It can't. Much of that speculation derives from just one phrase in the press release I think, where they say: "Today, and thousands of discoveries later, astronomers are on the cusp of finding something people have dreamed about for thousands of years -- another Earth."
The idea of what that means by "another Earth" for astronomers who know the capabilities of Kepler, is rather different from what most of the general public would think of when you say "another Earth".
Kepler is best for getting an idea of what proportion of stars have planets, and of what types, because it focuses on a small patch of the sky, using transit method, looking at lots of stars likely to be far away. It can't tell much except the diameter of the planet and its orbital period, and spectral type of its parent star. Anything else such as its mass is informed guesswork.
So, anyone with that background knew in advance that this announcement could only tell us things like that, and understood the press release accordingly. Just from knowing that it was a Kepler press release. Unless just through luck it happened to find some nearby star, that is, but typically you expect them to be distant stars, at their closest, hundreds of light years away, so far away any light signal due to the planet's atmosphere or surface would be very faint indeed and hard to analyse.
But now that it's found that some G type stars have planets like Earth - that means that maybe even some of the nearby G type stars, maybe even Alpha Centauri, - makes it a bit more likely we may find Earth like stars around those also.
There are many much closer potentially habitable exoplanets already known - the one NASA just announced is the one labelled "New" here::
The Habitable Exoplanets Catalog - Planetary Habitability Laboratory @ UPR Arecibo - organized by distance from Earth.
And this new exoplanet is not even the one most similar to Earth found so far if we show those same planets organized by their "Earth similarity index" then it is sixth in this ranking.
HEC: Graphical Catalog Results - Planetary Habitability Laboratory @ UPR Arecibo - organized by similarity to Earth.
The main thing that's notable about it is that its sun is very similar to our sun. Which given that our sun seems to have been pretty much ideal for life on Earth, may be a good sign.
But then on the other hand, might be that there are other stars that are also good stars for life, is hard to reason very far with a sample size of just one known inhabited star to date. The smaller and more numerous red and orange dwarfs also seem to have a lot of promise for habitable worlds, and because there are so many of them, could easily be that the best places to look for life are around, e.g., orange dwarfs (or red dwarfs), or whatever. We just don't know at present.
And note - that we know nothing about this planet except its size and orbit. Don't really know its mass - that's a guess. Amongst other possibilities:
There's no evidence yet to suggest the last of those possibilities is more likely than any of the others, or indeed to assign it a probability at all, we just don't know enough to say anything with any assurance there.
The chance that it is a rocky body rather than a miniature gas giant type planet they estimate as between 49% and 62% - that's based on statistical analyses of nearby rocky planets (around red and orange dwarf stars). such as this one. The Mass-Radius Relation for 65 Exoplanets Smaller than 4 Earth Radii
For the paper and the calculations:
Discovery and validation of Kepler-452b: a 1.6-r⊕ super earth exoplanet in the habitable zone of a G2 star
and short scientific summary: Kepler telescope identifies new ‘habitable zone’ planet, abstract: Page on iop.org
But is early days yet. We don't have much chance of finding out a lot about it at that distance, but given that there are likely to be many planets like that closer to Earth, other searches and telescopes will probably let us study those ones and eventually find answers to questions like that for the closer stars, especially e.g. after the launch of a giant telescope to the Sun Earth L2 position - pointing away from the sun especially designed to help with the search for habitable worlds (the James Webb telescope).
If close enough for spectroscopic observation we can look at its atmosphere and detect e.g. if there is oxygen, methane etc in its atmosphere. And also spectroscopic observation of its surface also and distinguish e.g. if it has oceans or ice, or even maybe detect organic chemicals produced by life e.g. whatever is its equivalent of chlorophyll if it has it. Eventually there are methods that may be able to pick out the larger permanent surface variations also such as ice caps and continents (based on the spin which lets us see different parts of it at different times).
There are many nearby planets that may well be habitable. List of nearest terrestrial exoplanet candidates
And even restricting search to sun like stars, quite a few nearby G stars.
