NASA has announced the discovery of a distant earth-like planet, Kepler-452b.
Kepler-452b is 60 percent larger in diameter than Earth and is considered a super-Earth-size planet. While its mass and composition are not yet determined, previous research suggests that planets the size of Kepler-452b have a good chance of being rocky.
While Kepler-452b is larger than Earth, its 385-day orbit is only 5 percent longer. The planet is 5 percent farther from its parent star Kepler-452 than Earth is from the Sun. Kepler-452 is 6 billion years old, 1.5 billion years older than our sun, has the same temperature, and is 20 percent brighter and has a diameter 10 percent larger.
“We can think of Kepler-452b as an older, bigger cousin to Earth, providing an opportunity to understand and reflect upon Earth’s evolving environment,” said Jon Jenkins, Kepler data analysis lead at NASA’s Ames Research Center in Moffett Field, California, who led the team that discovered Kepler-452b. “It’s awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; longer than Earth. That’s substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet.”
That’s all very interesting, but not too surprising. Don’t we expect to find rocky worlds a certain distance from stars with a certain frequency? I think it’s good research that will contribute to understanding how planets form outside our one local example, so the search for exoplanets is good research (unlike, in my opinion, the SETI boondoggle).
But if you’re going to call it “awe-inspiring”, I expect a little bit more than some basic parameters of mass and orbit, and the addition of one more data point. What next? It’s 1400 light years away, so we’re not going to get any probes there in my lifetime, or in the lifetime of my civilization, or even in the period that life exists on planet Earth. The rest of the article sounds like the goal is a catalog of planet sizes and year-lengths and ages. That sounds useful for understanding mechanisms, but is the discovery of one more planet something to be awed by? How does this contribute to our general knowledge of the formation of planetary systems?
I am totally unimpressed by all these articles that gush over exactly how earth-like this distant rock is. That seems to be missing the point completely.
That is one big “should”. I agree that this good research, but the “awe-inspiring” conclusions are way over the top.
I think some of the excitement is looking forward to the time when we will be able to get decent spectra. If we find water vapor and free oxygen, things will get very interesting.
The real gain here is that they found it around a G-class star like the Sun, which hasn’t been done before. There have been some promising “super-Earth” candidates found before, but most of them are around red dwarf stars, and I would very strongly bet that none of them are habitable – red dwarf stars go through an extended pre-main sequence period of 1-2 billion years where their luminosity is significantly higher than what it settles down to in the main sequence, meaning that any planets in their ostensible habitable zones would be Venus-ed before life could get off the ground unless they migrated inward afterwards.
Unfortunately, there isn’t much of a next step with this planet. As you said, it’s 1400 light-years away, meaning it’s much too far for us to hope that it might be imaged directly with any telescopes we can imagine inside of the next century. Now, if they had found it around Tau Ceti, or even around a G-class star somewhere inside of 50 light-years away, then we might have had a chance of eventually imaging it directly to see what its atmosphere and temperature actually are.
I don’t even think it’s the most “Earth-like” exo-planet we’ve found yet. It has a radius of 1.63 Earth’s, meaning that it’s about an even chance that it’s rocky vs “rocky with a thick, hot hydrogen-helium atmosphere”/gas dwarf. Some of the research and modeling on exo-planets found so far suggests that 1.5 Earth radius is an important threshold – below that, radius scales with mass and planets stay rocky. But above that, mass grows slower than radius, suggesting that planets are becoming less dense and maintaining large atmospheres full of volatiles and hydrogen. The most “earth-like” planet is still probably Kepler-62f.
There’s a tension in the astronomical community who want to discover Earth 2.0 and those who, like Dr. Myers, thinks the big benefit comes from large surveys of exoplanets to uncover mechanisms of formation and orbital evolution. So these Earth-like planets are often announced with adjectives like “awe-inspiring.”
One reason I am an ally of the demographics folks (my research is in another field) is that the discovery of exos has proven to be really surprising. In particular, many stars have “hot Jupiters.” which are as massive as Jupiter (about 300 Earth masses), but which have orbital periods measured in days to weeks. They probably did not form so close in, so orbital migration is likely to be important in many cases. Right now we do not have a good answer to the question in the post, “Don’t we expect to find rocky worlds a certain distance from stars with a certain frequency?”
