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Three Tiny Exoplanets Suggest Solar System Not So Special
ananyo writes "Adding to its already long roster of firsts, NASA's Kepler spacecraft has found the three smallest extrasolar planets ever detected — all of them smaller than Earth, and the most diminutive no larger than Mars. The newly discovered trio forms a miniature planetary system orbiting a cool, dim red dwarf star called KOI-961. Because they are so close to their star, the three exoplanets are too hot to support life. But unlike most previously known exoplanets, the vast majority of which are Jupiter-scale gas giants, all three are thought to be rocky worlds like Earth and the other worlds of the inner Solar System."
So, Kepler is up, in orbit, doing it's thing. Scientists expect to learn a lot, from finally being able to see alien worlds that are a similar size to earth.
Those of us who are non-scientists know that this isn't really going to be that exciting, unless they find something that differs from are assumptions. We expect that there are many small planets out there, that have not been visible until Kepler. We know that we will never actually "see" these planets. Kepler is just able to watch for periodic changes in brightness of the star, which indicates planets crossing our view of the star. Based on the period, we can "guess" the diameter of orbit, and the size of the planet.
When we see a spectrum of light produced by a stellar body, we know something of its composition. But, we aren't seeing that with alien worlds. We just see the star that they orbit getting dimmer. So, we'll never know the real composition. Once again, we "guess" the composition based on the size of the orbit, and the mass of the planet, both of which we guessed, based on the periodic nature of the brightness.
In a matter of 3 weeks, slashdot has seen 4+ articles about planets "discovered" by Kepler. None of them have findings different from what we've expected, yet they've all received prime coverage by pop-science publications. This leads me to a new theorem:
Kepler (spacecraft) is a spammer!
Wake me up when we get interesting news.
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I've read this nice book on how (1) *animal* life (or an equivalent with slightly different chemistry - but still complex and multicellular) might be rarer in the Universe than we previously thought - mainly due to temperature stability problems during the long evolution of said organisms (main sequence stars shining progressively (and significantly) brighter as they age and the ecosphere having somehow to cope with it, which in case of Earth means some kind of CO2 feedback mechanism that tends to stabilize the temperature in a fairly narrow band of temperatures and that might be quite rare in the universe - again, a speculation), whereas (2) an alien equivalent of extremophilic bacteria might actually be much more common than we thought and could make up the greatest potion of Universe's biomass (just as it is on Earth). The question here is whether there are other interesting self-replicating molecules than just DNA and RNA. If not, then I guess we have quite a good idea as to how alien life looks like. (But I love to be proven wrong every now and then...)
Ezekiel 23:20
But at that level of pedantry, we might as well assume that life can exist within a star itself, and that planets aren't really important. Or for that matter, maybe these plants are actually large balls of cheese! Until we actually land on extrasolar planets, we can hardly begin to speculate on if what we are detecting are actually rock and gas.
Astronomy offers only very limited opportunities for observation and basically none for testing. We must supplement what data we can gather heavily using theories and understandings rigorously tested on Earth. While we can't rule out Star Trek style energy beings, for example, we can look at plasmas and their behavior and realize that forming synaptic pathways out is it would basically be impossible. We can draw up some pretty loose limits on life... If it's cold enough that helium is about the only liquid available or so hot that what hasn't melted are only impermeable rigid ceramics, the probability life exists is nil. If it's too hot for a man built machine to function, then it's probably too hot for life as well. It's just a matter of extending what we know about chemical processes, materials and mechanics... Too hot or too cold and making functional and reliable processes, let alone life, is too hard.
In this case, they are estimating a temperature of 400C. For comparison, silicone and fluoroelastomers top out at about 300C, while highly engineered fluorocarbon oils can only barely get to 400C . Simple hydrocarbons, among other things, can beat that but are highly reactive and can't survive in a reactive environment (particularly with oxygen). Nitrates decompose around that temperature too. So in what medium would life exist? A eutectic salt mixture? But those are so corrosive, what would then contain it? These are the questions the look at and can't answer when they say "life doesn't exist". (And all this doesn't even cover other issues, like the radiation hazards of being closer to the star.)
If we see a rocky planet at 200C, then we can really discuss how stuck we are on water based life being the only option and how open our minds should be. But this one? It's dead, Jim.
which in case of Earth means some kind of CO2 feedback mechanism that tends to stabilize the temperature in a fairly narrow band of temperatures and that might be quite rare in the universe - again, a speculation
The "quite rare" speculation is certainly based on definition. It would be correct to say "quite rare" if even a fraction of a percent of stars have an Earth-like planet. The "quite rare" may not be correct considering that such a small fraction could be billions of planets.
It is quite amusing that humans want to consider ourselves unique and somehow believe we will be the superior beings when life is discovered elsewhere. I certainly hope not, because it is quite depressing to consider we are the best of what the universe has to offer.
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GP has a point. We have no tools to search for life (outside of the solar system), we can only search for certain materials (e.g. water, carbon) and certain temperature ranges.
The Earth has passed through galactic arms around every 100 million years, as your link says. Life seems to have coped.
Give or take a few mass extinctions.