Scientists have found that about 22% of Sun-like Stars have the planets in the habitable zone. These planets are comparable to the size of the Earth.
Kepler spacecraft was launched by NASA on March 7, 2009. Its main objective is to find the places in the universe which are just like Earth. It has observed the brightness of over 150,000 stars, recording a measurement every 30 minutes.
In the field of astronomy, one of the most interesting things is to find the planets, which are just right to host the known form of life.
In a recent study, scientists worked on about 42,000 sun-like stars (G and K type stars) by using Kepler spacecraft. They found 603 planets, out of which 10 are Earth sized planets and revolve in the habitable zone.
They have found that one in five Sun-like stars have Earth-sized planets that are present at the right place to host the life. Nearest such planet is could be present within 12 light-years of distance from us.
“What this means is, when you look up at the thousands of stars in the night sky, the nearest sun-like star with an Earth-size planet in its habitable zone is probably only 12 light years away and can be seen with the naked eye. That is amazing,” said UC Berkeley graduate student Erik Petigura, who led the analysis of the Kepler and Keck Observatory data.
There are about 200 billion stars in our galaxy and about 40 billion of them are just like Sun. This shows that there could be about 8.8 billion Earth-size planets in the Milky Way, according to planet-hunter Geoff Marcy.
However, habitability is not only determined by the presence of optimal temperature and therefore these habitable planets.
“Some may have thick atmospheres, making it so hot at the surface that DNA-like molecules would not survive. Others may have rocky surfaces that could harbor liquid water suitable for living organisms,” Marcy said. “We don’t know what range of planet types and their environments are suitable for life.”
“For NASA, this number – that every fifth star has a planet somewhat like Earth – is really important, because successor missions to Kepler will try to take an actual picture of a planet, and the size of the telescope they have to build depends on how close the nearest Earth-size planets are,” said Andrew Howard, astronomer with the Institute for Astronomy at the University of Hawaii. “An abundance of planets orbiting nearby stars simplifies such follow-up missions.”
Astronomers Conclude Habitable Planets Are Common – Institute for Astronomy (http://www.ifa.hawaii.edu/info/press-releases/HabitablePlanetsCommon/)
NASA Kepler Results Usher in a New Era of Astronomy – NASA (http://www.nasa.gov/press/2013/november/nasa-kepler-results-usher-in-a-new-era-of-astronomy/#.Unixgvlmj0t)
Astronomers answer key question: How common are habitable planets? – UC Berkeley (http://newscenter.berkeley.edu/2013/11/04/astronomers-answer-key-question-how-common-are-habitable-planets/)
One in Five Stars Has Earth-sized Planet in Habitable Zone – Keck Observatory (http://www.keckobservatory.org/recent/entry/one_in_five_stars_has_earth_sized_planet_in_habitable_zone)
Erik A. Petigura et al. (2013). Prevalence of Earth-size planets orbiting Sun-like stars PNAS DOI: 10.1073/pnas.1319909110