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	Jan Oort - Wikipedia, the free encyclopedia (Site not responding. Last check: 2007-10-20)
		Oort was born in Franeker in Friesland and studied in Groningen with Jacobus Cornelius Kapteyn.
		Another contribution of Oort was that he was able to demonstrate that the light from the Crab nebula was polarized.
		Oort calculated that the centre of the Milky Way was 30,000 light years from the Earth in the direction of the constellation Sagitarius.
	en.wikipedia.org /wiki/Jan_Oort (363 words)

	Oort cloud
		The Oort cloud (sometimes called the Öpik-Oort Cloud) is a postulated spherical cloud of comets situated about 50,000 to 100,000 AU from the sun (approximately 1000 times the distance from the Sun to Pluto); with an inner disk at the ecliptic from the Kuiper belt.
		The most widely-accepted theory of its formation is that the Oort cloud's objects initially formed much closer to the Sun as part of the same process that formed the planets and asteroids, but that gravitational interaction with young gas giants such as Jupiter ejected them into extremely long elliptical or parabolic orbits.
		It is thought that other stars are likely to possess Oort clouds of their own, and that the outer edges of two nearby stars' Oort clouds may sometimes overlap, causing the occasional intrusion of a comet into the inner solar system.
	pedia.newsfilter.co.uk /wikipedia/o/oo/oort_cloud.html (536 words)

	ORRERY: The Oort Cloud
		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.
		The furthest edge of the Oort cloud is believed to be 0·8 ly away.
	www.harmsy.freeuk.com /oort.html (305 words)

	Practical Info (Oort Symposium) (Site not responding. Last check: 2007-10-20)
		Jan Hendrik Oort is undoubtedly one of the greatest astronomers of the twentieth century.
		Oort realized that the theory had implications for the motions of stars near the sun, and that in fact material was available to prove that the theory was correct.
		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)

	Oort Cloud (Site not responding. Last check: 2007-10-20)
		The Oort cloud is an immense spherical cloud surrounding the planetary system and extending approximately 3 light years, about 30 trillion kilometers from the Sun.
		One sixth of an estimated six trillion icy objects or comets are in the outer region with the remainder in the relatively dense core.
		The Oort cloud is the source of long-period comets and possibly higher-inclination intermediate comets that were pulled into shorter period orbits by the planets, such as Halley and Swift-Tuttle.
	www.solarviews.com /eng/oort.htm (710 words)

	Planetary Society: Oort Cloud (Site not responding. Last check: 2007-10-20)
		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.
		While the Oort cloud has probably been around for several billion years, our knowledge of it is fairly recent.
		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)

	Abraham H. Oort
		Oort, A. H., and P. Chan, 1977: On the role of the Asian monsoon in the angular momentum and kinetic energy balances of the tropics.
		Oort, A. H., and H. Bowman II, 1974: A study of the mountain torque and its interannual variations in the northern hemisphere.
		Oort, A. H., and J. Peixoto, 1974: The annual cycle of the energetics of the atmosphere on a planetary scale.
	www.gfdl.noaa.gov /reference/bibliography/authors/oort.html (1706 words)

	THE OORT CLOUD (Site not responding. Last check: 2007-10-20)
		As a result, comets in the Oort Cloud are frequently perturbed by the gravity of passing stars.
		The combined effect is a "random walk" in the magnitude of the velocity perturbation such that, after 10,000 stars have passed by, the original orbit of the comet has been drastically altered.
		Closer to the sun, the Oort Cloud comets are tightly held and may never be dislodged by the gravity of passing stars.
	www.geocities.com /beyondearth2001/oort.htm (614 words)

	Jan Oort Bibliography
		Oort, J.H., “The Galaxy,” IAU Symposium 20, 1-9 (1964).
		Oort, J.H., “The Density of the Universe,”; Astronomy & Astrophysics 7, 405 (1970).
		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.
	www.phys-astro.sonoma.edu /BruceMedalists/Oort/OortRefs.html (911 words)

	ESA - Science - Home - Comet pioneer: Jan Hendrik Oort
		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.
		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.
		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.
	www.esa.int /esaSC/SEMBPC2PGQD_index_0.html (626 words)

