'New method may narrow down search for Earth 2.0'

A new method for analysing the chemical composition of stars may help scientists winnow the search for Earth-like planets where life like ours can form, a new study has found.
Researchers from Yale University in the US have found a computational modelling technique that gives a clearer sense of the chemistry of stars, showing the conditions present when their planets formed.
The system creates a new way to assess the habitability and biological evolution possibilities of planets outside our solar system, researchers said.
"This is a very useful, easy diagnostic to tell whether that pale blue dot you see is more similar to Venus or the Earth," said Debra Fischer, a Yale professor of astronomy.

"Our field is very focused on finding Earth 2.0, and anything we can do to narrow the search is helpful," said Fischer.
Lead author John Michael Brewer, a postdoctoral researcher at Yale, has used the technique previously to determine temperature, surface gravity, rotational speed, and chemical composition information for 1,600 stars, based on 15 elements found within those stars.

The new study looked at roughly 800 stars, focusing on their ratio of carbon to oxygen, and magnesium to silicon.
Brewer explained that understanding the makeup of stars helps researchers understand the planets in orbit around them.
"We're getting a look at the primordial materials that made these planets. Knowing what materials they started with leads to so much else," he said.

For instance, the study shows that in many cases, carbon is not the driving force in planetary composition.
Brewer found that if a star has a carbon/oxygen ratio similar to or lower than that of our own Sun, its planets have mineralogy dominated by the magnesium/silicon ratio.
About 60 per cent of the stars in the study have magnesium/silicon ratios that would produce Earth-like compositions; 40 per cent of the stars have silicate-heavy interiors.
"This will have a profound impact on determining habitability. It will help us make better inferences about which planets will be ones where life like ours can form," Brewer said.

In addition to helping identify planets more like Earth, the study sheds light on the occurrence of "diamond" planets - planets with a high carbon-to-oxygen abundance.
Brewer and Fischer found that it is "exceedingly rare" to find a star with a carbon/oxygen ratio high enough to produce a diamond planet.
In fact, the new data shows that the star of the much discussed diamond planet, 55 Cancri e, does not have a high enough carbon/oxygen ratio to support its nickname.
"They're even more rare than we thought a few years ago. Diamond planets truly are the most precious," Fischer said.

The study appears in the Astrophysical Journal.