Scientists Investigate Potential Exomoon Around HD 206893 B

Recent research has brought scientists closer to potentially confirming the existence of the first exomoon. A large international team has conducted an extensive study, set to be published in *Astronomy & Astrophysics*, which explores innovative methods to identify an exomoon orbiting the gas giant exoplanet HD 206893 B. This research could pave the way for future discoveries of exomoons, which have yet to be definitively confirmed.

Located approximately 133 light-years from Earth, HD 206893 B possesses a radius and mass of 1.25 and 28 times that of Jupiter, respectively. Its orbital period around its host star spans an impressive 25.6 years. The researchers employed a technique known as astrometry to detect subtle movements, or wobbles, that indicate the presence of a secondary object orbiting the exoplanet. Utilizing the VLTI/GRAVITY instrument, they were able to measure these wobbles over varying timeframes, ranging from several days to years.

The findings suggest the possibility of a secondary object orbiting HD 206893 B with an orbital period of approximately 0.76 years and a mass estimated at around 0.4 times that of Jupiter. Despite this promising data, astronomers still face challenges in confirming the existence of exomoons. Currently, only a handful of candidates exist, including those identified in previous studies like Kepler-1625 b-i and Kepler-1708 b-i, located roughly 7,500 and 5,500 light-years from Earth, respectively. A 2024 study, however, cast doubt on these candidates after re-evaluating data from the Hubble and Kepler missions.

The difficulty in detecting exomoons primarily stems from their relatively small size compared to their parent planets. For instance, while HD 206893 B is estimated to have a mass of 28 Jupiter masses, its potential exomoon candidate’s mass is only about 0.4 Jupiter masses. In comparison, previous candidates like Kepler-1625 b and Kepler-1708 b were estimated at 30 Earth masses and 4.6 Jupiter masses, respectively, while their corresponding exomoon candidates were significantly smaller.

This growing interest in exomoons reflects the diversity of moons found within our own solar system, which boasts over 200. Notably, several of these moons have become focal points for astrobiological studies. For example, NASA’s Europa Clipper spacecraft is currently en route to **Europa** to investigate its potential for habitability. Additionally, NASA is preparing to launch the **Dragonfly** quadcopter to Titan in 2028, further expanding our exploration of these celestial bodies. Although no missions are currently planned to revisit **Enceladus**, scientists continue to examine data collected by NASA’s **Cassini mission**, which concluded in 2017 after making significant discoveries, including plumes of water vapor erupting from Enceladus’ south pole.

The search for habitable exomoons extends beyond scientific exploration, often drawing inspiration from science fiction. The moon **Pandora**, featured in the *Avatar* film series, is depicted as a habitable environment for various intelligent beings, fueling further interest in the search for similar worlds.

As researchers continue to refine their methods of detection and analysis, the scientific community remains optimistic about the prospect of uncovering new exomoon candidates in the coming years. With each discovery, the quest for understanding our universe becomes more profound, urging continued dedication to scientific inquiry.