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Space

Planetary System Similar to Sol Discovered 321

Posted by michael from the all-the-way-back dept.
Anonymous Coward writes: "The Washington Post is carrying its own copy about a planetary system very similar to Sol in the Big Dipper. 47 Ursae Majoris has at least two large gas giants in circular orbits, similar to many of Sol's satellites, and the possibility exists for smaller, currently undetectable rocky planets closer to the primary. Circular orbits are less common than highly elliptical orbits, and are more promising. Read the whole article to find out why."
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Planetary System Similar to Sol Discovered More

Planetary System Similar to Sol Discovered

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  • Here are some things to think about.

    1) The age of the Universe is estimated to be about 12-14 billion years old.

    2) Earth has existed for about half that time and in all that time, through billions of years of Evolution, only ONE species has emerged sentient.

    Half the lifetime of the known Universe, and on one planet, it took about half that time to make ONE species remotely sentient on earth, with BILLIONS of years to try, "eveolution" or whatever the process is you want to call it, got it right once and only once.

    Sentient life, it would seem is pretty RARE. In fact, it would seem even in the most IDEAL conditions, such as Earth, it takes a HUGE amount of time to develop.

    This is a very very BAD thing. Continue reading on to find out why.

    3) We now know, that our Sun is NOT an ordinary star. How do we know that? Because we do spectroscopic studies and we can know the composition of nearby star systems, with no guess work.

    These studies reveal that 80 percent of most stars, many of them are not candidates for worlds that would require life. They end up:

    4) Having poor amounts of metal content. No metals means it is highly unlikely the star will be stable over its lifetime. Metals it would seem moderate the stars nuclear reactions, and keeps it radiating energy with very little variation of its lifespan.

    This finding is relatively new, thanks to Linux Beowulf clusters. :-) (Well that and the defense department....get to that later.)

    5) Stars that lack Metal cannot have formed from clouds of intergalactic material that contain any amount of heavy metals by definition. Why is that significant? It is significant because without heavy metals, planets, specifically rocky planets won't form around these stars. What you get is heavy Gas giant's like Jupitor or Saturn.

    6) Doesn't look good so far and it gets very much worse I am afraid. It turns out that a galaxy is a very very hostile place to live in.

    So what you say? It can't be that dangerous we are here? Right?

    Yes, but consider this. You have heard arguments that there are billions and billions of stars in our galaxy....yadda yadda yadda=life should be everywhere and lets give another billion to SETI to find it.

    7) No, I am afraid not my friends. You see the Sun and WHERE it is located is also VERY important, in our galaxy. You see those big dust clounds obscuring the core of our galaxy on a clear night called the Milky way? Consider them a security shield. In addition we are 2/3rd or more on the way out towards the outer middle of what we presume to be one of our galaxies arms. Very very far from the galactic core.

    I won't get into the complete details, but the galaxy is a very very VERY dangerous place to live anywhere near the core.

    Why is this important? It is important because the closer you move towards the center of our galaxy, the less likely you will have Stars that are stable for long periods, that do not expose thier accompanied planets (if any) to the extreme pasturizing effects of the galactic core, and dense stellar neighborhood. By definition, these populations of stars as one moves towards the center of the galaxy CANNOT be habitable because they have more materials available to them and are very large, have short life spans, and violently blow themselves up, along with the planets they carry, if any remember!

    Short lifetime stars we know, cannot provide enough time for life to evolve to sentient states if the earth is any example, it took HALF the lifetime of the KNOWN UNIVERSE to produce ONE species.

    Location, Location, Location. There may be billions and billions of stars, but it really doesn't matter. Most of them are not suitable, and we can prove that. It would seem, that a narrow band exists that goes around our galaxy that provides a habital region for the development of life. Very similair to the habital region around our own star, where luckily, earth is currently located, and I exist to type this!

    So, no, life just can't pop up ANYWHERE in our galaxy and more than likey it can ONLY pop up in a very narrow field or band around a galaxy.

    Each galaxy, should have its own band or habital region of stability where sentient life could evolve.

