The Art of Cosmic Chemistry
Imagine trying to figure out the ingredients of a cake just by smelling it from across a massive room. That's essentially what astronomers are doing, but on a cosmic scale. Using powerful tools like the James Webb Space Telescope (JWST), scientists are analysing
the light that passes through the atmospheres of exoplanets—planets orbiting other stars. This technique, called spectroscopy, splits starlight into a rainbow of colours, revealing a barcode of chemical information. When a planet passes in front of its star, certain chemicals in its atmosphere absorb specific colours of light, leaving dark lines in the spectrum. These lines are the chemical fingerprints that tell scientists what an alien world's air is made of.
Reading a Planet's Biography
An atmosphere is not just a random collection of gases; it's a direct link to a planet's past and present. The chemical mix can reveal how and where a planet formed. For example, the presence or absence of certain molecules can indicate whether a planet was born in a cold, distant orbit or a hot, close one before migrating. It tells a story of volcanic activity, geological processes, and even the potential for oceans. A recent study of the lava planet 55 Cancri e, for instance, found a hydrogen-rich atmosphere, likely supplied by gases escaping from its molten rock interior. This challenges older models and suggests a much more dynamic, evolving world, where volcanic outgassing shapes its environment.
From Rocky Worlds to Gas Giants
The diversity of exoplanets is staggering, and so is the diversity of their atmospheres. Some planets, like 'hot Jupiters', are gas giants orbiting perilously close to their stars, with atmospheres revealing exotic clouds made of silicate minerals—essentially, sand. Others are rocky super-Earths. In a major breakthrough, scientists recently confirmed the first atmosphere around a rocky planet in its star's habitable zone, on a world called LHS 1140 b. Its helium-rich atmosphere shows that even planets around volatile red dwarf stars can hold onto their air for billions of years, a crucial factor in the search for stable, potentially life-bearing worlds.
India's Contribution to the Search
This global quest has significant Indian involvement. Scientists at institutions like the Physical Research Laboratory (PRL) in Ahmedabad and the Indian Institute of Astrophysics (IIA) in Bangalore are at the forefront of exoplanet discovery and characterisation. Indian astronomers have developed innovative methods to improve data accuracy, creating algorithms to filter out noise from Earth's atmosphere and instruments, which helps in studying exoplanet environments with better precision. Using indigenous facilities like the PARAS spectrograph at Mount Abu, Indian teams have discovered several exoplanets, including a massive planet 13 times the mass of Jupiter, contributing vital pieces to the giant puzzle of planetary formation.
