Our Solar System Isn't Normal
npr.org
npr.org
Both methods are biased towards finding big planets (which produce clear, easy to detect spikes) that are close to their star. (so you get enough data points) Kepler tends to be a little more biased, simply because it hasn't been running long enough: http://en.wikipedia.org/wiki/File:Exoplanet_Period-Mass_Scat...
Kepler was launched in 2009. Realistically, you'd have to run it for another three or four centuries if you wanted to detect exoplanets that orbit as far out as Neptune. (orbital period: 165 years) No wonder we're seeing a lot of planets orbiting close in!
I have no idea of what the actual numbers are, but if we need to probe 100000 stars to find one that has an exo planet, it means that the radial velocity method might not be that efficient.
I'm not trying to single you out here. I'm just curious what one has to say on HN so as not to be corrected.
Is there some "don't assume I've implicitly made a bunch of unsupported remarks" initialism that I can tack on to the end of all my posts?
/DAIIMABOUR
Eventually, Kepler and Kepler-like probes will be able to locate all earth-like planets with orbits that cross the path between the star and us. However, this technique will find the larger planets with shorter orbits first.
Granted I don't know there search pattern but we are talking about less than 1,000 systems at this point. And I think we have found 2 reasonably earth like planets already which suggests there are at a minimum millions of them in this galaxy.
For instance, maybe they are able to model the effect of the bias, at least for some range of planetary masses, and the bias is not enough to explain the frequency-vs-mass curve they are getting. Or maybe their use of multiple techniques allows them to characterize the bias.
This excerpt from their recent paper on an Earth-like planet in the habitable zone of a nearby M-class star gives an indication of where they're going with this work:
"Using the relations given by Charbonneau et al. (2007), the reported candidates have non-negligible probabilities of transiting in front of the star (∼2.7%, 1.1%, and 0.6% for planets b, c, and d, respectively). [...] With the new generation of optical and infrared spectrographs, many nearby M dwarfs will be efficiently surveyed for low mass planets. If the detection rate holds, very soon now we may have a real chance of searching for spectroscopic signatures of water and life on one of these worlds."
In other words, detect a bunch of candidates, watch for transits, and use spectroscopic information to detect water.
Yes, scientists may have been quoted in this article, but I have seen how most journalists mangle, ignore, or sensationalize things that were said.
I only had time to look at the first few minutes, but around 6:50 she does say that our solar system is "not that common", which she quantifies as "it could only be as much as 10-20% of star systems". Maybe that means <= 10-20%?
So, this does not seem to contradict anything Vogt and Brown were quoted as saying.
Incidentally, I wasn't going by the statement in the NPR article, but also by the press release from UCSC (http://news.ucsc.edu/2012/12/tau-ceti.html), Vogt's home institution. I don't think that quote is subject to journalistic mangling.
IOW, I disagree with NPR's claim that "Our Very Normal Solar System Isn't Normal Anymore". Addendum: It may indeed be abnormal. But we don't have data to conclude that yet, or even to suspect it.
Listen carefully to the video. She says "It could only be as common as 10-20%". Just before saying that, she pauses and looks upward, to formulate the sentence correctly. The 10-20% number is an upper bound, not a direct estimate.
You have to give her credit for communicating the idea carefully. The difficulty of doing this in real time is extreme. And if you do it wrong, you really get taken to task by your colleagues.
All of science is based on sampling bias, by definition. That's one of the main reasons why science isn't a perfect lens for discovering truth. But just because something is probably wrong doesn't mean it isn't a 'scientific fact.'
1) Things which orbit rapidly are easy to spot as we get lots of observations from occlusion and wobble. You can identify a planet over the course of a few weeks if it has a period measured in days.
2) Things which are massive are easy to detect using wobble methods. The closer in they are, the more wobble there is. GMm/r^2 and all that.
3) Massive close-in things with short periods are the easiest planets to detect by a country mile, as you get a nice big occlusion along with a nice big wobble, all happening on nice short timescales.
