Scientific work
During 1843 and 1844, Struve participated in longitude measurements between Altona, Greenwich and Pulkovo, which were based on large displacement of chronometers over the Earth surface. This newly developed method was adopted in Russia, and from 1844, longitude was measured starting from Pulkovo Observatory instead of Tartu Observatory.
Struve dedicated much of 1844 to studying the Sun. He deduced its apex coordinates and linear velocity as 7.3 km/s. Although this was significantly smaller than the accurate value of 19.5 km/s measured in 1901, Struve was correct in that the velocity of the Sun was smaller than that of stars.
In 1865 Struve discovered NGC 8, a double star in the constellation Pegasus, and the spiral galaxy NGC 9 in the constellation Andromeda. He explored the constellation of Cassiopeia, finding double stars. He labeled them with his initials in the Greek alphabet, OΣ in his first catalogue, and OΣΣ in his appendix.
Struve continued his father's work in several directions. In particular, they compiled catalogues of stellar coordinates, including several thousands double stars observed with a 15-inch refractor. Between 1816 and 1852, the observatory completed survey triangulation measurements of the angular arc (named Struve Geodetic Arc). The measurements extended through over 2,820 km, from Hammerfest in Norway to the Staraya Nekrasovka village by the Black Sea, and aimed to establish the exact size and shape of the Earth.
In 1851, while observing a solar eclipse, Struve concluded that the solar corona and protuberances are physically connected with the Sun rather than being simply an optical effect, as most astronomers then believed. Later in 1860 he suggested a close connection between solar protuberances and flares. he also observed satellites of Uranus (Ariel and Umbriel, in 1851) and of Neptune. He measured the rings of Saturn and discovered (in parallel with other researchers) the dark inner ring of Saturn. In 1861, in his report to the Academy of Sciences, he supported and developed the ideas of William Herschel that stars are formed from the diffuse matter. In 1872, he organized assistance with equipment to the newly opened observatory in Tashkent – a more southerly location offering clear skies for observations. In 1874, he prepared several expeditions to monitor the transit of Venus across the solar disk in eastern Asia, Caucasus, Persia and Egypt. In 1887, he sent several groups within Russia to observe the solar eclipse. In some of those expeditions, he took part personally. In 1885, a 30-inch refracting telescope was installed at Pulkovo, at the time the largest in the world (see great refractor).
