There are about 400 billion stars in our Milky Way galaxy, we can only see a small fraction of them in our night sky. Not all of these stars will have planets, but a lot of them do. The Milky Way isn’t even considered a big galaxy, and there are around 100 billion other galaxies, each with countless stars and who knows how many planets. With so many planets, it is almost impossible that there isn’t another one with life out there.
The requirements for life
Scientists have made lists of requirements for life on other planets. The first thing on the list is temperature. The planet needs to be at a certain distance from its star where the temperatures allow life. Too close, and everything will burn. Too far, and it’ll be way too cold to stay alive. There are a lot of planets found by our telescopes that find themselves in this habitable zone, but that doesn’t mean there is life on them. The planet also needs an atmosphere. Without an atmosphere a planet will not have any nutrients. Methane is a good example. Our atmosphere has methane. This can produce carbohydrates and fats, crucial nutrients in the diets of life on our planet.
On Earth, we only know carbon based life so we kind of assume that on other planets water will also be very important. Water is used in so many chemical reactions that it is pretty much impossible to imagine life without it.
As mentioned in this article, life consists mainly of hydrogen, carbon, oxygen, nitrogen. These elements all come from outer space. When a star dies, these elements get spread around in the universe. They don’t only reach Earth, they reach all the other planets in the habitable zone as well.
How to find livable planets
NASA has been on the search for habitable planets for a while now. Looking for an exoplanet, a planet that resembles Earth enough for it to possibly contain life, is really like looking for a needle in a haystack. First the telescopes and satellites will have to find stars with planets. We look at stars with our telescopes and if the light slightly changes, it is likely that a planet orbited in front of it. Then those planets will have to be in the habitable zone. And even then it’s not guaranteed there will be life.
So we need technology to find these, but NASA tells us there is something else we need more than anything: luck. Since there are only so many stars we can look at at the same time, it is a matter of luck if one of those has a planet that might contain life.
Earth 2.0, or our cousin
At the moment, our biggest bet of finding life is resting on the shoulders of a planet called Kepler-452b, or Earth 2.0 as some call it. This planet is orbiting a sun-like star called Kepler-452 in the constellation Cygnus. Kepler-452b is a planet only 1.6 times as big as the Earth, finding itself in a habitable zone of its star.
Even if we discover life on Kepler-452b, it will be difficult to get in touch with those aliens, as the star around which Kepler-452b orbits is about 1400 light years away. With the technology we have today, it would take a satellite roughly 26 million years to get there.
So with all the stars and planets out there, it is quite likely that there is other life. It is just too far away from us now to get into contact with any of them.