Robert Luther and the Bilk Observatory

How a student of Encke found 24 asteroids from Düsseldorf — starting with Thetis.

Published 2026-10-23

Thetis was the first of many discoveries for Robert Luther, who worked at the Bilk Observatory in Düsseldorf for decades.^[3][2]

Early life

Karl Theodor Robert Luther was born on 16 April 1822 in Świdnica. He studied in Breslau, then moved to Berlin in 1843 to study astronomy under Johann Franz Encke, helping him with calculations and the astronomical almanac.^[3]

To Düsseldorf

In 1851, Franz Brünnow invited Luther to the Düsseldorf-Bilk Observatory to succeed him as director.^[3] The next year, on 17 April 1852 — a day after his 30th birthday — Luther found his first asteroid, Thetis.^[2][3]

A modest naming

Rather than name it himself, Luther deferred to Friedrich Wilhelm August Argelander, who chose Thetis from Greek mythology.^[2]

Twenty-four asteroids

Luther discovered 24 asteroids between 1852 and 1890. Two have unusual properties: 90 Antiope, a binary with two equal components, and the extremely slow-rotating 288 Glauke.^[3] He won the Lalande Prize seven times.^[3]

Numbered citations link to the sources list on the Thetis overview page.