The presence of planets similar to the planet Earth, or technically referred to as Earth analog, is more than what scientists have earlier predicted. In a recent study from NASA’s Ames Research Center, each sun-like star in the Milky Way Galaxy hosts between 0.4 to 0.9 rocky planets that are within its habitable zones. These zones have the right conditions and atmosphere for life, as we know it, to thrive. Water is, of course, necessary, as well as an atmosphere with the right mix of gas.
Scientists estimate that around 7% of the Milky Way, translating to about 200 billion stars, are G-dwarves, like our own Sun. In a statement, co-author of the study Jeff Coughlin, an exoplanet researcher at the Search for Extraterrestrial Intelligence Institute in Mountain View, California, said that this was the first time they came up with a reliable approximation of the potentially habitable planets in the galaxy. He revealed that they used the Drake Equation to come up with the estimation and that space scientists are a step closer to finding out whether we are indeed alone in this vast universe.
A large team led by Steve Bryson went through a great degree of effort to analyze data from the Kepler Data Office, which houses information gathered by NASA’s Kepler Space telescope from 2009 to 2018. The spacecraft discovered about 2,800 exoplanets so far, which is about two-thirds of all known alien planets. Bryson and his team also studied data from the European Space Agency’s Gaia spacecraft, which is tasked with mapping a billion Milky Way stars.
With all the information available to them, Bryson and his band of scientists estimated the rate of occurrence of rocky planets—which they defined as having a diameter of 0.5 to 1.5 that of the Earth and with a sun with a surface temperature of 8,180- and 10,880-degrees Fahrenheit. What was tricky was defining the habitable zone, as it depended on various factors such as the composition of the gas in the air and the overall thickness of the atmosphere. The amount of water is also a major consideration.
A conservative estimate of the occurrence rate of a habitable zone is 0.37 to 0.60 planets per star, while a more liberal estimate points to 0.58 to 0.88 planets per star. This tells us that there is an abundance of possible Earth-like planets surrounding us and that we might not be alone in the Galaxy. This means that when space travel is possible and that we may even make real estate investments in these unclaimed planets.
Traveling to other planets in the Galaxy, however, might still be far in the future as the researchers estimate the nearest habitable zone planet to be about six parsecs away—with one parsec equal to 3.26 light-years. That means to reach that planet, space tourists would need to travel about two decades one way at the speed of light.
The study did not take into account the red dwarf stars, which could also house life within its habitable zone. Future research might look into this as three-quarters of the Milky Way is composed of red dwarfs. It would also be easier to reach Proxima b, a planet orbiting Proxima Centauri, which is a red dwarf. Researchers who come up with a reliable number of habitable planets within a red dwarf solar system would likely be given credit for making such a discovery, just like Bryson and his team. True habitability of the planets in a red dwarf system, however, is still up for debate as these do not emit a bright light like that of a yellow star. They are also much active, and so solar flares are frequent occurrences.
The question of whether we are alone in the universe is likely going to be answered soon—and so we hope that they come to us waving flags of friendship.
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