The Hunt for Moons of Rogue Planets ⚡ экспресс
Observations of the free-floating planetary-mass object WISE 0855 (T≈250–285 K, M≈6.5±3.5 M_Jup, d=2.3 pc) over 11 hours with JWST/NIRSpec enabled an exomoon search via the transit method. The spectrograph's sensitivity combined with Gaussian process modeling allowed separation of transit signals from the object's intrinsic variability. No statistically significant transit evidence was found. Tests with injected artificial signals at depths of 0.1–1% (0.35–1.12 R⊕) showed that for depths ≥0.5% (1.96 R_Titan) detection reliability reaches 96%; this corresponds to a satellite-to-planet mass ratio akin to Titan and Saturn. Given the sensitivity, transit probabilities, and observation durations, the chance to register a Titan analogue after 18 such sessions is ~91% if each system hosts such a moon in a Galilean-like configuration. This work first demonstrates JWST's ability to detect Galilean-mass satellites around free-floating planets.
In the vast darkness of interstellar space, the rogue planet WISE 0855 flickers with a barely perceptible heat glow, like a cooling ember. Its temperature is only a few dozen degrees above freezing — if life existed there, it would see a sunless sky, in an eternal icy haze. The James Webb telescope stared intently at this faint light for 11 hours, hoping to catch the shadow of a passing moon — as if a microscopic soot particle momentarily eclipsed a smoldering ember.
Astronomers built a model predicting the “ember’s” wavering and hunted in the data for dips — moon traces. No direct finds occurred, but the researchers tested their method by injecting artificial moons into the data. If a shadow dimmed the light by at least 0.5%, the detector triggered in 96% of cases, corresponding to a Titan-sized moon.
🎯 WISE 0855 is one of the coldest objects known beyond the Solar System: its temperature is just a few dozen degrees above freezing. If intelligent life were there, it would see a sky without any sun, perpetually shrouded in water-ice fogs.
🎬 Rogue planets with moons are almost a ready-made illustration for Isaac Asimov’s story “The Wanderer”: the characters live on a moon of an orphan planet, warmed only by internal heat.