# Fame.am profile — machine-readable export
# Canonical URL: https://fame.am/person/jacobus-kapteyn
# Generated: 2026-08-13T03:19:47.330Z

schema: https://schema.org/Person
url: "https://fame.am/person/jacobus-kapteyn"
name: "Jacobus Kapteyn"
slug: "jacobus-kapteyn"
description: "Jacobus Cornelius Kapteyn was a Dutch astronomer. He carried out extensive studies of the Milky Way. He found that the apparent movement of stars was not randomly distributed but had two preferential directions: the two star streams. This discovery was later reinterpreted as evidence for galactic rotation. Kapteyn also suggested that these stellar velocities could be used to find the amount of non-luminous matter in the galaxy, which his student, Jan Oort, measured in 1932, referring to it as \"invisible matter\"."
tagline: "Dutch astronomer, best known for his extensive studies of the Milky Way and as the first discoverer of evidence for galactic rotation (1851-1922)"
image: "https://commons.wikimedia.org/wiki/Special:FilePath/Jacobus_Kapteyn.jpg?width=1200"
gender: "male"
category:
  name: "Scientists"
  slug: "scientists"
profileType:
  name: "Scientist"
  slug: "scientist"
  entityType: "https://www.wikidata.org/entity/Q39631"
birthDate: "1851-01-19"
deathDate: "1922-06-18"
livingStatus: "DECEASED"
scores:
  popularity:           50.87
  momentum:             0
  historical:           20.96015333333333
  currentAttention:     0
  sourceConfidence:     60
  profileCompleteness:  60
  trendDirection:       "FALLING"
ranks:
  global:   null
  country:  null
  category: null
sources:
  - url: "https://pl.wikipedia.org/wiki/Jacobus_Kapteyn"
    title: "Jacobus Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://ar.wikipedia.org/wiki/%D9%8A%D8%A7%D9%83%D9%88%D8%A8%D8%B3_%D9%83%D8%A7%D8%A8%D8%AA%D9%8A%D9%86"
    title: "ياكوبس كابتين"
    type:  "WIKIPEDIA"
  - url: "https://arz.wikipedia.org/wiki/%D9%8A%D8%A7%D9%83%D9%88%D8%A8%D8%B3_%D9%83%D8%A7%D8%A8%D8%AA%D9%8A%D9%86"
    title: "ياكوبس كابتين"
    type:  "WIKIPEDIA"
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    title: "ইয়াকোবুস কাপ্টাইন"
    type:  "WIKIPEDIA"
  - url: "https://ca.wikipedia.org/wiki/Jacobus_Kapteyn"
    title: "Jacobus Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://ckb.wikipedia.org/wiki/%D8%AC%D8%A7%DA%A9%DB%86%D8%A8%D9%88%D8%B3_%DA%A9%D8%A7%D9%BE%D8%AA%D9%86"
    title: "جاکۆبوس کاپتن"
    type:  "WIKIPEDIA"
  - url: "https://cs.wikipedia.org/wiki/Jacobus_Kapteyn"
    title: "Jacobus Kapteyn"
    type:  "WIKIPEDIA"
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    title: "Jacobus Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://de.wikipedia.org/wiki/Jacobus_C._Kapteyn"
    title: "Jacobus C. Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://el.wikipedia.org/wiki/%CE%93%CE%B9%CE%B1%CE%BA%CF%8C%CE%BC%CF%80%CE%BF%CF%85%CF%82_%CE%9A%CE%B1%CF%80%CF%84%CE%AD%CF%85%CE%BD"
    title: "Γιακόμπους Καπτέυν"
    type:  "WIKIPEDIA"
  - url: "https://en.wikipedia.org/wiki/Jacobus_Kapteyn"
    title: "Jacobus Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://eo.wikipedia.org/wiki/Jacobus_Kapteyn"
    title: "Jacobus Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://es.wikipedia.org/wiki/Jacobus_Kapteyn"
    title: "Jacobus Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://eu.wikipedia.org/wiki/Jacobus_Kapteyn"
    title: "Jacobus Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://fi.wikipedia.org/wiki/Jacobus_Kapteyn"
    title: "Jacobus Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://fr.wikipedia.org/wiki/Jacobus_Kapteyn"
    title: "Jacobus Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://he.wikipedia.org/wiki/%D7%99%D7%A7%D7%95%D7%91%D7%95%D7%A1_%D7%A7%D7%A4%D7%98%D7%99%D7%99%D7%9F"
    title: "יקובוס קפטיין"
    type:  "WIKIPEDIA"
  - url: "https://id.wikipedia.org/wiki/Jacobus_Kapteyn"
    title: "Jacobus Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://it.wikipedia.org/wiki/Jacobus_C._Kapteyn"
    title: "Jacobus C. Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://ja.wikipedia.org/wiki/%E3%83%A4%E3%82%B3%E3%83%96%E3%82%B9%E3%83%BB%E3%82%AB%E3%83%97%E3%82%BF%E3%82%A4%E3%83%B3"
    title: "ヤコブス・カプタイン"
    type:  "WIKIPEDIA"
  - url: "https://ko.wikipedia.org/wiki/%EC%95%BC%EC%BD%94%EB%B7%94%EC%8A%A4_%EC%BA%85%ED%85%8C%EC%9D%B8"
    title: "야코뷔스 캅테인"
    type:  "WIKIPEDIA"
  - url: "https://lb.wikipedia.org/wiki/Jacobus_Kapteyn"
    title: "Jacobus Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://nl.wikipedia.org/wiki/Jacobus_Cornelius_Kapteyn"
    title: "Jacobus Cornelius Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://nn.wikipedia.org/wiki/Jacobus_Kapteyn"
    title: "Jacobus Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://no.wikipedia.org/wiki/Jacobus_Kapteyn"
    title: "Jacobus Kapteyn"
    type:  "WIKIPEDIA"
  - url: "https://www.wikidata.org/wiki/Q156892"
    title: "Wikidata"
    type:  "WIKIDATA"

# bio (long form, separated for readability)
bio: |
  Imported from discovery source: wikidata-dump