Are we alone, Is there a life beyond the earth? Does Alien exist? These are the question humans have wondered about for millennia and one that people still have strong opinions about though there isn’t definitive evidence to answer the question one way or the other.
First, understand What is a galaxy
It is a collection of stars and gas that are held together in a gravitationally bound system. Every point of light that you see here is a star. When we say 200 billion stars, it is probably at least 200 billion stars. The galaxy is 100,000 light-years across. So the distance is unimaginable. One light-year is 10 trillion kilometers.
So an exoplanet is simply a planet that orbits a star than the sun. Exo means external, outside. Means outside our solar system. It’s just a planet.
Overall we know of over 800 planets that have been confirmed and another probably 2000 planets that are waiting for information, but they pretty strong candidates. So we don’t see the planet directly, we see its impact on the star that it orbits. We do it from the earth with an angle through the Australian Telescope and we look for the wobble of the stars as the planet orbits it.
The planet goes around and the star moves backward and forwards.
To find smaller planets NASA launched Kepler, a one-meter telescope with a 95-megapixel camera. Its mission is to observe 130,000 stars in our galaxy and look or dips in brightness caused by the planet passing in front of them.
Is there a life beyond the earth?
The probability is very high. Because there are at least 200 billion stars in our galaxy. We know that on average there is at least one planet per star in our galaxy alone and there are another 100 plus billion galaxies in the universe.
In the galaxy, 33 billion potential earth sized planets. Not all of them are going to be able to have life. But the probability is high at this stage. So there is no definitive evidence that alien life exists. But there are many chances that aliens must be out there somewhere.