WASP-127b is a peculiar planet for a lot of reasons. It is a puffy hot super-Neptune that orbits its star in about four days. It has 1.4 times the radius of Jupiter but only one-fifth of its mass, making it the least dense exoplanet ever found. There is no analog in our Solar System for it, and it's even considered rare among exoplanets. New observations have revealed that the planet also has a very interesting atmosphere.
As reported in Astronomy & Astrophysics, an international team has found the fingerprints of several alkali metals such as lithium, sodium, and potassium. Some of these metals have never been detected before in an exoplanet. The observations have also shown another important feature. The planet must have a clear atmosphere and cloud cover that only extends to about 50 percent.
"The particular characteristics of this planet allowed us to perform a detailed study of its rich atmospheric composition," first author Dr Guo Chen, from the Instituto de Astrofísica de Canarias (IAC), said in a statement. "The presence of lithium is important to understand the evolutionary history of the planetary system and could shed light on the mechanisms of planet formation."
The presence of lithium is not unsurprising. The exoplanet’s host star WASP-127 is lithium rich, a fact that gives astronomers a few ideas about its nature. The star is over twice the age of the Sun and it might have already evolved into a special type of red giant. Alternatively, the extra lithium might come from a nearby supernova explosion. The team might have also seen a hint of water in the data but it’s too early to tell.
"While this detection is not statistically significant, as water features are weak in the visible range, our data indicate that additional observations in the near-infrared should be able to detect it," explained co-author Enric Pallé, also from IAC.
The observations were conducted from ground-based telescopes in La Palma, in the Canary Islands. "The detection of a trace element such as lithium in a planetary atmosphere is a major breakthrough and motivates new follow-up observations and detailed theoretical modeling to corroborate the findings," said co-author Dr Nikku Madhusudhan from Cambridge's Institute of Astronomy.
Planet-hunting telescope TESS is currently in orbit and the James Webb Space Telescope, which will (hopefully) fly in the next few years, can provide corroboration on the current findings and see even further into this exoplanet’s weird atmosphere.