NASA's Webb detects water vapor but source remains a mystery
NASA's James Webb Space Telescope (JWST) has detected hints of water vapor but researchers are not sure, as yet, if the signals are from a rocky planet or the star it orbits. The exoplanet, GJ 486 b, lies too close to its host star to have an atmosphere, but Webb's finding suggests the opposite—challenging everything we know about exoplanets and their atmospheres.
Here's a little bit about the rocky world
GJ 486 b is roughly 30% larger than Earth and three times as massive, which means its gravity is stronger than that of Earth. The exoplanet is orbiting a red dwarf star, which is the most common type of star found in the universe. It completes an orbit around its host star in less than 1.5 Earth days.
GJ 486 b's surface temperature is about 430 degrees Celsius
If the water vapor signals detected by Webb were from GJ 486 b, it suggests that the exoplanet has an atmosphere in spite of its high surface temperature, roughly 430 degrees Celsius, and its close proximity to its host star. Water vapor has been seen on gaseous exoplanets before, but till now, "no atmosphere has been definitely detected around a rocky exoplanet," said NASA.
We can't tell if water from the planet's atmosphere: Moran
"We see a signal, and it's almost certainly due to water," said Sarah Moran of the University of Arizona in Tucson, lead author of the study. "But we can't tell yet if that water is part of the planet's atmosphere, meaning the planet has an atmosphere, or if we're just seeing a water signature coming from the star."
The exoplanet experiences heat and radiation from its host star
If the planet has a water vapor-containing atmosphere, it is expected to erode due to the heat and radiation arising from its host star. This implies that the planet's atmosphere would have to be "constantly replenished by volcanoes ejecting steam from the planet's interior," explains NASA. But how much water vapor is present in the planet's atmosphere? That's something only further observations can tell.
If the exoplanet has an atmosphere, it'll be "major breakthrough"
"Water vapor in an atmosphere on a hot rocky planet would represent a major breakthrough for exoplanet science," said Kevin Stevenson, from Johns Hopkins University Applied Physics Laboratory. "But we must be careful and make sure that the star is not the culprit."
Water vapor can exist on the Sun's cool starspots
It's equally possible that the water vapor signals are from the planet's host star. Even on our Sun, water vapor can exist in sunspots because such spots are "very cool compared to the surrounding surface of the star." GJ 486 b's host star is way cooler than the Sun, so much more water vapor can accumulate in its starspots.
Future observations can help gain a better understanding
Further studies may provide insights into Webb's findings of the water vapor signals. Observations carried out at shorter infrared wavelengths by Webb's onboard instrument, the Near-Infrared Imager and Slitless Spectrograph (NIRISS), can help differentiate between "the planetary atmosphere and starspot scenarios."
