ALMA images of the disk around HD 21997. The left image shows the emission of cold dust grains, situated in a ring around the central star. The middle image displays the emission from carbon monoxide and shows that gas can also be found closer to the star than dust. The right image depicts the velocity of the gas. The red-colored parts of the disk move away from us, while the blue-colored parts move towards us, indicating that the gas is rotating/orbiting around the central star.
Á. Kóspál (ESA)/A. Moór (Konkoly Observatory)