Two Swiss astronomers made history back in 1995 when they discovered the first exoplanet that circles around a Sun-like star. Since then, astronomers have discovered nearly 2000 exoplanets. This confirms that planets are unique only to our solar system and the universe is rich in strange alien worlds. Stars are born from the concentrated interstellar molecular cloud that finally collapsed under the weight of its own gravity. Many such enormous clouds are found in the universe. Eventually, these young brilliant stars are surrounded by numerous proto-planets that are still look like accretion disks.
Eventually baby planets emerge and initially, they are not even barren rocky planets. The Kepler Space Telescope itself has spotted thousands of potential alien worlds, which have yet to be confirmed. The bright Milky Way Galaxy could be populated by at least 100 billion planets and on average, this could represent one planet for each star, on average. In fact, our galaxy could also have many more orphan exoplanets that are not bound to any kind of star. They just wander around the space without orbiting any nearby star. These planets are usually evicted from their original solar systems, due to gravitational interaction with nearby planers.
About 20 percent sun-like stars are believed to have Earth-sized planets and many of them could be located in the habitable zones. The closest such planet could be located within twelve light year from our solar system. The habitable zone or also known as the Goldilocks zone is a place where water could form in liquid state, which is actually a very narrow temperature range. Where there’s water and warm climate, it is more likely for life to arise, evolve and finally flourish. So, there is a possibility that life is exists in these planets, because the Earth itself is a solid proof that life can emerge in a planet.
Unfortunately, just because a planet is located in the habitable zone, it doesn’t mean that life is guaranteed to exist. The planet could be too small that it doesn’t have the gravitational pull to maintain the atmosphere. Even if the planet has an atmosphere, there could be something wrong with the atmosphere and a higher level of specific gasses, such as CO2 could cause a greenhouse effect, which causes the planet surface to become hotter than it should. Venus is an example of planet with greenhouse effect with the surface temperature that’s hotter than it should.
The planet should also have active, iron core that can generate the magnetic field. Such a field can deflect much of the harmful rays from the nearby sun and the universe itself. An Earth-like planet doesn’t need to have an atmosphere composition similar to Earth that is dominated with Nitrogen and Oxygen, but it should have reasonable temperature levels. It is possible for the local organism to different atmospheric conditions, but they won’t survive excessively cold or hot temperature. So, it is clear that Earth seems like a very lucky combination of elements and it may take awhile before we could find life another planet.