Extrasolar planets is one of the most interesting astronomical research topics. It can help us answer questions such as whether there are aliens, or is it possible for us to find another “Earth” to live on.
An extrasolar planet is defined as a planet that is outside of solar system. The history of extrasolar planet can be traced back to 1917, but the first confirmed detection of extrasolar planet happened in 1988. As of April 1st, 2019, we have found 4023 confirmed planets with in 3005 systems.
Because of the bias in detecting extrasolar system due to the mythology of transit photometry and Doppler spectroscopy, most of the planets we found are huge in size and close to the star in the system. By in theory, there should be about 1 Earth-like size planet in the habitable zone in 5 sun-like star’s system. This number is amazing considered that we have 200 billion stars just in Milky Way — that’s about 11 billion Earth-like planets! Are we the only special one?
One example of a likely Earth twin is Kepler-452b. It’s one of the most Earth-like exoplanet we have found so far. It lies at 1,400 light year away from us, and it’s about 60% larger than Earth, orbiting a sun-like star that is 10% bigger and 20% brighter. Kepler-452b’s orbital period is about 385 days, making it lying in the habitable zone. Kepler-452b is likely to process thick atmosphere, lots of water and volcanos. The planet and its sum have been around for about 6 billion years, and is there any life on Kepler-452b? We expect future researches can reveal us the answer.