alien planets
(Illustration by Michael S. Helfenbein / Yale University)

Do Alien Planets Have the Right Stuff? New Method Makes it Easier to Determine

There is a field of study focused on finding Earth 2.0, i.e. a planet that is enough like Earth to support life. New research done at Yale University analyses stars’ chemical composition to determine the conditions that existed when the star’s planets were formed.

John Michael Brewer and Debra Fischer use a computational modelling technique on stars that reveal their chemical makeup. They describe their model as a new method to evaluate the biological evolution possibilities, and habitability of planets that are not in our solar system. Fischer, a Yale professor of astronomy, explains that the model is an easy diagnostic tool to determine whether that pale blue dot you see is more like Earth or in fact rather resembles Venus. She adds that any new methods are useful to narrow down the search for Earth 2.0.

The technique has previously been used by lead author Brewer, a postdoctoral researcher at Yale, to study 1,600 stars. Based on fifteen elements found within those stars, Brewer could ascertain their chemical composition, as well as rotational speed, surface gravity and temperature. The new study focuses on the magnesium to silicon and carbon to oxygen ratio of about 800 stars.

If researchers understand the makeup of stars, they can understand the planets around them much better. The star’s composition is an indication of the prehistoric materials from which the very planets were formed. Much, much more is known once the basic elements that make up a planet is revealed.

One example of the advantages of the new method is that is has shown that the driving force in planetary composition is not carbon as was previously thought. Planets have mineralogy that are primarily influenced by their magnesium to silicon ratio, if their star has a carbon to oxygen ratio lower than or the same as our Sun. Of the stars studied, Brewer has found that 40% have interiors that are heavy in silicate. The remaining 60% contain magnesium to silicon ratios appropriate to forming planets that are Earth like in composition.

Brewer predicts that if his computational model help researchers make better interpretations about which planets are likely candidates for forming life as it exists on Earth, it will affect the determination of habitability profoundly.

Planets with a high carbon to oxygen ratio are known as “diamond” planets. One of the most discussed of these is 55 Cancri e. Brewer and Fischer’s study has however shown that 55 Cancri e has not earned its nickname as its carbon to oxygen ratio is not high enough. Diamond planets have now been found to be even rarer than was though before.