11. Astronomers also measure the " apparent size " of objects as an angular diameter . 12. The angular diameter of Betelgeuse is only exceeded by R Doradus ( and the Sun ). 13. The angular diameters of the four smaller moons ( as seen from Pluto ) are uncertain. 14. The distance measured by a standard ruler is what is known as the angular diameter distance. 15. Uranus is a relatively faint object, and its visible angular diameter is smaller than 43. 16. Evans major contribution to astronomy was using the angular diameters of stars to calculate their surface brightness. 17. The dwarf planet Pluto has proven difficult to resolve because its angular diameter is about 0.1 arcsecond. 18. For bodies that appear smaller in angular diameter than the Sun, the proper term would be a transit. 19. So basically if what is the relationship between angular diameter and amount of energy it radiates and its wavelength. 20. From this distance, the sun's angular diameter is reduced to one and a quarter arcminutes across.
