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

Swedish Swedish or ' may refer to: Anything from or related to Sweden, a country in Northern Europe. Or, specifically: * Swedish language, a North Germanic language spoken primarily in Sweden and Finland ** Swedish alphabet, the official alphabet used by ...

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

. He was Professor of Astronomy at

Uppsala University Uppsala University ( sv, Uppsala universitet) 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 opera ...

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 Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other Astronomical object, celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, th ...

, 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 lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...

. He used the orbital motions of the moons of

Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus (mythology), Uranus (Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars (mythology), Mars), grandfather ...

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

solar corona A corona ( coronas or coronae) is the outermost layer of a star's atmosphere. It consists of plasma. The Sun's corona lies above the chromosphere and extends millions of kilometres into outer space. It is most easily seen during a total solar e ...

, 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 is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

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