Jan Oort

**Jan Hendrik Oort**  ([yan ort]; 28 April 1900 – 5 November 1992) adalah seorang ahli astronomi dari Belanda. Beliau dikenali atas sumbangan besar beliau kepada pemahaman umum mengenai galaksi Bima Sakti serta  merupakan perintis dalam bidang astronomi radio. Belasungkawa *[[The New York Times]]* menyebutnya "salah satu penjelajah terkemuka alam semesta"; laman web Agensi Angkasa Eropah menggambarkannya sebagai, "salah satu ahli astronomi terbesar abad ke-20", dan menyatakan bahawa beliau "merevolusi astronomi melalui penemuan pecah tanah beliau." Pada tahun 1955, nama Oort muncul dalam senarai 100 orang yang paling terkenal oleh majalah *[[Life (majalah)|Life]]*. Beliau telah digambarkan sebagai "meletakkan Belanda di barisan depan astronomi selepas perang."

Oort memutuskan bahawa Bima Sakti berputar dan membalikkan idea bahawa Matahari berada di tengahnya. Beliau juga mengisytiharkan kewujudan jirim gelap yang tidak dapat dilihat dalam misteri pada tahun 1932, yang dipercayai membentuk kira-kira 84.5% daripada jumlah perkara di Alam Semesta dan yang tarikan graviti menyebabkan "penggabungan bintang-bintang menjadi galaksi dan galaksi menjadi penyambung tali galaksi".Beliau menemui halo galaksi, sekelompok bintang yang mengarahkan Bima Sakti tetapi di luar cakera utama. Selain itu Oort bertanggungjawab untuk beberapa pandangan penting tentang komet, termasuk kesedaran bahawa orbit mereka "tersirat di sana adalah lebih banyak sistem surya daripada rantau yang diduduki oleh planet-planet."

Awan Oort, pemalar Oort, dan Asteroid, 1691 Oort, semuanya dinamakan sempena beliau.

## Kehidupan peribadi
Pada tahun 1927, Oort berkahwin dengan Johanna Maria (Mieke) Graadt van Roggen (1906-1993). Mereka telah bertemu di sebuah universiti di Utrecht, di mana abang Oort sedang mempelajari biologi pada masa itu. Oort dan isterinya mempunyai dua anak lelaki, Coenraad (Coen) dan Abraham, dan seorang anak perempuan, Marijke.

Menurut laman web Universiti Leiden, Oort sangat berminat dan berpengetahuan tentang seni. "Apabila mengunjungi negara lain dia akan selalu berusaha untuk meluangkan masa untuk melawat muzium dan pameran tempatan ... dan pada tahun lima puluhan berkhidmat selama beberapa tahun sebagai pengerusi jawatankuasa seni bergambar Pusat Seni Akademi Leiden, yang ada di antara lain-lain perkara yang menganjurkan pameran."

"Rakan-rakannya teringat kepadanya sebagai seorang lelaki yang tinggi, kurus dan sopan dengan cara yang baik," lapor belasungkawa New York Times.

