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There are approximately 300 million planets that exist outside our Solar System but within the Milky Way that could potentially host life, according to NASA.
Four of them are located just 30 light-years from Earth, with the closest just 20 light-years away, the space agency says.
The researchers came up with the figure of 300 million based on the conservative hypothesis that 7% of Sun-like stars have a habitable world orbiting them.
However, they warn that the real figure could reach 75%, which would see the figure of 300 million rise to around three billion.
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In the photo, Kepler-186f, the first validated Earth-sized planet to orbit a distant star in the habitable zone of a Sun-like star
Data from Kepler, the deep space telescope that was retired in October 2018 when it finally ran out of fuel, led to the discovery.
Kepler’s mission was originally intended to last 3.5 years, but rigorous use of the fuel allowed him to remain operational for 9 years, 7 months and 23 days.
Its mission was to scour the skies, near and far, looking for planets orbiting other stars.
Kepler discovered more than 2,600 worlds beyond our solar system and statistically proved that the Milky Way is home to more planets than stars.
It consisted of 42 image sensors called charge-coupled devices (CCDs), and each had a resolution of 1,024 by 2,200 pixels.
Kepler’s data is so vast that astronomers are still exploring his reserves to this day and publishing new findings.
NASA astronomers have done just that, with their work recently appearing in the Astronomical Journal.
“Kepler already told us there were billions of planets, but we now know that a good portion of those planets could be rocky and habitable,” said lead author Steve Bryson, a researcher at NASA’s Ames Research Center in California.
“Although this achievement is far from being a final value and water on a planet’s surface is only one of many factors that support life, it is extremely exciting that we have calculated that these worlds are so common with a certainty and a such high precision. “
The researchers set some parameters for the data, narrowing their search field to Earth-sized planets, half the diameter of 50%.
This ensures that the observed planets are rocky as they are the much larger planets that tend to be gaseous, just like Jupiter and Saturn in the Solar System.
Kepler’s mission was originally intended to last 3.5 years, but rigorous use of the fuel allowed him to remain operational for 9 years, 7 months and 23 days. Its mission was to scour the skies, near and far, looking for planets orbiting other stars. In the photo, the telescope before launch
There are approximately 300 million planets that exist outside our Solar System but within the Milky Way that could potentially host life. According to NASA research, four of them are located just 30 light-years from Earth, with the closest just 20 light-years away, NASA says.
They went in search of the Holy Grail of astronomical research, scouring the “Goldilocks Zone” where life can thrive.
A prerequisite is that the star resembles the Sun, so the researchers looked for distant stars that resemble it in age and temperature.
But this simplified approach isn’t a guarantee that life will thrive and it makes a lot of assumptions, the researchers acknowledge, so the astronomers have crossed this data with those from ESA’s Gaia telescope.
Gaia measures the energy output of individual stars, which provides valuable insight into whether it is emitting too much harmful radiation or too little heat energy for water to survive as a liquid, for example.
“We have always known how to define habitability simply in terms of the physical distance of a planet from a star, so that it wasn’t too hot or cold, it made us speculate,” said Ravi Kopparapu, an author of the paper and a NASA scientist.
“Gaia’s star data allowed us to look at these planets and their stars in a whole new way.”
Gaia allowed astronomers to observe how a planet’s atmosphere would impact its habitability.
This analysis led to the figure of 50 percent of Sun-like stars that have habitable planets.
A conservative estimate goes down to 7%, while an optimistic estimate can go as high as 75%.
Kepler was the first spacecraft to detect planets in our galaxy and over the years its observations have confirmed the existence of more than 2,600 exoplanets, many of which could be key targets in the search for alien life.
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