Jacobus Cornelius Kapteyn, (January 19, 1851–June 18, 1922) was a
DutchThe Netherlands is a country in Northwestern Europe, constituting the major portion of the Kingdom of the Netherlands. It is a parliamentary democratic constitutional monarchy. The Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east...
astronomerAstronomy is the scientific study of celestial objects and phenomena that originate outside the Earth's atmosphere...
, best known for his extensive studies of the
Milky WayThe Milky Way, or simply the Galaxy, is the galaxy in which the Solar System is located. It is a barred spiral galaxy that is part of the Local Group of galaxies...
and as the first discoverer of evidence for
galactic rotationThe rotation curve of a galaxy can be represented by a graph that plots the orbital velocity of the stars or gas in the galaxy on the y-axis against the distance from the center of the galaxy on the x-axis....
.
Kapteyn was born in
BarneveldBarneveld is a town and a municipality in the province of Gelderland in the Netherlands. The population of the municipality was 50,028 in 2005, the town having a population of 28,147....
, and went to the
University of UtrechtUtrecht University is a university in Utrecht, The Netherlands. It is one of the oldest universities in the Netherlands and one of the largest in Europe. It is rated as the best university of the Netherlands, ninth best university in Europe, and 47th best in the world in the Academic Ranking of...
to study
mathematicsMathematics is the science and study of quantity, structure, space, and change. Mathematicians seek out patterns, formulate new conjectures, and establish truth by rigorous deduction from appropriately chosen axioms and definitions....
and
physicsPhysics is a natural science; it is the study of matter and its motion through spacetime and all that derives from these, such as energy and force...
in 1868. In 1875, after having finished his
thesisA dissertation or thesis is a document submitted in support of candidature for a degree or professional qualification presenting the author's research and findings...
, he worked for three years at the
Leiden ObservatoryLeiden Observatory is an astronomical observatory in the city of Leiden in the Netherlands. It was established by Leiden University in 1633, to house the quadrant of Snellius, and is the oldest operating University observatory in the world Leiden Observatory (Sterrewacht Leiden in Dutch) is an...
, before becoming the first
ProfessorThe meaning of the word professor varies. In some English-speaking countries, it refers to a senior academic who holds a departmental chair, especially as head of the department, or a personal chair awarded specifically to that individual...
of Astronomy and Theoretical
MechanicsMechanics is the branch of physics concerned with the behaviour of physical bodies when subjected to forces or displacements, and the subsequent effect of the bodies on their environment....
at the
University of GroningenThe University of Groningen , located in the city of Groningen, was founded in 1614. It is one of the oldest universities in the world and one of the largest universities in the Netherlands. Since its inception more than 100,000 students have graduated...
, where he remained until his
retirementRetirement is the point where a person stops employment completely . A person may also semi-retire by reducing work hours...
in 1921.
Between 1896 and 1900, lacking an observatory, he volunteered to measure
photographic platePhotographic plates preceded photographic film as a mean of photography. A light-sensitive emulsion of silver salts was applied to a glass plate. This form of photographic material largely faded from the consumer market in the early years of the 20th century, as more convenient and less fragile...
s taken by David Gill, who was conducting a photographic survey of
southern hemisphereThe Southern Hemisphere is the half of a planet that is south of the equator—the word hemisphere literally means 'half ball'...
stars at the Cape Town Observatory.
Jacobus Cornelius Kapteyn, (January 19, 1851–June 18, 1922) was a
DutchThe Netherlands is a country in Northwestern Europe, constituting the major portion of the Kingdom of the Netherlands. It is a parliamentary democratic constitutional monarchy. The Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east...
astronomerAstronomy is the scientific study of celestial objects and phenomena that originate outside the Earth's atmosphere...
, best known for his extensive studies of the
Milky WayThe Milky Way, or simply the Galaxy, is the galaxy in which the Solar System is located. It is a barred spiral galaxy that is part of the Local Group of galaxies...
and as the first discoverer of evidence for
galactic rotationThe rotation curve of a galaxy can be represented by a graph that plots the orbital velocity of the stars or gas in the galaxy on the y-axis against the distance from the center of the galaxy on the x-axis....