	Oort clouds (Site not responding. Last check: 2007-10-20)
		The Oort Cloud is located approximately 50,000 AU from our sun (1 AU = average distance between the sun and Earth = 1.5 x 108 km).
		Astronomers believe the Oort Cloud was formed when left over planetary materials were flung beyond the solar system by the gravity of Neptune and Uranus.
		The key is in the part of Shawn's answer that says, "Astronomers believe the Oort Cloud was formed when left over planetary materials were flung beyond the solar system by the gravity of Neptune and Uranus." This, we think, produced the random orientation of the orbits.
	www.hcc.hawaii.edu:8000 /cgi-bin/HyperNews/get/forums/astro-f03-1/4.html?embed=-1&outline=1 (263 words)

	Oort cloud -- Britannica Concise Encyclopedia Online Article
		The Oort cloud is believed to be composed of primordial bodies dating from the formation of the solar system (see solar nebula).
		Whether the Oort cloud merges, in its inner region, into the disk-shaped Kuiper belt is not known.
		The Oort cloud is, however, gravitationally bound to the solar system, which it follows in its orbit around the Milky Way Galaxy.
	www.britannica.com /ebc/article?tocId=9374052&query=oort&ct= (865 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)

	Comets and the age of the solar system
		Oort proposed a large spherical cloud of comet nuclei that formed early in the history of the Solar System.
		Oort reasoned that this clumping at great distance represented the original distribution of comets, while the smaller numbers at closer distances represented the result of gravitational perturbations.
		Oort himself apparently believed that the short period comets were best explained by the disruption of a planet that once orbited between Mars and Jupiter, an old idea that has been largely discarded, but still has its supporters (for instance, van Flandern).
	www.answersingenesis.org /docs/4108.asp (8149 words)

	Homepage for Frans Oort
		A. de Jong \& F. Oort " Purity of the stratification by Newton polygons".
		ps file of F. Oort: Lifting an automorphism of a curve to characteristic zero, talk at the University of Pennsylvania, 7 - V - 2003.
		ps file of F. Oort: Foliations in moduli spaces of abelian varieties and dimension of leaves.
	www.math.uu.nl /people/oort (565 words)

	Astrophysics Homepage of John J. Matese
		However its location in the outer Oort cloud means that it is not possible that it formed in the protosolar planetary disk.
		We have initiated a study of the characteristics and frequency of weak shower of outer Oort cloud comets caused by a stellar impulse.
		Since the galactic tide dominates in making Oort cloud comets observable today (and is also likely to do so when averaged over long time scales) we can inquire about the long-timescale variability of the tidal interaction which is connected to the solar oscillation about the galactic midplane.
	www.ucs.louisiana.edu /~jjm9638/matese.html (1655 words)

	American Scientist Online - Perturbing the Oort Cloud (Site not responding. Last check: 2007-10-20)
		In the classical view, first proposed by the Dutch astronomer Jan Oort in 1950, these comets remain in the distant reservoir until a passing star perturbs the cloud, diverting some of the comets toward the inner solar system.
		According to the proponents of the theory, the Oort cloud was being greatly perturbed by something in the galactic midplane, and this caused a catastrophic rain of comets on the inner solar system (including the earth) every 30 million years.
		For the time being it appears that the Oort comet cloud and the galaxy will continue to be entangled with the dinosaur extinctions and extraterrestrial impactors.
	www.americanscientist.org /template/AssetDetail/assetid/24618 (1302 words)

	Universe Today Forums -> the Oort Cloud (Site not responding. Last check: 2007-10-20)
		The Oort Cloud of icy bodies is believed to extend out from 20,000 to about 100,000 AU from the Sun.
		The existance of the Oort cloud was the result of measurements done by Jan H. Oort in the 50's.
		Oort cloud objects are too small and too far away to be seen in their usual orbit by current technology.
	www.universetoday.com /forum/index.php?act=ST&f=8&t=1654&hl=& (2309 words)

	Oort Cloud solar system astronomy
		There is a strong tendency for the furthest points from the Sun (aphelia) of long-period comets to group at about 4.6 trillion miles (50,000 AU or 8/10 of a light-year) from the Sun.
		From these observations Oort proposed that (long-period) comets reside in an immense spherical cloud surrounding the planets and extending out about three light years from the Sun -- the boundary of the Sun’s influence.
		The Oort Cloud’s inhabitants are most strongly perturbed, however, by the tidal forces of giant molecular clouds.
	www.myastrologybook.com /Oort-Cloud-solar-system-astronomy.htm (495 words)

