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Topic: Jan Hendrik Oort

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	Practical Info (Oort Symposium) (Site not responding. Last check: 2007-10-22)
		Jan Hendrik Oort is undoubtedly one of the greatest astronomers of the twentieth century.
		Jan Hendrik Oort was born in the Dutch (Frisian) town of Franeker on April 28, 1900.
		Oort derived the laws for the dependence of the rotation speed on the distance from the center, introducing two constants, A and B, that are generally known as the Oort constants.
	www.strw.leidenuniv.nl /~oortsymp/jhoort.html (999 words)

	Jan Oort -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-22)
		Jan Hendrik Oort (April 28, 1900 – November 5, 1992) was an internationally famous (The West Germanic language of the Netherlands) Dutch astronomer.
		Oort was born in (additional info and facts about Franeker) Franeker in (One of the northernmost provinces of the Netherlands) Friesland and studied in (additional info and facts about Groningen) Groningen with (additional info and facts about Jacobus Cornelius Kapteyn) Jacobus Cornelius Kapteyn.
		Oort calculated that the centre of the (The galaxy containing the solar system; consists of millions of stars that can be seen as a diffuse band of light stretching across the night sky) Milky Way was 30.000 light years from the Earth in the direction of the constellation Sagitarius.
	www.absoluteastronomy.com /encyclopedia/j/ja/jan_oort.htm (533 words)

	AllRefer.com - Jan Hendrik Oort (Astronomy, Biography) - Encyclopedia
		Jan Hendrik Oort[Ort] Pronunciation Key, 1900–1992, Dutch astronomer.
		In the 1950s he and his colleagues used radio astronomical means to map the spiral-arm structure of the galaxy.
		Oort proposed (1950) that comets originate in a cloud of material (the Oort cloud) orbiting the sun at great distance and that they are occasionally deflected into the inner solar system by gravitational perturbation from the passing of nearby stars.
	reference.allrefer.com /encyclopedia/O/Oort-Jan.html (201 words)

	ORRERY: The Oort Cloud
		In 1950, Dutch astronomer Jan Hendrik Oort [1900-92] made a study of comets with the largest orbits.
		Oort discovered that not only were the orbits concentrated towards the very large, they actually peaked out, most falling in from around 50,000 AU.
		Piecing all the mathematical evidence together, Oort concluded that the solar system is surrounded by a vast sphere of icy rocks (comet nuclei) at a distance of 50,000 AU - over 1200× the distance of Pluto from the Sun - that occasionally fall in to visit us.
	www.harmsy.freeuk.com /oort.html (305 words)

	Oort, Jan Hendrik (1900-1992)
		More or less as a sideline, Oort studied comets as well and provided evidence for his theory, now widely accepted, that the Sun is surrounded by a distant cloud of ice-rock objects that has become known as the Oort Cloud.
		Oort studied stellar dynamics under Jacobus Kapteyn at Groningen and worked at the University of Leiden from 1924 to 1992.
		During World War II Oort started his compatriot Hendrik van der Hulst on the successful search for the 21-cm neutral hydrogen line and after the war led the Dutch group that used the 21-cm line to map the layout of the Galaxy, including the large-scale spiral structure, the galactic center, and gas cloud motions.
	www.daviddarling.info /encyclopedia/O/Oort.html (288 words)

	Jan Hendrik Oort History Summary (Site not responding. Last check: 2007-10-22)
		Oort was born in the Netherlands in 1900.
		Oort's discovery was also one of the first demonstrations that gravity didn't act only in our solar system or in nearby binary solar systems, but that the force was felt throughout the entire galaxy.
		Oort was one of the first astronomers to recognize the effect of the interstellar medium on the structure of galaxies.
	www.bookrags.com /history/sciencehistory/jan-hendrik-oort-scit-0712345 (695 words)

