Search for K2-18b Aliens Finds Nothing
A high-profile search for radio signals from exoplanet K2-18b—previously hyped as a potential "water world" with signs of life—has found no evidence of advanced alien civilization. The negative result follows last year's speculation about the planet's habitability and rules out current radio-transmitting civilizations on the distant world. Scientists continue searching other potentially habitable exoplanets for signs of technological civilizations.
- The initial excitement surrounding K2-18b was sparked by observations from the James Webb Space Telescope (JWST), which detected carbon-bearing molecules like methane and carbon dioxide in its atmosphere. These findings supported the theory that K2-18b could be a "Hycean" world—a planet with a water ocean beneath a hydrogen-rich atmosphere. - Adding to the intrigue was the possible detection of dimethyl sulfide (DMS) in the exoplanet's atmosphere, a molecule that on Earth is overwhelmingly produced by life, particularly marine phytoplankton. However, this finding was met with caution, as subsequent analysis suggested the signal could be attributed to other molecules not linked to biology. - K2-18b is located 124 light-years from Earth in the constellation Leo and orbits a red dwarf star called K2-18. It is classified as a sub-Neptune, with a radius about 2.6 times that of Earth and a mass approximately 8.6 times greater. - The search for technosignatures from K2-18b was a coordinated effort using the Karl G. Jansky Very Large Array (VLA) in New Mexico and the MeerKAT radio telescope in South Africa. - This comprehensive radio search spanned a wide range of frequencies, from 544 MHz to 9.8 GHz, and covered at least one full 33-day orbit of the exoplanet around its star. - The lack of a radio signal from K2-18b is significant because it suggests its host star, K2-18, is remarkably quiet. This low level of stellar activity is favorable for the potential habitability of an orbiting planet, as it would experience less atmospheric erosion from radiation and stellar winds.
