The nearby Trappist-1 star system could be up to twice as old as our own, a new study has found.
Researchers now estimate the star at the heart of Trappist-1 is between 5.4 and 9.8 billion years old, spurring new questions on the orbit stability of the seven planets circling it, and the potential for life to have evolved in this time.
As older stars are known to produce fewer flares than younger stars, this could be favourable for the planets’ habitability – but, the longer timeline could also mean any water or atmosphere has been boiled off under years of high-energy radiation.
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Researchers now estimate the star at the heart of Trappist-1 is between 5.4 and 9.8 billion years old, spurring new questions on the orbit stability of the seven planets circling it, and the potential for life to have evolved in this time. An artist’s impression is pictured
TRAPPIST-1 SOLAR SYSTEM, AT A GLANCE
The newly discovered star system is just 39 light years from Earth.
- Seven Earth-sized worlds are orbiting a dwarf star known as Trappist-1
- Six inner planets lie in a temperate zone where surface temperatures range from 0-100°C (32-212°F)
- Of these, at least three are thought to be capable of having oceans, increasing the likelihood of life
- -Scientists say life may have already evolved on at least three of the planets
- No other star system known contains such a large number of Earth-sized and probably rocky planets
- They were found using the ‘transit’ method that looks for tiny amounts of dimming caused by a world blocking light from its star
According to NASA, the age of a star system is an important factor in determining its potential habitability.
When the ultra-cool dwarf star Trappist-1 and its seven orbiting planets were first discovered 37 light-years away, scientists estimated it was at least 500 million years old, based on the size of low-mass star.
Now, a study led by researchers from NASA and the University of California, San Diego has found it’s much older.
To determine this, the researchers measured the speed of the star in its orbit around the Milky Way, the atmosphere’s chemical composition, and the number of flares during the observation period.
At up to 9.8 billion years old, Trappist-1 could be double the age of our solar system, which formed roughly 4.5 billion years ago.
‘Our results really help constrain the evolution of the Trappist-1 system, because the system has to have persisted for billions of years,’ said Adam Burgasser, an astronomer at the University of California, San Diego, and the paper’s first author.
While they may have honed in on its age, the scientists haven’t yet figured out what this means for its potential to support life.
An older star may be ‘quieter,’ the researchers explain, and the study confirms that, compared to other ultra-cool dwarf stars, Trappist-1 does in fact create fewer flares.
As older stars are known to produce fewer flares than younger stars, this could be favourable for the planets’ habitability – but, the longer timeline could also mean any water or atmosphere has been boiled off under years of high-energy radiation. An artist’s impression is pictured
|Name||Orbit (days)||Mass (where 1.0 = mass of Earth)||Distance to star (millions of miles)||Distance to star (millions of km)||Possibility of hosting alien life|
|1b||1.5||0.85||1.02||1.64||Less likely – too hot|
|1c||2.4||1.38||1.39||2.24||Less likely – too hot|
|1d||4||0.41||1.95||3.14||Less likely – too hot|
|1h||20||unknown||5.58||8.97||Less likely – too cold|
But, being so close to the star, the planets may have been subjected to high-energy radiation for billions of years, leading massive quantities of water up to the equivalent of an Earth ocean to evaporate from all but the two most distant.
The researchers point to Mars as a similar example, in our own solar system, that has experienced this type of stripping.
It’s possible, however, that the atmosphere has not been eroded, the researchers note.
The Trappist-1 planets have lower densities than Earth, and large reservoirs of volatile molecules such as water could create a thick atmosphere, which would protect the surface from radiation, NASA explains.
‘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,’ Burgasser said.
BLOW TO HOPES FOR LIFE IN THE TRAPPIST-1 STAR SYSTEM
The discovery of the Trappist-1 system 37 light-years away ignited hopes that alien life could soon be found just outside of our own stellar neighbourhood.
But, two separate studies have now cast doubts on the possibility of life existing on any of the three Trappist-1 planets situated within the star’s habitable zone.
The analyses led by researchers from the Harvard-Smithsonian Center for Astrophysics (CfA) found that radiation from the red dwarf star at the heart of the Trappist-1 system could be powerful enough to destroy a planet’s atmosphere, ultimately hurting the chances that any lifeforms could survive, or even form at all.
The researchers investigated several other conditions, including the impact of the temperature on ecology and evolution, and the effects of ultraviolet radiation from the Trappist-1 star.
Of the seven planets in the Trappist-1 system, three are located in the habitable zone, where it’s thought the conditions would be right to sustain liquid water at the surface.
While this may be a promising factor in the search for life, it isn’t the only thing that must be considered, the researchers explain.
‘Because of the onslaught by the star’s radiation, our results suggest the atmosphere on planets in the Trappist-1 system would largely be destroyed,’ said Harvard professor Avi Loeb.
‘This would hurt the chances of life forming or persisting.’
The researchers say a low-mass star such as Trappist-1 could exist for a very long time, even longer than our sun.
‘Stars much more massive than the sun consume their fuel quickly, brightening over millions of years and exploding as supernovae,’ said Eric Mamajek, deputy program scientist for NASA’s Exoplanet Exploration Program.
‘But Trappist-1 is like a slow-burning candle that will shine for about 900 times longer than the current age of the universe.’
The new measurements all indicated that the Trappist-1 star is far older than our sun.
And, in the future, additional observations with NASA’s Hubble Space Telescope and the James Webb Space Telescope could give further insight.