The Planet Toi-1227b is a cosmic newborn of “only” eight million years, his orbit too close to a killer star is exposing him to lethal radiation.
Stars and planets are linked by a gravitational relationship which, in most cases, maintain them united in ordered solar systems. But it does not always go like this: some planets end up getting too far from their star or approach dangerously, with often catastrophic results. It is in these exceptions that astronomers find precious clues to understand The evolution of the exoplanetsthat is, the planets that revolve around other stars.
In recent years, The exploration beyond the Solar System has revolutionized our vision of the cosmos: with about 6,000 exoplanets discovered so far, we have understood that our planetary system is not representative. There are worlds with characteristics and orbits that challenge our models. One of these is toi-1227b.
A giant young man in crisis. Discovered in 2022 thanks to the data of the NASA satellite Tes, Toi-1227b is a gaseous giant of the size of Jupiter but with a mass equal to only 20% of that of ours. Orbit around a red dwarf (a small relatively cold and not very bright star, which slowly burns hydrogen and can live for billions of years) – technically an M star – about 330 light years from the earth.
But it is not its structure that intrigues scientists, but its age: Only eight million years. A cosmic newborn, The second youngest exoplanet ever observed in transit in front of your star. Unfortunately, this young planet is facing an existential crisis. His extremely close orbit – only a fifth of the distance between Mercury and the sun – exposes it to one lethal dose of radiation. The dwarfs, in fact, are known for their restless behavior: due to their completely convective nature, they generate powerful magnetic fields and brilliant that releases intense X -rays.
A “killer” star. “The atmosphere of the planet simply cannot bear the high dose of X -rays that he receives from his star,” said Attila Varga, the main author of the study being published on The Astrophysical Journal and already available on Arxiv.org.
The observations conducted by the team, including optical spectroscopy and X -ray imaging, confirmed that Toi-1227b is losing atmospheric mass at an impressive rhythm: about one million tons per second, or two terrestrial atmospheres every two centuries. If the situation does not change, In a billion years the planet could completely lose its atmosphere.
How a planet disappears. The process of atmospheric erosion in place on Toi-1227b is linked to several Mechanisms triggered by X -rays.
The affected molecules are ionized and heated, increasing the temperature of the atmosphere up to thousands of degrees. The atmosphere expands and, reaching a certain threshold, can begin to escape the severity of the planet. In addition, X -rays can break molecules such as water, freeing hydrogen which, being light, disperses easily in space. The stellar wind also plays a role: heated by radiation, acquires sufficient energy to contribute to the dispersion of the atmosphere.
“A crucial aspect to understand the extrasolar planets is to consider the effect of high energy radiation, such as X -rays,” underlines Joel Kastner, co -author of the study. «We believe that Toi-1227b is a planet ‘swollen’ precisely because of the continuous assault of its star».
Planetary evolution. Toi-1227b represents a unique test bench to understand how planetary atmospheres are formed and destroyed. His future appears uncertain: according to Alexander Bings, co -author of the University of Tinginga, the planet could be reduced to a tenth of its current dimensions, losing over 10% of its mass – even if these estimates depend on variables still little known, such as the actual mass of the planet.
Photoevaporation. The case of Toi-1227b is particularly relevant also for another reason: He could help to explain a mysterious “gap” in the distribution of the exoplanets. Previous observations have in fact shown that the planets with rays between 1.5 and 2 times the terrestrial one are unusually rare. One of the hypotheses is that photoevaporation, such as the one in place on Toi-1227b, play a decisive role in the downsizing of these celestial bodies.
“The Toi-1227 system is a fundamental reference point to understand the very first phases of the planetary evolution around small stars”, concludes the researchers. “Subsequent control observations will be needed, both spectroscopic (analyze the light emitted or absorbed by an object to identify their chemical composition, temperature, speed and movements), both photometric (measure the brightness of a celestial object over time or in different wavelengths), To refine our understanding of its mass and atmospheric loss rates».