## Penulisan
* Oort, J.H., “The Development of our Insight into the Structure of the Galaxy between 1920 and 1940,” Ann. NY Acad. Sci. 198, 255-66 (1972).
* Oort, J.H., “Some Peculiarities in the Motion of Stars of High Velocity,” Bull. Astron. Inst. Neth. 1, 133-37 (1922).
* Oort, J.H., “The Stars of High Velocity,” (Thesis, Groningen University) Publ. Kapteyn Astr. Lab, Groningen, 40, 1-75 (1926).
* Oort, Jan H., “Asymmetry in the Distribution of Stellar Velocities,” Observatory 49, 302-04 (1926).
* Oort, J.H., “Observational Evidence Confirming Lindblad’s Hypothesis of a Rotation of the Galactic System,” Bull. Astron. Inst. Neth. 3, 275-82 (1927).
* Oort, J.H., “Investigations Concerning the Rotational Motion of the Galactic System together with New Determinations of Secular Parallaxes, Precession and Motion of the Equinox (Errata: 4, 94),” Bull. Astron. Inst. Neth. 4, 79-89 (1927).
* Oort, J.H., “Dynamics of the Galactic System in the Vicinity of the Sun,” Bull. Astron. Inst. Neth. 4, 269-84 (1928).
* Oort, J.H., “Some Problems Concerning the Distribution of Luminosities and Peculiar Velocities of Extragalactic Nebulae,” Bull. Astron. Inst. Neth. 6, 155-59 (1931).
* Oort, J.H., “The Force Exerted by the Stellar System in the Direction Perpendicular to the Galactic Plane and Some Related Problems,” Bull. Astron. Inst. Neth. 6, 249-87 (1932).
* Oort, J.H., “A Redetermination of the Constant of Precession, the Motion of the Equinox and the Rotation of the Galaxy from Faint Stars Observed at the McCormick Observatory,” 4, 94),” Bull. Astron. Inst. Neth. 8, 149-55 (1937).
* Oort, J.H., “Absorption and Density Distribution in the Galactic System,” Bull. Astron. Inst. Neth. 8, 233-64 (1938).
* Oort, J.H., “Stellar Motions,” MNRAS 99, 369-84 (1939).
* Oort, J.H. “Some Problems Concerning the Structure and Dynamics of the Galactic System and the Elliptical Nebulae NGC 3115 and 4494,” Ap.J. 91, 273-306 (1940).
* Mayall, N.U. & J.H. Oort, “Further Data Bearing on the Identification of the Crab Nebula with the Supernova of 1054 A.D. Part II: The Astronomical Aspects,” PASP 54, 95-104 (1942).
* Oort, J.H., “Some Phenomena Connected with Interstellar Matter (1946 George Darwin Lecture),” MNRAS 106, 159-79 (1946) [George Darwin]. Lecture.
* Oort, J.H., “The Structure of the Cloud of Comets Surrounding the Solar System and a Hypothesis Concerning its Origin,” Bull. Astron. Inst. Neth. 11, 91-110 (1950).
* Oort, J.H., “Origin and Development of Comets (1951 Halley Lecture),” Observatory 71, 129-44 (1951) [Halley Lecture].
* Oort, J.H. & M. Schmidt, “Differences between New and Old Comets,” Bull. Astron. Inst. Neth. 11, 259-70 (1951).
* Westerhout, G. & J.H. Oort, “A Comparison of the Intensity Distribution of Radio-frequency Radiation with a Model of the Galactic System,” Bull. Astron. Inst. Neth. 11, 323-33 (1951).
* Morgan, H.R. & J.H. Oort, “A New Determination of the Precession and the Constants of Galactic Rotation,” Bull. Astron. Inst. Neth. 11, 379-84 (1951).
