Trappist-1 Could Be Twice As Old As Solar System, Changing the Odds of Finding Life

Trappist-1
The Trappist-1 solar system. Three of the planets (e, f and g) are located firmly within the "habitable zone." NASA/JPL-Caltech

Since NASA announced the discovery of Trappist-1, a dwarf star, and its planetary system in February, astronomers and scientists have posited it as among the likeliest candidates for finding life outside our solar system.

Scientists thought the Trappist-1 system was at least 500 million years old when it was first discovered, based on its mass. But a new study has found that age to be a big underestimate: The planetary system could be more than twice as old as our own solar system.

At the very least, the Trappist-1 star is 5.4 billion years old, almost a billion years older than our solar system, which formed around 4.5 billion years ago. But it could be far older—up to 9.8 billion years old, according to the study by researchers from the University of California, San Diego, and NASA’s Jet Propulsion Laboratory, published in The Astrophysical Journal.

Old age does not necessarily mean there cannot have been, or still be, forms of life on the planets in this system. Trappist-1 is an ultracool dwarf star that flares less than younger stars, like our sun. Solar flares can damage nearby planets: A 2012 solar flare that tore through the Earth’s orbit could have caused major damage had it hit the planet. Some experts also propose that the longer a planet has been around, the more time it would have had for increasingly complex forms of life to develop.

But Trappist-1’s old age does mean that the planets in its system have soaked up billions of years worth of radiation that may have boiled off any liquid water and potentially even the planet’s atmospheres. Mars is an example of a planet in our solar system that may have once had liquid water on its surface but lost it due to gradual evaporation.

“If there is life on these planets, I would speculate that it has to be hardy life, because it has to be able to survive some potentially dire scenarios for billions of years,” said Adam Burgasser, astronomer at the University of California and the paper’s first author.

Located about 40 light years away from our solar system and one-eighth the size of the sun, Trappist-1 is orbited by seven planets that are relatively close in size to Earth. Three of these planets were found to be in the so-called habitable zone—a distance from the star that meant the planets were neither too hot nor too cold to prevent liquid water from pooling on their surfaces.

The fact that the planets are very close together has also raised the possibility of panspermia, or the spread of life between the different planets in the system. A mathematical model proposed by University of Chicago astrophysicists earlier in 2017 suggested that the chances of life transferring between Trappist-1’s planets was “orders of magnitude higher” than the same event occurring between Earth and Mars.