Exoplanets are heavenly bodies beyond our solar system where life could be possible.

The search for signs of life in the outside world took humans beyond our solar system and a lot of planets, orbiting different stars, were found there. They are called Exoplanets as they are located outside our solar system. They come in different sizes and orbits. Some of them are rocky while others have ice all over their surface. Some of these gigantic bodies are incredibly close to the host star they orbit. Finding exoplanets is a whole lot more difficult than it looks. They are extremely far and their visibility is billions of times poor than their parent stars.

It happens once in a blue moon that astronomers manage to visualize an exoplanet through a telescope. Most of these bodies are found through the Kepler Space Telescope launched in 2009. Generally, it locates them by monitoring the brightness variations of stars as a planet passes between the star and the telescope. Some other methods used to discover exoplanets include Wobble Method, Gravitational Lensing, and Direct Imaging. It is truly amazing that we know about thousands of exoplanets today considering the fact that the first one was found quite recently in the 1990s. We have more than 3,700 confirmed exoplanets and a lot of potential candidates are being observed to determine whether they can be categorized as exoplanets or not.

A lot of space agencies including NASA are trying to figure out an exoplanet which is about the same size as Earth, orbits a star like our Sun, and lies in the habitable zone of that star. The habitable zone is the range of orbits around a star within which liquid water can exist on the surface of the planets given sufficient atmospheric pressure. This is the most critical condition for supporting life on any heavenly body and the range of favorable distance varies according to the size and temperature of the star.

Normally, planets with rocky cores have more chances to have liquid water on their surface. Initially, only thermal stability was considered while defining the habitable zone of a star but recent calculations involve various factors including the greenhouse effect on the planet.

In August 2016, astronomers found a rocky exoplanet known as Proxima b, which was about 1.3 times more massive than the Earth. It revolves around Proxima Centauri and the name of this world also came from its host star. It is the closest exoplanet to Earth at a distance of 4.22 light years. Its location was also well within the Goldilocks zone of the star as it is 7.5 million kilometers away. The time taken by this planet to orbit the star accounted for 11.2 Earth days.

The researchers concluded that this exoplanet shows only one side of it to the star. This phenomenon is known as ‘Tidally Locked’ and humans have been experiencing that ever since because Moon shows only one of its face to the Earth.

A planetary system known as TRAPPIST-1 has the greatest number of planets (3) inside the habitable zone of a single star outside our solar system. All these planets can support liquid water and that’s the reason why a lot of research is being done as scientists might find some suitable conditions for life there. TRAPPIST-1 is 39 light years away from Earth. The fastest spacecraft that humanity has managed to develop can travel out a maximum speed of 32,000 miles per hour. This means that it will take more than 300,000 years to reach this planetary system.

Scientists were confident about their existence before they were actually detected. Jaymie Matthews, the Mission Scientist of MOST, explained the scientific reason that concreted this idea in their minds. The spinning speed of sun and similar stars should have been much faster than they observed. The reason deduced for slow spinning of the sun was that it had a very strong magnetic field which led to the formation of planets. These field lines did interact with the charged particles of gas all around it.

As a result, the spinning speed of sun slowed down with time as all the momentum was shifted to the spinning gas which resulted in planets. That’s the reason why planets account for 96% of the angular momentum of our solar system. Astronomers applied the same theory to all sun-like stars to conclude that planet formation makes them slow.