	Lamont-Doherty Earth Observatory - Biography of Vetlesen Prize Winner - Jan Hendrik Oort
		Jan Hendrik Oort, without a doubt one of the greatest astronomers of the twentieth century, was born in the Dutch town of Franeker on April 28, 1900.
		Oort is probably best known for showing that the motions of stars in the solar neighborhood reveal the effects of differential rotation.
		Jan Hendrik Oort died on November 5, 1992, leaving behind an impressive legacy in nearly every field of stellar astronomy and astrophysics.
	www.ldeo.columbia.edu /vetlesen/recipients/1966/oort_bio.html (458 words)

	EZGeography - Jan Oort (Site not responding. Last check: 2007-10-22)
		In 1935 he became professor at Leiden University at the faculty where Ejnar Hertzsprung was the director.
		After the Second World War he was a pioneer in the new field of radio astronomy, using an old radar antenna from the Germans.
		It consisted of twelve smaller telescopes working together as an interferometer to perform aperture synthesis observations, a technique which had been previously suggested by Oort, but which was first tested experimentally in Cambridge by Martin Ryle and in Sydney by Joseph Pawsey.
	www.ezgeography.com /encyclopedia/Jan_Oort (252 words)

	Planetary Society: Oort Cloud
		By using computer simulations of conditions in the Solar System 4.5 billion years ago, the researchers concluded that many of the objects that could have ended up in the Oort cloud were diverted from their course or ground to dust before they ever had a chance to reach their cloudy destination.
		In 1950 the Dutch astronomer Jan Hendrik Oort noted that the orbits of most observed comets are shaped like extremely elongated ellipses.
		Oort himself estimated that his cloud was composed of as many as 12 billion comets, and his estimate remains valid today.
	www.planetary.org /html/news/articlearchive/headlines/2001/Oort1.htm (957 words)

	Jan Hendrik Oort -- Britannica Concise Encyclopedia - The online encyclopedia you can trust!
		Oort was able to confirm this theory in 1927 through his own direct observations of star velocities in the galaxy, and he modified the theory substantially into the form used thereafter.
		Oort's subsequent work, as well as that of the school of astronomy he developed in The Netherlands, was directed toward strengthening and testing the Lindblad-Oort theory.
		In 1950 Oort proposed that comets originate from a vast cloud of small bodies that orbit the Sun at a distance of about one light-year, and the approach of other stars toward this cloud alters some comets' orbits so that they pass close to the Sun.
	www.britannica.com /ebc/article-9057161 (834 words)

	The Bruce Medalists: Jan Oort
		Jan Oort, who worked at the University of Leiden from 1924 to 1992, began studying stellar dynamics under Jacobus C. Kapteyn at Groningen.
		Oort found evidence for differential rotation and founded the mathematical theory of galactic structure.
		Oort was a leader in European astronomy and played a major role in the rise of the European Southern Observatory and other international organizations.
	www.phys-astro.sonoma.edu /brucemedalists/oort/Oort.html (407 words)

	ESA - Science - People - Comet pioneer: Jan Hendrik Oort (Site not responding. Last check: 2007-10-22)
		By the time of his death, at the age of 92, Professor Oort was recognised as one of the greatest astronomers of the 20th century.
		Jan Hendrik Oort was a physician's son, born at Franeker, Friesland, and educated at Leiden Gymnasium and Groningen University, before going to the USA to study at Yale University.
		Oort received some of the highest awards in astronomy, including the 1966 Vetliesen Prize from Columbia University.
	www.esa.int /esaSC/SEMBPC2PGQD_people_2.html (618 words)

	Oort Cloud (Site not responding. Last check: 2007-10-22)
		Thus, the nuclei of comets are icy balls of frozen water, methane, and ammonia, mixed with small pieces of rock and dust, rather than the largely volatile-free stones and irons that typify asteroids.
		In the original version of the theory, the Oort cloud extended tens of thousands of times farther from the Sun than the Earth, a significant fraction of the way to the nearest stars.
		At such locations, the comets would not be much perturbed by typical passing stars nor by the gravity of the planets of the solar system, and the comets could reside in the inner cloud or belt for long periods of time without detection.
	abyss.uoregon.edu /~js/glossary/oort_cloud.html (420 words)

