Free Astronomy Magazine July-August 2024

54 JULY-AUGUST 2024 ASTRO PUBLISHING To describe 55 Cancri e as “rocky,” however, could leave the wrong im- pression. The planet orbits so close to its star (about 1.4 million miles, or one-twenty-fifth the distance be- tween Mercury and the Sun) that its surface is likely to be molten – a bubbling ocean of magma. With such a tight orbit, the planet is also likely to be tidally locked, with a dayside that faces the star at all times and a nightside in perpetual darkness. In spite of numerous ob- servations since it was discovered to transit in 2011, the question of whether or not 55 Cancri e has an atmosphere – or even could have one given its high temperature and the continuous onslaught of stellar radiation and wind from its star – has gone unanswered. “I’ve worked on this planet for more than a decade,” said Diana Dragomir, an exoplanet researcher at the Univer- sity of New Mexico and co-author on the study. “It’s been really frustrat- Webb hints at possible atmosphere surrounding 55 Cancri e R esearchers using NASA’s James Webb Space Telescope may have detected atmospheric gases surrounding 55 Cancri e, a hot rocky exoplanet 41 light-years from Earth. This is the best evidence to date for the existence of any rocky planet atmosphere outside our solar system. Renyu Hu from NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, is lead author on a paper published in Nature . “Webb is pushing the frontiers of exoplanet characterization to rocky planets,” Hu said. “It is truly en- abling a new type of science.” 55 Cancri e, also known as Janssen, is one of five known planets orbiting the Sun-like star 55 Cancri, in the constellation Cancer. With a diame- ter nearly twice that of Earth and density slightly greater, the planet is classified as a super-Earth: larger than Earth, smaller than Neptune, and likely similar in composition to the rocky planets in our solar system. by NASA/ESA/CSA Margaret W. Carruthers & Christine Pulliam