As a biologist how are you not awed by the prospect of learning about life that had, potentially, an additional 1.5 billion years to evolve beyond what we currently understand? Sure we might not get pictures of them anytime soon… or ever, but if they exist then we will learn some things about them using technology currently being developed such as the James Webb Telescope and beyond. Who knows what that discovery might be or what revelations it would inspire. That would be in our lifetime and hopefully yours too :-P
Going to second Donterndrup @ 4, I think a lot of the scientific questions are ‘how well do we understand the population of planets that result from planet formation now that we can sample so many systems’. While Kepler-452b is interesting to the public because it’s a rather Earthlike planet for an exoplanet, there is a broader question of ‘what sorts of systems are common and rare*’.
(Or other things like how much the line between rocky and gassy planet varies between systems.)
While we can learn more about things like atmospheres via spectroscopy and photometry, and I think that it would be really neat. (Right now we have two examples of large terrestrial atmospheres, and both have changed a lot in the 5 billion years since they formed.) Kepler-452b (or other Kepler planets) are good places to look, given we can separate out planet and star in a transiting system. But right now, as I understand it, we don’t have the sensitivity for such a small planet.
Granted, I’m more interested in planets in general than that Kepler-452b might have life as we know it. Because we have four rocky planets (five counting dwarf planets, seven if you count all ’round rocky things’) to get good looks at, so it’s hard to generalize.
* And how that is affected by our ability to see them. A Venus or Earth is a lot harder to see than a 51 Pegasi b.
PZ asked:
Kepler has shown that there are more planets than there are stars, and that a few percent of those planets are of appropriate sizes and at appropriate distances from the stars they orbit that we might expect biologically-interesting chemistry to have happened on them. Kepler-452b is cool by itself, but that overall distribution is indeed more important for planning future research.
What happens next is expanded efforts to find the planets around nearby stars, most of which aren’t arranged such that a transit survey like Kepler can find them. Then we can study those planets in as much detail as one can from ten or thirty or a hundred lightyears away. Specifically, new hardware like the James Webb Space Telescope or the various extremely large ground-based telescopes under construction would let us get spectra of their surfaces / atmospheres.
Then we get to do a bunch of astrogeochemistry; and perhaps find some collection of compounds on at least one of the planets that suggests widespread biology.
Building the new hardware and finding the planets to study with it will take time.
Actually, astronomy (and most of the sciences) in general is pretty awe-inspiring to me. Even if it is just the mass and orbit of an obscure little planet orbiting an obscure little sun somewhere way off centuries of lightyears away. I find the fact that these things can even be discovered and observed awe-inspiring, in and of themselves. Sure, it’s just technology. And technology that gives pretty dull results (yay mass and orbit), but it’s technology that can bring us information from 1400 lightyears away!!! Yep, I may be naive, but that’s pretty darned awe-inspiring to me.
As for what will happen with that information? How is it useful to us? Fucked if I know. I don’t really care. It’s just awe-inspiring to have acquired it.
#5, Torish: Yes. Get back to me when there is any evidence of any kind of life at all on that planet.
Kepler-452b may not have had conditions conducive to life there before, but now that our esteemed host has thrown cold water on it…
Looks like 15-30% is the latest estimate. Of course, that data is from this mission, which is pretty damn revolutionary.
It’s weird how the news release seems to be talking about 2 Earth radii as an important threshold, when the actual data from radial velocity surveys of Kepler planets (to get the masses) suggest that the transition between terrestrial planets and Neptune-like planets occurs at a lower value around 1.5 to 1.6 Earth radii, which would suggest that Kepler-452b is not an Earthlike planet.
Then again, news releases with claims of habitable exoplanets have a history of being severely flawed. My favourite was the announcement of Gliese 581 c, where they didn’t bother with any of the already existing research into where the habitable zone would be but instead went with the “effective temperature looks nice” estimate. This was then used in the announcement of a habitable planet discovery, when a simple inverse square law calculation would have shown that the planet was substantially more strongly heated than Venus is.
I’m with rq on this – that fact that we can know anything at all about a planet 1400 ly away is pretty damn awe-inspiring.
And if we’ve found even one other rocky, habitable-zone planet in a G-class system so quickly, they can’t be that rare – which is kind of fun to know.
I’m with rq and opposablethumbs on this.
