The Mysterious Planet HD 63433d Exhibits Two Distinct Faces, Orbiting a Sun-like Star.
According to Sci-News, HD 63433d has garnered attention in data from NASA’s “Exoplanet Hunter” TESS due to being an Earth-sized rocky planet orbiting a sun-like star.
The HD 63433 star system with HD 63433d, the planet closest to its parent star, is tidally locked – (Photo: NASA)
HD 63433d is the third planet discovered in this star system. Its “siblings” include HD 63433b and HD 63433c, both classified as sub-Neptunes, which are planets similar to Neptune in our solar system but smaller.
Sub-Neptunes are a type of planet found to be quite common in other star systems.
However, the recent discovery of HD 63433d is particularly intriguing. It is the closest planet to its parent star, with an orbital period of just 4.2 days, and it is a “two-faced” planet.
This means that HD 63433d is so close to its parent star HD 63433 that it is tidally locked to this celestial body, similar to how the Moon is tidally locked to Earth.
As a result, HD 63433d has one side always facing the parent star, experiencing perpetual daytime, while the opposite side endures eternal night.
A research team led by astronomer Benjamin Capistrant from the University of Florida (USA) reported that its daytime side reaches temperatures of up to 1,257 degrees Celsius, potentially resembling a lava hemisphere.
This planet is also quite young—only about 500 million years old—and so is its parent star. Therefore, it presents an exciting target for studying how a planet can evolve over a billion-year period since its formation.
Worlds like HD 63433d are a primary target for the TESS spacecraft, a small satellite tasked with searching for a “second Earth.” Among all criteria, Earth-like size is the foremost factor that brings an exoplanet into NASA’s focus.
Not every planet that resembles Earth in this way—rocky and of similar size—may harbor life, but all provide essential data to develop better methods for screening for habitable planets.
Moreover, we cannot be certain about everything. Even a “half Earth, half hell” world like HD 63433d still has a small probability of harboring life.
A recent study from the University of California Irvine (UCI – USA) suggests that tidally locked planets like this may host “twilight life” in the regions where the day and night sides meet.
