NASA is like a dog with a bone when it comes to finding planets similar to Earth, adding a further 10 to what is becoming a growing list.
In the summer of 2015, NASA had big news: we might be alone, but we’re not tied down.
Earth 2.0, with the less-catchy real title of Kepler-452b, was found in a solar system very similar to our own, the right distance from its star to potentially be habitable.
The planet is 6bn years old, 60pc larger than Earth and receives 10pc more energy from its star, which is 1.5bn years older and 20pc brighter than our sun, though it has the same temperature.
“It’s the closest so far,” said NASA of the discovery, in terms of finding planets that could be our future home.
Wow. What a once-in-a-lifetime discovery.
One, two, three of a kind
The following May, astronomers found three planets ‘just’ 40 light years away, orbiting an ultra-cool dwarf star called TRAPPIST-1. These, too, could support life.
A few days later, NASA reported that its Kepler (planet-seeking) spacecraft found 1,284 new planets, with up to 550 showing potential for being in what the space agency calls the “habitable zone”.
By February this year, seven more planets with ‘Earth-like’ qualities were discovered. Of that number, it is estimated that six of them could have liquid water on their surfaces, with atmospheric temperatures similar to our planet’s.
In April, European scientists got in on the act, finding what it felt was the newest contender for the Earth 2.0 crown, located in the constellation of Cetus – otherwise known as the ‘Sea Monster’ – approximately 40 light years from Earth.
And now scientists are crying wolf once more, it seems.
Earth not unique
NASA’s Kepler space telescope team is at it again, releasing a mission catalogue of 219 new planets, 10 of which are near-Earth-size, and orbit in their star’s habitable zone, which is the range of distance from a star where liquid water could pool on the surface of a rocky planet.
This is the final catalogue from the spacecraft’s view of the patch of sky in the Cygnus constellation.
“The Kepler data set is unique, as it is the only one containing a population of these near-Earth analogues – planets with roughly the same size and orbit as Earth,” said Mario Perez, Kepler programme scientist with NASA.
“Understanding their frequency in the galaxy will help inform the design of future NASA missions to directly image another Earth.”
Using a Hawaiian observatory, the team measured the sizes of 1,300 stars in the Kepler field of view to determine the radii of 2,000 Kepler planets with exquisite precision.
Susan Thompson, Kepler research scientist for the SETI Institute, said: “This carefully measured catalogue is the foundation for directly answering one of astronomy’s most compelling questions: how many planets like our Earth are in the galaxy?”
The answer is, at the moment, an awful lot.