(1865–1939) Irish astronomer of French descent. He specialized in calculating cometary orbits, often working with P. H. Cowell; together they predicted the date of return of Halley's Comet in 1910, and calculated its previous apparitions back to the 3rd century bc. In 1929 he discovered that three comets (from 1818, 1873, and 1928) were one and the same; it was subsequently renamed Comet 27P/Crommelin, and returned in 1956 as he predicted.
From A Dictionary of Astronomy in Oxford Reference.
Subjects: Astronomy and Astrophysics.