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Life Detected on Distant Exoplanet K2-18b
Scientists detect signature of life on a distant planet, study suggests
Context: A team of astronomers has detected what may be the most promising signs of extraterrestrial life on the exoplanet K2-18b, located 124 light-years away. However, the researchers remain cautious and have not declared a definitive discovery of life beyond Earth.
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- The discovery was led by Dr. Nikku Madhusudhan, an Indian-origin astrophysicist and professor at the University of Cambridge.
- Data was collected using NASA’s James Webb Space Telescope (JWST), revealing potential biosignatures in the planet’s atmosphere.
What is K2-18b?
- K2-18b is an exoplanet—a planet that orbits a star outside our solar system.
- It orbits the cool red dwarf star K2-18, situated in the Leo constellation.
- Lies within the habitable zone of its star, where liquid water could potentially exist.
- Approximately 2.6 times the size of Earth and 8.6 times its mass.
- Classified as a sub-Neptune—a type of planet not found in our solar system but believed to have hydrogen-rich atmospheres and possibly liquid water oceans.
Key Findings
- Using JWST’s Near-Infrared Imager and Slitless Spectrograph (NIRISS) and Near-Infrared Spectrograph (NIRSpec) instruments, the team detected:
- Methane (CH₄) and Carbon Dioxide (CO₂).
- Absence of Ammonia (NH₃) — supporting the Hycean planet hypothesis.
- Most notably, a possible signal of Dimethyl Sulfide (DMS) — a molecule on Earth produced only by living organisms, especially marine phytoplankton. NASA emphasised the DMS detection is not yet confirmed and requires further observation.
- The presence of these sulfur-based molecules is consistent with predictions for a Hycean world, a new class of planet theorised to have warm oceans under a hydrogen-rich atmosphere.
Challenges in Interpretation
- Although these molecules have been detected, the possibility remains that they could be produced by non-biological processes. The team is still unsure about the exact source.
- Nikku Madhusudhan, lead author of the study, emphasised that more data is needed to confirm these findings, and follow-up observations over 16 to 24 hours are expected to provide further clarity.
Further Observations and the Road Ahead
- While the detection has reached a three-sigma significance (meaning there’s a 0.3% chance the result occurred by chance), astronomers typically require five-sigma significance (a 0.00006% chance of error) to confirm a scientific discovery.
- The team will conduct follow-up JWST observations within the next 1–2 years to confirm DMS.
- The European Space Agency’s Ariel mission, launching in 2029, will further investigate exoplanetary atmospheres including K2-18b.
Dr. Nikku Madhusudhan
- An Indian-British astrophysicist and Professor at the University of Cambridge’s Institute of Astronomy.
- Academic background:
- B.Tech from IIT-BHU
- MS & PhD in Physics from MIT
- Formerly affiliated with Yale, Princeton, and MIT.
- Awards include:
- 2019 MERAC Prize (European Astronomical Society)
- 2016 Young Scientist Medal (International Union for Pure and Applied Physics)
- Pioneered the concept of Hycean worlds in 2021.