This entire article is oriented around sample bias due to current instrumentation and techniques. We have little hope of spotting the equivalent of, say, Uranus, with the same orbital period and distance, as we'd need, um, a good few centuries of observations using wobble and occlusion to be certain - and the net effects measured would be tiny, so you'd need a huge pile of data to get a statistically significant measure.
Finally, earth-mass planets at an earth-like distance - again, tricky. Less tricky than the above, arguably, particularly if they have atmospheres (spectral changes are a dead giveaway), but still tricky.
JWST could serve up the goods.
Even with sampling bias, we could still be seeing something legitimately weird. We expect to detect some certain number of exo-planets with a certain range of characteristics with our current technology. We don't think this set of exo-planets is necessarily representative of the average exo-planet in the galaxy, because of the limits of our technology, but we expect to look at X stars, and see Y planets, which look about like Z (where Z is probably Jupiter-sized planets orbiting at Jupiter-like distances). We might also expect to see a few weird planets, where the solar systems are aberrations or we just got lucky and detected something better than we'd expect with our technology.
But what this article seems to be saying (maybe a little poorly) is that the set of planets observed is not the subset of planets we expected to observe. We expected (say) to look at 100,000 stars, see 100 normal Jupiters, fail to see 9,900 other normal Jupiters that were there but we didn't detect, and see 1 aberration, like an Earth-like planet we accidentally detected or a hot Jupiter representing a weirdly captured wandering planet. Instead, we saw 1000 aberrations, hot Jupiters. More than we expected to see based on how we thought solar systems formed.
Just because the unexpected thing is actually extremely easy to detect once you're looking at the universe in the right way doesn't make it any less unexpected. Even if we eventually find millions more solar systems that look like ours than ones with hot Jupiters, we might still have to figure out why there are so many more hot Jupiters than we expected.
I think this case falls under the lack of journalistic integrity, regardless of whether the overall claim is right or wrong. My view is that when a science article wants introduce the idea that reality may be different than conventionally believed, the goal should be to write an (at least mildly) well rounded, informative piece, not a strictly persuasive piece. When the first response in hundreds of armchair physicists' minds around the world is surprise that selection bias wasn't even mentioned (mine included), I think it's fair to say the article falls more into the persuasive category.
"Hot Jupiter" type planets aren't as much of a revelation as one might expect, however, given the prevalence of binary systems, many of which have very, very short periods (J0106-1000 has one of 39 minutes) - and there's still nothing to say that those same systems don't have rocky worlds tucked away that we can't see due to the overwhelming noise from the massive inliers.
The evidence in solar systems so far does NOT fit the theory involving a frost line, and giants like Jupiter are unexpectedly observed tightly orbiting suns. Whether our solar system is normal is conjecture, but our model for how solar systems are(were?) formed is obviously flawed. Pretty interesting find, imho.
The point about sampling bias is that our current techniques are bad at spotting systems like ours. If this is true (I think it is, but I'm not qualified to say), we wouldn't expect the evidence to fit our theory even if our theory were true because we are nearly incapable of finding evidence that does fit our theory no matter how much of it there is out there.
Mike Brown, an astronomer at Caltech, wrote me that while everybody is busy hunting for an Earth-like planet, they missed this story. "Before we ever discovered any [planets outside the solar system] we thought we understood the formation of planetary systems pretty deeply." We had our frost line. We knew how solar systems formed. "It was a really beautiful theory," he says. "And, clearly, thoroughly wrong."
Light has trouble pushing heavy materials outwards, so theres a denser percentage of them in close to a star, the lighter the material the more it gets pushed out, high percentage of hydrocarbons in outer planets. Like a giant centrifuge. So our system should be fairly standard unless the rules of physics are different elsewhere.
That doesn't exclude random formations as you are dealing with super heated eddies, explosions etc... during formation. Or even stars pulling there planets in. Both our planet set up, and hot Jupiters are to be expected because its a giant chaotic exploding mess.