	Jan Hendrik Oort -- Encyclopædia Britannica
		After studies at the University of Groningen, Oort was appointed astronomer to the Leiden Observatory in 1924 and became director in 1945, a position he held until 1970.
		Named for the Dutch astronomer Jan Oort, who demonstrated its existence, the Oort cloud comprises objects that are less than 100 km (60 miles) in diameter and that number...
		A forerunner of the Reformation, Jan Hus of Bohemia was burned at the stake as a heretic rather than recant his religious views and his criticisms of the clergy.
	www.britannica.com /eb/article-9057161 (591 words)

	Oort Cloud & Sol b?
		Oddly enough, Oort Cloud objects were probably formed in a region of the protoplanetary disk that was located closer to the Sun than the Edgeworth-Kuiper Belt objects that persist in the orbital plane of the planets (ecliptic) to this day.
		In addition, tidal forces affecting the Oort Cloud come from the differential gravitational forces exerted by stars in the Milky Way's galactic disk and by the galactic core on the Sun and comets as a result of their relative location in the Solar System.
		The Oort Cloud is the source of long-period comets and possibly higher-inclination intermediate comets, such as Halley and Swift-Tuttle, that were pulled into shorter period orbits by the planets (see schematic diagram of nomenclature and relationships among asteroids, Edgeworth-Kuiper bodies, and comets and their different subgroups by William K. Hartmann).
	www.solstation.com /stars/oort.htm (1999 words)

	ESA - Science - Home - Comet pioneer: Jan Hendrik Oort
		In the days before radio telescopes, Oort was one of the few scientists to realise the potential significance of using radio waves to search the heavens.
		It is said that Oort was one of the few people to have seen Comet Halley on two separate apparitions.
		On his return to The Netherlands in 1924, where he stayed for the rest of his career, he began the pioneering research that was to rewrite the text books.
	www.esa.int /esaSC/SEMBPC2PGQD_index_0.html (645 words)

	The Bruce Medalists: Jan H. Oort
		In 1927 Oort confirmed Bertil Lindblad’s hypothesis of galactic rotation by analyzing motions of distant stars.
		Chapman, David M.F., “Reflections: Jan Hendrik Oort—- Swirling Galaxies and Clouds of Comets,”; JRASC 94, 53-54 (2000).
		University of Leiden, From Comets To The Universe: J. Oort Centenary Symposium
	www.phys-astro.sonoma.edu /brucemedalists/oort (407 words)

	Jan Hendrik Oort (Site not responding. Last check: 2007-10-22)
		Oort was a Dutch astronomer, who made major contributions to the knowledge of the structure and rotation of our Galaxy.
		The result of this work was a theory, now widely accepted, that the Sun is surrounded by a distant cloud of cometary material, now called the "Oort Cloud", bits of which are occasionally hurled into the Solar System as comets.
		Oort was a leader in European astronomy and played a major role in the rise of many international organizations.
	www.elwood.k12.nf.ca /sciencepages/bingleh/webpage/jan.htm (104 words)

	Jan Hendrik Oort Biography / Biography of Jan Hendrik Oort Main Biography
		The Dutch astronomer Jan Hendrik Oort (1900-1992) overturned the idea that our sun is at the center of the Milky Way galaxy.
		Jan Oort was born on April 28, 1900, in the farming village of Franeker in Holland.
		Oort became a professor of astronomy (1935) and director of the observatory (1945) at the University of Leiden.
	www.bookrags.com /biography-jan-hendrik-oort (245 words)

	ninemsn Encarta - Search Results - Oort Jan Hendrik (Site not responding. Last check: 2007-10-22)
		Oort, Jan Hendrik (1900-1992), Dutch astronomer, noted for his determination that the Earth's galaxy, the Milky Way, rotates, and for his...
		Comets were once believed to come from interstellar space.
		Hofmeyr, Jan Hendrik (1845-1909), an Afrikaner born in Cape Town, South Africa, and known as “Onze Jan”, his great achievement was to have the Dutch...
	au.encarta.msn.com /Oort_Jan_Hendrik.html (94 words)

