Despite the progress in the development of more advanced technologies, humanity's search for intelligent alien life has yet to be successful. A recent theoretical study suggests that because the Earth was born early into the evolving universe, most habitable planets may not have been born yet.
Planetary scientists collected and analyzed data from NASA's Kepler space observatory and Hubble space telescope. They concluded that when the Earth was formed 4.6 billion years ago, only eight percent of livable planets had also most likely formed in the universe. Because of this, 92 percent of planets fit for habitation are most likely still just gas and dust.
Researchers explained that even after our sun burns out in 6 billion years, more planets will still be forming. All these findings are published [pdf] in the Monthly Notices of the Royal Astronomical Society.
The study said that the birth of stars 10 billion years ago had occurred at a fast rate. Back then, the universe's levels of helium and hydrogen were very low. Now, the formation of stars has been slowed down, but there are enough leftover helium and hydrogen for the universe to cook up more planets and stars.
"There is enough remaining material [after the "big bang"] to produce even more planets in the future, in the Milky Way and beyond," said Molly Peeples of Space Telescope Science Institute (STScI), co-author of the study.
About 1 billion rocky Earth-sized worlds exist in the Milky Way galaxy, the scientists said. Taking into account the vastness of the observable universe, the number will increase to 100 billion Earth-sized planets.
Meanwhile, the Search for Extraterrestrial Intelligence (SETI) Institute conducts research and projects that focus on finding intelligent alien life. The institute said that they aim to find answers to the questions that the previous generation has only dared to ask.
Currently, SETI has begun tracking down signs of alien life near the star KIC 8462852 through the Allen Telescope Array (ATA). The ATA is just one of their many technologies.
To fully understand the possibility of searching for signals given off by extraterrestrials, scientists use the famous Drake Equation devised by astronomer Frank Drake. It measures several factors based on the possible number of civilizations in our galaxy alone. However, scientists say that the equation is mostly speculative.
SETI also said that even though some Earth-sized planets have been discovered, probes cannot be sent because of the magnificent distance in light years between our planet and those other planets.
