1. Subscribersonhouse
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    10 Feb '12 15:45
    http://apod.nasa.gov/apod/ap120210.html

    Can you imagine what the nighttime sky would be from an Earthy planet in the middle of this cluster. It is said to be 10 billion years old, 100,000 stars! I bet there are some with inhabitable planets. I would love to see the night time sky from there.
  2. Standard memberSoothfast
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    11 Feb '12 00:38
    I take it these would all have to be type K or even type M stars.
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    11 Feb '12 01:56
    It's not one of the first places I would look for habitable planets...
    certainly not for ones with anything intelligent on them.

    The high density of stars mean that radiation levels are significantly higher.
    Also there is significantly more gravitational disturbance likely to mess up any planetary orbits.
    Coupled with the likelihood of the stars all lighting up at around the same time (followed shortly
    thereafter by all the big ones going nova) blasting most of the planet forming materiel out of the
    cluster.....

    It's not a promising environment for finding 'Earth like' planets.

    That's not to say that there aren't any... but It wouldn't be high on my list of likely places to look
    if it was my telescope time.

    Of course if I was studying planetary formation rather than looking for ET then it would be high on
    my list of places to look to see if my hypothesis that its a sucky place to look was right...
  4. Subscribersonhouse
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    11 Feb '12 05:301 edit
    Originally posted by googlefudge
    It's not one of the first places I would look for habitable planets...
    certainly not for ones with anything intelligent on them.

    The high density of stars mean that radiation levels are significantly higher.
    Also there is significantly more gravitational disturbance likely to mess up any planetary orbits.
    Coupled with the likelihood of the stars al ist of places to look to see if my hypothesis that its a sucky place to look was right...
    Well they aren't THAT close, take the cube of ten ly, 1000 cubic ly, 100,000 suns, so 100 suns per cubic ly, a lot closer than Alpha Centauri for sure, but that is 100 stars in a volume of about 8 E 38 cubic kilometers and that puts them about 2 trillion Km apart, some 13,000 AU apart. Don't think there would be a whole lot of extra radiation.

    These stars are about 10 billion years old so the early blowups would have happened in the first billion years or so giving the later stars a more even break radiation wise. I wonder if anyone has done a simulation on what the night sky would look like there? Dead center of the cluster. If you did have a faster than light drive, it would be like a kid in a candy store though.....

    First on my list of interstellar places to go would be Alpha Centauri, you get three stars for the price of one, I bet there are lots of planets we can't see yet and it's the closest tertiary system at only 4 ly.

    There would be some wicked gravitational lensing going on though....

    I figured out each star focuses a beam of light going by from another star, long story, but my work seems to show the beam of concentrated light being as long as the distance between the stars so there would be a lot of these beams going out about 1/5th of a light year, lot of gravitational lensing going on there for sure!
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    11 Feb '12 13:47
    Originally posted by sonhouse
    Well they aren't THAT close, take the cube of ten ly, 1000 cubic ly, 100,000 suns, so 100 suns per cubic ly, a lot closer than Alpha Centauri for sure, but that is 100 stars in a volume of about 8 E 38 cubic kilometers and that puts them about 2 trillion Km apart, some 13,000 AU apart. Don't think there would be a whole lot of extra radiation.

    These star ...[text shortened]... going out about 1/5th of a light year, lot of gravitational lensing going on there for sure!
    Hmm but you are talking about the average distance, the problem for making earth like planets is that you want
    LONG term stability, which is hard to come by in a globular cluster of that size.

    As for First on my list of interstellar places to go...

    Epsilon Eridani - http://en.wikipedia.org/wiki/Epsilon_Eridani

    Spectral Class K2V
    Age 0.5~1.0 Billion Yrs.
    Distance Approx 10.49 Years.
    1 Confirmed Exoplanet (Gas Giant) At least 1 more inferred (rocky planet Earth-ish size)
    Large debris rings perfect for harvesting for building mega-structure habitats.

    This is the closest Solar system likely to be suitable for colonisation. - http://en.wikipedia.org/wiki/List_of_nearest_stars

    Binary or trinary systems are less good due to the complex orbits and difficulty of finding a 'habitable' zone.
    Also highly unpredictable comet and asteroid activity.

    All other single star solar systems within 16 Years of us have unsuitable spectral classes.
  6. Subscribersonhouse
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    11 Feb '12 14:021 edit
    Originally posted by googlefudge
    Hmm but you are talking about the average distance, the problem for making earth like planets is that you want
    LONG term stability, which is hard to come by in a globular cluster of that size.

    As for First on my list of interstellar places to go...

    Epsilon Eridani - http://en.wikipedia.org/wiki/Epsilon_Eridani

    Spectral Class K2V
    Age 0.5~1.0 B

    All other single star solar systems within 16 Years of us have unsuitable spectral classes.
    Yeah, I read that about Eridani, there was an article in Scientific American a few years back analyzing the orbits of the three stars in Alpha Centuari and the conclusion was the orbits of planets similar to ours would not be in danger of being slung about by either star in the system that is basically a binary with a distant dwarf star way too far away to cause planets any problems either so if there were in fact planets around either large star in AC they would be stable.

    I guess you saw the report of the newly discovered planet in the goldilocks zone, a red dwarf about 20 ly away. In that case being around a weak star, the habitable zone is rather close to the star.

