たいようけいがいわくせい 太陽系外惑星
1. extrasolar planet; exoplanet
Wikipedia definition
2. Extrasolar planetAn extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of 770 such planets have been identified as of May 30, 2012. Estimates of the frequency of systems strongly suggest that more than 50% of Sun-like stars harbor at least one planet. In a 2012 study, each star of the 100 billion or so in our Milky Way galaxy is estimated to host "on average ... at least 1.6 planets. " Accordingly, at least 160 billion star-bound planets may exist in the Milky Way Galaxy alone.
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