* Oort, J.H. “Problems of Galactic Structure,” Ap.J. 116, 233-250 (1952) [Henry Norris Russell Lecture, 1951].
* Oort, J. H., “Outline of a Theory on the Origin and Acceleration of Interstellar Clouds and O Associations,” Bull. Astr. Inst. Neth. 12, 177-86 (1954).
* Oort, J. H., & H.C. van de Hulst, “Gas and Smoke in Interstellar Space,” Bull. Astr. Inst. Neth. 10, 187-204 (1946).
* van de Hulst, H.C., C.A. Muller, & J.H. Oort, “The spiral structure of the outer part of the Galactic System derived from the hydrogen mission at 21 cm wavelength,” Bull. Astr. Inst. Neth. 12, 117-49 (1954).
* van Houten, C.J., J.H. Oort, & W.A. Hiltner, “Photoelectric Measurements of Extragalactic Nebulae,” Ap.J. 120, 439-53 (1954).
* Oort, Jan H. & Lyman Spitzer, Jr., “Acceleration of Interstellar Clouds by O-Type Stars,” Ap.J. 121, 6-23 (1955).
* Oort, J.H., “Measures of the 21-cm Line Emitted by Interstellar Hydrogen,” Vistas in Astronomy. 1, 607-16 (1955).
* Oort, J. H. & Th. Walraven, “Polarization and Composition of the Crab Nebula,” Bull. Astr. Inst. Neth. 12, 285-308 (1956).
* Oort, J.H., “Die Spiralstruktur des Milchstraßensystems,” Mitt. Astr. Ges. 7, 83-87 (1956).
* Oort, J.H., F.J. Kerr, & G. Westerhout, “The Galactic System as a Spiral Nebula,” MNRAS 118, 379-89 (1958).
* Oort, J.H., “Summary - From the Astronomical Point of View,” in Ricerche Astronomiche, Vol. 5, Specola Vaticana, Proceedings of a Conference at Vatican Observatory, Castel Gandolfo, May 20–28, 1957, ed. by D.J.K. O'Connell (North Holland, Amsterdam & Interscience, NY, 1958), 507-29.
* Oort, Jan H., “Radio-frequency Studies of Galactic Structure,” Handbuch der Physik vol. 53, 100-28 (1959).
* Oort, J.H., “A Summary and Assessment of Current 21-cm Results Concerning Spiral and Disk Structures in Our Galaxy,” in Paris Symposium on Radio Astronomy, IAU Symposium no. 9 and URSI Symposium no. 1, held 30 July - 6 August 1958, ed. by R.N. Bracewell (Stanford University Press, Stanford, CA, 1959), 409-15.
* Rougoor, G. W. & J.H. Oort, “Neutral Hydrogen in the Central Part of the Galactic System,” in Paris Symposium on Radio Astronomy, IAU Symposium no. 9 and URSI Symposium no. 1, held 30 July - 6 August 1958, ed. by R.N. Bracewell (Stanford University Press, Stanford, CA, 1959), pp.&nbsp;416–22.
* Oort, J. H. & G. van Herk, “Structure and dynamics of Messier 3,” Bull. Astr. Inst. Neth. 14, 299-321 (1960).
* Oort, J. H., “Note on the Determination of Kz and on the Mass Density Near the Sun,” Bull. Astr. Inst. Neth. 15, 45-53 (1960).
* Rougoor, G.W. & J.H. Oort, “Distribution and Motion of Interstellar Hydrogen in the Galactic System with Particular Reference to the Region within 3 Kiloparsecs of the Center,” Proc. Natl. Acad. Sci. 46, 1-13 (1960).
* Oort, J.H. & G.W. Rougoor, “The Position of the Galactic Centre,” MNRAS 121, 171-73 (1960).
* Oort, J.H., “The Galaxy,” IAU Symposium 20, 1-9 (1964).
* Oort, J.H. “Stellar Dynamics,” in A. Blaauw & M. Schmidt, eds., Galactic Structure (Univ. of Chicago Press, Chicago, IL, 1965), pp.&nbsp;455–512.
* Oort, J. H., “Possible Interpretations of the High-Velocity Clouds,” Bull. Astr. Inst. Neth. 18, 421-38 (1966).
