2023-05-03 12:45:28
From a geological point of view, rocky-type planets, like Earth, are prime candidates for hosting life as we know it. Considering that the most common stars in the universe are red dwarfs, it can be deduced that quite a few rocky planets must be orbiting stars of that type.
Red dwarfs are cooler stars than the other types. For this reason, in order for a rocky planet to receive the ideal heat that allows it to have liquid water on its surface, it must orbit around the red dwarf from a smaller distance than the one that separates other rocky planets from their stars with higher temperatures. .
Red dwarf stars also tend to experience bursts of activity, especially when they are young, releasing bursts of ultraviolet and X-ray radiation that could destroy planetary atmospheres. As a result, an important question that has long awaited an answer is whether a rocky planet orbiting a short distance from a red dwarf could maintain or restore an atmosphere in such a hostile space environment.
To help answer that question, Sarah Moran’s team at the University of Arizona in Tucson used the James Webb Space Telescope to study a rocky planet known as GJ 486 b. In this case, it is too close to its star (a red dwarf) for liquid water and other conditions necessary for life to exist on its surface. The temperature that reigns on its surface is about 430 degrees Celsius. And yet, observations with Webb’s Near Infrared Spectrograph (NIRSpec) show hints of water vapor.
If water vapor is on the planet, that would indicate that it has an atmosphere despite its scorching temperature and proximity to its star. Water vapor has already been observed on exoplanets (planets outside our solar system) of the gaseous type, but no atmosphere around a rocky exoplanet had been unequivocally detected to date.
Artist’s impression of the planet GJ 486 b. (Image: NASA, ESA, CSA, Joseph Olmsted (STScI))
However, as the team warns, the water vapor might not come from the planet at all, but rather be on the star itself, specifically in some areas with lower temperatures than other regions.
GJ 486 b is 30 percent larger than Earth and three times as massive, meaning it is a rocky world with stronger gravity than Earth. It takes a little less than a day and a half to go around its star completely. It is believed that, due to its close proximity to the star, it has synchronized its rotation with its translation, in such a way that it always has the same side exposed to the sun and another on which the sun never shines. In other words, in one hemisphere it is always day, while in the other it is always night.
This solar system is only 26 light-years away from Earth, in the constellation Virgo.
An atmosphere on a planet that receives so much heat from its star is doomed to slowly dissipate. Therefore, if GJ 486 b has an atmosphere, it must be subject to constant erosion and can only be maintained if it is replenished by volcanoes that expel gas (including water vapor) from the interior of the planet.
Future observations by the Webb Space Telescope could provide new, perhaps revealing, data about this planet and its star.
The James Webb Space Telescope (JWST) is the result of an international collaboration led by NASA, ESA and CSA, respectively the US, European and Canadian space agencies. (Fountain: NCYT de Amazings)
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