The anthropic principle, that is. Isn't it possible that, while gas planets clustered closely around the star is the normal shape of solar systems, such a configuration is not amenable to complex life?
Looking at our own planet, I would guess that it's a combination of a) it being simply infeasible to send large animals to distant stars (we haven't yet colonised the moon or even made a serious attempt to colonise low earth orbit, and we might not do so before we run out of cheap energy) and b) technological singularities.
I don't know. Robin Hanson blogs a lot about it, but none of the steps seem terribly plausible although my favorite currently is big brains being feasible - in a number of ways, heads seem to be rare, big brains even rarer, and the costs of big brain almost too expensive to bear because neurons seem to be unable to get more efficient; one paper I liked on the topic was http://www.pnas.org/content/early/2012/06/19/1201895109.full... but you can find a lot of relevant material in http://www.gwern.net/Drug%20heuristics
I imagine that if there were another planet in the solar system capable of supporting native life with just 18th-century technology, we would already have sent people there, even if it were a multi-year trip. Which would provide big economic drivers for interplanetary transport.
Although I'd immediately agree that those are filters hindering the spread of any humanlike civilisation, it doesn't at all stop the spread of other, technological forms - the "vile offspring", to borrow a term.
Honestly, I have no idea what might work as a future filter, at this point. I don't think the expense could be it; that's going to drop, quite abruptly once uploading (or straight-up AI) works well enough.
Call it the "two neptune filter", to borrow from the article. :-)
Now that only our system's configuration - as special or as common as it may be - is amenable to complex life is completely unrelated and unfounded.
One of JWSTs mission objectives is to study the planetary systems discovered by Kepler, and the origins of life.
http://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Miss...
It's large aperture infrared sensors will have an unobstructed view of the universe (unlike Hubble which is in low earth orbit, and so only gets 90 minute windows of observation).
Basically, using IR spectroscopy we will be able to analyse the atmospheric composition as well as the thermal emissions of exoplanets.
Finally, JWST won't be limited to a small, fixed field of view like Kepler.
"Or maybe it got ejected — astronomers are finding emigrant planets, lonely orbs that wander the universe with no star, just drifting. Maybe one of those used to live here."
There are planets not orbiting stars? I searched Google for "emigrant planets" and the npr article is the number 1 result for that. I think he invented the term. What are these called if I wanted to find more information about them?
http://www.nbcnews.com/id/49823152/ns/technology_and_science...
http://en.wikipedia.org/wiki/Rogue_planet#Known_or_possible_...
One could argue that these are proto-stars, or brown dwarves, I guess - but to me, no fusion == planet.
It probably wouldn't be intelligent life, but maybe there are microbial lifeforms somewhere in the universe which call a rogue planet their home. That's awesome to think about, although it is extremely likely that such a planet will never be discovered. It's just really hard to track down a rogue planet, even a large one.
http://www.youtube.com/watch?v=LhAobPugvsk#t=3s
The year: 1994. From out of space comes a runaway planet hurtling between the Earth and the moon, unleashing cosmic destruction!
I always thought that intro was ridiculous until they discovered that runaway planets actually do exist and they are in fact hurtling through space...
Now the question that remains is, which configurations are more favorable to life, not just as we know it.
It's a little weird in that all players take turns simultaneously (you still have movement restrictions, etc, but it adds a real-time component because you want to wait to react to your opponent's movements, but also there's a time limit). The impression I got was that it was a way to speed up gameplay (less sitting around while others make their moves).
But it's a cool little game, lots of race customisation (with a few truly unique race benefits), interesting four-category tech tree (and equivalently, four ways to win), custom ship classes built out of components (like Gal Civ).
The combat is a little weird, they have some card-game-like thingy that can significantly influence battle outcomes.
