Astronomers are testing a quiet way to search for moons outside our solar system by carefully measuring movement rather than changes in light. The new study focuses on HD 206893 B, a quasi-stellar star about 133 light-years from Earth that is already known to orbit a nearby star. By tracking its location over days, months, and years, researchers noticed small, irregular movements that didn’t quite match its expected path. Although these signals have not yet been confirmed, they suggest the presence of a large companion object, perhaps the Moon. This work makes no claims of discovery. Instead, it has been shown that high-precision astronomical measurements can be used to investigate problems that have hitherto been largely out of reach.
HD 206893 B was observed as a test case for exomoon detection
Most previous attempts to discover exomoons relied on how planets block or change starlight. These methods are difficult and often vague. In this study, the researchers looked at astronomy, which measures precise positions in space. The idea is simple in principle. If the moon is orbiting a planet or substellar body, its gravity should cause a slight wobble in the host body’s motion. Detecting that wobble requires extreme precision, far beyond standard telescopes.
HD 206893 system provides useful test cases
HD 206893 B is heavier than a typical planet, but lighter than a star. Such objects lie in a gray area, making them interesting targets for testing new techniques. The research team used the Very Large Telescope Interferometer’s GRAVITY instrument to monitor its position. Observations were made over a short period of time and revisited over several years. This combination of timescales is important because the Moon produces a repeating signal rather than a one-time shift.
Small residual movements increase cautious interest
After calculating HD 206893 B’s main orbit, the team discovered a small residual motion. These residues can be caused by the orbiting moon, but they can also be caused by measurement limits and instrument effects. Interpreted as a moon, the data suggests an object with about 0.4 times the mass of Jupiter and an orbital period of about 9 months. The researchers stress that this is a preliminary interpretation and the detection is not confirmed.
The possible moon would be unusually large.
It’s the implied mass that makes the signal noteworthy. A companion star of this size would be much larger than any moon in the solar system. It would blur the lines between moons, planets, and binary star systems. This raises questions about how such objects are formed and how they should be classified. This study does not resolve these questions, but it highlights how little is known about large moons outside of our star system.
Spectroscopy supports the quality of observations
Alongside the behavioral analysis, the team examined the light from HD 206893 B itself. They detected water in the atmosphere and confirmed that the data quality was high. No carbon monoxide was detected. This also helps refine the compositional model of the object. Although this does not prove the moon’s signal, it lends credibility to the overall observation.
Future observations are needed to confirm the signal
The main value of this study is to show that astronomical measurements can be used to search for exomoons in a realistic way. For now, the signal around HD 206893 B remains uncertain. This is a hint rather than an answer, pointing to possible ways to shape your future exploration of the world with your peers.