Yrjö Väisälä
   HOME

TheInfoList



OR:

Yrjö Väisälä (; 6 September 1891 – 21 July 1971) was a
Finnish Finnish may refer to: * Something or someone from, or related to Finland * Culture of Finland * Finnish people or Finns, the primary ethnic group in Finland * Finnish language, the national language of the Finnish people * Finnish cuisine See also ...
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 ...
and
physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate caus ...
. His main contributions were in the field of
optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviole ...
. He was also active in
geodetics Geodesy ( ) is the Earth science of accurately measuring and understanding Earth's figure ( geometric shape and size), orientation in space, and gravity. The field also incorporates studies of how these properties change over time and equival ...
,
astronomy Astronomy () is a natural science that studies astronomical object, celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and chronology of the Universe, evolution. Objects of interest ...
and optical
metrology Metrology is the scientific study of measurement. It establishes a common understanding of units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to standardise units in Fran ...
. He had an affectionate nickname of ''Wizard of Tuorla'' (Observatory/Optics laboratory), and a book with the same title in Finnish describes his works. His discoveries include 128 minor planets and 3 comets. His brothers were mathematician Kalle Väisälä (1893–1968) and meteorologist Vilho Väisälä (1889–1969). His daughter
Marja Väisälä Marja Ilmatar Väisälä (9 May 1916, Helsinki, Finland – 21 December 2011, Turku) was a Finnish teacher of mathematics and natural sciences, who in 1950 founded a private school in Swakopmund in what is now Namibia, where she taught the chil ...
(1916–2011) was an astronomer and
discoverer of minor planets This is a list of minor-planet discoverers credited by the Minor Planet Center with the discovery of one or several minor planets (such as near-Earth and main-belt asteroids, Jupiter trojans and distant objects). , the discovery of 612,011 numb ...
. Väisälä was a fervent supporter of
Esperanto Esperanto ( or ) is the world's most widely spoken constructed international auxiliary language. Created by the Warsaw-based ophthalmologist L. L. Zamenhof in 1887, it was intended to be a universal second language for international communi ...
, presiding over the ''Internacia Scienca Asocio Esperantista'' ("International Association of Esperanto Scientists") in 1968.


Optician

He developed several methods for measuring the quality of optical elements, as well as a lot of practical methods of manufacturing said elements. This allowed the construction of some of the earliest high-quality
Schmidt camera A Schmidt camera, also referred to as the Schmidt telescope, is a catadioptric astrophotographic telescope designed to provide wide fields of view with limited aberrations. The design was invented by Bernhard Schmidt in 1930. Some notable exa ...
s, in particular a "field-flattened" version known as Schmidt-Väisälä camera. Contemporary to
Bernhard Schmidt Bernhard Woldemar Schmidt (, Naissaar, Nargen – 1 December 1935, Hamburg) was an Estonian optician. In 1930 he invented the Schmidt camera, Schmidt telescope which corrected for the optical errors of spherical aberration, coma, and astigmatis ...
's design, but unpublished was also Prof. Yrjö Väisälä's identical design which he had mentioned in lecture notes in 1924 with a footnote: "problematic spherical focal surface". Once he saw Schmidt's publication, he promptly went ahead and "solved" the field flattening problem by placing a doubly convex lens slightly in front of the film holder – back in the 1930s, astronomical films were glass plates ''(also see
photographic plate Photographic plates preceded photographic film as a capture medium in photography, and were still used in some communities up until the late 20th century. The light-sensitive emulsion of silver salts was coated on a glass plate, typically thinn ...
s)''. The resulting system is known as the Schmidt-Väisälä camera or sometimes as the ''Väisälä camera''. (This solution is not perfect, as images of different colour end up at slightly different places.) Prof. Väisälä made a small test unit of 7 mirrors in a mosaic on stiff background steel frame, however it proved to be impossible to stabilize as "just adjust and forget" structure, and next time anybody tried it, was with active controls on
Multiple Mirror Telescope The MMT Observatory (MMTO) is an astronomical observatory on the site of Fred Lawrence Whipple Observatory (IAU observatory code 696). The Whipple observatory complex is located on Mount Hopkins, Arizona, US (55 km south of Tucson) in the S ...
.


