[写真]27年間「小惑星」とされた天体が実は「ダークコメット」と判明、地球防衛の軌道予測モデルに修正迫る

This artist’s concept depicts a near-Earth asteroid with an elongated orbit. A few objects such as these can exhibit significant perturbations in their motion around the Sun and could turn out to be regular comets with a weak tail and coma . (JPL-Caltech/Nasa.gov)