TRAPPIST-1 is an ultra-cool red dwarf star with seven planets. Moons can orbit the TRAPPIST-1 planets but only in a limited region around each planet. planets’ gravity makes this stable zone slightly smaller. Only tiny moons are likely to survive long term — bigger ones would be torn away or fall in over time.
Scientists used the REBOUND N-body code with the IAS-15 integrator which is a high-precision gravitational solver.
A moon can remain in a stable orbit from very close to the planet (just outside the Roche limit) up to about 40–45% of the planet’s Hill radius. The Roche limit sets the innermost safe distance — closer than this, tidal forces would break the moon apart. The Hill radius is the outermost gravitational influence of the planet — beyond this, the star’s gravity dominates.
The gravitational interactions between the TRAPPIST-1 planets slightly reduce the stable region for moons.
The tidal decay equation is used which gives the maximum possible mass of a moon that can survive around a planet for a long time while tidal force is considered.
It shows that moons survive more easily if the planet is massive, compact, and weakly dissipative, and if the moon orbits farther out. In contrast, strong stellar gravity, large planetary radius, and strong tidal dissipation make moon survival harder.
Source: https://arxiv.org/html/2512.19226v1
0 comments:
Post a Comment