-ph.EP

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

Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey. III. Detectability of Giant Exomoons of Wide Separation Giant Planets

by Keith CowingSeptember 7, 2025September 7, 2025

Roman should be sensitive to lenses with mass down to ~ 0.02 M⊕, or roughly the mass of Ganymede. Thus the detection of moons with masses similar to the giant […]

Velocity at infinity vs. parameter α for ejected test particles -- astro-ph.EP

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

Free-floating Planets Produced by Planet-Planet Scatterings: Ejection Velocity and Survival Rate of Their Moons

by Keith CowingAugust 27, 2025August 27, 2025

The discovery of numerous free-floating planets (FFPs) has intensified interest in their origins and dynamical histories.

Sensitivity maps for the four CHEOPS visits of HD 95338. The first row represents the best-fit box depth (i.e. moon radius) in the ∆T0–W space. The 3σ lower limit of the moon radius is shown in the second row, while the third and fourth rows represent the ∆BIC and ∆AIC values between a solution with and without a moon. The empty (blank) areas are values that are below a threshold of 0 R⊕ for the moon radius (first 2 rows) and a threshold of 2 for the ∆BIC and ∆AIC (last 2 rows). The grey squares (and corresponding dotted lines) show the position of the transit of HD 95338b in this parameter space for each visit. An underlying linear trend is assumed for each of the four visits. -- astro-ph.EP

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

The CHEOPS View Of HD 95338b: Refined Transit Parameters, And A Search For Exomoons

by Keith CowingJuly 25, 2025July 25, 2025

Despite the ever-increasing number of known exoplanets, no uncontested detections have been made of their satellites, known as exomoons.

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.

Exomoon

Exomoon Search With VLTI/GRAVITY Around The Substellar Companion HD 206893 B

A JWST Transit Of A Jupiter Analog: II. A Search For Exomoons

The Coupled Tidal Evolution of the Moons and Spins of Warm Exoplanets

A Deep Search For Exomoons Around WISE 0855 With JWST

Webb Studies A Carbon-rich Moon-Forming Disk Around A Massive Planet

Astrometric Exomoon Detection By Means Of Optical Interferometry

Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey. III. Detectability of Giant Exomoons of Wide Separation Giant Planets

Free-floating Planets Produced by Planet-Planet Scatterings: Ejection Velocity and Survival Rate of Their Moons

The CHEOPS View Of HD 95338b: Refined Transit Parameters, And A Search For Exomoons

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

Alta-X Drone Tests Future Astrobiology / Astrogeology Droid Technology

Landforms In Ares Vallis Carved Out By Ancient Water Flow

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

Radial Velocity Detection Of The TRAPPIST-1 Planetary System With SPIRou And NIRPS

Structure Of An RNA polymerase Ribozyme Replication Complex