    8) Oh my, and then we have the observations of a naturalist I am a fan of, Mr. Stephen J Gould. A quote from Mr. Gould:

    "Sentient life has occurred in only one species over billions of years of life on this planet. It is not at all clear if this is a survival trait, as so many have put forth. Dinosaurs and thier kind ruled this planet quite successfully for 100's of millions of years and they didn't need intelligence at all, and in fact did quite well without it. Far better than we have and we have only been around for about 100 thousand or so years. In fact, long term, one could argue that sentient intelligence is a negative survival trait and actually hurts a species long term survival."

    I could not agree more. We have debates that long term, with Nuclear Bombs in suitcases available now for your local nut case, intelligence is probably not a good thing if you are a life form and want to be here, or your decendents, 100 million years from now.

    9) It gets even worse with current research comming down the pipe my friends, and well, then we have SETI and thier Radio antenna.

    Stupid.

    Why?

    This is my opinion of course, given our current observations and understanding of how life works and why another billion should not go to SETI in the future, they already spent a Billion, with ZERO results, and I think it speaks volumes about current research into life at the moment.

    Any life that has survived as long as it has on Earth, and develops sentient life forms, you have to understand, will not use Radio waves for communication. The time spans we are talking about are so enourmous, that the civilization we are looking for either has either died a long time ago or is so advanced, our preconcieved notions about what sorts or kinds of travel with our pitiful little science books, is at a child like understanding at best. If they do have those solutions, they won't use radio waves to communicate, it would take too long to manage a galactic empire on that scale.

    They won't, Oh God, another DUMB idea, use lasers either. Stupid, idiotic, and DUMB.

    Which is why SETI after plowing through about a billion dollars now, hasn't found DINGY.

    And they won't find what they are looking for.

    10) Now, during this whole discussion I point out why SENTIENT life is probably not very wisespread . Certainly not enough widepread to devote anothe r billion dollars to SETI to look for it.

    I by no means, claim there is not life out there. I bet we find life in our general vacinity in our part of the galactic neighborhood because it would seem we are in a fine part of town, the Earth and the Sun. We probably will find life, or possibly hints that it at one time existed outside Earth.

    I believe life is very resiliant and if given the right conditions, will spring up.

    I don't claim to know why, but if it happened here, it can happen again someplace else nearby. Life has survived some enourmous catastrophes on this planet we call earth in the past, so it must be rather resilient and not easy to snuff out.

    But given this series of arguments, I believe life is not as wide spread as we believe. What IS neat about this new evidence is it allows us to focus more of our searches, instead of what SETI is doing just pointing an antenna up in the air and waiting for a signal in any direction.

    These are things SETI doesn't want you to know, and given what we know already, I would LOVE to see that money put to taming space for economic and peaceful uses.

    We may disagree about SETI, but I bet we dont' disagree that having all of our eggs in one basket with nuts running around today and people killing each other, we should probably put a human outpost OFF OF THE PLANET. Just so we don't become a layer in the fossil record just like the dinosaurs.

    Because that is something we CAN prevent and is a very very REAL danger every day.

    Certainly a better investment than another billion for great screen savers, which is about what SETI is, in my opnion.

    -hack
    • It's clear that you made most of this rant up. Time to fight misinformation....

      2. We don't know that sentient life is RARE. It's very possible, but it's difficult to extract our experience on one planet to the rest of the Universe, don't you think? Even if sentient life is RARE, why is that necessarily a BAD thing? If we're the only ones, then that makes us pretty important, in some sense.

      3. The Sun is a rather ordinary star. Yes, it is more metal-rich than the average star in our galaxy, but not by much. There are many millions of stars in the Milky Way that are reasonably similar to our beloved Sol.

      4. Low metal content does not make a star "unstable" in any way. Heavy elements do not significantly regulate fusion reactions. If anything, they cause a lower burning efficiency, which would make a star burn hotter, which would make its lifetime shorter. There are no stars with "No metals"; all stars have at least some component of heavy elements. Finally, not to nitpick, but stars form from interstellar material, not intergalactic material.

      6. This bit of misinformation is why I just had to reply. Ahem...
      SETI isn't using ANY taxpayer money. None. Several years ago a republican congressman beat his chest about the millions (NOT billions, as you slander) of dollars we were pissing away on little green men, so all federal funding of SETI was ended. They continue operations today on grants from private foundations (Notably, the Packard foundation).

      7. The Sun is NOT in a special part of the galaxy. Yes, it is shielded from the harmful radiation at the galaxy center, but so is much of the Milky Way disk, where over 90% of the Mily Way's stars are. Stars do not get more massive as you move toward the galactic center. I have no idea where you get that from.

