Typically it takes quite a few months before a submitted article in nature has passed the peer review process and has been accepted – and then until it is actually printed, it usually takes even more then a quarter of a year. So it is of course surprising when in the journal of 03/02/2011 an article was published which was filed on 13/12/2010 and was exactly a week later already accepted on 12/20/2010. The subject of the article was worth the journal an editorial and two further articles in the same issue, and furthermore an artistic representation of the article’s contents adorns the cover.
A big deal then, nature headlines “Six new worlds”. The article of the NASA research team  reports – in a sober tone, as it should be – the discovery of a solar system with 6 relatively light planets orbiting a star that is relatively similar to our sun. The name of the star is simply Kepler-11, its planets are simply called Kepler-11b and Kepler-11g.
The scientists have done not only an amazing performance of the measurement technique, but also the solution to a tricky math problem.
You can not see with the space telescope Kepler directly that a planet orbiting a star. A regular decrease in the luminosity of the star is measured – and trom these data one can calculate the size and orbit of the planet.
If one imagines that it is not just one planet, but many, which revolve around the star at different orbital periods, then the course of the shading looks irregularly, as the planets (which have different sizes and orbital periods), sometimes simultaneously, sometimes wandering one after another in front of the star. And at this point of investigation the calculation starts. You have to try to figure out how many planets fit the luminosity of the star with the best turnaround times and sizes of the shapes.
But that’s not all: When the planets orbiting relatively close around the star, they influence mutually by their gravitational fields, thereby the orbital periods vary and therefore the luminosity of the star. But this additional difficulty is also a chance to find out more about the planets. From the fluctuations then the different planet masses can be calculated, and with the sizes of the planets is then given the density and from this one can even derive assumptions about the composition of the planets material.
At the end of the whole calculation the researchers found that six planets are orbiting Kepler-11, all of them have a much smaller orbit than Earth, and thus much shorter years. The slowest of them, Kepler-11g provides nearly four passes while the earth circling in one year. The planets are all larger and heavier than the Earth, but they have a lower density, so there consist probably less of stone and iron rather than of water, helium and hydrogen.
Maybe Kepler-11 has even more planets, the star is observed only since one and a half year and if the planet orbital period is longer, it has perhaps not yet passed by in front of their star. So maybe there is a planet that is even more similar to the Earth than Kepler-11b to g. And that’s what caused all the excitement, which the very title of editorial nature brings to the point: “Earth 2.0″.
When a planet is found being similar to the Earth, then there it might have supported life, perhaps including “intelligence” – that is the hope that revolves around the whole research program that is ultimately the motivation of the whole planet-hunting.
But must the residence of other life forms be truly Earth-like? Somehow it seems that we can think of nothing else. There must be water; it must be not too hot, not too cold. Only under such conditions life is be possible, this seems to be the general consensus that also is reflected in the concept of the “habitable zone”, the area around each star, in which these conditions are met.
But complex structures and processes can emerge probably in conditions that we consider extreme and hostile. The life arising there probably will be as alien to the human, that we can not recognize it at all – especially if we are only looking for something that is similar to us. As long as we are looking for a second Earth, we will probably learn many interesting details about other stars and their planets, and we will be amazed about the findings scientists can derive from a couple of variations in brightness, but other life, other intelligence we will hardly find. Perhaps that is even better because we have to be scary about the consequences of our own intelligence.
 Lissauer JJ, Fabrycky DC, Ford EB, Borucki WJ, Fressin F, Marcy GW, Orosz JA, Rowe JF, Torres G, Welsh WF, Batalha NM, Bryson ST, Buchhave LA, Caldwell DA, Carter JA, Charbonneau D, Christiansen JL, Cochran WD, Desert JM, Dunham EW, Fanelli MN, Fortney JJ, Gautier TN 3rd, Geary JC, Gilliland RL, Haas MR, Hall JR, Holman MJ, Koch DG, Latham DW, Lopez E, McCauliff S, Miller N, Morehead RC, Quintana EV, Ragozzine D, Sasselov D, Short DR, & Steffen JH (2011). A closely packed system of low-mass, low-density planets transiting Kepler-11. Nature, 470 (7332), 53-8 PMID: 21293371
Editorial (2011). Earth 2.0. Nature, 470 (7332) PMID: 21293328
Reich ES (2011). Astronomy: Beyond the stars. Nature, 470 (7332), 24-6 PMID: 21293349
Billings L (2011). Astronomy: Exoplanets on the cheap. Nature, 470 (7332), 27-9 PMID: 21293350