Exomoon Archives

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.

Astronomy & Telescopes, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Gas Giants, Habitable Zones, Ice Giant, Imaging & Spectroscopy, Science Fiction, Status Report, Water/Hycean Worlds & Oceanography

Formation Of Habitable Moons Around Giant Planets

by Keith CowingMay 27, 2025May 27, 2025

Of the few thousand discovered exoplanets, a significant number orbit in the habitable zone of their star.

Snapshots of the latitude-longitude simulation of Europa’s surface evolution when it first enters the red giant branch habitable zone (12.25 Gyr, Seff = 0.32, Jupiter at 2 AU Cahoy et al. (2010) albedo).

Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Europa, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Status Report, Stellar Cartography

Life After Death: Europa In The Evolving Habitable Zone Of A Red Sun

by Keith CowingMay 22, 2025May 22, 2025

Most stars end their main-sequence (MS) lives by evolving through the red-giant and asymptotic-giant branches before ending as a quiescent, stable white dwarf. Therefore, it is imperative to model the […]

Four types of mutual events simulated for a phase angle of 225◦ . The RGB images are based on individual maps simulated for wavelengths of 440 nm (blue), 555 nm (green), and 700 nm (red). The total flux was normalized to the geometric albedo separately at each of the wavelengths. The dashed circles indicate the position and size of the planet (blue) and moon (gray). To improve the visibility of the moon and to fit both bodies into the images for shadow and eclipse, the lunar surface albedo am was increased to 0.3 and the moon’s semimajor axis was set to 2.8 rp for this graphic. -- astro-ph.EP

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

Polarimetry Of Exoplanet-Exomoon Systems

by Keith CowingApril 15, 2025April 15, 2025

We investigated the potential of polarimetric observations in the optical wavelength range for the detection of exomoons and the characterization of exoplanet-exomoon systems.

A comparison between the values of the various mean opacities defined by Eqns. 14-16, the wavelength dependence of the different radiation fields and actual cross-sections. The left panel sketches the conditions under which 𝛾 > 1 occurs when averaging opacity functions 𝜅 (𝜆) (solid black line). When irradiated by a stellar black-body, the opacity ratio of incoming to outgoing mean opacities is 𝛾 < 1 (the constant red value is below the constant green value). When the irradiating black-body cools, it moves up to the high opacity range in the infrared, but the outgoing radiation remains in the far-infrared, resulting in 𝛾 > 1 (the constant blue line is above the constant green one) and vigorous hydrodynamic escape occurs. The right panel shows that 𝜅out readily remains low for realistic and cold, molecules such as NH3, as the natural spacing between the molecular band peaks outpaces the width of a black-body. -- astro-ph.EP

Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Gas Giants, Status Report, Titan

Efficient And Inefficient Hydrodynamic Escape of Exo-satellite Atmospheres Driven By Irradiation From Their Young Giant Planets

by Keith CowingMarch 26, 2025

The bolometric radiation from a central body is potentially a powerful driver of atmospheric escape from planets or satellites.

The Chinese Space Station Telescope (CSST) - CNSA/Xinhua

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

Chinese Space Station Telescope: Detecting Exomoons in Free-Floating-Planet Events from Space-based Microlensing Surveys

by Keith CowingJanuary 9, 2025January 9, 2025

When a planet is ejected from its star-planet system due to dynamical interactions, its satellite may remain gravitationally bound to the planet.

Schematic diagram (not to scale) of four angular momentum vectors in the β Pictoris system: total angular momentum (Lˆ), orbital angular momentum of planets b and c (nˆorbit,b, nˆorbit,c), and the spin vector of planet b (nˆspin,b). The mutual inclination between nˆorbit,b and nˆorbit,c is ∼ 1 ◦. Secular spin-orbit resonance can occur when the period of orbit nodal regression (path along grey dotted circle on the left) has a similar period to the spin axis precession (path along black dotted circle on the right). The period of spin axis precession can be greatly shortened in the presence of a close-in equatorial exomoon, which acts as a lever and effectively extends the planet’s equatorial bulge. I is the orbital inclination of β Pictoris b (orange ellipse) relative to the invariable plane (grey ellipse). -- astro-ph.EP

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

A Potential Exomoon From The Predicted Planet Obliquity Of β Pictoris b

by Keith CowingDecember 17, 2024December 17, 2024

Planet obliquity is the alignment or misalignment of a planet spin axis relative to its orbit normal. In a multiplanet system, this obliquity is a valuable signature of planet formation […]

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

Exomoons Of Circumbinary Planets

by Keith CowingDecember 5, 2024December 5, 2024

Exomoon discovery is on the horizon. Although several exomoon candidates exist around single stars, there are currently no candidates around circumbinary planets (CBPs).

Exomoon

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?

Formation Of Habitable Moons Around Giant Planets

Life After Death: Europa In The Evolving Habitable Zone Of A Red Sun

Polarimetry Of Exoplanet-Exomoon Systems

Efficient And Inefficient Hydrodynamic Escape of Exo-satellite Atmospheres Driven By Irradiation From Their Young Giant Planets

Chinese Space Station Telescope: Detecting Exomoons in Free-Floating-Planet Events from Space-based Microlensing Surveys

A Potential Exomoon From The Predicted Planet Obliquity Of β Pictoris b

Exomoons Of Circumbinary Planets

NASA Spaceline Current Awareness List #1,206 2 July 2026 (Space Life Science Research Results)

Older Than The Sun: Astronomers Find New Clues To The Origin Of Interstellar Comet 3I/ATLAS

Carl Sagan Month: Call For Participation

The Habitable Worlds Observatory Technology Development Plan

Searching For The Elusive CH2+ With The James Webb Space Telescope. Another Carbocation To Constrain Astrochemical Networks