Nasa research finds 10 new potentially habitable ‘Earth-like’ worlds
UNITED STATES: Astronomers using the Kepler space telescope have detected 219 possible new exoplanets in our galaxy, including 10 relatively small, rocky and possibly habitable planets similar to our own, Nasa announced yesterday.
These are the last additions to the catalogue of exoplanets compiled during the first phase of the Kepler mission, when the space telescope scanned some 200,000 stars in the Cygnus constellation in an effort to find worlds beyond our own.
The official catalogue now contains 4034 total ‘‘candidates’’ – tiny blips in the data that are thought to signal the presence of a planet around a star. Of these, 49 fit squarely into their star’s ‘‘habitable zone’’, that Goldilocks region where liquid water can pool on the surface and life may thrive.
The Kepler space telescope was launched into orbit around the sun in 2009. Its charge: Take a census of a small slice of the Milky Way in an effort to understand the ‘‘demographics’’ of our galaxy. How many stars are like our sun? How many of those host planets? How many planets orbit in the habitable zone? Is there any place else in this vast universe that living beings might call home?
In its first four years, Kepler surveyed just .025 per cent of the sky. And for every potential planet detected, Nasa estimates that 100 to 200 lurk beyond the telescope’s reach. Given a little time and some sophisticated models, scientists will use the Kepler catalogue to estimate how many stars in our galaxy could host an ‘‘Earth 2.0’’.
Based on how many habitablezone planets have already been identified, Caltech astrophysicist Courtney Dressing thinks that number could be sizeable.
‘‘I, for one, am ecstatic,’’ she said.
‘‘The important thing for us is, are we alone?’’ added Kepler programme scientist Mario Perez. ‘‘Kepler today tells us, indirectly . . . that we are probably not alone.’’
This is the eighth update of the Kepler planet catalogue and the most thorough survey of the space telescope’s data to date. Of the 4034 candidates, more than half have already been confirmed as exoplanets and not the result of miscalculations or false signals.
Kepler research scientist Susan Thompson, the lead author of the catalogue study, said her team is confident about all 10 of the new ‘‘Earth-like’’ planets found in their stars’ habitable zones.
Several of these planets orbit G dwarfs – the same species of star as our own sun. And one, dubbed KOI 7711 (for Kepler Object of Interest), is a possible ‘‘Earth twin,’’ a rocky world just 30 times bigger than our own and roughly the same distance from its star.
It’s too soon to say whether KOI 7711 truly merits the label ‘‘Earthlike’’, Thompson cautioned. Kepler is incapable of determining whether an exoplanet bears an atmosphere or liquid water. If aliens were observing our solar system using a similar instrument, they might think it contained three rocky, potentially habitable worlds – Venus, Earth and Mars.
A second research group combined the Kepler data with measurements from ground-based telescopes to calculate the approximate sizes and compositions of 2000 exoplanets. They found that smaller worlds, the kind that Kepler was designed to detect, fall into two distinct groups: rocky planets that could be up to 1.75 times the size of our own, called ‘‘super-Earths,’’ and gaseous ‘‘mini-Neptunes’’, which lack a solid surface and are 2 to 3 times bigger than Earth.
Nearly every star surveyed hosted a planet in one of these two categories. But, curiously, no planets straddled the divide. Each world was either smaller and rocky, or larger and gassy.
Benjamin Fulton, an astronomer at Caltech and the University of Hawaii, compared the new categories to species of animal.
‘‘Finding two distinct groups of exoplanets is like discovering mammals and lizards make up distinct branches of a family tree.’’ And just as discovering distinctions between species helps us understand evolution, this revelation could help astronomers determine how planets take shape.
Fulton and his colleagues believe that the sharp distinction between ‘‘super-Earths’’ and ‘‘mini-Neptunes’’ may be a result of how much hydrogen and helium contributed to their formation. These elements are extremely light and exist as gas at all but the lowest temperatures.
Rocky worlds like Earth, with thin atmospheres and nice, firm surfaces, contain relatively little of these elements. Perhaps they started off with less, or perhaps the light elements were burned or blown away.
‘‘It feels a bit like the end of an era,’’ Thompson said of the programme, ‘‘but actually I see it as a new beginning. It’s amazing the things that Kepler has found.
‘‘It has shown us these terrestrial worlds, and we still have all this work to do to really understand how common Earths are in the galaxy.’’ – Washington Post