Solar Systems Like Ours Are Likely To Be Rare 394
KentuckyFC writes "Astronomers have discovered some 250 planetary systems beyond our own, many of them with curious properties. In particular, our theories of planet formation are challenged by 'hot Jupiters,' gas giants that orbit close to their parent stars. Current thinking is that gas giants can only form far away from stars because gas and dust simply gets blown away from the inner regions. Now astronomers have used computer simulations of the way planetary systems form to understand what is going on (abstract). It looks as if gas giants often form a long way from stars and then migrate inwards. That has implications for us: a migrating gas giant sweeps away all in its path, including rocky planets in the habitable zone. And that means that solar systems like ours are likely to be rare."
Re:Rare? (Score:1, Informative)
Agreed - where's the jump to conclusions mat? These are not my idea of scientific statements. First, a sample of 250 planetary systems is a grossly insufficient sample size to derive such assertions in a universe so large. Second, and amplifying the prior, is the samples are severely lacking in data. We are still using "stone tools" to analyze these systems. Much more sophisticated equipment is needed to obtain sufficient data to get a real collection of data for analysis of these systems, granted good theories can still be derived by our brightest minds with even such small details. We have a long road ahead, and responding to the "are we there yet"s with "just a little further" is patronizing, not analyzing.
Re:Sweeping out Earths (Score:4, Informative)
Is one of the implications that solar systems could at one point be similar to ours? Gas giants far away with smaller planets towards the sun? And then the gas giants slowly creep towards the sun, wiping out the smaller planets that get in the way?
That's a possibility, although I would turn around your phrasing: our solar system could at one point be like the ones we're detecting far away, with Jupiter sweeping away Earth and our small neighbourhood friends.
Re:giants (Score:3, Informative)
Other way around. They are saying that gas giants form far away and move inward.
Re:Rare? (Score:5, Informative)
Re:giants (Score:3, Informative)
I saw AFA on this a couple of days ago. They're not referring to observed star systems; we can't yet detect earth sized (or earth massed) planets yet.
They ran a computer simulation of star formation and the simulations had gas giants migrating inward, which ate rocky planets like ours. It is yet to be determined how accurate the simulations are.
Re:wake me up (Score:5, Informative)
That's Gliese 581c, which is merely five times the mass of the Earth --- and they only detected it because it orbits at one fourteenth of Earth's orbit. In other words, it's a heavy planet very, very close to its sun. The only reason it was described as 'Earth-like' is that Gliese 581 itself is a red dwarf, which means it's much cooler than Sol, which puts 581c in the star's life zone.
So, while it's theoretically possible that 581c could support life, it's still not really Earth-like. We're still a long way off from being able to detect Earth-sized planets at Earth-orbit distances from Sol-like stars.
Re:Well, that does it... (Score:5, Informative)
Haha. I don't know about sending Bruce WIllis, but this does make me wonder why we have never (to my knowledge...) sent a probe INTO one of the gas giants.
Your geek credits have been officially revoked.
Galileo had a probe that was dropped into the atmosphere of Jupiter and it transmitted data for 58 minutes [nasa.gov] before it stopped. Hell, we even crashed the Galileo spacecraft into Jupiter to prevent contaminating Europa or Callisto with organisms from Earth.
Re:Rare? (Score:5, Informative)
Re:This appears to be a "When you are a hammer ... (Score:2, Informative)
Seems like this article belongs in the "Are US Voters Informed Enough About Science?" thread if you ask me.
If you're an American then you made your own point. TFA isn't talking about observation, but theory and computer simulation.
It's not all hot Jupiters out there (Score:5, Informative)
The interesting data is not how many hot Jupiters are found, but how many stars do not have hot Jupiters.
Here's a list of extrasolar planets [exoplanets.org] (last updated in January); and another list [exoplanet.eu]. Note the large number of stars that have planets found with mass less than Mj. The converse of that is that those stars do not have planets of mass greater than Mj. The problem, of course, is that negative results are much less published than positive results. However, here is a list of three published papers that listed stars with no planets found [exoplanet.eu] (that is, no planets large enough to detect-- which is to say, no hot Jupiters. This list is somewhat out of date, as of 2006.)