      You seem to know everything about ET (even though he can't possibly exist). You know he won't use radio, and he won't use lasers. I bet he won't use ALL CAPS, either.

      Bottom line: nobody has any idea how rare life in the universe is, much less how rare sentience is. Anyone who claims they know how rare life is is lying, or "DUMB". Which are you?


  • " ... the two planets hint at the presence of smaller, Earth-like bodies in tighter orbits."

    So it seems that they have shorter days then? Wow ... their Engineers must be really good to keep to the release schedule even with them there shorter days (says the PHB)
    • Nope, tighter orbits would mean shorter years. The spin period is the length of the day.


      • "Nope, tighter orbits would mean shorter years. The spin period is the length of the day. "

        Yep, you're right. They're great engineers because they meet the schedule even though the years are shorter. So I guess engineers on short term projects are no better, just the ones who measure in man-years rather than man-months. Fredrick Brooks would be proud! It turns out though, that though the variable was mis-named it still serves the 'year' function. The error is merely semantic, you see. 8^}

        Cheers,

        Zero__Kelvin
  • There are many unique characteristics that make up earth and it's location. Hugh Ross, an astrophysicist, has calculated the probability that earth exists with all its characteristics at 10^53. He also says that the maximum possible number of planets in the universe is about 10^23. Now I don't know what the error bars on these figures would look like, but I think it is fairly safe to say that earth is quite the unique planet in a quite unique location in the universe.

    I got these numbers from his book "The Creator and the Cosmos". I should also say that Hugh Ross is an "Old Earth Creationist". (That is he believes the universe is 14-17 billion years old and that there was a creator.) He puts together a good argument in favor of some creator fine tuning the universe for life on earth.

  • This is good news. If the inner region is empty and our earth explodes someday in the future, we can move our earth there. Even if we can't move the entire earth there, we may build a new one. All it needs are some dirts and lots of energy, anyway.

    What is sol?
  • Indeed Ursa Major should be a probable place to find life and stuff.

    After all, Ursa Minor Beta already has more life than it can handle: "When you're tired of Ursa Minor Beta, you're tired of life"

  • More than 70 planetary systems have been found around stars other than the sun, including three with multiple planets, but most have orbits that are sharply elliptical.
    I'm clearly confused.
    • By focusing extremely precise measuring techniques at 47 Ursae Majoris, which is about 45 light years (more than 200 trillion miles) away, astronomers measured wobbles of 36 feet per second and inferred the presence of one of the large planets.

    Uh huh. When I did astronomy, back in the day, we worked in powers of ten. Anything with the right number of digits was "close enough".

    Now here we have a bunch of astronomers who have been funded to find planets. They come up with a single observation technique that they reckon will prove the existence of planets. They have no way of correlating their findings. They look for this observation, expecting to find it. They find it. This proves the existence of planets.

    Remind me, what would be the effects on the funding of this project if they hadn't "proven" both their technique and the existence of planets?

    • Now here we have a bunch of astronomers who have been funded to find planets. They come up with a single observation technique that they reckon will prove the existence of planets. They have no way of correlating their findings. They look for this observation, expecting to find it. They find it. This proves the existence of planets.

      Remind me, what would be the effects on the funding of this project if they hadn't "proven" both their technique and the existence of planets?

      It's amazing how scientists, who work in a world of almost bizarre openness, are often subject to more suspicion than, say, corporate CEOs.

      People were looking for extrasolar planets for a good five years before they refined their techniques enough to find one. Funding continued because it was good science. Their findings were immediately subject to intense scrutiny from a large community of astronomers. Independent observations were done and continue to be done. Alternative theories were proposed. Some supposed planets have been removed from the list; those that remain have, by and large, very clear signatures, well-defined periods, and no obvious alternative theories. One (which is about the number expected) has been extremely well-confirmed by observations of its transit. As a researcher in this field, believe me, mistakes are found quickly and fraud is extremely rare.

      Incidentally, Geoff Marcy's team out in California has demonstrated precision in their observations to about 3 m/s- a good factor of three better than needed for this particular detection. The papers are all on-line and not even hard to find. It might be prudent to look at them before making vague accusations.

