7.3 Star Streams
133
Fig. 7.8 Karl Schwarzschild. He has become particularly famous for his work on the
radius of a black hole, which is named after him [71]
metry in the random velocities of the stars. All stars moved through space in
all directions, but in the direction of the apparent streams the average random
velocity of the stars would be larger than in other directions. In reality, the
stars go around the center of the Milky Way at a velocity of about 220 km/s in
the vicinity of the Sun, but the random velocities are much smaller relative to
each other. These velocities are larger in the direction to and from the center of
the Galaxy than in the direction of rotation, and they are even smaller perpendicular to the plane of the Milky Way. Eddington found, in accordance with
this, that the number of stars in the two Streams of Kapteyn was about the
same. But both he and Kapteyn remained preferring the idea of two streams
because of the observation—which later turned out to be incorrect—that the
types of stars in the two streams were very different. In Schwarzschild’s model
this would be difficult to explain. Only after Kapteyn’s death did Eddington
become convinced of the correctness of Schwarzschild’s idea; Kapteyn always
continued to believe in his Star Streams.
133
Fig. 7.8 Karl Schwarzschild. He has become particularly famous for his work on the
radius of a black hole, which is named after him [71]
metry in the random velocities of the stars. All stars moved through space in
all directions, but in the direction of the apparent streams the average random
velocity of the stars would be larger than in other directions. In reality, the
stars go around the center of the Milky Way at a velocity of about 220 km/s in
the vicinity of the Sun, but the random velocities are much smaller relative to
each other. These velocities are larger in the direction to and from the center of
the Galaxy than in the direction of rotation, and they are even smaller perpendicular to the plane of the Milky Way. Eddington found, in accordance with
this, that the number of stars in the two Streams of Kapteyn was about the
same. But both he and Kapteyn remained preferring the idea of two streams
because of the observation—which later turned out to be incorrect—that the
types of stars in the two streams were very different. In Schwarzschild’s model
this would be difficult to explain. Only after Kapteyn’s death did Eddington
become convinced of the correctness of Schwarzschild’s idea; Kapteyn always
continued to believe in his Star Streams.