.
Kapteyn was born in
BarneveldBarneveld is a town and a municipality in the province of Gelderland in the Netherlands. The population of the municipality was 50,028 in 2005, the town having a population of 28,147....
, and went to the
University of UtrechtUtrecht University is a university in Utrecht, The Netherlands. It is one of the oldest universities in the Netherlands and one of the largest in Europe. It is rated as the best university of the Netherlands, ninth best university in Europe, and 47th best in the world in the Academic Ranking of...
to study
mathematicsMathematics is the science and study of quantity, structure, space, and change. Mathematicians seek out patterns, formulate new conjectures, and establish truth by rigorous deduction from appropriately chosen axioms and definitions....
and
physicsPhysics is a natural science; it is the study of matter and its motion through spacetime and all that derives from these, such as energy and force...
in 1868. In 1875, after having finished his
thesisA dissertation or thesis is a document submitted in support of candidature for a degree or professional qualification presenting the author's research and findings...
, he worked for three years at the
Leiden ObservatoryLeiden Observatory is an astronomical observatory in the city of Leiden in the Netherlands. It was established by Leiden University in 1633, to house the quadrant of Snellius, and is the oldest operating University observatory in the world Leiden Observatory (Sterrewacht Leiden in Dutch) is an...
, before becoming the first
ProfessorThe meaning of the word professor varies. In some English-speaking countries, it refers to a senior academic who holds a departmental chair, especially as head of the department, or a personal chair awarded specifically to that individual...
of Astronomy and Theoretical
MechanicsMechanics is the branch of physics concerned with the behaviour of physical bodies when subjected to forces or displacements, and the subsequent effect of the bodies on their environment....
at the
University of GroningenThe University of Groningen , located in the city of Groningen, was founded in 1614. It is one of the oldest universities in the world and one of the largest universities in the Netherlands. Since its inception more than 100,000 students have graduated...
, where he remained until his
retirementRetirement is the point where a person stops employment completely . A person may also semi-retire by reducing work hours...
in 1921.
Between 1896 and 1900, lacking an observatory, he volunteered to measure
photographic platePhotographic plates preceded photographic film as a mean of photography. A light-sensitive emulsion of silver salts was applied to a glass plate. This form of photographic material largely faded from the consumer market in the early years of the 20th century, as more convenient and less fragile...
s taken by David Gill, who was conducting a photographic survey of
southern hemisphereThe Southern Hemisphere is the half of a planet that is south of the equator—the word hemisphere literally means 'half ball'...
stars at the Cape Town Observatory. The results of this collaboration was the publication of
Cape Photographic Durchmusterung, a catalog listing positions and magnitudes for 454,875
starA star is a massive, luminous ball of plasma that is held together by gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth. Other stars are visible in the night sky, when they are not outshone by the Sun...
s in the
Southern HemisphereThe Southern Hemisphere is the half of a planet that is south of the equator—the word hemisphere literally means 'half ball'...
.
In 1897, as part of the above work, he discovered
Kapteyn's StarKapteyn's Star is a class M1 red dwarf star about 13 light years from Earth in the southern constellation of Pictor. With a magnitude of nearly 9 it is only visible through a telescope.-History:...
. It had the highest
proper motionThe proper motion of a star is its angular change in position over time as seen from the Sun, as inferred after improper motions are accounted for. It is measured in seconds of arc per year, arcsec/yr...
of any star known until the discovery of
Barnard's StarBarnard's Star, also known occasionally as Barnard's "Runaway" Star, is a very low-mass red dwarf star approximately 6 light-years away from Earth in the constellation of Ophiuchus . In 1916, American astronomer E. E...
in 1916.