    • Their funding has been going for at least 10 years, and their technique is as accurate as it sounds. Iodine absorption spectroscopy *is* as accurate as the the numbers claim (about 3m/s at the last look).

      The phrase "By focusing extremely precise measuring techniques..." is poor english - they don't need a sharp image of the star, they just need as much light as possible to put into spectrograph.

      And although 99% of astronomers agree they're probably detecting planet-mass objects, there are a couple of people who think they're seeing brown dwarf stars at high orbital inclinations, and they're not planets at all.
  • Ofcourse it would be mega-cool to find that there's other 'life' out there, but more as a 'new gadget' kind of thing than anything else. If we were to find 'life' on any planet, their development would either be much ahead or much behind our own development. Sure, perhaps we could learn a thing or two when they're ahead of us. And maybe we can dissect a thing or two when they're behind us. But is that really so important?

    Earth is quickly running out of resources. Fusion reactors seem to become promising but commercial use is still decades away. Nuclear reactors create too big a waste problem. Oil is running out (ofcourse I'm thinking 'decades' here). The number of humans on this planet is going up dramatically. Hopefully before the time comes that we're out of energy sources, we will somehow be able to set out on a trip to a planet that could support us.

    • Well, if they are ahead of us, odds are they have solved some problems that we are currently facing. If they could show us how to make sky scrappers 200 stories high cheaply, (think big apartments downtown), and how to grwo food a lot more efficantly then we do now, many population problems would be solved.

      If they are behind us, it can't be far because we have just barely got the ability to communicate. We can quickly bring us up to our level, and odds are good they have discovered something that we haven't yet. 45 years isn't a lot of scientific progress. That isn't to say we won't discover something while the knowledge is in transit, but even still it is useful to exchange knowedge.

      Just a warning though, if we exchange information we can't determin who is in the right in their local wars for years to come, we should therefore make sure that knowledge we transmit is avaiable to all.

  • On detecting other planets that may sustain life, we could point a radio telescope their way and see if anything intelligent has been broadcasting something as of 45 years ago. Sure, it's highly unlikely, but if we could eliminate the background noise and pick up the extraordinarily faint signal, we'd know. If we hear nothing, it doesn't seem like we're any worse off than we were.

    Of course if there is life there, and they're getting our signals, they'll at least know we're an inquisitive race, because the first episodes of Perry Mason [imdb.com] should just be arriving...

  • Circular orbits are less common than highly elliptical orbits, and are more promising.

    Actually, in the planets detected thus far, ciruclar orbits extremely close to the star and highly elliptical orbits are about equally common, with big circular orbits indeed being much rarer.

    However, it should be noted that the stellar-wobbling method of planet detection is highly biased toward detecting large (Jupiter sized or larger) planets in close orbits. We can't even detect Earth-sized planets, or a Saturn-sized planet at Saturn's distance from its star. So we are getting a very distorted picture of what constitutes a "common" type of planet. It may be that Earth-sized planets in wide circular orbits are the norm, but we won't ever see them with the tools currently available.

  • ...it'd be 47 [47.net]

  • What is this 'Sol' ?

    Furthermore, is its version 8 any better than its version 7?

  • Attention: (Score:3, Funny)

    by bluephone ( 200451 ) <grey@nOspam.burntelectrons.org> on Thursday August 16, 2001 @12:24AM (#2155206) Homepage Journal
    Ok, they're about 45 light years away, which means that they're probably watching I Love Lucy, a great comedy show. Sadly, by decoding the signal, they're violating the DMCA. I'm sorry, but they're going to have to be arrested. Anyone know if California courts take Buckazoids for bail?
    • Of course we wouldn't find out about the DMCA infringement for 45 years, and the statute of limitations is only 5 years.
    • Why aren't we watching their TV shows? There's something to be said about the degradation of the signal after a certain point, especially omnidirectional broadcasts. Background radiation and interference would make NTSC decoding impossible after a certain point.

  • .. (Score:2, Funny)

    by vbrtrmn ( 62760 )
    Fry: Are there an unlimited number of alternate universes?
    Professor: No, just one.
  • In an incident unknown since the early 60's, Yhwh, a diety in good standing, has demanded that Earthbound scientists "return my friggen mirror". Apparently his shaving problems, as well as those of his son during his brief stint in the middle east, all stem from the inability to see one's own reflection probably.