	iqexpand.com (Site not responding. Last check: 2007-10-22)
		Look for Jan hendrik oort in the Commons, our repository for free images, music, sound, and video.
		Jan Hendrik Oort Dutch astronomer who calculated the distance to the middle of the galaxy Jan Hendrik Oort (1900-1992) is a Dutch astronomer.
		Jan Hendrik Oort, who made Dutch radio astronomy happen Next: The earliest years of Up: Historical Notes: Four Decades Previous: Historical Notes: Four Decades Jan Hendrik Oort, who made Dutch radio...
	jan_hendrik_oort.iqexpand.com (374 words)

	What's in the News: Activities: Where on Earth
		However, most people felt that Oort’s talents were being wasted at Yale and in 1926, he returned to the Netherlands to become a Research Assistant at the Leiden Observatory.
		Oort proposed that this cloud contained the nuclei of comets and that every once in awhile, a nucleus would break free, forming the comets that passed through our solar system.
		Oort retired from his position as Director of the Leiden Observatory in the 1970s.
	www.witn.psu.edu /activities/newsmaker.phtml?show_id=64 (544 words)

	The Oort Cloud (Site not responding. Last check: 2007-10-22)
		The Oort cloud is a body of comets orbiting the Sun at great distances away.
		The Oort cloud was first hypothesised be a Dutch Astronomer called Jan Hendrik Oort.
		The Oort cloud might even contain 10 trillion comets, and their mass could be up to 10 Earth masses.
	evula.org /solarsystem/oort.html (177 words)

	Zoom Astronomy Glossary: O
		The Oort Cloud is a cloud of rocks and dust that may surround our solar system.
		It has been hypothesized that the Oort Cloud is responsible for the periodic mass extinctions on Earth.
		OORT, JAN H. Jan Hendrik Oort (1900-1992) was a Dutch astronomer who calculated the distance to the middle of the Milky Way galaxy, mapped our galaxy, proved that the areas around the center of a galaxy revolves, and proposed the existence of the Oort Cloud in the 1950's.
	www.enchantedlearning.com /subjects/astronomy/glossary/indexo.shtml (1355 words)

	Question of the Week (Site not responding. Last check: 2007-10-22)
		The comets reside at distances from the Sun ranging from 5,000 to 100,000 AU (465 billion to 930 billion miles, 750 billion to 1.5 trillion km).
		The Oort Cloud is thought to contain perhaps as many as 10 billion comets.
		JWST is planning on exploring the Kuiper Belt, another reservoir of icy bodies much closer to the Sun, a "mere" 40 to 50 AU (3.5 billion to 4.5 billion miles, 6 billion to 7 billion km) away.
	www.jwst.nasa.gov /QuestionOfTheWeek/2003/2003-02-14.html (406 words)

	Jan Oort - Encyclopedia Glossary Meaning Explanation Jan Oort (Site not responding. Last check: 2007-10-22)
		Jan Oort - Encyclopedia Glossary Meaning Explanation Jan Oort.
		Here you will find more informations about Jan Oort.
		The orginal Jan Oort article can be editet
	www.encyclopedia-glossary.com /en/Jan-Oort.html (318 words)

	Uraniborg, an art + music collection by Fleur Helsingor (Site not responding. Last check: 2007-10-22)
		According to Oort's theory, there's a spherical shell of debris about half a parsec (or 1.63 light years) from the sun, and this cloud of debris is believed to be the source of millions of comets.
		Early in his career, Oort demonstrated that the Milky Way Galaxy rotates like a giant wheel, and that each of the stars in the galaxy travels independently through space.
		Jan Oort saw Halley's Comet twice, in 1910 (at the age of 10), and again in 1986.
	www.well.com /~fhelsing/Uraniborg/Oort.html (261 words)

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