Context

The European Space Agency (ESA) has formally adopted Ariel, the explorer that will study the nature, formation and evolution of exoplanets. 

About

What is the Ariel Space Mission?

• Ariel is the first mission of its kind dedicated to measuring the chemical composition and thermal structures of hundreds of exoplanets.
• Ariel (Atmospheric Remote-sensing Infrared Exoplanet Large-survey) will perform a large-scale survey of over a thousand exoplanets over a period of four years.
• These thousand exoplanets will range from gas giants to rocky planets, which will help them to compile a list of their compositions and properties thereby providing insights about how planetary systems form and evolve.
• The mission is expected to be launched in 2029.

What are Exoplanets?

• Planets that lie outside of the Solar System and orbit around stars other than the Sun are called exoplanets or extrasolar planets.
• Exoplanets are not easy to detect since they are much less brighter than the stars they orbit and hence it is difficult to see them directly using telescopes.

The numbers As of now the existence of more than 4,000 exoplanets is considered confirmed, while there are thousands of other candidate exoplanets that need further observations to say for certain if they are exoplanets. Proxima Centauri b is the closest exoplanet to Earth and is four light-years away and inhabits the “habitable zone” of its star, which means that it could possibly have liquid water on its surface.

How to track exoplanets?

• As per NASA, only a handful of exoplanets have been found using telescopes and the rest have been detected using indirect methods.
• One of these methods involves tracking the dimming of a star that happens when a planet passes in front of it. NASA’s Kepler Space telescope uses this method to spot thousands of planets.
• Other methods to track exoplanets include gravitational lensing and the “wobbling method”, which is based on the idea that an orbiting planet will cause its parent star to orbit slightly off-centre.

The need of the mission

• According to the ESA, while a large number of exoplanets have already been discovered, there is no clear link between the presence, size or orbital parameters of the planet and the nature of their parent stars.
• Therefore, a large-scale survey that Ariel will perform is required to know more about exoplanets and exoplanetary systems.