![This figure from the paper shows the abundance of different elements in stars versus their abundances of iron. In each square, you can see a plot of the abundance of one element (represented by [x/Fe]) against the abundance of iron (represented by [Fe/H]). Each red dot, black square, or blue X represents a star. The red dots are the small planet-hosting stars studied in this new work. You can see how they do not stand out from the rest of the stars, which were studied in other publications, some of which host planets and some of which have no known planets. The green dashed lines show these values for our Sun. Credit: From the team's paper](https://images.sciencedaily.com/2015/12/151203150323_1_540x360.jpg "Click to enlarge")
This figure from the paper shows the abundance of different elements in stars versus their abundances of iron. In each square, you can see a plot of the abundance of one element (represented by [x/Fe]) against the abundance of iron (represented by [Fe/H]). Each red dot, black square, or blue X represents a star. The red dots are the small planet-hosting stars studied in this new work. You can see how they do not stand out from the rest of the stars, which were studied in other publications, some of which host planets and some of which have no known planets. The green dashed lines show these values for our Sun. Credit: From the team’s paper
New work from a team including Carnegie’s Johanna Teske extended this idea by measuring a large suite of elements besides iron. They found that stars with Earth-sized rocky planets are overall chemically similar to those with Neptune-sized planets, and to stars with no planets, but not to stars with gas giant planets. The team examined the abundance of 19 different elements found in 7 stars that are orbited by at least one Earth-like rocky planet, all discovered by NASA’s Kepler mission. Their work shows that small rocky planets like Earth don’t preferentially form around stars rich in metallic elements such as iron and silicon. The result is surprising because iron and silicon are among the most abundant elements in rocky planets.
“There has been much ongoing debate about the stellar conditions necessary for planet formation,” said lead author Simon Schuler of the University of Tampa. “Our results support the theory that the formation of small, rocky planets can occur around stars with diverse elemental compositions.”…”This means that small, rocky planets may be even more commonplace than we previously thought,” Teske added.
The planetary-formation from the gas-and-dust disk surrounding a new star as described above has also raised the question of whether the process itself depletes stars of the elements that are concentrated in the planets. If so, this could be used to improve our planet-searching abilities, as looking specifically for stars that show signs of this kind of chemical depletion could narrow the hunt. However, none of the seven stars the team studied displayed this suggested depletion signature.
https://carnegiescience.edu/node/1944
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