I find the Fermi Paradox really fascinating. This directly relates to one of the major points in the argument. We know there’s billions of galaxies with billions of stars. What about planets or earth like planets? Honestly, the rate at which we find these planets is a lot higher then I would have expected.
I see this as the basic leg work before we even consider the question of life.
Knowledge that has no direct economic benefit is a waste of time. (AKA ‘Old Man Yells at Clouds Again’)
I’m starting to think you just don’t like the universe, Professor Myers. Would you be happier if Earth were the entirety of the universe? :p
I kid, I kid. I know better than that, obviously. Just poking fun.
For me, the very fact is awe-inspiring, but I think that’s because I find space awe-inspiring. I really really love basically everything about space, without exception… and that includes the scary, creepy stuff and the seemingly boring, useless stuff. I love every time we find a new planet, and this discovery is no less exciting to me. And yes, I want to visit, even if it’s just the moon, or even the ISS. I would adore being able to fly out into space and being able to look at Earth from the outside. In my dreams, I imagine being able to go into orbit around Saturn for a bit, taking pictures and stuff, but I know that’s not likely… I have more chance of visiting the Moon than Saturn, and I don’t have much chance of ever visiting the Moon (or really leaving Earth’s atmosphere), either, despite it being high on my bucket list.
If you were to ask me why I feel this way about space, I’d have to say that I have no clue.
I think it’s awe-inspiring that we actually found it. I’m in awe of the fact that we can find planets outside our solar system. I think my biggest disappointment is that I won’t be alive to see direct, good images of those planets like we just got with Pluto, unless, by the time I reach my 80s, science has progressed such that I could live well into my hundreds, or later, while still being perfectly healthy, both physically and mentally. And even then… even if science affords me the opportunity to live well into my hundreds, or even to 200, I probably still won’t live long enough.
Don’t you hate those people that know nothing about your research field, but feel qualified to dismiss it out of hand anyway? Those people are so annoying
Sarah Palin whom as you recall mocked earmarked funds for fruit fly research in France. In no way I’m implying that your critique is identical to Palin’s foolish reasoning. But cutting down research of this kind in my opinion only provides fodder to the wacky Sarah Palins out there. Remember that nitric oxide was discovered in the yak testicular muscle which at the very outset probably was not so “awe inspiring” or something to “gush over”. Fast forward and it became the molecule of the year in 1992. Today, much of the pathophysiology research and ultimate treatments in stroke, Parkinson’s disease, ALS and cardiovascular disease hinge on understanding this free radical. I think the more we discover “earth-like” exo-planets, this is and will always be a good thing for science.
It’s still an entire planet PZ, isn’t every planet awe worthy? I know those shots of Pluto were pretty amazing to me anyway, and we’ve got basically zero expectation of life on that thing. I guess it all comes down to just how passionate one is for any particular field of study.
BTW… if anyone’s interested, this exoplanet is in the Exoplanetary Archive here, and here’s the pdf of the paper published to Astrophysical Journal (it’s a download link).
@18 ragdish
Isn’t nitric oxide the chemical whose production is stimulated by Viagra, and which results in, well… results?
aziraphale @2:
Do you know what the current distance limits (say for Sunlike stars and Earthlike planets) are for getting decent spectra?
things will get very interesting.
1400ly away. If things get interesting, they’ll get “interesting” on a time-scale of millenia. Which is hardly “interesting” to anyone at all.
yak testicles for the win
You’re forgetting it wasn’t until recently there was no proof (even if there was an expectation) of any extra-solar planets, let alone rocky ones.
Venus is an Earth-like planet…
Still, I’m pretty wowed by all these exoplanet discoveries. I was an adult before *any* planet was discovered. Sagan said there were big numbers of big numbers of them, but we had no proof beyond extrapolation from our own world. Now we’re seeing that in fact there are quite a lot of solar systems around, and quite a few have planets more or less similar to ours — as well as solar systems that are completely unlike ours.
An exciting discovery.
However, this star system is almost 2 billion years older than our own. That’s a lot of time for life to arise and get established, as some have said, but that’s also a lot of time for life to wither and die out.
The star’s luminosity is 20% greater than Sol, in keeping with G-type star stellar evolution for a star that old. Current projections of our sun’s own evolution has its steady brightening making earth inhospitable for all but bacteria some time within the next 1 billion years, and possibly a Venusian runaway greenhouse within that time span too.
