Are we alone in the universe? It’s a question that’s been on the minds of astronomers and philosophers for hundreds of years. But if we’re not alone, where is everyone?
“If you ask, ‘When is life most likely to emerge?’ you might naively say, ‘Now,'” said lead author Avi Loeb of the Harvard-Smithsonian Center for Astrophysics. “But we find that the chance of life grows much higher in the distant future.”
For humans, it’s difficult to grasp the actual timescale of the universe. After all, it’s roughly 13.8 billion years old, and our solar system about 4.5 billion years old. That seems like an extremely long time to a species with lifespans of roughly 75 years. But in terms of the universe, our solar system is a mere fledgling.
About 30 million years after the Big Bang, which created our universe, elements like carbon and oxygen were created by new stars. This made it possible for life as we know it to emerge.
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All about the stars
It’s believed that most stars host planetary systems. But not all stars are the same. Some are bloated, hot and short-lived. While others are small with long lifespans. This is important when taking into consideration the chances for life to develop. A planet around a short-lived star doesn’t have the same chance that a planet orbiting a long-lived star does.
The smallest stars will burn out 10 trillion years from now and our universe will end. That means the chances for life to emerge get better over time. In fact, the researchers believe that the chances of life are 1,000 times higher in the far future.
“So then you may ask, why aren’t we living in the future next to a low-mass star?” said Loeb.
“One possibility is we’re premature. Another possibility is that the environment around a low-mass star is hazardous to life.”
This figure shows the habitable zone for stars of different temperatures, as well as the location of terrestrial size planetary candidates and confirmed Kepler planets described in new research.
The problem is these small stars, called red dwarfs, emit ultraviolet radiation and strong stellar flares. This would strip any potential planet of its atmosphere.
While the news may seem disappointing, that doesn’t mean that no life exists beyond our own. It just means that it may be harder to find.
This week an international study that examined more than 4,000 potential exoplanets — planets orbiting other stars — found 216 planets in the habitable zone, an area around a star where an orbiting planet could have liquid water. Of those, they found 20 potentially Earth-like planets.
“It’s exciting to see the sheer amount of planets that are out there, which makes you think that there is zero chance of there not being another place where life could be found,” Michelle Hill, one of the paper’s authors.
“There are a lot of planetary candidates out there, and there is a limited amount of telescope time in which we can study them,” said Stephen Kane, an associate professor of physics and astronomy at San Francisco State University and lead author of the study. “This study is a really big milestone toward answering the key questions of how common is life in the universe and how common are planets like the Earth.”