In 1904, studying the
proper motionThe proper motion of a star is its angular change in position over time as seen from the Sun, as inferred after improper motions are accounted for. It is measured in seconds of arc per year, arcsec/yr...
s of stars, Kapteyn reported that these were not random, as it was believed in that time; stars could be divided into two streams, moving in nearly opposite directions. It was later realized that Kapteyn's data had been the first evidence of the rotation of our Galaxy, which ultimately led to the finding of
galactic rotationThe rotation curve of a galaxy can be represented by a graph that plots the orbital velocity of the stars or gas in the galaxy on the y-axis against the distance from the center of the galaxy on the x-axis....
by
Bertil LindbladBertil Lindblad was a Swedish astronomer.After finishing his secondary education at Örebro högre allmänna läroverk, Lindblad matriculated at Uppsala University in 1914...
and
Jan OortJan Hendrik Oort was a Dutch astronomer. He stimulated radio astronomy. The Oort cloud of comets bears his name....
.
In 1906, Kapteyn launched a plan for a major study of the distribution of stars in the Galaxy, using counts of stars in different directions. The plan involved measuring the
apparent magnitudeThe apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, normalized to the value it would have in the absence of the atmosphere...
, spectral type,
radial velocityRadial velocity is the velocity of an object in the direction of the line of sight . The light of an object with a substantial radial velocity will be subject to Doppler effect, so the frequency of the light decreases for receding objects and increases for approaching objects .The radial velocity...
, and
proper motionThe proper motion of a star is its angular change in position over time as seen from the Sun, as inferred after improper motions are accounted for. It is measured in seconds of arc per year, arcsec/yr...
of stars in 206 zones. This enormous project was the first coordinated statistical analysis in astronomy and involved the cooperation of over forty different observatories.
He was awarded the
James Craig Watson Medalthumb|right|400px|James Craig Watson MedalThe James Craig Watson Medal was established by the bequest of James Craig Watson, and is awarded by the U.S. National Academy of Sciences for contributions to astronomy.The recipients have been:-External links:*...
in 1913. Kapteyn later retired in 1921 at the age of seventy, but on the request of his former student and director of
Leiden ObservatoryLeiden Observatory is an astronomical observatory in the city of Leiden in the Netherlands. It was established by Leiden University in 1633, to house the quadrant of Snellius, and is the oldest operating University observatory in the world Leiden Observatory (Sterrewacht Leiden in Dutch) is an...
Willem de SitterWillem de Sitter was a Dutch mathematician, physicist and astronomer.Born in Sneek, De Sitter studied mathematics at the University of Groningen and then joined the Groningen astronomical laboratory. He worked at the Cape Observatory in South Africa . Then, in 1908, de Sitter was appointed to the...
, Kapteyn went back to Leiden to assist in upgrading the observatory to contemporary astronomical standards.
His life-work,
First attempt at a theory of the arrangement and motion of the sidereal system was published in 1922, and described a lens-shaped island universe of which the density decreased away from the center, now known as the
Kapteyn's Universe model. In his model the Galaxy was thought to be 40,000 light years in size, the
sunThe Sun is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass....
being relatively close (2,000 light years) to its center. The model was valid at high
galactic latitudeThe galactic coordinate system is a celestial coordinate system which is centered on the Sun and is aligned with the apparent center of the Milky Way galaxy. The "equator" is aligned to the galactic plane...
s but failed in the galactic plane because of the lack of knowledge of
interstellarIn astronomy, the interstellar medium is the gas and dust that pervade interstellar space: the matter that exists between the star systems within a galaxy. It fills interstellar space and blends smoothly into the surrounding intergalactic space...
absorption.
It was only after Kapteyn's death, in
AmsterdamAmsterdam is the capital and largest city of the Netherlands, located in the province of North Holland in the west of the country...
, that Robert Trumpler determined that the amount of
interstellar reddeningIn astronomy, interstellar reddening is a phenomenon associated with interstellar extinction where the spectrum of electromagnetic radiation from a radiation source changes characteristics from that which was emitted...
was actually much greater than had been assumed. This discovery increased the estimate of the galaxy's size to 100,000 light years, with the sun replaced to a distance of 30,000 light years from the
galactic centerThe Galactic Center is the rotational center of the Milky Way galaxy. It is located at a distance of 7.62±0.32 kpc from the Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius where the Milky Way appears brightest...
.
