Recent data collected by NASA’s Hubble Space Telescope and Kepler Space Telescope suggests that most Earth-like exoplanets have yet to be born, reports a study in the Monthly Notices of the Royal Astronomical Society.
Earth first formed some 4.8 billion years ago. That was during a time when only eight percent of the potentially habitable planets that will ever form in the universe existed, Discovery News reports. Based on that number, 92 percent of all potentially habitable planets still need to be created before the universe no longer has the proper materials to produce the stars that create planets.
Using data collected from Hubble, researchers found that young galaxies were making stars at a rapid rate about 10 billion years ago. Over time, that production slowed. However, there is currently more gas available for the building of stars than there was when the universe first formed.
The information from Hubble, in conjunction with exoplanetary data collected from Kepler, allowed researchers to form a picture of the habitable planet potential of our galaxy. They then used that potential as a model to see the chances of other habitable worlds existing throughout the universe.
The researchers also discovered that Earth is an “early bloomer” by universe standards. That means it formed very quickly. The reason there are so few habitable worlds is that the universe simply has not had the time to create very many.
“Our main motivation was understanding the Earth’s place in the context of the rest of the universe,” said study author Peter Behroozi of the Space Telescope Science Institute (STScI) in Baltimore, Maryland, in a statement. “Compared to all the planets that will ever form in the universe, the Earth is actually quite early.”
Kepler first started collecting data back in 2009. Since then, it has allowed researchers to observe many different rocky worlds orbiting sun-like stars. Some of those worlds have even been found to be in the so-called habitable zone, the region around a star that is the perfect temperature to allow liquid water to exist on the planet’s surface. Such discoveries have allowed astronomers to predict there should be around 1 billion Earth-sized worlds orbiting within their stars’ habitable zones just in the Milky Way alone.
Furthermore, the universe has a lot of time left to create planets. Models suggest it will take at least 100 trillion years for the last star to die out. However, the same does not hold true for the Milky Way, as most of the gases in the galaxy have already been used up.
While interesting, the study is highly theoretical. It does not prove the rarity of Earth-like worlds, nor does it make any claims regarding the existence of extraterrestrial life. It raises many interesting questions about cosmic evolution, however, and gives a glimpse into how truly immense the universe really is.