USA: In our quest to find other planets that might harbour life, we could be just around the corner from a significant advancement.
The James Webb Space Telescope (JWST) was used by astronomers to observe water vapour in the vicinity of a far-off rocky planet. The presence of water vapour could be an indication that the extrasolar planet, or exoplanet, has an atmosphere. This finding could be crucial in the quest to find habitable planets beyond our solar system. However, the discovery's researchers warn that rather than the planet itself, this water vapour could be coming from the planet's host star.
"Water vapour in an atmosphere on a hot rocky planet would represent a major breakthrough for exoplanet science," said Kevin Stevenson, the lead researcher and researcher at the Johns Hopkins University Applied Physics Laboratory. But we must exercise caution and make sure the star is not the offender.
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The exoplanet, known as GJ 486 b, revolves around a red dwarf star in the Virgo constellation that is 26 light-years away. Despite being less than a third the size of Earth, it has three times the mass of our planet. GJ 486 b orbits its star in less than 1.5 Earth days and is likely tidally locked to the red dwarf, which means it always presents the same face to its star.
Given that red dwarf stars, like the parent star of GJ 486 b, are the most prevalent type of stars in the universe, rocky exoplanets are statistically more likely to be discovered orbiting red dwarf stars.
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Because red dwarf stars are cooler than other types of stars, a planet must orbit them closely in order to stay warm enough to support liquid water, a crucial component required for life. However, when red dwarfs are young, they also emit a powerful and violent ultraviolet and X-ray radiation that could potentially destroy the atmospheres of nearby planets, making them extremely inhospitable to life.
In light of this, astronomers are now eager to learn whether a rocky planet in such a harsh environment could manage to both form an atmosphere and then hang on to it long enough for life to take hold, a process that took place on Earth over a billion years ago.
The team used the JWST and its Near-Infrared Spectrograph (NIRSpec) instrument to observe GJ 486 b as it crossed, or transited, the face of its star in an effort to find an answer to this question. Even though the planet's temperature is 800 degrees Fahrenheit (430 degrees Celsius), making it unfavourable for liquid water, and it is extremely close to its star, the astronomers found evidence of water vapour.
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From our vantage point, GJ 486 b transits its star, which means that when it is in front of the red dwarf, starlight passes through the exoplanet's atmosphere. Looking at the light coming from the planet during a trip around its star can reveal what its potential atmosphere is made of because different elements and chemical compounds absorb and emit various wavelengths of light that enable them to be identified. This process of looking for these chemical traces in starlight that has been filtered by the atmosphere is known as "transmission spectroscopy."
Two transits of GJ 486 b, each lasting an hour, were observed by the astronomers using the JWST. The data was then analysed using three dispersed techniques, all of which revealed the same pattern: a flat spectrum with an intriguing peak in short-wave infrared light. They came to the conclusion that water vapour was the peak's most likely origin.
