New York, June 8 (IANS) Formed in the early stages of universe, carbon planets consisting of graphite, carbides and diamonds might have been the first potentially habitable worlds, suggests a new research.

"This work shows that even stars with a tiny fraction of the carbon in our solar system can host planets," said lead author and Harvard University student Natalie Mashian.

"We have good reason to believe that alien life will be carbon-based, like life on the Earth, so this also bodes well for the possibility of life in the early universe," she added.

The early universe consisted mostly of hydrogen and helium, and lacked chemical elements like carbon and oxygen necessary for life as we know it.

Only after the first stars exploded as supernovae and seeded the second generation did planet formation and life become possible.

The study, published recently in the journal Monthly Notices of the Royal Astronomical Society, examined a particular class of old stars known as carbon-enhanced metal-poor stars (CEMP).

"These stars are fossils from the young universe," said Mashian's PhD thesis advisor Avi Loeb from Harvard-Smithsonian Centre for Astrophysics. 

"By studying them, we can look at how planets, and possibly life in the universe, got started," he added.

Although lacking in iron and other heavy elements compared to Sun, CEMP stars have more carbon than expected given their age. 

According to the researchers, a dedicated search for planets around CEMP stars would help in finding out "how early planets may have formed in the infant universe". 

"We'll never know if they exist unless we look," Mashian said.​