A new website was released that allows you to compare the sizes of various celestial bodies, including planets, stars, and black holes.
The website is called Space Object Comparison. It includes the following categories of space objects that can be compared: black holes (TON 618, H1821+643, Hercules A, NGC 3115, Messier 84, Sombrero Galaxy, Messier 49, Messier 59, Messier 81, Sagittarius A*), objects from the solar system (Sun, Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Ganymede, Titan, Mercury, Callisto, Io, Moon, Europa, Triton, Pluto, Titania, Rhea, Oberon, Iapetus, Umbriel, Ariel, Dione, Tethys, Ceres, Enceladus, Miranda, Mimas), Alpha Centauri (α Centauri A, α Centauri B, α Centauri C), Kepler-10 system (Kepler-10, Kepler-10c, Kepler-10b), Sirius system (Sirius A, Sirius B), and others (UY Scuti, Betelgeuse, Antares, Rigel A, Aldebaran, Arcturus, Pollux).
Each space object's diameter is indicated. To compare their sizes, simply select the celestial bodies of interest in the two drop-down lines. You can access the website here.