Now this planet’s orbit is somewhat further away than earth’s, so that might mitigate the effect, but we must not discount the possibility that while this planet may well have been very earthlike, oh, 2 billion years ago, it may not be so anymore….
jonmelbourne:
numerobis:
I’m not sure what I’m supposed to make of statements like these. I mean, it’s obvious that before we observed any we hadn’t yet observed any. But you’d have to assume some extremely bizarre and improbable physical conditions all over the universe to get no planets, except for those around our star. Gravity makes planets in exactly the same way as it makes stars, and the absurdly high probability that results, of planet formation all over the place along with star formation all over the place, is as close as you need to be to say there’s “proof” when it comes to empirical facts like this.
I mean, look, if you really want to play that game, there’s a tiny tiny chance that our observations are all flawed or illusory so we still haven’t observed any — and disregarding silly possibilities like that looks the same to me as disregarding the tiny tiny chances of the dynamics being fed some totally wacky initial conditions which prevent extrasolar planet formation but allow it in our solar system. So it’s not as if that’s more like “proof,” meaning a probability so high you’d be perverted to act uncertain about it, than calculating how the dynamics plays out given various conditions and noticing how totally generic/normal/non-conspiratorial/non-miraculous planet formation is. Observing them is obviously another great piece of evidence that raises the probability there’s an extrasolar planet, but that can’t be a distinction between “proving” it and “not proving” it.
I think the point is that there was no proof because the technology did not exist to detect them. It’s not that the existence was really in doubt, it was the feeling that it would never be possible to actually observe them.
Then, all of a sudden, it was possible.
It seems silly to view things like this through the prism of today’s technology. To go from having no proof of extra-solar planets to proof of thousands in a few short years seems incredibly exciting to me. Who knows what it will be possible to prove in the future. (and no, I’m not saying warp drive is just around the corner. But perhaps direct imaging of extra-solar planets is.)
Just because there’s no direct applications of the science doesn’t make it any less exciting or worthwhile.
So they estimate that there’s about a 50/50 chance this object is actually a mini-Neptune rather than a terrestrial (let alone a habitable terrestrial). Don’t scientists usually demand a somewhat higher threshold than this before accepting a result? If so, why would they go and tell the media they’ve found “Earth 2.0” when the probabilities do not meet accepted standards of proof?
consciousness razor: I fail to understand where you actually disagree with anything I said, or what game you think I might be playing.
From theory we had a pretty strong prediction. In my lifetime it has been largely confirmed by consilient streams of observational evidence — and the observations have driven a need to refine the theories.
jonmelbourne@29 says it like I feel it, thanks for the rephrasing!
As far as I can tell no one directly associated with this is actually telling the media its “earth 2.0”. “Earth’s older, bigger cousin” is as close as it gets.
It’s the media that is running with the “Earth 2.0” stuff, all on its own.
The 50/50 chance for being a mini-Neptune seems to be simply because the data that determines that is the planet’s mass, which would give the density, and we don’t know that yet. So, no evidence one way or another, 2 possibilities, 50% each.
jonmelbourne:
Like I said, I don’t agree that “detection” means the same thing as “proof,” or that one is implied by the other. Of course it’s a great engineering or technological achievement that somebody built machines to do this, but we shouldn’t confuse things by suggesting that’s equivalent to an epistemic achievement. We already knew very well that there were extrasolar planets, and that didn’t suddenly change when we saw the first one.
I don’t get why anybody would’ve thought it’s impossible. Light keeps going and going and going. You build a big enough eyeball that’s sensitive enough, and you can see whatever there is to see. What exactly were you starting with if you had a feeling that can’t be done? Those things have been fairly well understood for a long time, and technologically speaking we had been making steady progress on it for nearly the same amount of time. It’s hard to pinpoint when that should’ve been totally obvious to somebody who’s reasonably well-informed about the science, but nobody around today was alive when that was something that you should’ve worried about.
consciousness razor @ 28:
like the totally wacky (but artistically fantastic—the curtain line of the book is, I think, the best in all science fiction and perhaps all fiction period; better than the curtain line of Asimov’s End of Eternity, which is merely witty) initial conditions that allowed planet formation in our solar system according to A. E. van Vogt’s The Weapon Shops of Isher.
