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Scientists Find Earth-Eating Stars Not Likely to Host Terrestrial Planets

Wednesday, 21 May 2014 - 2:04PM
Wednesday, 21 May 2014 - 2:04PM
Scientists Find Earth-Eating Stars Not Likely to Host Terrestrial Planets
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They say, "you are what you eat". Well, the saying seems to hold true for stars. Researchers at Vanderbilt University have developed a new model that demonstrates how a star's chemical signature is impacted by how many Earth-like planets the star has ingested.


The model shows that, during their development, so-called "Earth-eater" stars which are quite similar to our sun, ingest large amounts of rocky debris hailing from terrestrial planets similar to Earth, Mars, and Venus. The specific diet changes the star's signature on an elemental level. Keivan Stassun, Professor of Astronomy who supervised the study explains, "After obtaining a high-resolution spectrum for a given star, we can actually detect that signature in detail, element by element."


Stars are made up of over 98% hydrogen and helium, with other elements making up less than 2% of their remaining mass. Astronomers have arbitrarily labeled these remaining elements as "metals", and a star's chemical makeup is defined by its "metallicity", or the ratio of iron to hydrogen in its chemical makeup. It's been presumed that high metallicity stars are more likely to develop planetary systems than ones with low metallicity.


This knowledge led astronomers to examine stars' chemical compounds beyond iron content and to pay attention to elements with melting points higher than 1,200 degrees Fahrenheit, because these are the materials that eventually become the building blocks for Earth-like planets. Scientists then conducted an experiment on the stars HD 20791 and HD 20782, which both should have formed from the same clouds of dust and gas. Both stars are G-class dwarf stars that, like the sun, host planets — with one hosting a single Jupiter-sized planet and the other hosting two Neptune-sized planets. Since these stars are so similar, and their exoplanets are quite different, this was an ideal case study.


After analyzing the chemical spectrum of the two stars, and finding that the one that hosts the Jupiter-sized planet had a higher abundance of elements with high melting points than the one that produced two Neptune-sized ones, scientists concluded that there is a strong link between a star's chemical composition and the nature of its planetary system. They also found that the star that produced the Jupiter-sized planets had consumed an extra ten Earth masses, showing that it not able to host Earth-like planets because it would much rather eat them.


- Spectrums like the one below taken of our sun can help scientists identify the chemical make-up of different stars. -

(Image Credit: Vanderbilt University)


This knowledge will help astronomers better understand the process of planet formation, and will help them know where to look for Earth-like exoplanets. If scientists search through the galaxy, and locate a star with a chemical component that suggests chemicals associated with Earth-like planets are not its cuisine of choice, then it's quite likely that it will have a planetary system similar to ours. Another heartwarming message that this study shows is that, even though the sun seems like a super fierce ball of flaming gas, it's actually a gentle giant seeing as it hasn't decided to consume us yet!