311. Jacobus Cornelius KAPTEYN Doctor
BIOGRAPHY: Jacobus Cornelius Kapteyn (1851 - 1922)
Jacobus Cornelius Kapteyn was born in Barneveld, the Netherlands on 19th January 1851. He studied at the University of Utrecht from 1868. He moved to the Leiden astronomical observatory in 1875, and three years later became the first Professor of Astronomy and Theoretical Mechanics at the University of Groningen.
Kapteyn's initial work was analysing photographs of Southern hemisphere stars taken at the Cape Town Observatory in South Africa. This resulted in the publication between 1896 and 1900 of the Cape Photographic Durchmusterung, listing positions and magnitudes for nearly 455,000 stars.
His subsequent work, published in 1904, used the technique of trigonometric parallax to measure the proper motion of stars. He found the first evidence that proper motions were not random, but that stars could be divided into two streams apparently moving in opposite directions. This represented the first evidence for the rotation of our galaxy.
In 1906 Kapteyn started a major study of the distribution of stars in the galaxy, using counts of stars in different directions. This involved measuring the magnitude, spectral type, radial velocity and proper motion of stars in 206 zones. It represented the first major international collaborative project in astronomy, involving over 40 observatories.
The conclusions were published in 1922, and described a lens-shaped island universe, whose density decreased away from the centre. This galaxy was thought to be 40,000 light-years in size, the sun being relatively close (2,000 light-years) to the centre. The discovery of interstellar extinction after Kapteyn's death resuled in the estimated size of the galaxy being increased to 100,000 light-years, and the sun being relegated to a distance of 30,000 light years from its centre.
Kapteyn was a member of the French Academy of Science, a Fellow of the Royal Society and a founder member of the International Astronomical Union. He died in Amsterdam on 18th June 1922.
Deep Sky Objects:
Kapteyn's Star is a fairly faint (8.8) red dwarf known for its large proper motion, which is second only to Barnard's Star (in Ophiuchus).
The star's discovery was made nearly a century ago, in 1897, by Professor Jacobus Cornelius Kapteyn (1851-1922) of the University of Groningen in Holland.
Kapteyn's lasting discovery was that all stars which have a measurable proper motion are part of one of two streams which move in different directions at different speeds.
Kapteyn's Star has a radial velocity of 242 km/s and a distance of 12.73 light years (=parallax of 0.256" or 3.91 pc). The star has a luminosity of only 0.004 suns (i.e. an absolute magnitude of 10.85). It is found roughly 8.5 degrees NW of beta Pictoris (Burnham, p. 1463, has a finder's chart).
From The Publisher:
Among the most influential, world-renowned scientists during the early decades of the twentieth century was the Dutch astronomer Jacobus Cornelius Kapteyn (1851-1922). Kapteyn's influence resulted from and contributed to the golden age of Dutch science. In the words of the brilliant English astrophysicist Arthur S. Eddington: "Holland has given many scientific leaders to the world: it is doubtful whether any other nation in proportion to its size can show so fine a record. J.C. Kapteyn was among the most distinguished of its sons - a truly great astronomer". The present text is an English translation of Kapteyn's 1928 (Dutch) biography by his daughter Henrietta Hertzsprung-Kapteyn. While the original biography suffers from - but in many ways is also enriched by - the emotional excesses of a loving daughter writing of her famous father, this new translation provides an annotated assessment of Kapteyn as family man, scientist and world leader. This new volume also opens up to a much wider reading public many of the enormously rich contributions, not only of Kapteyn the man but also of the Dutch, to the emergence of astronomy as a major intellectual force world. Perhaps equally important, the translated biography reproduces many biographical and technical details from Kapteyn's correspondence with numerous other scientists and scholars. Access to the Kapteyn biography becomes an archival treasure for future studies dealing with Kapteyn himself, as well as with the history of both modern and Dutch astronomy and with the rise of international astronomy
344. Abraham Kaptein DEN BOUWMEESTER
Occupation: Paper hanger
651. Paulus Jan Kaptein DEN BOUWMEESTER
Occupation: Shoemaker
According to the notes on the tree fragment that I recieved from Christian Kapteyn in Berlin, Adriana and Jacob moved to South Africa.