Detecting signs of life on exoplanets beyond our solar system is a complex task. Some methods include:

1. Biosignatures in Atmospheres:
   We study exoplanet atmospheres for specific gases (by transit spectroscopy, etc) that could indicate life.
   • Oxygen (O₂): Oxygen is produced by photosynthetic organisms. Detecting abundant oxygen could suggest biological activity.
   • Methane (CH₄): Methane can be produced by microbes or geological processes. Nitrous Oxide (N₂O) is used in microbial activity.
   • Water Vapor (H₂O) and Carbon Dioxide (CO₂) are essential for life and photosynthesis.
2. Fluorescence and Reflectance:
   Some organisms exhibit fluorescence when exposed to UV light. Detecting such fluorescence from an exoplanet could be a sign of life. Analyzing the reflected light spectrum can reveal unique signatures related to pigments or biological processes.
3. Temporal Variations:
   Seasonal changes or irregular patterns in light (due to vegetation growth, ocean currents, etc.) might indicate life cycles.
4. Technosignatures:
   We look for artificial signals (techno-signatures) like radio waves, laser emissions, or megastructures (e.g., Dyson spheres).

Obstacles:

• Distance: Exoplanets are located at a distance of light-years, which makes it challenging to conduct detailed observations.
• False alarms: Non-biological activities can imitate signs of life.
• Current telescopes do not have enough sensitivity to definitively detect what is needed.