Rob Grigjanis @22:
The distance limit for good spectra depends on your definition of “good” and on the size and orbit of the planet that you’re looking at. So far, exoplanet spectroscopy has been limited to gas giants – they are a factor of 100 easier than something the size of Earth the same orbit. For example, the 8-m Very Large Telescope has observed water vapor in the atmosphere of Tau Boötis b; which is 51 lightyears away ( Tau Boötis b is also about 6 times the mass of Jupiter and about 1300 C at the top of the cloud deck).
_
For new instruments, such as the E-ELT and some aspects of JWST, I’ve frequently seen design specifications for getting spectra of the Earth as it would appear 10 pc away (32.6 lightyears). Should give hundreds of rocky planets for which spectra will be useful for composition.
That will be the job of the James Webb telescope, and probably mass spectrometry to identify volatile gasses in it’s atmosphere that would be indicative of biological processes.
What, we should give up on research because we can’t perform it perfectly well right now? I think PZ demonstrates a prejudice against the ambition to find life elsewhere as this is the second time in a week he appears to argued we can’t do it now so give up.
Since MS requires the sample to ionized, that means a probe is at the planet.
What I think PZ is saying, is stop the exaggeration that because a planet is in X and Y ranges, it has life.
For examlple, I’ve seen a couple of essays/papers where the Earth’s moon might have been necessary for the primordial soup to start making biopolymers, either in tectonic vents or tidal flats, during the early Earth where the moon was close, and tidal heating and tides were large and frequent.
michaelbusch @36: Thanks.
fentex @37:
Did you read the OP?
Oops, I guess I meant spectra analysis?
That can be done remotely.
It’s quite a challenge to observe these distant planets and the planetary folks have been thinking of all sorts of schemes to work out whether a planet may sustain lifeforms of some sort. I’m not convinced that we will ever be able to make such an assessment. One proposed technique is to attempt to detect O2 in the atmosphere of the remote planet, which is in itself quite a challenge. The idea is that O2 will not exist in appreciable amounts in an atmosphere unless there is O2 producing life on the planet; this proposition of course depends on the current models of planetary formation being correct about O2 not being available unless there’s life on the planet – a proposition not easily established. At any rate, no SETI is involved here and I think it’s all very interesting stuff even though I’d prefer to put my own efforts elsewhere.
Considering the reactivity with oxygen with almost any other element, not a far fetched idea. In fact, it is almost required that some type of photosynthesis releasing dioxygen is required for an atmosphere with a stable amount of dioxygen over a few percent, and required for our present 20%.
I’m with the posters who think that it’s pretty awe inspiring that we can detect, and even get a good idea of the mass and orbit of, planets that are more than 1000 light years away. Anything about life, though, is pure speculation, on this and any other extrasolar planet. It’s likely to be pure speculation for a long, long time, as much as I wish we could get some solid evidence for or against life on various extrasolar planets. As far as I know, the only way we could likely get any evidence for even the possibility of life on extrasolar planets is what madscientist said at #42 – try to detect large amounts of oxygen in the atmosphere, or perhaps some other highly reactive chemical that could be generated by life and that would need to be constantly replenished – methane, maybe? Even if we did detect this, it wouldn’t be a guarantee of life, since it could be generated by an unknown geochemical process that we haven’t seen up close because conditions aren’t right for it in our solar system.
Still, I find the whole field of study fascinating in my enthusiastic layperson sort of way!
Perhaps a water world on the cusp of losing its water to a runaway greenhouse, with water vapor entering its upper atmosphere in large quantities, where UV from the star splits it, and the H2 is lost to space, would on spectroscopic analysis look like it has a significant amount of O2 in its atmosphere.
Such a world would still be very interesting to study from a habitability standpoint, since it is basically a world that was once habitable on the verge of becoming not so anymore.
I am always very suspicious of claims like that. There are solar tides, after all. And tides on the moons of Jupiter raised by resonant interactions with the other moons and the planet. The planetary systems of low mass stars, with multiple rocky planets in close and in orbital resonance with one another could easily generate similar tides on the habitable zone worlds.
And we humans synthesize biopolymers all the time without having to rely on the moon! Any process that produces repeated cycling of temperature and/or reagent availability should do the trick. And absolutely anything that is in an orbit will have all kinds of cycles going on. Even something like a short period icy comet on an elliptical orbit will have a cycle of warming and cooling, external sublimation and interior melting, once per orbit.
