KOI-868.01

Lore & Background

KOI-868.01 was first suggested to exist as a Kepler Object of Interest in 2013 after observations with the Kepler Space Telescope using the transit method. It is currently categorized as a planet candidate by the NASA Exoplanet Archive. In 2026, it was found to be an extremely promising candidate, with further studies potentially confirming its existence.

The planet candidate is similar in size to Saturn, with an estimated radius of 0.945 Jupiter radii and a mass of 0.689 Jupiter masses. It orbits its star every 236 days at a distance of 0.65 astronomical units, placing it within the habitable zone. Its equilibrium temperature is 188 K.

In 2018, an anomaly during transits led to the suggestion that KOI-868.01 may host rings extending up to 88,000 kilometers from the planet's surface, which would be stable for over 3 billion years. However, with only two transits available, the existence of rings is considered unlikely, and the anomalies are believed to be caused by stellar activity. In 2015, David Kipping discovered using transit timing variations that a potential exomoon, KOI-868.01 I, may orbit the planet, with a radius of 1.23 Earth radii and a mass of 0.31 Earth masses, orbiting approximately 0.0221 AU from the planet. Because KOI-868.01 lies in the habitable zone, this exomoon could potentially be a habitable exomoon similar to 2MASS J1119-1137 I.

Reader's Guide

KOI-868.01 holds significance as a Saturn-sized exoplanet candidate located within the habitable zone of its M-type host star, making it a target for studies of potentially habitable worlds. Its status as a candidate rather than a confirmed planet underscores the ongoing process of exoplanet validation, with the 2026 assessment highlighting it as extremely promising for future confirmation. The planet candidate is also notable for the two unconfirmed features proposed around it: a potential ring system suggested by transit anomalies in 2018, and a possible exomoon identified through transit timing variations in 2015. Both features remain uncertain—the rings are considered unlikely due to limited transit data and likely stellar activity, while the exomoon candidate, KOI-868.01 I, would itself be a habitable-zone object if confirmed. The system thus exemplifies the challenges and opportunities in exoplanet science, where candidate worlds can host multiple proposed substructures that require further observation to verify. Its legacy lies in demonstrating how Kepler data continues to yield intriguing possibilities for ringed planets and exomoons, even when the primary planet remains unconfirmed.

Did You Know?

• KOI-868.01 has an equilibrium temperature of 188 K, placing it within the habitable zone of its star.
• A potential exomoon, KOI-868.01 I, was discovered in 2015 using transit timing variations.
• Hypothetical rings extending up to 88,000 km from the planet's surface would be stable for over 3 billion years.