The Second Earth

              Is there a second earth? That is a habitable planet to the earthlings? Scientists are searching for several decades and never found a solid answer. But some credible news comes out from National Aeronautics and Space Administration (NASA), European Space Agency (ESA) and other space agencies that they are succeeding to find a second earth.

              Last year, Nasa has announced that it has found an extraordinarily similar planet to Earth orbiting around a distant star. The planet named, Kepler-452b, is described as a larger, older Earth  and  is located around a star 1400 light years from Earth. It is the 

first terrestrial planet found in the habitable zone in a star just like our sun. Nasa said it is about 60 percent larger than Earth and lies in the constellation Cygnus.

            The exact nature of the planet is not known specifically, but Nasa's modelling suggesters it is a rocky planet, about five times as massive as Earth, orbiting its star once every 385 days. The planet's star is 1.5 billion years older than our own, and is now growing hotter and brighter -- as our star will do in about a billion years.

            Nasa also announced that 521 new  exoplanet candidates had been discovered, 

12 of which have diameters between one and two times Earths, and orbit in their star's habitable zone. Nine orbit stars similar to ours in size and temperature. Exoplanets, especially small Earth-size worlds, belonged within the realm of science fiction just 21 years ago.

         Also Germany’s European Southern Observatory announced the discovery of a new habitable planet. The new world is just slightly bigger than Earth and sits about four light years away, orbiting Proxima Centauri. That star is the nearest one to our solar system. The planet, known as Proxima b, is close enough that future generations of space craft might be able to travel there, taking robotic probes with them. Eventually it could even be close enough to become a new home for travellers from Earth

            Proxima b is far closer to its star, taking just 11.2 days to complete one orbit and sitting only 5% as far away from its star as we do from ours. But because that star is much dimmer, it is still within the habitable zone where there could be water on the planet – and, as a consequence, life. 

      But there are other issues with Proxima b, the star pelts its planet with powerful  ultraviolet rays and X-rays, which would mean that anything  living  there would  find it  much harder and so would have  to  become hardened  against 

that radiation.

         The planet is thought to be in the star's 'habitable zone' - an area around a star in which an orbiting planet's surface could hold liquid water.  For humans to survive we need oxygen, therefore any planet which does not have oxygen would be unsuitable for us to live on. We also need a supply of water. We need water for many reasons such as to grow food or for other animals. We need a certain amount of sunlight and we need a planet which is neither too hot nor too cold. A planet with stable temperatures between 0C and 40C would be suitable.  We also need an atmosphere to shield off the harmful rays from the sun. Below the different planets in our solar system are considered whether they fulfill the basic requirements for life.


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