JWST discovers Exoplanet’s surface may be covered in oceans

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The James Webb Space Telescope (JWST) has once again proven its prowess in unraveling the mysteries of distant exoplanets.

K2–18 b
An illustration of the exoplanet K2–18 b, which dwells in the habitable zone of its star and is now known to have carbon-based molecules in its atmosphere. (Image credit: NASA, ESA, CSA, Joseph Olmsted (STScI))

In a groundbreaking discovery, the JWST has detected compelling evidence of carbon-based molecules in the atmosphere of K2–18 b, a tantalizing exoplanet residing 120 light-years away from our solar system. This remarkable find has ignited the excitement of astronomers and astrobiologists alike, as it potentially paves the way for uncovering the secrets of life beyond Earth.

K2–18 b: The Hycean World

K2–18 b, with a radius between two and three times that of Earth’s, has long been a subject of fascination for scientists. Its location in the habitable zone of its host star, where conditions are just right to support liquid water, makes it an ideal candidate for harboring life. This region, known as the “Goldilocks zone,” is neither too hot nor too cold, offering the perfect recipe for life to flourish.

The recent observations made by the JWST have unveiled the presence of carbon dioxide and methane in K2–18 b’s atmosphere. Notably, the absence of ammonia is a significant clue, suggesting the existence of a water ocean beneath a hydrogen-rich atmosphere. This finding challenges traditional notions of habitable exoplanets and underscores the importance of exploring a diverse range of environments in our quest to find extraterrestrial life.

Spectrum of K2-18 b, obtained with Webb’s NIRISS (Near-Infrared Imager and Slitless Spectrograph) and NIRSpec (Near-Infrared Spectrograph), displays an abundance of methane and carbon dioxide in the exoplanet’s atmosphere, as well as a possible detection of a molecule called dimethyl sulfide (DMS). The detection of methane and carbon dioxide, and shortage of ammonia, are consistent with the presence of an ocean underneath a hydrogen-rich atmosphere in K2-18 b. K2-18 b, 8.6 times as massive as Earth, orbits the cool dwarf star K2-18 in the habitable zone and lies 120 light-years from Earth. [Image description: The graphic shows the spectra of the exoplanet K2-18 b from NIRISS and NIRSpec in the form of a graph, with the vertical y-axis labelled as Amount of Light Blocked and the horizontal axis labelled as Wavelength of Light (microns). The spectra is plotted as dots with vertical short vertical lines across the plot, with the best-fit model as a blue jagged white line.There are green, yellow and light blue vertical columns of varying thicknesses scattered across the plot indicating where variations in the line represent the presence of methane, carbon dioxide, and dimethyl sulphide, respectively. Behind the graph is an illustration of the planet and star.]

The Enigmatic Sub-Neptunes

K2–18 b belongs to a unique category of exoplanets known as “sub-Neptunes.” These enigmatic worlds, distinct from any planet in our solar system, have baffled astronomers with their unusual characteristics. With a mass approximately 8.6 times that of Earth, K2–18 b occupies a middle ground between our home planet and the ice giant Neptune.

One of the key debates in the field of exoplanetary science revolves around the nature of sub-Neptunes’ atmospheres. The recent research on K2–18 b is poised to shed light on this mystery, providing valuable insights into the atmospheric conditions of such celestial bodies.

The Potential for Alien Life

While the presence of carbon molecules in K2–18 b’s atmosphere is a tantalizing discovery, an even more intriguing possibility looms. The JWST has detected dimethyl sulfide (DMS) in the exoplanet’s atmosphere, a molecule associated with life on Earth, primarily produced by phytoplankton.

However, caution must be exercised in interpreting this finding. The presence of DMS, while exciting, is far from definitive proof of alien life. It could have alternative explanations, and further observations are needed to confirm its significance. The quest for life beyond our solar system remains a complex and challenging endeavor.

Unraveling the Mysteries with JWST

The JWST’s ability to analyze the atmospheres of distant worlds like K2–18 b is a testament to its technological prowess. By carefully observing the planet as it transits its host star, the JWST has deciphered the unique “fingerprint” of chemical elements and compounds in its atmosphere.

This achievement was made possible by the JWST’s extended wavelength range and unprecedented sensitivity, which outperforms its predecessor, the Hubble Space Telescope. In just two transits, the JWST delivered data equivalent to eight Hubble observations conducted over several years.

The Path Forward

As we eagerly anticipate more observations of K2–18 b with the JWST, the ultimate goal remains clear: the identification of life on a habitable exoplanet. Such a discovery would revolutionize our understanding of the universe and our place within it.

In conclusion, the James Webb Space Telescope’s recent findings on K2–18 b have opened a new chapter in our quest to explore and comprehend the cosmos. While the mysteries of this distant exoplanet are far from fully unraveled, each discovery brings us closer to unlocking the secrets of alien worlds.

This research has been accepted for publication in the Astrophysical Journal Letters.


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