Carl Östen Emanuel Bergstrand (1 September 1873 – 27 September 1948) was a Swedish

astronomer An astronomer is a scientist in the field of astronomy who focuses on a specific question or field outside the scope of Earth. Astronomers observe astronomical objects, such as stars, planets, natural satellite, moons, comets and galaxy, galax ...

. He was Professor of Astronomy at

Uppsala University Uppsala University (UU) () is a public university, public research university in Uppsala, Sweden. Founded in 1477, it is the List of universities in Sweden, oldest university in Sweden and the Nordic countries still in operation. Initially fou ...

from 1909 until 1938 and from where he received his Ph.D. in astronomy in 1899 under Nils Christoffer Dunér. His early work was focused on astrometrics, particularly in the examination of photographic plates to measure stellar

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

. He used the orbital motions of the moons of

Uranus Uranus is the seventh planet from the Sun. It is a gaseous cyan-coloured ice giant. Most of the planet is made of water, ammonia, and methane in a Supercritical fluid, supercritical phase of matter, which astronomy calls "ice" or Volatile ( ...

to measure the rotation period and equatorial flattening of the planet. He also made studies of the

solar corona In astronomy, a corona (: coronas or coronae) is the outermost layer of a star's Stellar atmosphere, atmosphere. It is a hot but relatively luminosity, dim region of Plasma (physics), plasma populated by intermittent coronal structures such as so ...

, using photographs from the 1914 solar eclipse expedition. He wrote works on astronomy for the general public, including ''Astronomi'' (1925). The crater Bergstrand on the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

is named after him.

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Östen Bergstrand (1873-1948)
1873 births 1948 deaths 20th-century Swedish astronomers Members of the Royal Swedish Academy of Sciences Burials at Uppsala old cemetery {{Europe-astronomer-stub