A newfound exoplanet may be the exposed core of a gas giant
A dense, scorched planet around a faraway star may be the naked core of a gas giant. Satellite and Earth-based telescope observations show that the newly discovered exoplanet has a radius nearly 3.5 times Earth’s and a mass about 39 times as big. Those dimensions combined point to a density roughly the same as Earth’s, suggesting that the exoplanet is mostly rock. Unlike other massive planets, this world, called TOI 849b, has a barely there atmosphere, making up 4 percent of its mass at most, a new study suggests. That atmosphere is “absolutely minuscule for a planet of its size,” says astronomer David Armstrong of the University of Warwick in Coventry, England. “This one is almost entirely an exposed rocky ball.” The planet’s large mass and near lack of an atmosphere suggest that TOI 849b may be the remnant core of a gas giant, Armstrong and colleagues report July 1 in Nature. It...