Mysterious ‘Phoenix’ world challenges theories of planetary evolution

Astronomers have discovered an unusual exoplanet that has managed to maintain its atmosphere despite intense nearby radiation from a giant red star.

Researchers at Johns Hopkins University found that the rare planet, which should have been stripped to rock by radiation from its nearby host star, instead developed a puffy, less dense atmosphere.

The planet, nicknamed ‘Phoenix’ for its ability to survive, has sparked debate among scientists about how planets can adapt to extreme environments over time. In about 5 billion years, our own sun will turn into a red giant – a dying star in the final stages of stellar evolution – and expand, engulfing Earth.

Sam Grunblatt, an astrophysicist from Johns Hopkins University who led the study, said Newsweek: “Planets like Phoenix give us a glimpse into the final stages of a solar system that may once have looked similar to ours.

“Current understanding of the future evolution of Earth’s atmosphere suggests that as the Sun evolves into a red giant, it will strip most or all of the planet’s atmosphere before eventually engulfing the entire planet.”

However, this study suggests that Earth’s atmosphere may be more resilient than previously thought.

“The Earth can survive until and even beyond the beginning of the planet’s engulfment, and can also swell in the process,” Grunblatt said. “This also suggests that the timing of other stages of Earth’s atmospheric evolution may occur later than expected, or in a different order than models currently predict, which could have major implications for the longevity of life on Earth and beyond. “

The newly discovered planet, officially named TIC 365102760 b, was found using the TESS space and WM Keck Observatory telescopes. It is about 6.2 times larger than Earth and completes an orbit around its parent star – a giant red star that emits enormous amounts of radiation – every 4.2 days.

According to the team that found Phoenix, the planet won’t survive more than 100 million years before it begins to die by spiraling toward its giant star.

Phoenix is ​​classified as a ‘hot Neptune’ because it is similar to the planet – the planet farthest from the Sun in our solar system, and therefore experiences subzero temperatures – despite being much hotter. It is about six times closer to its own star than Mercury is to the Sun.

So-called “swollen” planets are less dense than others in the solar system and are made of gases, ice or other light materials. According to the study, these types of exoplanets are very rare and only 1 percent of stars have them.

They are more difficult to discover due to their small size, compared to larger, denser planets. The newly found Phoenix is ​​smaller, older and hotter than scientists thought possible for this type of exoplanet. It is 60 times less dense than the closest ‘hot Neptune’ yet discovered.

However, the planet’s high temperature and low density may have allowed it to survive the radiation from its parent star. According to the researchers, the process of stripping the atmosphere must have occurred at a slower pace than scientists thought possible.

Grunblatt said: ‘Hot Neptunes are thought to be rare due to the process of photoevaporation, or the stripping of a planet’s atmosphere by high-energy radiation given off by the planet’s host star.

“Hot Neptunes are difficult to detect because they are generally rare for the reason described above, and the signal from a hot Neptune is not as large as a signal from a hot Jupiter,” he explained.

“Since the signals from all planets around giant stars are smaller, this means that detecting a hot Neptune around a giant star is akin to detecting an Earth-sized planet around a Sun-like star, and thus right on the edge of detectability lies with the current flow.” technology.”

The full findings of the study have been published in The astronomical magazine.