    Science claims ignorance, swearing that it was like that when we got here, all we did was find it. The classic battle between faith and reason is expected to reach yet other heights later this week, when God discovers what we have done with His slippers.

  • I love this metric... (Score:3, Funny)

    by ct ( 85606 ) on Thursday August 16, 2001 @12:17AM (#2155746) Homepage
    By comparison, Jupiter exerts a wobble on the sun of 40 feet per second. Earth, being much lighter, exerts a wobble of about 4 inches per second, Fischer said.

    It doesn't matter how scientific the context is, the word "wobble" just makes me giggle like a fool.

    //ct

  • Why look? (Score:5, Interesting)

    by DarkHelmet ( 120004 ) <<ten.elcychtneves> <ta> <kram>> on Thursday August 16, 2001 @12:12AM (#2157901) Homepage
    Yes, there might be life. There might be signs of biological life on a planet that's far away. But what's the point? The only confirmed life on other planets far away will be from "Intellegent Life" (Meaning they have access to radios). And even if communication is possible, there's a latency of 45 years just to say hello back and forth.

    "Hi" (45yrs)
    "Hi" (90yrs)
    "How are you?" (135yrs)
    "We're fine on this planet, how are you?" (180yrs)
    "We're doing okay. Too bad the person who originally sent you this message is dead now." (225yrs)
    Our condolences. (270yrs)

    Looking for life this way is not only difficult, but nearly futile. Anything lower than 20th century technology on their side and they won't hear us. Anything greater than 21st technology and chances are they'll find us a LOT sooner than we'll find them.

    That, and they'll be using something other than radio waves to communicate. Maybe I'm just dreaming.

    Either that, or bend space just to send an alien over here to bitchslap us and tell us how silly we are.

    • Anything greater than 21st technology and chances are they'll find us a LOT sooner than we'll find them.

      Chances are they'd have blown themselves to kingdom come.
    • I wouldn't wait for an ack if the distance was 45 Light Years. I'd keep broadcasting. At least 45 years later, we'd have a pretty good rate of information coming through.
    • Its one heck of a way for a PING.

      Perhaps we should start by sending them Comer & Stevens as UDP (I wouldn't wish the RFCs on anyone) and follow it with a connect?

    • Damn! Only a slashdotted site has a higher latency than that! :>

    • Re:Why look? (Score:4, Insightful)

      by stevelinton ( 4044 ) <sal@dcs.st-and.ac.uk> on Thursday August 16, 2001 @05:24AM (#2131423) Homepage
      Of course, this isn't what you do. You say.

      "Hi, we think we have detected someone who might be able to receive this message. Here are 90 years of transmissions from our encyclopedias, archives, libraries, etc., with lots of redundancy, various frequencies etc. etc."

      90 years later, if all goes well, you start receiving replies like

      "Hey, good to talk, we've decoded your language primers. Here are our encyclopedias etc."

      Then a few months later

      "Based on what you've sent so far, we'd like to hear more about fly fishing, barbecue cookery and string theory (or whatever). We're also starting to skip the basic physics in our encyclopedias where it matches up with what you're telling us you already know."

      If you haven't already sent the requested info, you slip it in when the question arrives.

      It's not exactly a conversation, but if both sides are willing, you can learn a lot about one another in a couple of centuries.
      • You mean you want to just send them all of our valuable intellectual property? What if they aren't as open with theirs and we get nothing out of the deal? Are you going to include some sort of EUL? "By decoding the rest of this message you agree not to come and eat humans or use the technology described within to further your own interstellar kingdom in a way that harms the interests of humans...."

    • Forget talking to them, what about playing quake with them? 45 light-years?! Thats a ping of 141 Billion. I guess I can forget trying to headshot a grey any time soon...
    • The only confirmed life on other planets far away will be from "Intellegent Life" (Meaning they have access to radios).

      Unfortunately, there is only a very short span of time between "Intelligent Life" with access to radios and access to television which destroys all "Intelligent Life" it comes into contact with.

      Now, get your hands of my TiVo control. <grrrr>

    • The only confirmed life on other planets far away will be from "Intellegent Life" (Meaning they have access to radios).

      This isn't true at all, although I guess you can seriously restrict your definition of confirm to make it true.