EDIT: Not a turn-based game but there's also this: http://triton.ironhelmet.com/
Neptune's Pride is an always-on real time game played over several weeks in matches of up to 12 players. The mechanics are refreshingly simple, and there's a focus on diplomacy and betrayal in order to come out top.
I would think that a gassy planet close to a star would have to have a really big solid or liquid core of heavy elements.
Maybe if they're Jupiter-sized, then they would make some orbits further out unstable, but if they're smaller...
The system can be different than ours but still just as habitable, or even more so.
Space... space... so much space... gotta see it all...
Not entirely—we have to understand statistics and the anthropic principle, which states "observations of the physical Universe must be compatible with the conscious life that observes it." (Wikipedia: http://en.wikipedia.org/wiki/Anthropic_principle). In other words, our situation appears "perfect" because it was one of the many random combinations available which produced an observer able to look at it. In other words, the fact that our solar system is so stable might just be a random anomaly, but the fact that it was so stable resulted in our existence, and therefore our contemplation of the fact.
As an analogy, winning the lottery is extremely rare—if you go and interview the person who won the lottery, they must think themselves very lucky. But on the grand scale, the probability of someone winning the lottery in the entire pool is exactly one. We know that a winner necessarily exists—just as we know that we, as winners of the cosmic lottery, necessarily exist. But that just tells us that someone won the lottery—something we already knew.
It may be that the lottery is rigged, and that there are some characteristics of our particular solar system which are amenable to life, and those things are definitely valuable to study and find out, so that we might be able to recognize other solar systems capable of supporting life in some way.
But by no means is our solar system special in any light: it's only special in that its particular conditions produced lifeforms able to observe it.
"We are a way for the cosmos to understand itself." - Carl Sagan
Another random question: are the planetary systems we've discovered similar to each other? If ours is significantly deviant from a significant clustering that would be pretty interesting. And of course, that's surely what the original findings were probably about.
The point was that a few years ago we had a solid, broadly-agreed-upon scientific theory of planetary formation. And it was wrong. That's interesting for scientific reasons, not philosophical ones.
That is absolutely true to some degree—we want to find out what conditions support life, and why the Earth did end up how it did, and resulted in conditions stable enough and correct enough to allow life to evolve for millions of years essentially uninterrupted.
It's the tone that I read into, and I have a tendency to look out for the earth-centric perspective, mainly because I find the alternative way to look at it basically mind-blowing and fascinating. That doesn't make study of the development of our solar system any less important, any more than the study of evolution makes biology less important. The study of planetary formation, the solar system, geology and every other related field are all extremely important to broadening and deepening our understanding of how the universe works. Understanding statistics and the anthropic principle just gives us a framework in which to view that knowledge that is even more true and complete, in my opinion.
(Aside: I'd guess it's because there are people like me, who often read comments before or without reading the article, that a well-written but not on-point comment like this can get upvoted. I wonder how you'd fix that?)
My bad, move along.
I don't even disagree with your point. But I posted because I did find the linked article interesting (if a little fluffy) and thought your digressive correction was missing some of that substance.
If you intentionally mean to go off-topic (which you usually shouldn't, but we'll assume you have something really amazing to say), it's best to explain that you're not actually talking about the topic at hand but you thought it was interesting because X. That way people will be able to read your comment in the light in which it was intended rather than straining to find relevance.
(Incidentally, I have no idea why you responded this way to my comment, which is explicitly about ways to ensure people read articles before voting on comments about the articles, and is not about you at all. Maybe you assumed it was on the topic of your comment?)
sorry, but i don't understand what's the logic here? it's not special, but it's only very special in sustaining/producing life? isn't that more than enough to call it special? :-)
Our existence (whether likely or not) does not constitute evidence that our existence was guaranteed or predetermined. Low-probability events happen sometimes, their actually having happened once does not make them high-probability.
Hubris alert!
Here's a "lightbulb" for you: A large gas giant near a star is created in the same fashion as a binary star system (a formation that is quite common) with the simple difference that the planet did not get enough material to actually become a star.