Even Alpha Centauri, closest G type star known to Earth, only 4.24 light years away, only a little further than Proxima Centauri, the closest known star to Earth, could have planets in its habitable zone.
These authors in a 2008 paper raised the possibility that we could detect those planets: Page on arxiv.org
And there is a search underway to try to find them: The Mt John University Observatory search for Earth-mass planets in the habitable zone of α Centauri
Once we find many of these planets, and are able to study them in detail, surely many of them will be Venus like, or ice covered worlds, or mini gas giants or in other ways not easy for life to inhabit - and perhaps some will be habitable but not have life on them. All telling us a lot about the possibilities for solar systems like ours.
In short this is one significant step along the road to detecting habitable exoplanets - as to whether this particular one is habitable, nobody knows, and maybe the chances aren't that great that it is (depending on how easy it is for a habitable planet to arise around a G type star) but the evidence suggests its one example of a large population of planets around sun like stars - and so with so many planets this increases the chances that we may be able to detect one, or indeed most likely many such planets close enough to study - not just like Earth but also orbiting a sun-like G class star.
And - whether they are Earth like to the extent of having life on them or not, they are also of interest as planets in solar systems like ours, so telling us things about past and future and alternative present for evolution of planets in our own solar system.
BTW they said that the age of 6 billion years is correct to about +- 2 billion years. So - though probably older than our solar system, it's still within the bound of possibility that it is younger. If older, it could also give us an idea of some of the possibilities for future evolution of planets in a solar system similar to ours, though this particular planet is five times more massive than Earth.
See also: Robert Walker's answer to Is there a way to detect if there is intelligent life on Kepler-452b?
The idea of what that means by "another Earth" for astronomers who know the capabilities of Kepler, is rather different from what most of the general public would think of when you say "another Earth".
Kepler is best for getting an idea of what proportion of stars have planets, and of what types, because it focuses on a small patch of the sky, using transit method, looking at lots of stars likely to be far away. It can't tell much except the diameter of the planet and its orbital period, and spectral type of its parent star. Anything else such as its mass is informed guesswork.
So, anyone with that background knew in advance that this announcement could only tell us things like that, and understood the press release accordingly. Just from knowing that it was a Kepler press release. Unless just through luck it happened to find some nearby star, that is, but typically you expect them to be distant stars, at their closest, hundreds of light years away, so far away any light signal due to the planet's atmosphere or surface would be very faint indeed and hard to analyse.
But now that it's found that some G type stars have planets like Earth - that means that maybe even some of the nearby G type stars, maybe even Alpha Centauri, - makes it a bit more likely we may find Earth like stars around those also.
There are many much closer potentially habitable exoplanets already known - the one NASA just announced is the one labelled "New" here::
And this new exoplanet is not even the one most similar to Earth found so far if we show those same planets organized by their "Earth similarity index" then it is sixth in this ranking.
The main thing that's notable about it is that its sun is very similar to our sun. Which given that our sun seems to have been pretty much ideal for life on Earth, may be a good sign.
But then on the other hand, might be that there are other stars that are also good stars for life, is hard to reason very far with a sample size of just one known inhabited star to date. The smaller and more numerous red and orange dwarfs also seem to have a lot of promise for habitable worlds, and because there are so many of them, could easily be that the best places to look for life are around, e.g., orange dwarfs (or red dwarfs), or whatever. We just don't know at present.
And note - that we know nothing about this planet except its size and orbit. Don't really know its mass - that's a guess. Amongst other possibilities:
- It could be a tiny version of Jupiter - a miniature gas giant with no solid surface.
- Its oceans could have boiled away like Venus. Like Venus it could have a dense atmosphere and a surface temperature of hundreds of degrees centigrade.
- It could be a snowball planet, just solid ice on the surface to depths of tens or hundreds of kilometers (which might or might not have a habitable ocean beneath it but we'd have no way of knowing either way by observation from Earth with present day technology).
