The most "steamy" exoplanet ever discovered: here a year lasts 4 days, there are clouds and its orbit is "counter". Scientists have found a special planet
The alien planet WASP-127b was first observed back in 2009 and observed by more powerful means only in 2016, when scientists began to stroke the hypothesis that it was a kind of "hot Saturn".
This is a gas giant, just like Saturn, that is 525 light-years away from Earth and has a mass similar to that of the planet in our solar system, although engaged in a much tighter orbit around its star.
Il pianeta con le nuvole
I nuovi risultati sullo studio dell’affascinante esopianeta WASP-127b sono stati illustrati nel corso dell’Europlanet Science Congress (EPSC) dal professor Romain Allart delle Università di Montréal e Ginevra.
L’osservazione dell’esopianeta è riuscita grazie alla combinazione di due degli strumenti di osservazione più potenti oggi a disposizione: il telescopio Hubble, che ha ottenuto i dati a infrarossi, e lo spettrografo ESPRESSO installato presso il Very Large Telescope, struttura europea che si trova in Cile.
Scopo delle osservazioni era quello di studiare più da vicino la particolare atmosfera di WASP-127b, ed i risultati sono di stupefacente interesse per la comunità scientifica.
Innazitutto, è stato rilevato che il sodio presente nell’atmosfera del gigante gassoso si trova ad altitudini molto più basse del previsto. The biggest "surprise" for the scientists, however, was the observation of strange water vapor signals perceived by infrared instrumentation but not picked up at visible wavelengths.
As Allart says, the inability to "see" such signals "implies that such vapors at low altitudes are shielded by clouds, opaque and visible at the surface but invisible to infrared."
The presence of sodium so close to the exoplanet's surface, along with the discovery of the "screen" of clouds that would cover WASP-127b, has intrigued the study's authors, who wonder "why the sodium was found in such an unexpected place" but more importantly, what these clouds are.
"We don't know the composition of the clouds," adds Allart, "all we know is that they are not composed of water droplets like on Earth," and that they have a pressure between 0.3 and 0.5 millibars.
On WASP-127b a year lasts 4 days
WASP-127b is not among the favored candidates to host life for a future multiplanetary humanity. Over the course of its orbit, the exoplanet reaches temperatures of more than 1000° Celsius, with a rate of "solar" radiation from its star about 600 times that of Earth.
In addition, WASP-127b is considered one of the most "vaporous" planets - i.e. with a lower density - ever discovered, and its special orbit seems to go "counterclockwise": according to the findings of ESPRESSO, the orbit of the exoplanet would go just in the opposite direction to that of its star, and on a different plane from the equatorial one on which generally orbit the planets of the "ordered" systems.
This and other peculiarities, in addition to being able to provide important answers about exoplanets and the atmospheres of planets outside the solar system, also seem to suggest that WASP-127b is not the only planet in its system. "Such an alignment," says Allart, in fact, "is unexpected for a hot Saturn in an old star system and could be caused by an unknown companion."
The peculiarities of WASP-127b do not end there: in addition to having an "inverted" orbit and presenting an atmosphere full of surprises, the gas giant orbits so close to its own star that a calendar year here lasts four days, and despite having a size greater than that of Jupiter its mass is just one-fifth, compared to the large planet in our system. Indeed, the most "vaporous" planet ever discovered, and one of those that will be studied more closely in the near future, according to Allart.