Wefa, Abu'l (940-998) - from Baghdad he made observations of equinoxes, solstices, and the obliquity of the ecliptic.
Weizsacker, Carl Friedrich (b. 1912) - German astronomer who developed a more complex theory about the formation of the solar system. He expanded upon earlier works to detail a theory of how the solar system formed from rotating nebular material containing several vortices.
Whipple, Fred Lawrence (1906-2004) - American astronomer who in 1949 suggested that comets were primarily composed mostly of frozen hydrogen containing compounds.
Wildt, Rupert (1905-1976) - German-American astronomer who primarily studied the atmospheres of the the planets. He was the first to identify methane and ammonia in the atmosphere of Jupiter.
Wolf, Maximillian Franz (1863-1932) - Astronomer who specialized in finding asteroids. Using photography he was able to find over 500 asteroids. He also discovered the first Trojan asteroid, which has the same orbit as Jupiter, in 1906.
Young, Charles Augustus (1834-1908) - American astronomer who was the first scientist to photograph the spectra of the solar corona. He also wrote several popular astronomy textbooks of the nineteenth century.
Yunus, Abu' Hasan Ali ibn Abd al-Rahman ibn (950-1009)- published the Hakemite Tables which included theory and computing methods, along with information about observations of eclipses and conjunctions.
Zhang Heng [Chang Heng] (78-139) - created the first rotating celestial globe (armillary sphere) in China. Postulated that the Moon moved around the Earth and was eclipsed by the shadow of the Earth.
Zollner, J.C.F. (1834-1882) - created the photometer used in astronomy to measure the brightness of objects. He used the device to make accurate measurements of the brightness of the Moon during several phases.
Zwicky, Fritz (1898-1974) - Swiss astronomer who researched the differences between nova and supernova. His research indicated that only two or three supernova occur every thousand years in any given galaxy. He also researched the distributions of galactic clusters in the universe.