Nucleus radius versus perihelion-normalized NGA of 289P (blue symbol) and comparison with those of well-studied short-period comets (yellow symbols). The dashed red line indicates the trend found by fitting from the latter data, which is Halley type (1P and 55P), Encke type (2P, 87P, and 147P), and JFCs (4P, 6P, 7P, 8P, 9P, 10P, 19P, 21P, 22P, 24P, 26P, 43P, 65P, 67P, 76P, 81P, 96P, 103P, and 106P).