    I think it is found closer than Mercury is to Sol. But stars like that have a nasty habit of throwing out really bad flares at unpredictable times so a planet around a dwarf is in a lot more danger of getting flare radiation than a nice quiet star like Sol. Especially being so frigging close.

    The one thing that bugs me about AC is, and I don't know why, there seems to so far been no planets detected there. I would like to assume there would have to be, considering the stars are so close to Sol, temperature and size wise. I would have thought AC would be a natural for the search being only 4 odd ly away and all.

    I think AC and Sol were made together, part of the same cloud that condensed into stars. There was another article in Scientific American asking the question as to where are the stars that were made in the same cloud as Sol and so far they seem to find them scattered in a rough line about 5,000 ly long stretched out in this neck of the galactic arm.

    It would seem to me prime ground to find Earthy planets but we could not even consider going there physically for a long time if ever, if we are forever stuck to travel below c velocity.

    It's funny, so far our solar system is far and away the odd man out in terms of what we have discovered planet wise so far, hundreds of planets detected now and almost all of them the gas giants are so close to their star they are hotter than Venus but at least the size of Jupiter.

    That result might just be because of the present sensitivity of our sensors, our present level of technology. I sure hope that is the case, when we get better scopes in space I am hoping we find more solar systems like ours with inner rocky planets and outer giants.

    It is said the outer giants make for a shield of the inner planets, and stabilize the orbits of the small 4 here but clearly that can't happen with the planetary systems so far found, giants so close to its primary would cause havoc on tiny planets like Venus, Earth and Mars.
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    11 Feb '12 14:34
    These kind of clusters, this old, do they really have planets at all? The sun is a 2nd generation star, how many 2nd generation stars are there in the cluster? I would think of that there are none, they are all 1st generation ones, and therefore without earthlike planets.
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    11 Feb '12 14:44
    Originally posted by sonhouse
    Yeah, I read that about Eridani, there was an article in Scientific American a few years back analyzing the orbits of the three stars in Alpha Centuari and the conclusion was the orbits of planets similar to ours would not be in danger of being slung about by either star in the system that is basically a binary with a distant dwarf star way too far away to ...[text shortened]... giants so close to its primary would cause havoc on tiny planets like Venus, Earth and Mars.
    Well the thing about our current detection methods for planets is that they are naturally much more sensitive to
    so called 'hot Jupiter's' as the Doppler wobble from a close in gas giant is much easier to detect and the dimming
    from a hot Jupiter passing in front of its star is bigger and more frequent than that of a small planet farther out
    meaning that they are the first things likely to be found. So there is a significant selection bias.

    Also these methods are tuned to detect planets that are orbiting edge on or close to edge on to us.
    If the planets are orbiting perpendicular to us then they wont eclipse their star and there will be no Doppler wobble
    we can detect.
    As we are not currently looking with anything that can really see planets directly even at 4 years out we are reliant on
    the solar system being edge on to us.
    Statistically this means that the likelihood of any given star system appearing to us to have planets is significantly reduced
    Due to the relatively small proportion of solar planes we can detect.
    This is why our planet hunting techniques involve looking at large numbers of stars simultaneously over a large proportion
    of the sky in the hope that we catch a few with planets. Which has to date been very successful.


    However if you are interested in finding an earth like object in space then I wouldn't rule out close in gas giants just yet.
    If a gas giant is sitting in a stars habitable zone it might well be a better bet for finding life than a solitary rocky planet
    in the same orbit.

    The reason being that if gas giants in other solar systems are anything like ours they will have dozens of moons.
    some perhaps even bigger than the earth.

    And given that one of the problems with small rocky planets (or moons) is that they cool down too fast and lose there
    magnetic field and volcanism before life can really develop much there is even more hope with gas giant moons because its
    perfectly possible for the gas giant to keep the moon hot with tidal stressing.
    Also one of the plus points of the earth is that our moon keeps our axis tilt stable again promoting conditions for life (as well
    as on the early earth providing massive tides that are thought to be crucial (or at least very beneficial) for early life development)

    and a moon orbiting a gas giant gets it's axial tilt stabilised by the gas giant in exactly the same way.

    So a gas giant orbiting in it's stars habitable zone might very well be a better bet for life hunting than a solitary planet.
    And due to the ease of panspermia between moons it might well be that if you have one life bearing moon around a gas giant
    you would probably have several.
  9. Subscribersonhouse
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    11 Feb '12 15:23
    Originally posted by googlefudge
    Well the thing about our current detection methods for planets is that they are naturally much more sensitive to
    so called 'hot Jupiter's' as the Doppler wobble from a close in gas giant is much easier to detect and the dimming
    from a hot Jupiter passing in front of its star is bigger and more frequent than that of a small planet farther out
    meanin ...[text shortened]... at if you have one life bearing moon around a gas giant
    you would probably have several.
    Sounds reasonable for sure. Do you know if AC plane is out of reach for our methods? I guess statistically it would be out of plane to us.

    Getting back to the cluster, the chaotic motions of the stars would certainly have some of them blasting planets out of its system on at least some of those stars, kind of like how we have hypothesized that star supposedly coming close to the sun every 33 million years, forget the name of that one, there would be a lot of that for sure if the stars are 1/5th of a ly apart on average.

    I would love to see a planetarium simulating being in the center of that cluster though!
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    11 Feb '12 15:49
    Originally posted by sonhouse
    I would love to see a planetarium simulating being in the centre of that cluster though!
    Yes that would be cool.
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