An astronomer who specializes in the search for aliens in the universe, says humanity may really be alone, because there are fewer places where life is likely to exist than previously discovered.

According to the Daily Star, the amount of toxic gas present in the atmospheres of most planets makes these places unsuitable for higher life forms.

Combined with other factors, the researchers say it’s almost impossible for life to exist in outer space.

Study co-author, Timothy Lyons, said: “This is the first time that the life-on-Earth limit has been used to assess where there is life in the universe. The results of our study show that most planets are not suitable for habitation.”

One of those factors is the distance needed for the planet to maintain warm water, creating the basis for the formation of life.

The study, published in the Journal of Astrophysics, uses computer modeling to assess the elements needed for life on planets. If a planet is too cold, large amounts of greenhouse gas emissions are needed to compensate.

But study author Edward Schwieterman said: “To create the ideal conditions, that planet would need 10,000 times more CO2 than Earth does today. But a large amount of CO2 is also not suitable for creating life.”

Scientists’ research has dealt a blow to the hope of life in seven planets that NASA once announced as “very Earth-like”.

Apart from Earth, “there is not a planet in the Solar System that has ideal conditions for life”.

“That means that the Earth is completely unique in the universe, in terms of sustaining life, and we need to protect the habitat on Earth,” Schwieterman stressed.