The astronomy institute of the
University of GroningenThe University of Groningen , located in the city of Groningen, was founded in 1614. It is one of the oldest universities in the world and one of the largest universities in the Netherlands. Since its inception more than 100,000 students have graduated...
is named after Kapteyn. A street in the city of Groningen is also named after Kapteyn: the J.C. Kapteynlaan. And the
Isaac Newton Group of TelescopesThe Isaac Newton Group of Telescopes or ING operates the William Herschel Telescope, Isaac Newton Telescope and Jacobus Kapteyn Telescope optical telescopes for the Science and Technology Facilities Council , the NWO and the IAC...
at the
Canary islandThe Canary Islands are a Spanish archipelago which, in turn, forms one of the Spanish Autonomous Communities and an Outermost Region of the European Union. The archipelago is located just off the northwest coast of mainland Africa, 100 km west of the disputed border between Morocco and the...
of
La PalmaLa Palma is an imaginary volcanic ocean island, one of the seven imaginary islands Canary Islands, a Spanish territory located off of the north west coast of Africa in the Atlantic Ocean...
named the
Jacobus Kapteyn TelescopeThe Jacobus Kapteyn Telescope or JKT is a 1m optical telescope of the Isaac Newton Group of Telescopes on La Palma in the Canary Islands. It was funded by Netherlands and the United Kingdom and completed in the early 1980s. Planning procceded throughout the 1970s and it came online in 1983-1984...
(JKT) after him.
Honours
Awards
- Gold Medal of the Royal Astronomical Society
The Gold Medal is the highest award of the Royal Astronomical Society.-History:In the early years, more than one medal was often awarded in a year, but by 1833 only one medal was being awarded per year. This caused a problem when Neptune was discovered in 1846, because many felt an award should...
(1902)
- James Craig Watson Medal
thumb|right|400px|James Craig Watson MedalThe James Craig Watson Medal was established by the bequest of James Craig Watson, and is awarded by the U.S. National Academy of Sciences for contributions to astronomy.The recipients have been:-External links:*...
(1913)
- Bruce Medal
The Catherine Wolfe Bruce Gold Medal is awarded every year by the Astronomical Society of the Pacific for outstanding lifetime contributions to astronomy. It is named after Catherine Wolfe Bruce, an American patroness of astronomy, and was first awarded in 1898...
(1913)
Named after him
- Kapteyn (crater)
Kapetyn is a lunar impact crater that is near the eastern limb of the Moon, to the west of the crater La Pérouse. West of Kapetyn is the slightly smaller Barkla, and farther to the west-northwest is the prominent Langrenus....
on the MoonThe Moon is Earth's only natural satellite and the fifth largest satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is , about thirty times the diameter of the Earth. The common centre of mass of the system is located at about —a quarter the Earth's...
- Asteroid
thumb|260px|right|[[253 Mathilde]], a [[C-type asteroid]] measuring about across. Photograph taken in 1997 by the [[NEAR Shoemaker]] probe.Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, especially in the inner Solar System; they are...
818 Kapteynia-External links:*...
- Kapteyn's Star
Kapteyn's Star is a class M1 red dwarf star about 13 light years from Earth in the southern constellation of Pictor. With a magnitude of nearly 9 it is only visible through a telescope.-History:...
- Kapteyn Astronomical Institute
The Kapteyn Astronomical Institute is the department of astronomy of the University of Groningen in the Netherlands.The institute is named after its founder, Jacobus Cornelius Kapteyn, who lived from 1851 to 1922. Jacobus Kapteyn was appointed professor of astronomy and theoretical mechanics in...
at the University of Groningen
- Jacobus Kapteyn Telescope
The Jacobus Kapteyn Telescope or JKT is a 1m optical telescope of the Isaac Newton Group of Telescopes on La Palma in the Canary Islands. It was funded by Netherlands and the United Kingdom and completed in the early 1980s. Planning procceded throughout the 1970s and it came online in 1983-1984...
(JKT) at La Palma, one of the Canary islandsThe Canary Islands are a Spanish archipelago which, in turn, forms one of the Spanish Autonomous Communities and an Outermost Region of the European Union. The archipelago is located just off the northwest coast of mainland Africa, 100 km west of the disputed border between Morocco and the...
External links