Astronomers have discovered a Jupiter-sized world orbiting a brown dwarf within the CD-35 2722 system, challenging traditional definitions of planets and moons through a unique nested orbital structure observed between October 2023 and February 2026 using the Very Large Telescope in Chile.
Nested Orbit Found in CD-35 2722
Astronomers expected to find standard planetary orbits, but instead discovered a Jupiter-sized world circling a brown dwarf that itself orbits a small star. A team led by astronomer Kevin Hoy of the University Diego Portales in Santiago, Chile discovered the unusual Jupiter-sized world using the Very Large Telescope.
Researchers monitored the system from October 2023 to February 2026. They tracked repeated changes in the wavelengths of light emitted by the central brown dwarf.
These spectral variations revealed a gravitational tug from an unseen companion. The team used the radial velocity technique to confirm the nested structure.
Classifications Clash Over Planetary Definitions
International Astronomical Union standards adopted in 2018 state that a planet-mass object orbiting a brown dwarf is an exoplanet, even if the brown dwarf is not the most massive body in the system. David Kipping of Columbia University supports this reading.
If you accept that this is a brown dwarf, that kind of forces the companion to be a planet
, Kipping noted.
Hoy and his co-researchers disagree, arguing that the object’s orbital location makes it behave differently from conventional planets. They prioritize physical context over mass.
Stability Tests Limit Exomoon Finds
Confirmed exomoons remain unproven despite thousands of known exoplanets. A catalogue of 24 proposed exomoon candidates compiled by Alicia Pérez-Rodrigo and Isabel Rebollido shows that many literature candidates fail stability criteria or fall below the sensitivity thresholds of instruments like Kepler.
Only 8 of 13 candidates meet at least one stability criterion. The rest either violate long-term dynamical limits or produce signals too weak for current tools.
This investigation, submitted on September 7, 2026, and revised on September 11, 2026, applied Hill, Roche, and Laplace stability criteria across 6,038 confirmed exoplanets. The researchers identified 27 promising targets for future searches using PLATO.
The study attributes the lack of confirmed exomoons to limited instrumental sensitivity, early moon loss from giant impacts or planetary migration, and the inefficient formation of massive stable moons.
Whether these 27 targets will yield the first confirmed exomoons depends on the results of future PLATO observations.