* Oort, J. H., “Infall of Gas from Intergalactic Space,” Nature 224, 1158-63 (1969).
* Oort, J.H., “The Formation of Galaxies and the Origin of the High-Velocity Hydrogen.,” Astronomy & Astrophysics 7, 381-404 (1970).
* Oort, J.H., “The Density of the Universe,” Astronomy & Astrophysics 7, 405 (1970).
* Oort, J.H., “Galaxies and the Universe,” Science 170, 1363-70 (1970).
* van der Kruit, P.C., J.H. Oort, & D.S. Mathewson, “The Radio Emission of NGC 4258 and the Possible Origin of Spiral Structure,” Astronomy & Astrophysics 21, 169-84 (1972).
* Oort, Jan H. “On the Problem of the Origin of Spiral Structure,” Mitteilungen der AG 32, 15-31 (1973) [Karl Schwarzschild Lecture, 1972].
* Oort, J.H. & L. Plaut, “The Distance to the Galactic Centre Derived from RR Lyrae Variables, the Distribution of these Variables in the Galaxy's Inner Region and Halo, and A Rediscussion of the Galactic Rotation Constants,” Astronomy & Astrophysics 41, 71-86 (1975).
* Pels, G., J.H. Oort, & H.A. Pels-Kluyver, “New Members of the Hyades Cluster and a Discussion of its Structure,” Astronomy & Astrophysics 43, 423-41 (1975).
* Rubin, Vera C., W. Kent Ford, Jr., Charles J. Peterson, & J.H. Oort,“New Observations of the NGC 1275 Phenomenon,” Ap.J. 211, 693-96 (1977).
* Oort, J.H., “The Galactic Center,” Annual Reviews of Astronomy & Astrophysics 15, 295-362 (1977).
* Oort, J.H., “Superclusters and Lyman α Absorption Lines in Quasars,” Astronomy & Astrophysics 94, 359-64 (1981).
* Oort, J.H., H. Arp, & H. de Ruiter, “Evidence for the Location of Quasars in Superclusters,” Astronomy & Astrophysics 95, 7-13 (1981).
* Oort, J.H., “Superclusters,” Annual Reviews of Astronomy & Astrophysics 21, 373-428 (1983).
* Oort, J.H., “Structure of the Universe,” in Early Evolution of the Universe and its Present Structure; Proceedings of the Symposium, Kolymbari, Greece, August 30-September 2, 1982, (Reidel, Dordrecht & Boston, 1983), 1-6.
* Oort, Jan H. “The Origin and Dissolution of Comets (1986 Halley Lecture),” Observatory 106, 186-93 (1986).
* Oort, Jan H. “Origin of Structure in the Universe,” Publ. Astron. Soc. Japan 40, 1-14 (1988).
* Oort, J.H., “Questions Concerning the Large-scale Structure of the Universe,” in Problems in Theoretical Physics and Astrophysics: Collection of Articles in Celebration of the 70th Birthday of V. L. Ginzburg (Izdatel’stvo Nauka, Moscow, 1989), pp.&nbsp;325–337.
* Oort, J.H., “Orbital Distribution of Comets,” in W.F. Huebner, ed., Physics and Chemistry of Comets (Springer-Verlag, 1990), pp.&nbsp;235–44 (1990).
* Oort, J.H., “Non-Light-Emitting Matter in the Stellar System,” public lecture of 1926, reprinted in The Legacy of J. C. Kapteyn, ed. by P. C. van der Kruit and K. van Berkel (Kluwer, Dordrecht, 2000) [abstract].
* Strom, R. G., G.K. Miley, & J. Oort, “Giant Radio Galaxies,” Sci. Amer. 233, 26 (1975).
* Oort, J.H., “A New Southern Hemisphere Observatory,” Sky & Telescope 15, 163 (1956).
* Oort, J.H., “Exploring the Nuclei of Galaxies,” Mercury 21, 57 (1992).

