Free Astronomy Magazine March-April 2023

30 MARCH-APRIL 2023 ASTRO PUBLISHING planets (iREx) at the University of Montreal, published a detailed study of a planetary system known as Kepler-138 in the journal Nature Astronomy . Piaulet, who is a member of Björn Benneke’s research team at the Uni- versity of Montreal, observed the exoplanets Kepler-138 c and Kepler- 138 d with both the NASA/ESA Hub- ble Space Telescope and NASA’s Spitzer Space Telescope. She found that the planets could be composed largely of water. Water wasn’t directly detected, but by comparing the sizes and masses of the planets to models, they con- clude that a significant fraction of their volume — up to half of it — should be made of materials that are lighter than rock but heavier than hydrogen or helium (which Two waterworlds in the Kepler-138 system by NASA/ESA Bethany Downer R esearchers have found evi- dence for the existence of a new type of planet they have called a “water world,” where wa- ter makes up a large fraction of the entire planet. These worlds, discov- ered in a planetary system 218 light-years away, are unlike any planets in our Solar System. The team, led by Caroline Piaulet of the Institute for Research on Exo-