      If you can examine the atmosphere of a planet, you can tell how much of what elements are present. From this it's possible to make a good judgement if life was needed to generate it.

      Examining the atmosphere from this distance isn't exactly easy, but it's possible under the right circumstances. You might watch changes to a light spectrum as the planet occults a background star, or compare refracted light from the star that it's orbiting.

      Don't underestimate the amount of information that data-starved astronomers can get out of what's available, though.

    • Re:Why look? (Score:2, Funny)

      by koreth ( 409849 )
      Worse, the conversation might go more like:

      "Hi" (45yrs)
      "Oh, so THAT'S where we left our science project." (90yrs)

  • just next door (Score:2, Informative)

    by GlassUser ( 190787 )
    according to my sources [ucdavis.edu], this little system is only 46 lightyears away. It looks like it's going to be a while before anything can get there. Darn, and I was really hoping to hear some more info before my children were dead.

    Seriously, this doesn't really seem to be too far away. Probably related to the fact that it's easier to see something closer. If I weren't so tired, I would probably be excited!

    • Of course there's life in that system! But, don't expect to hear from them anytime soon.

      How do I know? Well...during my last alien abduction, they told me so (The captain even has a pet shnitzoid named Spazmork). While passing through our solar system, their systems were knocked offline when they encountered an intense wall of RF energy packets originating from atop a coffee shop in NYC. They called it the /. effect. Took them several days to restart their systems while they muttered something about a something called a "cmdr taco" and intergalactic war.

      They are now posting warnings and to other civilizations warning of the danger of passing through the Sol system.
  • Easy does it!

    This comment has been submitted already, 277205 hours , 7 minutes ago. No need to try again.

    Nice to see the slashcode is as tight as ever

    //ct
  • It's been a while since I read the stories, but I'm pretty sure this is the system of the Kzinti homeworld!

    Quick, somebody get Larry Niven on the phone for a comment!

  • killing serious discussion (Score:5, Funny)

    by emir ( 111909 ) on Thursday August 16, 2001 @01:09AM (#2158263)
    i'm probably going to be modded down for this post but i'm going to post it anyway.

    why does discussions about any science/space article has to be ruined by people who do nothing else but posts idiotic comments that has nothing to do with the article, and then some even greater idiot mods them up and we end up having like 10 comments who are at 5 Funny ? This usually kills all serious discussion on the subject. There are actually people who prefer to read something smart and not just your idiotic comments.

    Goto segfault.org and be funny there!!! stop posting if you dont have anything serious to say!!!
    • "The greater the mind, the greater the need for simplicity of play."

      I think that this would be a very sterile environment indeed if all we had were serious comments on each subject. I myself look for both funny and interesting comments on a subject, to keep my interest and to just have fun.

      I look forward to the 'geek jokes,' funny remarks said on a subject that only we would get. I think it makes for a better sense of comradery with the people around here.

      I do like the suggestion of having the option in the slashcode to filter out Funny, but I would be the last person to use it.

    • slashcode bug/feature... (Score:3, Insightful)

      by Anonymous Coward
      a feature currently suggested on sourceforge for slashcode [slashcode.org] is to be able to filter out all funny comments... that'd solve your problem
      • I am very surprised at the low score this line of suggestions gets. Moreover it's been ignored by slashcode developpers so far. Isn't the following principle obvious ? Humor should not be imposed I suppose that's the reason for the funny flag in slashcode. That flag is quite useless without filtering capabilities. PS : I like fun, less so at work.
    • Maybe things become more serious once all of the obvious jokes are used up.
    • Some of us come here because it's funny.
      • it is funny, but I'm glad the previous poster pointed out what he did.

        However much it kills my karma, I always use my moderator points to moderate down all +5 funny comments because information and insights are more valuable than comedy.

        Well, the occasional Simpson-quality post that is insightful and put in a funny way I leave alone.

  • more stats (Score:3, Informative)

    by Alien54 ( 180860 ) on Thursday August 16, 2001 @12:19AM (#2158364) Journal
    You can see a quick summary of the star here [planetarybiology.com] They estimate that the inner planet will remain in the habitable zone for 1.2 gigayears. Right now it is on the outside edge, in the cold zone, with a 3 year orbit. but the expect the star to start to get warmer, and that may heat things up nicely for a while.
    • Wait a second here... If I understand correctly the table you link to, the planet you are talking about has almost 3 times Jupiter's mass, which is not really one where one would search life as we know it - except if it has satellites.

