Formation of super-Earths is limited near metal-poor stars | Science & Technology

Using the sun as a baseline, astronomers can measure when a star formed by determining its metallicity, or the level of heavy elements present within it. Metal-rich stars or nebulas formed relatively recently, while metal-poor objects were likely present during the early universe.

Previous studies found a weak connection between metallicity rates and planet formation, noting that as a star’s metallicity goes down, so, too, does planet formation for certain planet populations, like sub-Saturns or sub-Neptunes.

Yet this work is the first to observe that under current theories, the formation of super-Earths near metal-poor stars becomes significantly more difficult, suggesting a strict cut-off for the conditions needed for one to form, said lead author Kiersten Boley, who recently received a PhD in astronomy at The Ohio State University.

“When stars cycle through life, they enrich the surrounding space until you have enough metals or iron to form planets,” said Boley. “But even for stars with lower metallicities, it was widely thought that the number of planets it could form would never reach zero.”

Other studies posited that planet formation in the Milky Way should begin when stars fall between negative 2.5 to negative 0.5 metallicity, but until now, that theory was left unproven.

To test this prediction, the team developed and then searched a catalog of 10,000 of the most metal-poor stars observed by NASA’s Transiting Exoplanet Survey Satellite (TESS) mission. If correct, extrapolating known trends to search for small, short-period planets around one region of 85,000 metal-poor stars would have led them to discover about 68 super-Earths.

Surprisingly, researchers in this work detected none, said Boley. “We essentially found a cliff where we expected to see a…