Jacobus Kapteyn
Encyclopedia
Barneveld
Barneveld is a town and a municipality in the province of Gelderland in the center of the Netherlands. It is known for its poultry industry and large protestant community. The population of the municipality was 52.629 in June 2010, the town having a population of 29.756.-Transport:Barneveld is...
, Gelderland
Gelderland
Gelderland is the largest province of the Netherlands, located in the central eastern part of the country. The capital city is Arnhem. The two other major cities, Nijmegen and Apeldoorn have more inhabitants. Other major regional centers in Gelderland are Ede, Doetinchem, Zutphen, Tiel, Wijchen,...
– June 18, 1922) was a Dutch
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
astronomer
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
, best known for his extensive studies of the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
and as the first discoverer of evidence for galactic rotation
Galaxy rotation curve
The 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 Barneveld
Barneveld
Barneveld is a town and a municipality in the province of Gelderland in the center of the Netherlands. It is known for its poultry industry and large protestant community. The population of the municipality was 52.629 in June 2010, the town having a population of 29.756.-Transport:Barneveld is...
, and went to the University of Utrecht
Utrecht University
Utrecht University is a university in Utrecht, Netherlands. It is one of the oldest universities in the Netherlands and one of the largest in Europe. Established March 26, 1636, it had an enrollment of 29,082 students in 2008, and employed 8,614 faculty and staff, 570 of which are full professors....
to study mathematics
Mathematics
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...
and physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
in 1868. In 1875, after having finished his thesis
Thesis
A dissertation or thesis is a document submitted in support of candidature for an academic degree or professional qualification presenting the author's research and findings...
, he worked for three years at the Leiden Observatory
Leiden Observatory
Leiden Observatory is an astronomical observatory in the city of Leiden, 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 Professor
Professor
A professor is a scholarly teacher; the precise meaning of the term varies by country. Literally, professor derives from Latin as a "person who professes" being usually an expert in arts or sciences; a teacher of high rank...
of Astronomy and Theoretical Mechanics
Mechanics
Mechanics is the branch of physics concerned with the behavior of physical bodies when subjected to forces or displacements, and the subsequent effects of the bodies on their environment....
at the University of Groningen
University of Groningen
The University of Groningen , located in the city of Groningen, was founded in 1614. It is one of the oldest universities in the Netherlands as well as one of its largest. Since its inception more than 100,000 students have graduated...
, where he remained until his retirement
Retirement
Retirement is the point where a person stops employment completely. A person may also semi-retire by reducing work hours.Many people choose to retire when they are eligible for private or public pension benefits, although some are forced to retire when physical conditions don't allow the person to...
in 1921.
Between 1896 and 1900, lacking an observatory, he volunteered to measure photographic plate
Photographic plate
Photographic plates preceded photographic film as a means 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
David Gill (astronomer)
Sir David Gill FRS was a Scottish astronomer who is known for measuring astronomical distances, for astrophotography, and for geodesy. He spent much of his career in South Africa.- Life and work :...
, who was conducting a photographic survey of southern hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
stars at the Royal Observatory at the Cape of Good Hope. The results of this collaboration was the publication of Cape Photographic Durchmusterung, a catalog listing positions and magnitudes for 454,875 star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s in the Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
.
In 1897, as part of the above work, he discovered Kapteyn's Star
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 visible through binoculars or a telescope.-History:...
. It had the highest proper motion
Proper motion
The proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system. It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree. This contrasts with radial velocity, which is the time rate of change in...
of any star known until the discovery of Barnard's Star
Barnard's star
Barnard's Star, also known occasionally as Barnard's "Runaway" Star, is a very low-mass red dwarf star approximately six light-years away from Earth in the constellation of Ophiuchus . In 1916, the American astronomer E.E...
in 1916.
In 1904, studying the proper motion
Proper motion
The proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system. It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree. This contrasts with radial velocity, which is the time rate of change in...
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 rotation
Galaxy rotation curve
The 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 Lindblad
Bertil Lindblad
Bertil Lindblad Bertil Lindblad Bertil Lindblad (Örebro, 26 November 1895 – Saltsjöbaden (outside Stockholm, 25 June 1965) was a Swedish astronomer.After finishing his secondary education at Örebro högre allmänna läroverk, Lindblad matriculated at Uppsala University in 1914...
and Jan Oort
Jan Oort
Jan Hendrik Oort was a Dutch astronomer. He was a pioneer in the field of 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 magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
, spectral type, radial velocity
Radial velocity
Radial velocity is the velocity of an object in the direction of the line of sight . In astronomy, radial velocity most commonly refers to the spectroscopic radial velocity...
, and proper motion
Proper motion
The proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system. It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree. This contrasts with radial velocity, which is the time rate of change in...
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 Medal
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:*...
in 1913. Kapteyn later retired in 1921 at the age of seventy, but on the request of his former student and director of Leiden Observatory
Leiden Observatory
Leiden Observatory is an astronomical observatory in the city of Leiden, 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 Sitter
Willem de Sitter
Willem de Sitter was a Dutch mathematician, physicist and astronomer.-Life and work: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...
, 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 sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
being relatively close (2,000 light years) to its center. The model was valid at high galactic latitude
Galactic coordinate system
The 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
Galactic plane
The galactic plane is the plane in which the majority of a disk-shaped galaxy's mass lies. The directions perpendicular to the galactic plane point to the galactic poles...
because of the lack of knowledge of interstellar
Interstellar medium
In astronomy, the interstellar medium is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space...
absorption.
It was only after Kapteyn's death, in Amsterdam
Amsterdam
Amsterdam is the largest city and the capital of the Netherlands. The current position of Amsterdam as capital city of the Kingdom of the Netherlands is governed by the constitution of August 24, 1815 and its successors. Amsterdam has a population of 783,364 within city limits, an urban population...
, that Robert Trumpler determined that the amount of interstellar reddening 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 center
Galactic Center
The Galactic Center is the rotational center of the Milky Way galaxy. It is located at a distance of 8.33±0.35 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 Groningen
University of Groningen
The University of Groningen , located in the city of Groningen, was founded in 1614. It is one of the oldest universities in the Netherlands as well as one of its largest. 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 Telescopes
Isaac Newton Group of Telescopes
The 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 island
Canary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...
of La Palma
La Palma
La Palma is the most north-westerly of the Canary Islands. La Palma has an area of 706 km2 making it the fifth largest of the seven main Canary Islands...
named the Jacobus Kapteyn Telescope
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) after him.
Honours
Awards- Gold Medal of the Royal Astronomical SocietyGold Medal 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 jointly be made to John Couch Adams and Urbain Le Verrier...
(1902) - James Craig Watson MedalJames 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:*...
(1913) - Bruce MedalBruce MedalThe 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)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 MoonMoonThe Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more... - AsteroidAsteroidAsteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
818 Kapteynia818 KapteyniaThis asteroid is named for the Dutch astronomer Jacobus Kapteyn.818 Kapteynia is a minor planet orbiting the Sun.-External links:*... - Kapteyn's StarKapteyn'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 visible through binoculars or a telescope.-History:...
- Kapteyn Astronomical InstituteKapteyn Astronomical InstituteThe 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 TelescopeJacobus 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) at La Palma, one of the Canary islandsCanary IslandsThe Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...