Rare: astronomers observe a hot Jupiter migrating towards its star

A new type of giant gas planet, with an elliptical and retrograde orbit, could upend our understanding of "hot Jupiters." Discovered using NSF's 3.5-meter WIYN telescope, the exoplanet named TIC 241249530 b exhibits unique orbital characteristics, suggesting a fascinating future trajectory.


Currently, more than 5,600 exoplanets have been confirmed. Among them, 300 to 500 are "hot Jupiters," large gas planets orbiting very close to their star. The discovery of TIC 241249530 b, which follows an extremely stretched orbit and in the reverse direction of its star's rotation, offers a new perspective on the formation and evolution of these planets.

The initial observations were made thanks to NASA's TESS satellite, detecting a drop in starlight. Astronomers then used the WIYN telescope and its instruments NESSI and NEID to confirm and analyze these variations, revealing the nature of the exoplanet.

Spectral analysis confirmed that TIC 241249530 b is about five times more massive than Jupiter and follows an orbit with an eccentricity of 0.94, one of the highest ever recorded for a transiting planet. This unique behavior implies extreme temperatures, ranging from those of a summer day to hot enough to melt titanium.


The retrograde motion of this exoplanet, meaning its orbit is in the opposite direction to its star's rotation, is rare and sheds light on its formation history. The tidal forces of the star should gradually circularize its orbit, providing crucial insight into the stabilization and evolution of hot Jupiters.

Arvind Gupta, a postdoctoral researcher at NOIRLab and the study's lead author, highlights that TIC 241249530 b, with its unique nature, allows for a better understanding of the migration process of giant gas planets towards tighter and more circular orbits.

With only two known examples of this pre-migration phase of hot Jupiters, this discovery supports the idea that giant gas planets evolve towards closer and circular orbits, providing valuable data for astronomers.