We have been looking for planets around other stars for a while (see related https://space.stackexchange.com/questions/1484 ) and we are finding lots of planets, some of them are Earth like According to an the answer at https://space.stackexchange.com/questions/4062 there are over 14,000 stars within 100 light years of Earth, the answer goes on to say there are "1,500 potentially habitable planets within 100 light-years" of Earth

Based on current trends it looks like there are lots of stars with lots of planets. I am beginning to assume that our solar system is not unique and that every star has several planets.

Are there any Stars that we know are without any planets?

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    $\begingroup$ Wikipedia: Searches for companions orbiting Proxima Centauri have been unsuccessful, ruling out the presence of brown dwarfs and supermassive planets. Precision radial velocity surveys have also ruled out the presence of super-Earths within the star's habitable zone. The detection of smaller objects will require the use of new instruments, such as the James Webb Space Telescope, which is scheduled for deployment in 2018. If we don't know for certain for the closest star, we ain't know zilch. $\endgroup$ Jul 24 '15 at 11:47
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    $\begingroup$ @TildalWave Eddy has a pretty good answer below (+1), He (and Deer Hunter) suggest that multiple star systems are not capable of holding a planet in a stable orbit. So if you can define the criteria that = no planet with a couple of examples and reasons. that would be good. $\endgroup$ Jul 24 '15 at 12:29
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    $\begingroup$ @TildalWave - a good point on binaries (with a possible exception of Tattooine - "I saw it on big screen it must be true" :). $\endgroup$ Jul 24 '15 at 12:51
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    $\begingroup$ @TildalWave actually, it wasn't my intention to imply that isn't possible, just that it was surprising a few years ago (many astronomers used to consider it impossible). I've edited my answer to clarify that some binary systems HAVE since been found with planets, together with a nice link. $\endgroup$
    – Eddy
    Jul 24 '15 at 13:49
  • $\begingroup$ "I narrowed the question.." I deleted an obsolete comment. :) $\endgroup$ Jul 24 '15 at 14:59

I am beginning to assume that our solar system is not unique and that every star has several planets.

Not quite, but indeed a study published in Nature in 2012 found that, based on our observations so far, roughly 17% of stars host Jupiter-mass planets, 52% host "Cool Neptunes" and 62% host Super-Earths. (Note that these percentages do not add up to 100%, because they are not mutually exclusive possibilities). This was particularly surprising, because half of all visible stars are believe to be in binary systems, which would make planetary systems very unstable, but some binary systems have been found to have planets too.

So indeed it seems the majority of stars have planets, but it's very unlikely that all of them do.

However, the exact answer to your question "do we know of any stars with no planets" has got to be "no", because there remains a possibility that they have planets that we simply haven't been able to detect, because of limitations in our techniques to detect them.

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    $\begingroup$ I think there are some important points here. In my opinion, it should be surprising if a star doesn't have planets, and you'd generally need to give a mechanism for why there aren't. For example, instability of orbits due to companion stars, or a past pass by a massive object. Think about this for comparison: Based evidence from our solar system, it certainly appears that gas giants have many satellites. A Jupiter with no moon would be very surprising unless you had a reason why it was moonless. What is different about stellar formation? $\endgroup$ Jul 24 '15 at 20:08
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    $\begingroup$ I just want to add this on Binary systems. The belief based on observation that most stars were in a binary system was wrong: space.com/1995-astronomers-wrong-stars-single.html Your link mentions that as well, and goes on to talk about planets in binary systems: en.wikipedia.org/wiki/Binary_star#Research_findings $\endgroup$
    – userLTK
    Jul 24 '15 at 20:40
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    $\begingroup$ The percentages quoted are lower limits, because they refer to the percentage of stars that have planets within a certain (fairly small) orbital separation. We really don't know of any stars that definitely don't have planets. $\endgroup$
    – ProfRob
    Sep 13 '15 at 21:24

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