XO-6b

Lore & Background

XO-6b was discovered in 2016 by the XO planet search team. It orbits the star XO-6, a 10th magnitude F-type main-sequence star in Camelopardalis. The star is too faint to be seen with the naked eye but is visible with a telescope. XO-6 has about 1.30 times the mass of the Sun, 1.4 times its radius, and radiates three times as brightly. It is hotter than the Sun, giving it the typical hue of an F-type star, and rotates rapidly at 43 km/s, unlike most other stars of its kind.

The planet has an orbital period of just 3.8 days and an average orbital separation of 0.082 astronomical units. Due to its close proximity to its host star, XO-6b is highly irradiated, with a surface temperature estimated to be around 1670 K. The discovery paper suggested a very large radius, which would have made it among the largest known exoplanets, but more recent papers, considering measurements of the host star's distance by the Gaia satellite, found the radius to be smaller.

Reader's Guide

XO-6b is significant as a hot Jupiter with an extremely short orbital period of 3.8 days, placing it among the class of highly irradiated exoplanets. Its discovery by the XO planet search team in 2016 added to the growing catalog of transiting exoplanets. The planet's legacy is tied to the refinement of its measured radius: initial estimates suggested it was among the largest known exoplanets, but later work incorporating Gaia satellite distance measurements revised the radius downward. This highlights the importance of accurate stellar distance data in exoplanet characterization. The host star XO-6 is also notable for its rapid rotation (43 km/s), which is unusual for an F-type main-sequence star. The planet's high surface temperature of approximately 1670 K underscores the extreme conditions faced by hot Jupiters in very close orbits. XO-6b remains a target for further study, particularly in understanding the effects of stellar irradiation and the accuracy of planetary radius measurements.

Did You Know?

• XO-6b orbits its star every 3.8 days at a distance of 0.082 AU.
• The planet's surface temperature is estimated to be around 1670 K.
• The host star XO-6 rotates rapidly at 43 km/s, unusual for an F-type star.
• The planet's radius was initially thought to be very large, but later revised downward using Gaia satellite data.