So the story is a little incomplete. Some solar systems have hot Jupiters, which in their migration inward disrupt smaller, earthlink planets... but by no means all.
Re:Well, that does it... (Score:5, Informative)
We have.
in 1995 by the Galileo a probe was dropped into Jupiter.
http://apod.nasa.gov/apod/ap951207.html [nasa.gov]
But if you think it will just sink in until it 'hits' then check your physics on large gas giants again.
Re:Well, that does it... (Score:5, Informative)
Whatever... this is naval gazing and conjecture, no more credible than Intelligent Design. These guys have a few data points, they create a highly convoluted system that seems to account for their data points, then the moment they get more data, they start over. Again and again.
Data points which are skewed by the fact that planets with a large mass (relative to the star) orbiting close to the star are easier to detect by techniques based on star wobble and transit light level and so are going to be massively over represented in the list of known planetary systems.
Re:first post (Score:5, Informative)
Outsider theories always have the burden of proof on their own shoulders. To paraphrase someone famous, "there are many questions fools can ask that wise men struggle to answer." There's no where this applies more than in science. Creation Science can throw out some sticky questions and make some points that are hard to disprove.
But Science is about proving things, not suggesting every possible idea and disproving them one by one. For a well established idea that has made a lot of successful predictions, even a known incomplete idea like the standard cosmological model, to be tossed aside, there needs to be an overwhelming amount of evidence, not just some compelling questions.
If an alternative model of the universe explains the preponderance of evidence we already have (such as the background radiation, the count of galaxies, the scarcity of structures above a certain scale, the calculated mass of galaxies, the total amount of gamma radiation etc.) as well as a current theory, as well as making successful new predictions that existing models failed to make, then over a process of several years, people in the field would become convinced, and as the literature is peer reviewed, the dogma would shift. But established scientific ideas are SUPPOSED to be dogma. It isn't politics. Equal time isn't given to competing ideas, that's not the way it works. There are too many bad scientists and professional crackpots, the system would collapse without a hierarchy of opinion.
And all science works this way and always has. Even the sciences that cure disease and deliver technological miracles. Since those things keep happening, I'm confident as a semi lay person that science, while certainly getting many small details wrong and making mistakes and sometimes taking too long to come to the right conclusions, is still heading in a monotonically positive direction.
Re:wake me up (Score:3, Informative)
The point is not about being able to detect rocky planets. It is that according to the old models a gas giant close to a star could not exist. We now found 250 of these impossible planets, so after adjusting the theory so these are possible, we find that rocky inner planets are all of a sudden a lot less likely.
Galileo's atmospheric entry probe (Score:3, Informative)
(From the Galileo Wiki) http://en.wikipedia.org/wiki/Galileo_probe#Galileo.27s_atmospheric_entry_probe [wikipedia.org]
"The 339 kilogram atmospheric probe, built by Hughes Aircraft Company at its El Segundo, California plant, measured about 1.3 meters across. Inside the heat shield, the scientific instruments were protected from ferocious heat during entry. The probe had to withstand extreme heat and pressure on its high speed journey at 47.8 km/s.
The probe was released from the main spacecraft in July 1995, five months before reaching Jupiter, and entered Jupiter's atmosphere with no braking beforehand. It was slowed from the probe's arrival speed of about 47 kilometers per second to subsonic speed in less than 2 minutes."
Well, if the computer said so, it must be true! (Score:3, Informative)
Do you know why they though solar systems like ours would be common? Computer simulations of solar system formation. In fact, the "standard model" was even published in Creative Computing, back in the day...
What were these models based on? The only example of a solar system we knew; our own. "Of course" there will be rocky planets near the sun and gas giants further out, it only makes sense.
So then we get better telescopes that can detect Jupiter-sized planets, and they show us lots of systems with gas giants in close. The model, based on a single example, is wrong. So we re-jigger the model to match the new observations, and conclude THAT one must be right.
