Possible first discovered exomoon

[Toliman]

Giant doubts about giant exomoons
https://www.mpg.de/21217437/1205-aero-giant-doubts-about-giant-exomoons-151060-x?c=2249

Discovery of giant exomoons around the planets Kepler-1625b and Kepler-1708b called into question

Just as it can be assumed that the stars in our Milky Way are orbited by planets, moons around these exoplanets should not be uncommon. This makes it all the more difficult to detect them. So far, only two of the more than 5300 known exoplanets have been found to have moons. A new data analysis now demonstrates that scientific statements are rarely black or white, that behind every result there is a greater or lesser degree of uncertainty and that the path to a statement often resembles a thriller.

[Toliman]

Large planets may not form fractionally large moons
https://arxiv.org/ftp/arxiv/papers/2312/2312.15050.pdf

One of the unique aspects of Earth is that it has a fractionally large Moon, which is thought to have formed from a Moon-forming disk generated by a giant impact. The Moon stabilizes the Earth's spin axis at least by several degrees and contributes to Earth's stable climate. Given that impacts are common during planet formation, exomoons, which are moons around planets in extrasolar systems, should be common as well, but no exomoon has been confirmed. Here we propose that an initially vapor-rich moon-forming disk is not capable of forming a moon that is large with respect to the size of the planet because growing moonlets, which are building blocks of a moon, experience strong gas drag and quickly fall toward the planet. Our impact simulations show that terrestrial and icy planets that are larger than ~1.3−1.6R⊕ produce entirely vapor disks, which fail to form a fractionally large moon. This indicates that (1) our model supports the Moon-formation models that produce vaporpoor disks and (2) rocky and icy exoplanets whose radii are smaller than ~1.6R⊕ are ideal candidates for hosting fractionally large exomoons.

[Toliman]

Did We Find Exomoons or Not? The Question Lingers.
https://www.universetoday.com/165400/did-we-find-exomoons-or-not-the-question-lingers/#google_vignette

[Toliman]

Did We Find Exomoons or Not? The Question Lingers.
https://www.universetoday.com/165400/did-we-find-exomoons-or-not-the-question-lingers/#google_vignette

Are they exomoons or not? Scientists debate existence of 1st moons seen beyond our solar system
https://www.space.com/exomoon-discovery-scientists-debate-kepler-hubble-study

[Toliman]

The spectroastrometric detectability of nearby Solar System-like exomoons
https://arxiv.org/pdf/2402.07517.pdf

Context. Though efforts to detect them have been made with a variety of methods, no technique can claim a successful, confirmed detection of a moon outside the Solar System yet. Moon detection methods are restricted in capability to detecting moons of masses beyond what formation models would suggest, or they require surface temperatures exceeding what tidal heating simulations allow.
Aims. We expand upon spectroastrometry, a method that makes use of the variation of the centre of light with wavelength as the result of an unresolved companion, which has previously been shown to be capable of detecting Earth-analogue moons around nearby exo-Jupiters, with the aim to place bounds on the types of moons detectable using this method.
Methods. We derived a general, analytic expression for the spectroastrometric signal of a moon in any closed Keplerian orbit, as well as a new set of estimates on the noise due to photon noise, pointing inaccuracies, background and instrument noise, and a pixelated detector. This framework was consequently used to derive bounds on the temperature required for Solar System-like moons to be observable around super-Jupiters in nearby systems, with ϵ Indi Ab as an archetype.
Results. We show that such a detection is possible with the ELT for Solar System-like moons of moderate temperatures (150-300 K) in line with existing literature on tidal heating, and that the detection of large (Mars-sized or greater) icy moons of temperatures such as those observed in our Solar System in the very nearest systems may be feasible.

[Toliman]

Large exomoons unlikely around Kepler-1625 b and Kepler-1708 b
https://www.nature.com/articles/s41550-023-02148-w

[Toliman]

JWST Will Finally Hunt for Alien Moons—And Much More
https://www.scientificamerican.com/article/jwst-will-finally-hunt-for-alien-moons-and-much-more/

The next year of science for the James Webb Space Telescope has been selected. It includes remote galaxy observations and, at last, a hunt for exomoons

It's no secret that the James Webb Space Telescope (JWST) is the most advanced telescope in history. As such, demand to use it is high—incredibly high. Last week the Space Telescope Science Institute (STScI) in Maryland announced which programs it had picked to win some of the telescope's precious time in its third year of science observations. Beginning this July and officially called Cycle 3, JWST's latest solicitation received a record-breaking 1,931 proposals—the most ever for any space telescope in history. Such immense interest is "not surprising," says Christine Chen, an associate astronomer at STScI. "Basically, out of the box, everything has worked extremely well." With that popularity, there are winners and many more losers; only 253 proposals were selected.* But among the winners there is a wealth of exciting science, including surveys to look for the universe's first galaxies (JWST's primary forte), studies of possibly life-harboring exoplanets and, for the first time, an attempt to leverage JWST's power to find exomoons—natural satellites orbiting worlds beyond the solar system.

[Toliman]

On the Impact and Utility of Single-Exomoon Modeling for Multi-Moon Systems
https://arxiv.org/pdf/2402.17324.pdf

The search for exomoons in time-domain photometric data has to-date generally consisted of fitting transit models that are comprised of a planet hosting a single moon. This simple model has its advantages, but it may not be particularly representative, as most of the major moons in our Solar System are found in multi-moon satellite systems. It is critical that we investigate, then, the impact of applying a single-moon model to systems containing multiple moons, as there is the possibility that utilizing an inaccurate or incomplete model could lead to erroneous conclusions about the system. To that end, in this work we produce a variety of realistic multimoon light curves, perform standard single-moon model selection, and analyze the impacts that this model choice may have on the search for exomoons. We find that the number of moons in a system fit with a single-moon model generally has little impact on whether we find evidence for a moon in that system, and other system attributes are individually not especially predictive. However, the model parameter solutions for the moon frequently do not match any real moon in the system, instead painting a picture of a "phantom" moon. We find no evidence that multi-moon systems yield corresponding multi-modal posteriors. We also find a systematic tendency to overestimate planetary impact parameter and eccentricity, to derive unphysical moon densities, and to infer potentially unphysical limb darkening coefficients. These results will be important to keep in mind in future exomoon search programs.

[Toliman]

Magnetic field of gas giant exoplanets and its influence on the retention of their exomoons
https://arxiv.org/pdf/2402.07387.pdf

We study the magnetic and tidal interactions of a gas-giant exoplanet with its host star and with its exomoons, and focus on their retention. We briefly revisit the scaling law for planetary dynamo in terms of its mass, radius and luminosity. Based on the virial theorem, we construct an evolution law for planetary magnetic field and find that its initial entropy is important for the field evolution of a high-mass planet. We estimate the magnetic torques on orbit arising from the star-planet and planetmoon magnetic interactions, and find that it can compensate tidal torques and bypass frequency valleys where dynamical-tide response is ineffective. For exomoon's retention we consider two situations. In the presence of a circumplanetary disk (CPD), by comparison between CPD's inner and outer radii, we find that planets with too strong magnetic fields or too small distance from its host star tend not to host exomoons. During the subsequent CPD-free evolution, we find, by comparison between planet's spindown and moon's migration timescales, that hot Jupiters with periods of several days are unlikely to retain large exomoons, albeit they could be surrounded by rings from the debris of tidally disrupted moons. In contrast, moons, if formed around warm or cold Jupiters, can be preserved. Finally, we estimate the radio power and flux density due to the star-planet and planet-moon magnetic interactions and give the upper limit of detection distance by FAST.