      Furthermore, given that Jupiter orbits the Sun at 5.2AU, preventing planet formation between 2 and 5AU (cf. our asteroid belt), and that one is at 2.1AU from its star, I don't see how an Earth-like planet could be within that star's habitable zone, between 1 and 1.5AU.

      In fact, I think the data from this table and that from the article are incompatible, even though the latter is scarce in hard numbers. Has the data been revised for the solar system of 47Uma since the table was written, or is it the article that has it all wrong?

      • Furthermore, given that Jupiter orbits the Sun at 5.2 AU, preventing planet formation between 2 and 5 AU (cf. our asteroid belt), and that one is at 2.1 AU from its star, I don't see how an Earth-like planet could be within that star's habitable zone, between 1 and 1.5 AU.

        There is considerable study going on at the present time in things like planetary in-migration. Just because a planet is currently at 2.1 AU, doesn't mean that it has always been there. Other possibilities include resonances and trojan points. It's quite hard to simulate this well, but at our present state of knowledge it is definitely not time to rule things out categorically.

      • Hmmmm. I thaought that Bode's "Law" was a little more accurate than that.

        But, OK. We have Earth a 1.0 AU, Mars at 1.5AU and Jupiter at 5.2AU. That puts the place of the missing planet at about 2.25AU.

        The precise location of the habitable zone is dependant on the star's brightness, but lets assume that it's in roughly the same place as on Earth.

        That means that this star's asteroid belt is about at Mars location leaving room for a rocky planet at or slightly in closer to that star than Earth is to the Sun.

      • Re:more stats (Score:3, Informative)

        by Soft ( 266615 )
        (Hate to reply to myself...)

        OK, I found another article about this [spaceref.com] at SpaceRef. Your data is correct, and they found a second planet beyond that one. Still, I'm not sure how a rocky planet could form with those two monsters nearby; it's the "far away from the star" in the WP article that confused me. Of course, they're comparing with those other star systems discovered recently, where gas giants are insanely close to the stars...

        • Still, I'm not sure how a rocky planet could form with those two monsters nearby; it's the "far away from the star" in the WP article that confused me.

          Consider that it has an year that is 3 years long. This would put it where we have the asteroid belt now, roughly. I suspect that Jupiter could be in closer without causing too much of a problem for us.

          On a separate, but slightly related angle, there was a paper released a couple months back (see CNN Story) [cnn.com] that came to the conclusion that something very weird happened in the Solar system about 65 million years ago. Studies of ocean sediment patterns reveal that the earth has been going through a 400,000 year climate cycle that is directly related to planetary distance. The problem is that these patterns change at about 65 million years ago. This is obviously related to the asteriod thast knocked of the dinosaurs.

          Fringe groups have been looking at this and speculated that this is when the asteroids were formed, and when mars got its weird pattern of craters that cover only half the planet. You can download a nicely done 60 page document of this sort of thing (PDF [enterprisemission.org] - HTML [enterprisemission.com]). Unfortunately, the authors like to occasionally bring in things that are not relevant, so it sort of ruins the flavor, but it is not bad, and interesting reading, even if you do not take it seriously.

          Which of course goes to the question in orbital mechanics of how close can you have a gas giant before it messes things up.

  • Circular orbits are less common than highly elliptical orbits, and are more promising.

    Is that true? If so, how do we know?

    Remember that the only way we can currently detect planets outside our own solar system is by their gravitational influence on the primary star, and the effect is right on the edge of what we can detect. We're seeing lots of massive gas giants in orbits that bring them close to their primaries because we can't (yet) detect anything else.

    In our own solar system, the gas giants are in large circular orbits. If our solar system is typical, we're only seeing a small distorted sample of what's out there.

    • We also have planetary formation theories, which while we don't have a lot of data to test them, can be useful.

      The problem is that not only do you need a planet with a circular orbit in the habitation zone, you need a solar system free of other massive objects with eliptical orbits. If 50 % of the large objects in a solar system have highly elliptical orbits, it is going to be hard for life to form on one of the other 50%. If you have a large gas giant like Jupiter in a circular orbit, it is going to capture or eject most of those objects, leaving the habitible zone relatively clean.

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