• Kowshika Ravichandran

The Exoplanets!

Have you ever heard about exoplanets? No, I am not talking about the musical band! Exoplanets are one of the interesting topics in Astronomy. Exoplanets revolve around a heavenly body instead of the sun external to our solar system.


Some Exoplanets are at least 100X bigger than the Earth and some are smaller like our moon. The majority of the Exoplanets are primarily made of gases like Hydrogen and Helium. in 1995, the first-ever Exoplanet 51 Pegasi b was discovered by Michel Mayor and Didier Queloz which revolves around a star similar to our sun. Before that, there was evidence for the exoplanet research recorded in 1917 and was not recognized.

The latest discovery in the Exoplanet hunt is TOI – 2076c in 2021 which is a Neptune-like one. The mass is 18X the earth and the radius is 0.396X of Jupiter with 10.4 earth days orbital period. Approximately there may be a trillion Exoplanets. NASA’s Kepler space telescope is mostly used for extrasolar planet discovery.

Nearest ones

The nearest Exoplanet ever found is Alpha Centauri B bin the nearest start system Binary in the size of the earth which is 4.3 light-years away. Xavier Dumusque of the Geneva Observatory and the Porto Portugal university discovered this exoplanet using HARPS.

The second nearest is eps Eridani b at a distance of 10.44 light-years away from the earth. The farthest exoplanets are two, SWEEPS-04 and SWEEPS-11 at 27,700 light-years away from the earth. The naming of the exoplanets is based on the parent star and adding a lowercase letter. The WFIRST also called the upcoming Nancy Grace Roman Space telescope will carry on wide-field imaging and Spectroscopy of the infrared sky.

Other than Kepler’s, there are many space telescopes like NASA’s Spitzer space telescope, Transiting Exoplanet Survey satellite for the discovery of the exoplanets.

How many are they?

Till June 28, 2021, there are 4,438 confirmed Exoplanets found and 6,000 are on the waiting list. The presence of hydrogen and helium on the surface paved the way for the research of super-earth. A super-Earth is an object with a radius range of 1.25 to 2 times the earth radius.

Such found planet named Proxima b is 1.3 times bigger than Earth and 4 light-years away from our earth with a rocky surface. One of the amazing discoveries is TRAPPIST – 1 which consists of seven rocky Earth-like worlds with a potential water surface.


The scientists distinguish exoplanets surface as Neptune-like or gas dwarfs, super-earth, gas giant or super Jupiter’s, terrestrial, and unknown ranging from very rocky to the gas-rich atmosphere. The Exoplanets are very difficult to find. The hot Jupiter’s type exoplanets are easy to find because of their massive size and fast-moving.

There are different methods used to find Exoplanets like the Transit method, Radial velocity, Microlensing, and Imaging method. With a combination of all these methods, we can find information about the Exoplanet like the distance, diameter, surface, and others.

Methods to find

The most successful method of finding is the Radial velocity method which was used to find the 51 Pegasi b where we can find the change in color of the star while orbiting the planet cause wobble in space. But 75.5% of the exoplanets are found by the transit method.

In this method, the star’s light got dull in huge amounts when the planet passes between the star and the observer. The Exoplanets are still in discoveries with the hope of another habitable planet like Earth in our universe. Habitable planets are the planets with liquid water which supports the existence of any life. Till now, only one habitual planet Kepler- 1632b been found.

Pictures of future

The first-ever picture of the exoplanet was taken in 2004 of the planet 2M1207b. The strangest exoplanets are many where in HD 189773b, 64 light-years away it rains glass in sideways. 55 Cancri e is a planet with an interior made of diamond with 2,700’c. Research about exoplanets is very important to find life in other worlds.

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