Is Life on Earth Premature from a Cosmic Perspective?

August 3, 2016


Is Life on Our Planet Premature from a Cosmic Perspective?

This artist’s conception shows a red dwarf star orbited by a pair of habitable planets. Because red dwarf stars live so long, the probability of cosmic life grows over time. As a result, Earthly life might be considered “premature.”

New research from the Harvard-Smithsonian Center for Astrophysics examines the possibility that present-day life is actually premature from a cosmic perspective.

The universe is 13.8 billion years old, while our planet formed just 4.5 billion years ago. Some scientists think this time gap means that life on other planets could be billions of years older than ours. However, new theoretical work suggests that present-day life is actually premature from a cosmic perspective.

“If you ask, ‘When is life most likely to emerge?’ you might naively say, ‘Now,'” says 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.”

Life as we know it first became possible about 30 million years after the Big Bang, when the first stars seeded the cosmos with the necessary elements like carbon and oxygen. Life will end 10 trillion years from now when the last stars fade away and die. Loeb and his colleagues considered the relative likelihood of life between those two boundaries.

The dominant factor proved to be the lifetimes of stars. The higher a star’s mass, the shorter its lifetime. Stars larger than about three times the sun’s mass will expire before life has a chance to evolve.

Conversely, the smallest stars weigh less than 10 percent as much as the Sun. They will glow for 10 trillion years, giving life ample time to emerge on any planets they host. As a result, the probability of life grows over time. In fact, chances of life are 1000 times higher in the distant future than now.

“So then you may ask, why aren’t we living in the future next to a low-mass star?” says Loeb.

“One possibility is we’re premature. Another possibility is that the environment around a low-mass star is hazardous to life.”

Although low-mass, red dwarf stars live for a long time, they also pose unique threats. In their youth they emit strong flares and ultraviolet radiation that could strip the atmosphere from any rocky world in the habitable zone.

To determine which possibility is correct — our premature existence or the hazard of low-mass stars — Loeb recommends studying nearby red dwarf stars and their planets for signs of habitability. Future space missions like the Transiting Exoplanet Survey Satellite and James Webb Space Telescope should help to answer these questions.

The paper describing this work has been accepted for publication in the Journal of Cosmology and Astroparticle Physics and is available online. Its co-authors are Avi Loeb (Harvard-Smithsonian Center for Astrophysics) and Rafael Batista and David Sloan (University of Oxford). Loeb simultaneously wrote an extended review on the habitability of the universe as a chapter for a forthcoming book.

PDF Copy of the Study: Relative Likelihood for Life as a Function of Cosmic Time

Source: Harvard-Smithsonian Center for Astrophysics

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5 Responses to “Is Life on Earth Premature from a Cosmic Perspective?”

  1. Harold W Miller Says:

    I’ve always thought that a late M star that has a life span of 5-10 trillion years could last a thousand times longer than a G2 star like the sun. That would give a planet in the right orbit around that star a thousand times more time for life to develop. I should think that after that star has lasted ten percent of its lifetime, something we’ve could never observe, it would settle down to a very stable situation and the flares we see now would disappear giving the stellar environment an extremely long period of stability.


  2. Deryl McCarty Says:

    Two points:

    (a) Determining that we are “Premature” is probably technically correct, but “immature” is more accurate. Our all-earth-life-shared 90+% DNA is cosmically not older than a day old newborn, alas, our wisdom is closer to that of a 13 yo boy or girl. Pathologically clueless.

    (b) There is probably some irony that one of the great themes of Sci-Fi literature revolves around “forerunners” or “the ancient ones”, only to discover that those Sci-Fi authors were not looking backwards through the translucent glass of history but into a mirror.


  3. Madanagopal.V.C. Says:

    Life on any exoplanet is dependent on its star. The time taken for a suitable atmosphere is dependent on the cooling of the planet away from the star.This apart comet spray will bombard the distant planets very frequently and also the nearby planets by mateors and comets. The balancing act will only select few exoplanets to sustain life and that too for a very short period. After all living phase in any planet is very much a microscopic portion of its age which runs into billions of years. That is why I always hold the belief that UFO s are humbug and possibility of contacting any alien civilization is mathematically not possible. (Browse vcmadan2 and find the article).Thank You.


  4. bobjay Says:

    where does all this space/time and mass go after the flame is extinguished?


  5. Mark Wallace Says:

    Earth’s oceans will evaporate in a billion years or so. So how could we reasonable expect a planet around a longer-lived star to keep it’s oceans for a 1000 times longer?


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