- Could be a bare rock with no water or atmosphere at all.
- It could be an ocean world, but with no continents or shallow regions, everywhere hundreds of kilometers deep oceans, with the floors of the oceans covered in thick layers of dense ice (if the ocean is very deep then you get a form of ice that sinks rather than floats) - so insulating the water from minerals and rocks making it rather unlikely that life evolves according to modern ideas.
- Or it could be a world with shallow oceans and continents, and an atmosphere of some sort, not necessarily an Earth like atmosphere, with or without life.
- Or a second Earth closely resembling our planet geologically.
- Or, even a planet with life and multicellular life closely resembling Earth life.
There's no evidence yet to suggest the last of those possibilities is more likely than any of the others, or indeed to assign it a probability at all, we just don't know enough to say anything with any assurance there.
The chance that it is a rocky body rather than a miniature gas giant type planet they estimate as between 49% and 62% - that's based on statistical analyses of nearby rocky planets (around red and orange dwarf stars). such as this one. The Mass-Radius Relation for 65 Exoplanets Smaller than 4 Earth Radii
For the paper and the calculations:
Discovery and validation of Kepler-452b: a 1.6-r⊕ super earth exoplanet in the habitable zone of a G2 star
and short scientific summary: Kepler telescope identifies new ‘habitable zone’ planet, abstract: Page on iop.org
But is early days yet. We don't have much chance of finding out a lot about it at that distance, but given that there are likely to be many planets like that closer to Earth, other searches and telescopes will probably let us study those ones and eventually find answers to questions like that for the closer stars, especially e.g. after the launch of a giant telescope to the Sun Earth L2 position - pointing away from the sun especially designed to help with the search for habitable worlds (the James Webb telescope).
If close enough for spectroscopic observation we can look at its atmosphere and detect e.g. if there is oxygen, methane etc in its atmosphere. And also spectroscopic observation of its surface also and distinguish e.g. if it has oceans or ice, or even maybe detect organic chemicals produced by life e.g. whatever is its equivalent of chlorophyll if it has it. Eventually there are methods that may be able to pick out the larger permanent surface variations also such as ice caps and continents (based on the spin which lets us see different parts of it at different times).
There are many nearby planets that may well be habitable. List of nearest terrestrial exoplanet candidates
And even restricting search to sun like stars, quite a few nearby G stars.
Even Alpha Centauri, closest G type star known to Earth, only 4.24 light years away, only a little further than Proxima Centauri, the closest known star to Earth, could have planets in its habitable zone.
These authors in a 2008 paper raised the possibility that we could detect those planets: Page on arxiv.org
And there is a search underway to try to find them: The Mt John University Observatory search for Earth-mass planets in the habitable zone of α Centauri
Once we find many of these planets, and are able to study them in detail, surely many of them will be Venus like, or ice covered worlds, or mini gas giants or in other ways not easy for life to inhabit - and perhaps some will be habitable but not have life on them. All telling us a lot about the possibilities for solar systems like ours.
In short this is one significant step along the road to detecting habitable exoplanets - as to whether this particular one is habitable, nobody knows, and maybe the chances aren't that great that it is (depending on how easy it is for a habitable planet to arise around a G type star) but the evidence suggests its one example of a large population of planets around sun like stars - and so with so many planets this increases the chances that we may be able to detect one, or indeed most likely many such planets close enough to study - not just like Earth but also orbiting a sun-like G class star.
And - whether they are Earth like to the extent of having life on them or not, they are also of interest as planets in solar systems like ours, so telling us things about past and future and alternative present for evolution of planets in our own solar system.
BTW they said that the age of 6 billion years is correct to about +- 2 billion years. So - though probably older than our solar system, it's still within the bound of possibility that it is younger. If older, it could also give us an idea of some of the possibilities for future evolution of planets in a solar system similar to ours, though this particular planet is five times more massive than Earth.
See also: Robert Walker's answer to Is there a way to detect if there is intelligent life on Kepler-452b?
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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