| Willem Hendrik van den Bos | |
| Birth Date: | 25 September 1896 |
| Birth Place: | Rotterdam |
| Death Place: | Johannesburg, South Africa |
| Fields: | Astronomy |
| Workplaces: | Union Observatory |
| Alma Mater: | Leiden University |
| Thesis Title: | Micrometer measurements of double stars |
| Thesis1 Url: | and |
| Thesis2 Url: | )--> |
| Thesis Year: | 1925 |
| Doctoral Advisor: | Willem de Sitter |
| Known For: | double stars discovered |
| Spouses: | )--> |
| Partners: | )--> |
Willem Hendrik van den Bos (25 September 1896 – 30 March 1974) was a Dutch astronomer who worked at the Union Observatory in South Africa and became its director in 1941. He discovered nearly new double stars, made more than astronomical measurements and compiled a catalogue of Southern hemisphere double stars. He computed the orbits of more than 100 double stars using a method he invented and which later became the accepted standard.
Van den Bos was born in Rotterdam in 1896. He studied astronomy at Leiden University and worked at the Leiden Observatory. In 1925 he completed his PhD in astronomy under the supervision of Willem de Sitter and was invited by R.T.A. Innes to join the Union Observatory in Johannesburg for a three-year appointment as assistant to the director, H.E. Wood. Innes was eager to have an experienced observer of double-stars to share the workload on the newly erected telescope.
Van den Bos extended his appointment at the Union Observatory indefinitely and in 1941 was appointed Director of the observatory. He retired from the observatory in 1956 but continued his observations both in South Africa and the United States until 1966 when he was forced to stop owing to severe illness.
During the 31 years of his career he discovered new double stars and made astronomical measurements. He compiled a catalogue from previous observations of southern hemisphere double stars that was incorporated into the Index Catalog of Visual Double Stars, published in 1963, with the collaboration of H.M. Jeffries and F.M. Greeby of the Lick Observatory, California. The catalogue later became the Washington Double Star Catalog.
Van den Bos developed his own method of measuring the orbits of double stars and used it to measure the orbits of more than 100 binary stars. His method became the accepted standard procedure.