Free Astronomy Magazine January-February 2022

50 JANUARY-FEBRUARY 2022 ASTRO PUBLISHING A stronomers have discovered thousands of planets orbit- ing stars in our galaxy — known as exoplanets. However, it’s difficult to know what exactly these planets are made of, or whether any resemble Earth. To try to find out, astronomer Siyi Xu of NSF’s NOIRLab partnered with geologist Keith Putirka of California State University, Fresno, to study the at- mospheres of what are known as polluted white dwarfs. These are the dense, collapsed cores of once- Rocky exoplanets are even stranger than we thought by NOIRLab / Vanessa Thomas