## Beberapa penemuan Oort
* Pada tahun 1924, Oort menemui halo galaksi, sekelompok bintang yang mengarahkan Bima Sakti tetapi di luar cakera utama.
* Pada tahun 1927, beliau mengira bahawa pusat Bima Sakti adalah 5,900 parsek (19,200 tahun cahaya) dari Bumi ke arah konstelasi Sagittarius.
* Pada tahun 1932, dengan mengukur usul bintang-bintang dalam Bima Sakti, dia adalah orang pertama yang menemui bukti untuk perkara gelap, apabila dia mendapati jisim pesawat galaksi mestilah lebih daripada massa bahan yang dapat dilihat.
* Beliau menunjukkan bahawa Bima Sakti mempunyai massa 100 bilion kali dari Matahari.
* Pada tahun 1950, beliau mencadangkan bahawa komet datang dari kawasan umum Sistem Suria (kini dikenali sebagai awan Oort).
* Beliau mendapati bahawa cahaya dari Nebula Ketam terpolarisasi, dan dihasilkan oleh pelepasan sinkrotron.

## Penghargaan

**Anugerah**
* Bruce Medal of the Astronomical Society of the Pacific in 1942
* Gold Medal of the Royal Astronomical Society in 1946
* Janssen Medal from the French Academy of Sciences in 1946
* Prix Jules Janssen, the highest award of the Société astronomique de France, the French astronomical society (1947)
* Henry Norris Russell Lectureship of the American Astronomical Society in 1951
* Gouden Ganzeveer in 1960
* Vetlesen Prize in 1966
* National Radio Astronomy Observatory, Jansky Prize, 1967
* Karl Schwarzschild Medal of the Astronomische Gesellschaft in 1972
* Association pour le Développement International de l’Observatoire de Nice, ADION medal, 1978
* Balzan Prize for Astrophysics in 1984
* Inamori Foundation, Kyoto Prize, 1987

**Dinamakan sempena beliau**
*Asteroid 1691 Oort
*Awan Oort
*Pemalar Oort struktur galaksi
*Bangunan Oort , bangunan terkini Leiden Observatory

**Keahlian**
* Ahli Akademi Seni dan Sains Kerajaan Belanda (1937–1943, 1945–)

Setelah kematiannya, ahli astrofizik Subrahmanyan Chandrasekhar memenangi Hadiah Nobel, "Oak besar Astronomi telah ditebang, dan kami hilang tanpa bayangannya."

## Rujukan

### Catatan

### Bahan biografi
* Blaauw, Adriaan, Biographical Encyclopedia of Astronomers (Springer, NY, 2007), pp.&nbsp;853–55.
* Chapman, David M.F., “Reflections: Jan Hendrik Oort—- Swirling Galaxies and Clouds of Comets,” JRASC 94, 53-54 (2000).
* ESA Space Science, “Comet Pioneer: Jan Hendrik Oort,” 27 February 2004.
* Oort, J.H., “Some Notes on My Life as an Astronomer,” Annual Reviews of Astronomy & Astrophysics 19, 1 (1981).
* Katgert-Merkelijn, J., University of Leiden, Jan Oort, Astronomer
* van de Hulst, H.C., Biographical Memoirs of the Royal Society of London 40, 320-26 (1994).
* van Woerden, Hugo, Willem N. Brouw, and Henk C. van de Hulst, eds., Oort and the Universe: A Sketch of Oort’s Research and Person (D. Reidel, Dordrecht, 1980).

### Belasungkawa
* Blaauw, Adriaan, Zenit jaarg, 196-210 (1993).
* Blaauw, Adriaan & Maarten Schmidt, PASP 105, 681 (1993).
* Blaauw, Adriaan, “Oort im Memoriam,” in Leo Blitz & Peter Teuben, eds., 169th IAU Symposium: Unsolved Problems of the
* Milky Way, (Kluwer Acad. Publishers, 1996), pp. xv-xvi.
* Pecker, J.-C., ”La Vie et l’Oeuvre de Jan Hendrik Oort,” Comptes Rendus de l’Acadèmie des Sciences: La Vie des Science 10, 5, 535-540 (1993).
* van de Hulst, H.C., QJRAS 35, 237-42 (1994).
* van den Bergh, Sidney, “An Astronomical Life: J.H. Oort (1900-1992),” JRASC 87, 73-76 (1993).
* Woltjer, L., J. Astrophys. Astron. 14, 3-5 (1993).
* Woltjer, Lodewijk, Physics Today 46, 11, 104-05 (1993).

### Sastera
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## Pameran dalam talian
* Jan Oort, astronomer (Leiden University Library, April–May 2000) 

## Pautan luar

* Jan Oort di Projek Genealogi Matematik