Astronomers have revealed the clearest evidence yet of an atmosphere surrounding a rocky exoplanet outside our solar system, an opening that opens up prospects for understanding the nature and evolution of extreme worlds.
A team led by the Carnegie Institution, using NASA's James Webb Space Telescope, studied 'TOI-561 b', a rocky, extremely hot planet that completes a full orbit around its star in just 10.56 hours.
The surprising presence of an atmosphere on this planet poses a major challenge to old hypotheses about how small, very hot planets evolve, which had suggested they lose their atmosphere quickly after formation.
The size of 'TOI-561 b' is about twice that of Earth, but it is completely different from it. It orbits very close to its star, a distance equal to one-tenth the distance between Mercury and the Sun, which means one side is always illuminated and never experiences darkness.
It was expected that such a small, hot planet would quickly lose its atmosphere. Although the planet's star is much older than the Sun, the planet's atmosphere appears intact, which is partly due to its lower density compared to Earth, but it is not classified among the large, inflated gas giants known as 'puffy giants'.
The team studied whether the planet's low density is due to a small iron core and a lighter mantle, which is consistent with the properties of the host star.
Lead researcher Joanna Teski explained that 'TOI-561 b' is different from other planets with very short orbital periods in that it orbits a very old and iron-poor star.
