909 Ulla

Also known as (909) Ulla, Ulla

outer main-belt asteroid

Picture of the Day · NASA

Jupiter and Venus from Earth

2026-06-07

It was visible around the world. The sunset conjunction of Jupiter (left) and Venus (right) in 2012 was visible almost no matter where you lived on Earth. Anyone on our planet with a clear western horizon at sunset could see them. That year, a creative photographer traveled away from the town lights of Szubin, Poland to photograph a near closest approach of the two planets. The bright planets were then separated by only three degrees and his daughter struck a humorous pose. A faint red sunset still glowed in the background. Jupiter and Venus are together again this week after sunset, passing within a degree of each other about two days from today.

Key facts

Discovered by: K. Reinmuth
Discovery site: Heidelberg Obs.
Discovery date: 7 February 1919
Pronunciation: German: [ ˈʊlaː ] , Classically: / ˈ ʌ l ə /
Named after: Ulla Ahrens , (observatory donor)
Alternative designations: 1919 FA · 1936 SJ, 1949 OF 1 · 1949 PW, 1966 BU · 1966 DM, A912 CA · A919 CA

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Article

909 Ulla is a large and dark asteroid from the outermost regions of the asteroid belt, that measures approximately 116 kilometers (72 miles) in diameter. It is the parent body and namesake of the Ulla family, which belongs to the larger group of Cybele asteroids. It was discovered on 7 February 1919, by German astronomer Karl Reinmuth at the Heidelberg Observatory in southwest Germany. The X-type asteroid has a rotation period of 8.7 hours and a notably low value for its Jupiter Tisserand's parameter. It was named after Ulla Ahrens, daughter of a friend of the discoverer.

Orbit and classification