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Some planetary systems just aren't into heavy metal

Researchers have discovered that compact, multiple-planet systems are more likely to form around stars that have lower amounts of heavy elements than the Earth's sun. This runs counter to a good deal of current research, which has focused on stars with higher metallicity. The research team looked at 700 stars and their surrounding planets for the study. The researchers considered any element heavier than helium -- including iron, silicon, magnesium and carbon -- as a heavy metal. An abundance of compact, multi-planet systems around low-metallicity stars suggests several things: 1) It may indicate that there are many more of these systems than previously assumed; 2) small planetary systems may be the earliest type of planetary system, making them an ideal place to search for life on other planets; and 3) there is a connection between iron and silicon in the birth of planets.

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