Do the math : billions of planets per galaxy , and billions of Galax urceolata in the universe of discourse . It ’s unlikely that only one of those has all the characteristics of our own – worldly concern - sized , orbiting a Sun - like star , and slap bang in its habitable zone where water can form .
Why are those characteristics so crucial ? Well , Earth is the only planet we know to have lifetime on it . It constitute sentiency , therefore , that if we find a world exactly the same as our own , then it would at least be potentially inhabitable , and may have spirit existing on it shortly .
A so - called “ Earth 2.0 ” is the holy grail for satellite hunters . So , how near are we , what are we looking for precisely , and what tools have we got ? Given that it ’s officiallyexoplanet week , let ’s take a look at where we stand .
How tight are we ?
The chance are that over the next few years , more and more ground - corresponding planets will make the news , in all likelihood culminating in a planet exactly like ours that can unfeignedly be dubbed Earth 2.0 . “ I ’m somewhat confident that in the next 10 year , perhaps shorter than that , we ’ll be able to orient to a bunch of stars in the sky and say they have planets around them that are similar enough to Earth that they might tolerate life , ” NASA ’s Division Director of Astrophysics , Dr. Paul Hertz , tell IFLScience .
Why will it take a few more years , though ? Well , it ’s all due to the method acting through which most satellite have been found . The vast majority of the several thousand exoplanets we jazz of have been feel by theKepler space telescope , which spots them by looking at many star at once and watching for “ drop ” in light if a satellite passes in front . The intensity of the drop can even denote the size of the satellite . It is known as thetransit method .
The limitations are obvious . First , we must rely on a planet kick the bucket in our furrow of sight congener to the virtuoso , and hope we are not looking at the system face - on . secondly , and most significantly , for a body to be confirmed as a major planet , three freestanding transits must be observed . This will clarify the period of the object ’s orbit , and also support it is actually in orbit rather than just flying by .
Thus , when Kepler was found in 2009 , many of the planets it find first were those in very little orbits , as these could be confirmed quickly . For planets in land - like orbit , that is orbiting their headliner in a twelvemonth or so , we have had to wait for three years of observations .
It is only now scientists are beginning to sift through the data for those longer - period planet , hence recent declaration such asKepler-186fand Kepler-452b . “ This exciting result brings us one step closer to finding an Earth 2.0 , ” NASA ’s Science Mission Directorate , John Grunsfeld , said of the latter’sannouncementin July 2015 .
There are almost certainly many more Earth - like major planet hiding in the datum , much of which has not yet been looked through . you could actually aid do this , via thePlanet Hunterswebsite .
This is n’t the only method of finding satellite , though – we can also point out their gravitational effect on their host star , known as theradial speed method , and we have even pop out todirectly imagesome exoplanets . But the huge bulk of our notice bank upon the transit method , and will continue to do so in future .
Image in schoolbook above : Artist ’s impression of the Kepler space telescope . NASA .
Kepler-452b , exemplify justly compared to Earth , is the most world - like satellite notice to engagement . NASA / JPL - Caltech / T. Pyle .
What are we bet for ?
Chances are , there are a broad chain of mountains of planets that are potentially inhabitable . Perhaps planets in tight orbits have organisms that can survive inextreme environments . Perhaps life around huge stars has evolved to cope with radiation . Perhaps liquid water system can live in more shoes than we suppose . The trouble is , we only have one representative of a human beings where animation has thrive , and that ’s Earth . So , it makes sense to look for major planet on the nose like ours .
“ We ’re look for life as we know it , because it ’s the only sort of animation we know how to search for , ” Dr. Hertz told IFLScience . “ Some twenty-four hour period we may find animation as we do n’t know it , but only because it may stumble us over the head . ”
Thus , if we can feel a planet that is the same sizing as Earth , orbit a star topology monovular to our Sun in the same lieu as our own macrocosm , it would be reasonable to assume that it would have the potential to be habitable . We have come close : Kepler-452b is jolly like , but it is 60 % bigger than Earth . Kepler-186f is 10 % larger than Earth and orbits in a habitable zone , but its parent star is a red nanus , not Sun - like . So the hunting continues for one that is an precise clon of our own world .
It may well be that dissimilar planets are also inhabitable . regrettably , at the moment , we do n’t cognize the limits of habitability . We do n’t even hump how life began on our major planet , or if it came from somewhere else . “ It depends if life arises commonly when conditions are right , or if it is a uncommon coincidence when conditions are perfect , ” added Dr. Hertz .
Rise of the major planet hunters
To avail in the James Henry Leigh Hunt for Earth 2.0 and other intriguing worlds , there are a people of new planet - hunting telescopes on the way .
In 2017 , theTransiting Exoplanet Survey Satellite(TESS ) will establish . While Kepler used to look at only a small portion of the sky , TESS will be an all - sky survey , observing 400 times more than what Kepler could see , totaling 500,000 stars including the unaired 1,000 cherry dwarfs to Earth . The proximity of these stars , around which TESS will centre on notice Earth - sized rocky planets , makes them select for keep abreast - up observation from other telescopes .
One of those is theJames Webb Space Telescope(JWST ) , due to launch in 2018 . This observatory will skylark a vast mirror made up of smaller hexangular segment , and is seen as the replacement to Hubble , able to resolve objects seven times salutary than its herald . Such is its business leader , it should be able to study the atmospheres of some exoplanets that are relatively close to Earth , within several dozen light - year , for signs of habitability , including flatulency such as methane and carbon paper dioxide and other biosignatures .
“ When we started design JWST , we did n’t know much about exoplanets , ” pronounce Dr. Hertz . “ But if we had tried to plan just the right capabilities into it so that it would be really well - suit for analyse exoplanet atmosphere , we would have ended up with the same JWST . ”
A few years after JWST comes into procedure , it ’s not unfathomable to hope that it might have a handful of Earth 2.0s run along up to see at from TESS data .
The habitable universe of discourse
determination and studying Earth replicas will be a huge achievement , and scientist are eagerly awaiting the discovery of another Earth . But perhaps an even more of import find is on the purview – that Earth is part of a much grander family of inhabitable human beings .
“ I think that it would be very presumptuous of us to think Earth was the only kind of inhabitable satellite , ” said Dr. Hertz . “ Just as we know Earth is n’t the centre of the universe any more , we should accept that Earth is n’t the centre of the inhabitable universe , either . ”
persona in schoolbook : Artist ’s impression of TESS , courtesy of NASA .
