Ringed planet candidate near Boyajian's star explains unusual size measurements

A giant planet candidate orbiting Boyajian's star appears significantly larger than theoretical models allow. By analyzing light curve data, researchers suggest that the object is not inherently oversized but instead surrounded by an extensive, opaque system of rings. This ringed structure accounts for the unusual transit depth and aligns with the star's history of irregular brightness dips caused by dusty debris.

Star system: KIC 8462852 A | Distance from the Sun: 1470 light years

Boyajian's star, also known as Tabby's star, is famous for its mysterious and irregular dimming events. A giant planet candidate orbiting this star recently presented a new puzzle: its measured radius is nearly 70 percent larger than standard models predict for a planet of its mass. Such a large size contradicts our understanding of how cool giant planets should behave, as they are typically expected to have physical dimensions similar to that of Jupiter.

To address this anomaly, researchers tested the hypothesis that the planet is surrounded by a vast ring system. By developing specialized software to model how light changes as a ringed object passes in front of a star, they re-examined data from the Transiting Exoplanet Survey Satellite (TESS). This model shows that the planet is likely a Jupiter-sized body enveloped by an opaque, flattened ring extending to over three times the planet's radius. This structure accounts for the extra depth observed during the planet's transit, effectively resolving the size discrepancy.

The existence of such a ring is consistent with the environment around Boyajian's star, which is known for hosting clouds of dust and debris. The ring potentially represents material orbiting the planet, reaching out to its Roche limit, which is the distance where a planet's gravity is strong enough to keep orbiting debris from being pulled away. This configuration suggests that the planet's unusual transit profile is a result of geometry and surrounding material rather than the planet being physically expanded.

Key findings
The giant planet candidate has a measured radius of 1.7 times that of Jupiter, which is inconsistent with standard physical models for its mass.
A ring model suggests the companion is actually a Jupiter-sized planet, measuring 1.1 times the radius of Jupiter.
The planet features an opaque, highly flattened ring system extending 3.1 to 4.4 planetary radii.
The ring orientation is nearly polar, providing a geometric solution to the previously reported radius anomaly.
This discovery aligns with the existing understanding of Boyajian's star as a system surrounded by significant amounts of dusty debris.

Scientific study

The anomalously large transiting planet around Boyajian's star: evidence for a circumplanetary ring (external link)