Geodesy

In the 1920s and 1930s
Finland Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of B ...
was doing its first precision triangulation chain measurements, and to create long-distance vertices Prof. Väisälä proposed usage of flash-lights on altitude balloons, or on some big fireworks rockets. The idea was to measure the exact position of the flash against background stars, and by precisely knowing one camera location, to derive an accurate location for another camera. This required better wide-field cameras than were available, and was discarded. Later, Prof. Väisälä developed a method to multiply an optical length reference using
white light interferometry As described here, white light interferometry is a non-contact optical method for surface height measurement on 3D structures with surface profiles varying between tens of nanometers and a few centimeters. It is often used as an alternative name f ...
to precisely determine lengths of baselines used in triangulation chains. Several such baselines were created in Finland for second high-precision triangulation campaign in 1950s and 1960s. Later GPS made these methods largely obsolete. The
Nummela Standard Baseline Nummela Standard Baseline is a baseline used to calibrate rangefinders, in Finland, located in the municipality of Vihti, Nummelanharju (esker) where it was built in 1932. Winding ridge of stratified gravel and sand was chosen as a location fo ...
established by Väisälä is still maintained by the
Finnish Geodetic Institute The Finnish Geospatial Research Institute ( fi, Paikkatietokeskus), formerly Finnish Geodetic Institute (FGI, fi, Geodeettinen laitos, sv, Geodetiska institutet) is a research institute in Finland specializing in geodesy and geospatial informati ...
in Nummela for the calibration of other distance measurement instruments. Prof. Väisälä also developed excellent tools to measure earth rotational axis position by building so called
zenith telescope A zenith telescope is a type of telescope that is designed to point straight up at or near the zenith. They are used for precision measurement of star positions, to simplify telescope construction, or both. A classic zenith telescope, also know ...
s, and in the 1960s Tuorla Observatory was in the top rank of North Pole position tracking measurements. In the 1980s radioastronomy was able to replace earth rotation tracking by referring things against "non-moving background" of
quasar A quasar is an extremely Luminosity, luminous active galactic nucleus (AGN). It is pronounced , and sometimes known as a quasi-stellar object, abbreviated QSO. This emission from a galaxy nucleus is powered by a supermassive black hole with a m ...
s. For these Zenith Telescopes, Prof. Väisälä made also one of the first experiments at doing mirrors of liquid mercury. (Such mirror needs extremely smooth rotational speeds which were achieved in the late 1990s.)


Astronomer

The big Schmidt-Väisälä telescope he built was used at the
University of Turku sv, Åbo universitet , latin_name = Universitas Aboensis , image_name = University of Turku.svg , motto = ''Vapaan kansan lahja vapaalle tieteelle'' , established = 1920 , type ...
for searching
asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...
s and
comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...
s. His research group discovered 7 comets and 807 asteroids. For this rather massive photographic survey work, Prof. Väisälä developed also a protocol of taking two exposures on same plate some 2–3 hours apart and offsetting those images slightly. Any dot-pairs that differed from background were moving, and deserved follow-up photos. This method halved the film consumption compared to method of "blink comparing", where plates get single exposures, and are compared by rapidly showing first and second exposures to human operator. (Blink-comparing was used to find e.g.
Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the S ...
.) Yrjö Väisälä is credited by the
Minor Planet Center The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory. Function ...
with the discovery of 128 asteroids ''(see below)'' during 1935–1944. He used to name them with the names of his personal friends that had birthdays. One of them was the professor Matti Herman Palomaa, after whom an asteroid 1548 Palomaa was named. For this reason the Palomar Mountain Observatory in California has never had an asteroid bearing its name – the rules for naming asteroids state that the names have to differ from each other with more than one letter. Besides minor planets, he has also discovered 3
comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...
s. The parabolic comet C/1944 H1 observed in 1944 and 1945, as well as the two short period comets, 40P/Väisälä, a Jupiter-family comet, and C/1942 EA, a Halley-type and
near-Earth comet A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (Apsis, perihelion) is less than 1.3 astronomical unit ...
. Together with
Liisi Oterma Liisi Oterma (; 6 January 1915 – 4 April 2001) was a Finnish astronomer, the first woman to get a Ph.D. degree in astronomy in Finland. She studied mathematics and astronomy at the University of Turku, and soon became Yrjö Väisälä's as ...
he co-discovered the Jupiter-family comet 139P/Väisälä–Oterma, which was first classified as asteroid and received the provisional designation "1939 TN".


Honors and awards

The University of
Turku Turku ( ; ; sv, Åbo, ) is a city and former capital on the southwest coast of Finland at the mouth of the Aura River, in the region of Finland Proper (''Varsinais-Suomi'') and the former Turku and Pori Province (''Turun ja Porin lääni''; ...
Astronomy department is known as ''VISPA: Väisälä Institute for Space Physics and Astronomy'' in honour of its founder. The lunar crater '' Väisälä'' is named after him, and so are the minor planets 1573 Väisälä and
2804 Yrjö 8 (eight) is the natural number following 7 and preceding 9. In mathematics 8 is: * a composite number, its proper divisors being , , and . It is twice 4 or four times 2. * a power of two, being 2 (two cubed), and is the first number of t ...
.


List of discovered minor planets


Gallery

File:Väisälä brothers childhood home (elliptic cut).jpg, An early 20th century wooden house in
Joensuu Joensuu (; krl, Jovensuu; ) is a city and municipality in North Karelia, Finland, located on the northern shore of Lake Pyhäselkä (northern part of Lake Saimaa) at the mouth of the Pielinen River (''Pielisjoki''). It was founded in 1848. Th ...
at the corner of Sepänkatu and Papinkatu streets. The building was Väisälä brothers' home in 1904–19. File:Väisälä lapsuuskoti muistolaatta.jpg, A commemorative plaque attached to the building in 1976. The text reads: "At this place was Väisälä scientist brothers, Vilho, Yrjö and Kalle's, home in 1904–1919. Joensuu Lyceum ex-students".


Notes


References


External links


Turun Ursa
{{DEFAULTSORT:Vaisala, Yrjo 1891 births 1971 deaths 20th-century astronomers Finnish astronomers Discoverers of asteroids Discoverers of comets * Finnish Esperantists Finnish geodesists Optical engineers People associated with the University of Turku People from Joensuu Astronomy-optics society