Exciting space news everyone – chances of a neighbouring star system hosting life have increased. Yep, scientists have confirmed that two of its planets are rocky, like the Earth.

In case you’re wondering, the planets are orbiting a star 40 light years away called Trappist-1. They’re both about the size of Earth, plus they’re situated in the “habitable zone” where mild temperatures make liquid surface water possible.

And now astronomers have shown that 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 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.

rocky planet
Artist’s impression of two planets passing in front of the “ultracool” red dwarf star Trappist-1 (NASA, ESA, and STScI/PA)

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.

FYI, the planets were discovered by Trappist (Transiting Planets and Planetisimals Small Telescope), a new kind of ground telescope in Chile designed to capture infrared light.

Their parent star is described as an “ultracool dwarf”, a type of star much cooler than the Sun that emits most of its radiation at infrared wavelengths.

Four larger versions of the Trappist telescope are now being built in Chile to focus on other ultracool dwarf stars in the southern sky.

“With more observations using Hubble, and further down the road with James Webb (a new space telescope), we can know not only what kind of atmosphere planets like Trappist-1 have, but also what is within these atmospheres,” said Dr de Wit.

“And that’s very exciting.”