Scientists have identified traces of multiple metals, along with possible signs of water, in one of the least dense exoplanets ever found. The team, from the University of Cambridge in the UK and the Instituto de Astrofisica de Canarias (IAC) in Spain used the Gran Telescopio Canarias (GTC) to observe WASP-127b, a giant gaseous planet with partly clear skies and strong signatures of metals in its atmosphere.
WASP-127b has a radius 1.4 times larger than Jupiter but has only 20 per cent of its mass. Such a planet has no analogue in our solar system and is rare even within the thousands of exoplanets discovered to date. It takes just over four days to orbit its parent star and its surface temperature is around 1127 degree Celsius. The observations of WASP-127b reveal the presence of a large concentration of alkali metals in its atmosphere, allowing simultaneous detections of sodium, potassium and lithium for the first time in an exoplanet.
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The sodium and potassium absorptions are very broad, which is characteristic of relatively clear atmospheres. According to modelling work done by the researchers, the skies of WASP-127b are approximately 50 per cent clear. “The particular characteristics of this planet allowed us to perform a detailed study of its rich atmospheric composition,” said Guo Chen, a postdoctoral researcher at IAC. “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,” said Chen.
The planet’s host star, WASP-127, is also lithium rich, which could point to an AGB star – a bright red giant thousands of times brighter than the Sun – or a supernova having enriched the cloud of material from which this system originated. The researchers also found possible signs of water. “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,” said Enric Palle also from IAC. The results demonstrate the potential of ground-based telescopes for the study of planetary atmospheres.