Patience is required in the search for exoplanets. Thousands of stars must be studied in order to detect just a few planets. Astronomers have patience to spare, but they soon realised that certain stars provide happier hunting grounds than
Iron to make planets. The probability of detecting planets around a solartype star (vertical axis) is very dependent on the amount of heavy elements in the star's atmosphere: here, the quantity of iron compared to that of hydrogen, with reference to the solar value (logarithmic units). The Sun lies at [Fe/H = 0]. Only a very small number of stars with metallicities less than or equal to the Sun's are known to have planets. As metallicity increases, so does the planet count - and steeply. The abrupt decrease in the detection rate below [Fe/H = 0.4] is simply due to there being no iron-rich star in the vicinity of the Sun.
3.6 Cannibal stars? 53
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