Astronomers Discover a “Intermediate” Exoplanet 138 Light-Years Away That May Be Water-Laden and Transforming.
According to research published on arXiv, the new planet, named HD 207496b, orbits the dwarf star HD-207496 with an orbital period of just 6.44 days. It has a radius 2.25 times that of Earth and a mass over 6.1 times greater, Science Alert reported on March 13.
Simulation of a water-laden exoplanet surface. (Image: Darryl Fonseka).
Astronomers found HD 207496b using NASA’s Transiting Exoplanet Survey Satellite (TESS), then employed the High-Accuracy Radial Velocity Planet Searcher (HARPS) on the 3.6-meter telescope at La Silla Observatory in Chile for further examination.
They discovered that this exoplanet has a density of approximately 3.27 g/cm3, placing it between gas giants like Neptune (1.64 g/cm3) and rocky planets like Earth (5.51 g/cm3). This suggests that HD 207496b is not entirely rocky.
“HD-207496b has a significantly lower density than Earth, and therefore we believe it contains a large amount of water, gas, or both in its composition,” the research team stated in their report. “By modeling its internal structure, we conclude that this planet has a water-rich, gas-rich crust, or a mixture of both.”
Simulation of HD-207496b having its gas layer stripped away by its host star. (Image: ESA/NASA).
Evaporation modeling reveals that if HD-207496b has a hydrogen and helium-rich atmosphere, that state may be temporary, as its host star is expected to “completely strip” the exoplanet of its atmosphere within the next 520 million years. It is also possible that the atmosphere of HD-207496b has entirely vanished, and HD-207496b is currently a bare ocean world.
The host star HD-207496 is relatively young, estimated to be only a few hundred million years old, which means it represents a rare opportunity to study the exoplanet in its early stages before transforming into a super-Earth.
In the next phase of research, astronomers aim to further describe the atmosphere of HD-207496b, if it exists. This may reveal the true nature and ultimate fate of this mysterious world.
