Prof Jacobus Cornelius Kapteyn FRS FRSE LLD was a Dutch astronomer. He carried out extensive studies of the Milky Way. He found that the apparent movement of stars was not randomly distributed but had two preferential directions: the two star streams. This discovery was later reinterpreted as evidence for galactic rotation. Kapteyn also suggested that these stellar velocities could be used to find the amount of non-luminous matter in the galaxy.
Jacobus Kapteyn. Painting by Jan Veth (1921).
Jacobus Kapteyn on the occasion of his 40th anniversary as professor in Groningen. Sir David Gill in background. Painting by Jan Veth.
The Milky Way is the galaxy that includes the Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye.
The Galactic Center as seen from Earth's night sky (featuring the telescope's laser guide star). Listed below is Galactic Center's information.
The Milky Way as seen from a dark site with little light pollution
Photograph of the "Great Andromeda Nebula" from 1899, later identified as the Andromeda Galaxy
Bright X-ray flares from Sagittarius A* (inset) in the center of the Milky Way, as detected by the Chandra X-ray Observatory.