At the present time, the tides from the sun are 45% of contribution of the moon. What would it have been like 4.X billion years ago, with the same moon mass orbiting inside of the geosynchronous orbit at 20,000 miles or so. I’ve seen reports of 200′ tides, about 6-8 hours apart. The heating of the mantle would be enormous too, large tectonic movement with lots of hot rupture zones.
I searched for an hour, but didn’t dig up a good reference one way or the other.
So its just something to consider.
fentex @37:
I think you’re misreading him. He never said anything about giving up on the search for life elsewhere. He didn’t argue that “we can’t do it now, so give up”, so I’m not sure why you’re claiming he did.
1400 times the distance light travels in a year is pretty far away. I think that is a pretty remarkable ability to even see it. No we are not seeing it really are we, we are deducing it from differences in luminosity of the star it orbits and wobble in the stars orbit .
it is so far away it is almost absurd to think about it.
uncle frogy
So…
60% larger diameter means d(new planet) = 1.6*d(earth)
Assuming that it’s a rocky planet with a density ~earth’s density, you get a mass of 4.1*m(e) = m(np)
Of course, gravity falls off with d^2.
This leaves us with approximately 60% more weight if we were to visit such a planet’s surface.
Even if life comparable to earthly metazoans were to evolve (after an event crossing the threshold from chemo ==> bio), it seems 60% more weight for the same mass would have to have some significant impact on how evolution on land would proceed. Non-flying small mammals and reptiles (say less than 1kg, thus weighing less than ~3.5 pounds) would likely be impacted very little. Flying vertebrates of any size as well as larger mammals/reptiles would be impacted to some extent. I imagine that the non-flying vertebrate-analogues would be impacted more noticeably when you reach 10kg/35 lbs and probably dramatically starting somewhere between 30kg/105 lbs and 100kg/350 lbs.
As for land plants, as I understand it, hydrologic transpiration is the limiting factor for the height of the largest earthly trees. How would that be impacted by a surface gravity = 1.6g’s? I really have no idea. (Though remember: the height limit is a function of water’s self-attraction, the same force that gives rise to surface tension. This force shouldn’t be increased with increased gravity. Just because evaporation is pulling a water molecule free of a leaf-analogue that doesn’t mean that the higher force needed to pull that water molecule into the atmosphere increases the pulling force on the plant’s interior water column. Surface tension is a function of the electroweak force and cannot be increased simply by moving the water to a higher gravity environment.)
At heights clearly reachable for NP analogues of earthly plants, given the impact on transpiration, – heights that even with my ignorance I would expect to be clearly reachable would be over 6m/20 ft but no more than 10-15m/ 30-50 ft. – the “plants” would have to have somewhat more structural strength than an early counterpart.
Again, I’m ignorant here, so perhaps much taller plants would be practical given the transpiration limit, but I’m just talking here about what heights I feel confident could be achieved given my lack of knowledge. If it was a linear relationship, the 350 feet or so that represents transpiration’s hard limit on earth’s surface would represent a limit of approximately 220 feet (or so google tells me). 220 feet, if memory serves, is very close to 66.666666 meters. Since that’s actually 218 feet and change (again, if memory serves), let’s just call 220 feet (approximately) equal to 67m.
I really don’t know if the relationship would hold in a linear way, but that’s about the biggest I could imagine an NP sequoia-analogue getting.
Would the increased gravity create a more favorable environment for preserving higher-cost but higher-strength biological or bio-mineral structural elements?
I’m not sure that it would, if life evolved first in large bodies of water and only later advanced across the land. If it happened that way, the NP “metazoans” would have been under selection pressure for quite some time in an environment where buoyant forces would mitigate against spending too much energy on creating extra-strong structural elements.
On the other hand, mollusca.
I’m trying to imagine life on this world, and 60% diameter with 4xmass – especially where 10-12 time earth mass puts you in a neptune-class nearly every time – seems like it should have a dramatic impact, but it still seems reasonable to me that you could have trees, small analogues of earth’s small animals, and even medium-sized animals that wouldn’t of necessity be too different at the human weight scale.
Unless I’ve gone drastically wrong somewhere?
Crip Dyke @49:
Terminology quibble. There never was such a thing as the electroweak force*. Before and after electroweak symmetry breaking (via the Higgs mechanism), there are two forces/couplings. Before, there were weak hypercharge and weak isospin. After the symmetry breaking (at about 10^-12 seconds), electromagnetism and the weak interaction. And intermolecular forces are electromagnetic.
