Possibility of life among stars is given boost by new observations
THE chances of a neighbouring star system hosting life have increased after scientists confirmed that two of its planets are rocky, like the Earth.
The planets, orbiting a star 40 light years away called Trappist-1, are both about the size of Earth and situated in the “habitable zone”, where mild temperatures make liquid surface water possible.
Now astronomers have shown the worlds are primarily rocky rather than gaseous and probably have tightly contained atmospheres.
The observation, made by Nasa’s Hubble Space Telescope, shortens the odds on the planets hosting Earth-like life.
Three Earth-sized worlds were discovered in the system’s habitable zone on Monday, May 2.
Scientists were able to take a more detailed look at two of them when they happened to pass in front of their parent star at almost the same time.
The “double transit” allowed astronomers to use the Hubble telescope to measure tiny light fluctuations as each planet caused the star’s “sunshine” to dip.
The narrow range of dipping starlight wavelengths showed that both planets had compact, rocky-planet atmospheres.
If the wavelengths had varied significantly it would have signalled the presence of a large, puffy atmosphere similar to the one that blankets Jupiter.
US lead scientist Dr Julien de Wit, from the Massachusetts Institute of Technology’s Department of Earth, Atmospheric and Planetary Sciences, said: “The data turned out to be pristine, absolutely perfect, and the observations were the best that we could have expected. The Force was certainly with us.
“Now we can say that these planets are rocky. Now the question is, what kind of atmosphere do they have? The plausible scenarios include something like Venus, where the atmosphere is dominated by carbon dioxide, or an Earth-like atmosphere with heavy clouds, or even something like Mars, with a depleted atmosphere.
“The next step is to try to disentangle all these possible scenarios that exist for these terrestrial planets.”
The research is published in the journal Nature.
The planets were discovered by Trappist (Transiting Planets and Planetesimals Small Telescope), a new kind of ground telescope in Chile that captures infrared light.
Their parent star is described as an “ultra-cool dwarf”, a type of star much cooler than the Sun that emits the majority of its radiation at infrared wavelengths.