spaceSpace and Physics

Earth May Have Formed Earlier Than 92% Of Other Habitable Planets


Jonathan O'Callaghan

Senior Staff Writer

3051 Earth May Have Formed Earlier Than 92% Of Other Habitable Planets
Many Earth-like planets could form in the next trillion years. NASA/ESA/G. Bacon (STScI)

The reason we haven’t heard from any other intelligent life in the universe remains a perplexing problem, known as the Fermi Paradox, considering how abundant planets are thought to be. What if, though, Earth was simply incredibly early onto the scene? What if we are among the first sentient life in the universe?

That’s a theory proposed by new research, using data from the Hubble and Kepler space telescopes, which suggests that 92% of potentially habitable planets in the universe are yet to be born. Based on the slowing rate of star formation, but the huge amounts of interstellar dust and gas remaining, researchers at the Space Telescope Science Institute (STScI) in Maryland suggest that the vast majority of Earth-like worlds that will ever exist simply haven’t formed yet.


“Compared to all the planets that will ever form in the universe, the Earth is actually quite early,” study co-author Peter Behroozi of STScI said in a statement.

In their study, published in the Monthly Notices of the Royal Astronomical Society, the researchers say that gas stored in dark matter halos around galaxies will continue to feed the creation of stars and planets for trillions of years. “We show that this would imply at least a 92% chance that we are not the only civilisation the universe will ever have,” the researchers wrote.

And when you think about it, it sort of makes sense. The Earth itself is 4.5 billion years old, roughly a third of the age of the universe, which is 13.8 billion years old. While stellar formation has slowed in many galaxies in the last 10 billion years, the last star in the universe isn’t expected to burn out for 100 trillion years. That leaves a lot of time for more planets to form.

“There is enough remaining material [after the Big Bang] to produce even more planets in the future, in the Milky Way and beyond,” said study co-author Molly Peeples of STScI in the statement.


Most planets will form in 100 billion to 1 trillion years, according to the study. Mopic/Shutterstock.

The study is in part based on observations from the Kepler Space Telescope, which indicates that Earth-like planets in habitable zones may be common. Indeed, there are expected to be one billion currently in our Milky Way, itself one of hundreds of billions of galaxies. If those are just the first 8% of all Earth-like planets, then there are a lot still to form. Thus, in trying to find out where everyone else is in the universe, maybe the simple and unnerving answer is we are among the first sentient life.

In their paper the researchers also reference the famous Drake Equation, which predicts how likely life is to evolve. It suggests there are between one and 10,000 civilizations in our Milky Way, and up to 1,000 trillion in the universe. The researchers say, though, that it is unlikely to be at the lower level. If our civilization was the only one the universe will ever have, it would be unlikely our planet would have formed so early in its expected lifetime of 100 trillion years. And even if the Milky Way has just one other civilization, that would imply there are 10 billion others across other galaxies.

But there’s a somber thought, too; most planets are expected to form 100 billion to 1 trillion years from now. While we are right now early enough to see evidence for the expansion of the universe in the form of cosmic background radiation and so on, that evidence will be mostly erased in one trillion years due to the expansion of the universe. This means any future civilizations born around this time will have no idea how the universe began. Maybe it will be down to us to teach them.


spaceSpace and Physics
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