*A Grand Unified theory might have just one coupling. But then you’d have to refer to the electroweakstrong force :-)
Correction to #50:
Terminology quibble quibble. Shouldn’t ever really say “never was”. Should say “may never have been”.
I for one think it is pretty exciting to be able to pencil in some numbers supported by actual data into the Drake equation, and I’m not gonna let PZ rain on my parade.
So there!
What I understand PZ to say – and what I completely agree with – is, fine research, cut the unjustified hype.
The fact that you found a planet that is a bit larger and older than earth, and a bit further from a somewhat warmer star, with a slightly longer year, and we don’t really know anything useful beyond that, is no reason to go gushing to the press about your wonderful discovery – there were others before, and there will no doubt be lots more, and this particular one isn’t really all that sensational (at least so far).
“We found yet another exoplanet” is fine, “we found a planet almost like earth” is not – as someone already pointed out, we have a planet in this very system that’s very earth-like by those arguments, and it’s not all that earth-like in things like day length, athmosphere, or temperature, which seem rather important parameters.
consciousness razor (#34): We already knew very well that there were extrasolar planets, and that didn’t suddenly change when we saw the first one.
Well, some people were sure that was the case. But another large group of people didn’t believe them, and therefore the recent actual observations of extrasolar planets are very significant. It’s not unreasonable IMO to call these discoveries awe-inspiring. Even though they don’t provide even a hint of evidence for life, and won’t for some time to come, they make it that much more likely that life is out there somewhere.
Alas, the evolution of this star, while remaining inside the Main Sequece, will have increased luminosity by 30% more since the system was born. By now any s eas of the World have likely boiled off, like on Venus. And erosion alter the thickness of Continental plates. Those on Earth grew thick enough to rise above sea levels 3 billion years ago, and will be submerged again in ca. 2 billion years, except by then our oceans will be gone.
birgerjohansson @55:
Kepler-452b currently receives ~1.1x as much incident energy per unit surface area as the Earth does; far less than Venus (which is at about 1.9x Earth). It may be in a runaway greenhouse state, to the point that there is no clear distinction between the bottom of the atmosphere and the supercriticial liquid of a deep ocean. Or it may be relatively pleasant at its surface – we simply don’t have the information to say.
_
If 452b does have plate tectonics and continents, they will not necessarily have been completely eroded. Continental crust on Earth doesn’t follow a simple pattern; but has been episodically built over the last several billion years – there was some crust above water as early as 4 billion years ago (e.g. Jack Hills zircons from Western Australia). There is a prediction that episodes of continent-building should decrease with time as the Earth cools down and the geothermal heat flux that drives plate tectonics decreases. But, as you say, with Earth’s current atmosphere the oceans will boil into steam in about 1 billion years.
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What has happened on 452b again depends on its detailed composition, which we don’t know. It did have more geothermal heat per unit surface area to begin with than Earth or Venus.
Crip, are you suggesting that Kepler-452b is full of cephalopods?
Gravity at the surface is linear in diameter for bodies with the same density. But density varies quite a bit in our solar system: Earth is 5.5 g/cm^3, Mercury is 5.4, Venus is 5.2, Mars is 3.9. With Martian density, Kepler-452b beasts would only face 13% more gravity than Earth beasts would. But they’d have rather a lot less access to metals than we do.
numberobis @57:
For an Earth-like, Venus-like, or Mars-like composition, Kepler-452b would be denser than Earth or Venus. Greater gravity and greater radius means greater internal pressure compressing the materials. For example: the Earth’s inner core has a density of 13 to 14 grams per cubic centimeter, whereas similar iron-dominated mixes only have density ~9 grams/cc in the center of Mars and around 8 grams per cc at zero pressure. We don’t know the equation of state (the relationship between pressure and density) for Kepler-452b’s interior, so we can’t derive its overall density without actually measuring its mass.
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Different composition would give different densities. e.g. Mercury lost most of its rocky mantle, leaving behind a relatively-uncompressed iron core that still pushes the average density up to 5.43. There are a few known small exoplanets that are comparable in size to Earth but much denser; and there are others that are much less dense. The former are inferred to be iron-rich, the latter to be predominately water and/or other low-density volatiles.