$50 says once the interferometric planet finders come online this model goes into the trash heap as well. The universe clearly doesn't give a crap about our models, and builds whatever it wants.
Maury
Re:Lot's of reasons our system might be rare (Score:3, Informative)
> The energy from this decay melted the early earth.
No it didn't. Gravitiopotential from infalling rocks did.
> Look up the term "iron catastrophe" for more information.
Yes, please do so...
http://en.wikipedia.org/wiki/Iron_catastrophe
Maury
Re:Rare? (Score:3, Informative)
What this does do, in terms of some realistic statistical calculations in regards to earth-like planets, is to adjust the Drake Equation [wikipedia.org] downward by reducing statistically the number of potential planets that might be capable of supporting carbon-based life in aqueous solutions.
This paper is significant so far as to reduce the potential number of planets possible by a couple orders of magnitude.
Yeah, out of the billions of stars in our galaxy and out of the billions of galaxies in our universe, this still means there may be a bunch of other intelligent beings on other planets living sort of like we are right now, perhaps even communicating electronically and debating topics like this.
Even if that were true, this estimate means that what we thought was a somewhat common event happening is actually something much more rare... and IMHO makes this special little planet we live upon something all that more important to preserve and take care of properly.
Re:The universe is big. (Score:2, Informative)
Really, in terms of the universe, EVERYTHING is rare....
If that is serious statement, then you are missing the point. What article means is:
Given that there is a randomly chosen solar system in front of us, it would be rare for this solar system to look like ours.
In other terms "For all solar systems S, P{S_1 is an element of the set of systems_looking_like_ours} $RARE_PERCENT"
Re:first post (Score:5, Informative)
The most important thing that you need to understand is that the large number of "hot jupiters" that have been found have essentially disproven existing theories of solar system formation. This is not a case where a new theory is proposed to replace an existing theory that already explains most of the evidence ala Einsteinian physics replacing Newtonian physics. This is a case where we have essentially no theory at all that explains the observed evidence.
Re:Depends on what your definition of stable is (Score:3, Informative)
here's a good chance that one or more of the inner planets is in trouble before the Sun goes nova.
A nova is caused when a white dwarf star accrets a significant amount of mass from a neighboring body. Our Sun will end up as a white dwarf, but without a companion of any significant size, it is high unlikely that it will ever go nova.
It's also not massive enough to go supernova. So basically, the Sun is simply not likely to ever explode in any way. Eventually it'll swell into a red giant and after that it'll mostly start to slowly dissolve it's outer layers. It'll go out with more of a fizzle than a bang.
That said, when the Sun swells into a red giant the inner planets are effectively screwed. Mercury, Venus, and quite likely Earth will be engulfed within the Sun.
Re:Well, that does it... String along? (Score:2, Informative)
So the answer to your question is no.
Re:Calculating a planetary system. (Score:2, Informative)
....A gas giant may be good for life too, but maybe not the life we know here.....
If you mean physical life based on chemistry, then there can be no other life other than what we know right here. On the molecular level, life's binding energies are such that bonds can be easily made, changed and broken. If this were not so, the complexity of life's processes could not exist. These bonds can only form and dissolve in the rather narrow temperature range where liquid water is available.
This means that by temperature specification alone, half of all known stars are disqualified from having an earth-like temperature environment because they are spaced too close to each other. Relatively straight forward gravity and orbit calculations show that similar sized stars closer than about 3.8 light years to one another cannot host a planet with a stable enough temperature. A planet that would support complex, larger non-microscopic life-forms must freely rotate so it doesn't get too hot during the day or too cold at night. If it rotates too quickly, the atmospheric winds become too high.
Besides temperature, the main elemental components of life must exist, as well as the absence of components hostile to life. The spectrum of the parent star must well matched to the energies involved in photosynthesis. Light too blue or red will not allow efficient use of such light energy.
There are a number of other characteristics that a planetary "laboratory" has to have, in order for life to flourish. All of these taken together make the likelihood of another planet hospitable enough to have life, exceedingly remote. It appears that we may be quite alone in this big universe.