	Articles - Oort cloud (Site not responding. Last check: 2007-10-20)
		The Oort cloud (sometimes called the Ã–pik-Oort Cloud) is a postulated spherical cloud of comets situated about 50,000 to 100,000 AU from the Sun.
		In 1950 the idea was revived and proposed by Dutch astronomer Jan Hendrick Oort to explain an apparent contradiction: comets are destroyed by several passes through the inner solar system, yet if the comets we observe had existed since the origin of the solar system, all would have been destroyed by now.
		The star with the greatest possibility of perturbing the Oort cloud in the next 10 million years is Gliese 710.
	www.sidepoint.com /articles/Oort_cloud (601 words)

	SPACE.com -- Report Sullies Pristine Reputation of Comets
		The Oort cloud's immensity means passing stars "regularly penetrate it" on cosmic time scales, Stern says, resulting in elevated temperatures that could strip some the most volatile cometary gases, such as neon and oxygen.
		But theory holds that the Oort cloud comets were formed closer in and booted to their new orbits as the giant outer planets formed between 4.5 billion and 4 billion years ago.
		"Although collisions in the Oort cloud itself are rare and apparently of little effect, recent work indicates that collisions probably greatly affected the surfaces and interiors of many of these bodies during their ejection from the planetary region to the Oort cloud," Stern says.
	www.space.com /scienceastronomy/comets_eroded_030807.html (1031 words)

	Astronomy & Space
		Comets, the Kuiper Belt, and the Oort Cloud In 1950 Jan Oort noticed that 1.no comet has been observed with an orbit that indicates that it came from interstellar space, 2.there is a strong tendency for aphelia of long period comet orbits to lie at.
		The Oort cloud and long period comets The significant number of long period comets (> 1000 years) and non-periodic comets led Jan Oort to speculate in 1950 that a cloud of objects surrounds the Solar System.
		Comet Reservoirs The Oort Cloud Based on the orbits of long period comets, in 1950 Jan Oort proposed that a distance, spherical distribution of cometary nuclei surrounding the solar system.
	groups.msn.com /AstronomySpace/kuiperbeltoortcloud.msnw (835 words)

	Oort cloud (Site not responding. Last check: 2007-10-20)
		Response #: 1 of 2 Author: hawley The Oort Cloud (note: singular tense) is the theoretical region associated with our solar system where most comets spend most of their time.
		This may be beyond the level of a high school student, but a possible project might be to use the orbital parameters of known reappearing comets to calculate the dimensions of the Oort Cloud.
		Some astrono- mers believe that in addition to the Oort cloud, there is another reservoir of comets (the source of "short-period" comets) called the Kuiper belt.
	www.newton.dep.anl.gov /newton/askasci/1995/astron/AST144.HTM (240 words)

	oort (Site not responding. Last check: 2007-10-20)
		A typical Oort cloud is about 0.5 to 1 light year from its primary and has an aggregate mass about that of Terra; density is thus extremely low.
		Bodies in the Oort cloud are occasionally perturbed by collisions or by the influence of nearby stars into orbits which pass near the star; these form the visible comets.
		The Oort cloud is named after its discoverer, Terran astronomer Jan Oort.
	members.cox.net /imperiallibrary/o/oort.html (96 words)

	More problems for the ‘Oort comet cloud’
		Evolutionary theories of the origin of the solar system state that comet nuclei came from material left over from the formation of the planets.
		According to the theory, this icy material was sent out to the Oort cloud in the outer reaches of the solar system by the gravity of the newly formed planets.
		Since it cannot be detected, the Oort cloud is not a scientific concept.
	www.answersingenesis.org /docs2001/0221oort_cloud.asp (559 words)

	The Bruce Medalists: Jan H. Oort
		Oort found evidence for differential rotation and founded the mathematical theory of galactic structure.
		Following the war Oort led the Dutch group which built a 25-m radio telescope at Dwingeloo and used the 21-cm line to map hydrogen gas in the Galaxy.
		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 (407 words)

	Kuiper-Oort
		The Oort Cloud may account for a significant fraction of the mass of the solar system, perhaps as much or even more than Jupiter.
		In 2004, the discovery of an object known as 2003 VB12 "Sedna" was announced.
		The Kuiper Belt is a disk-shaped region past the orbit of Neptune extending roughly from 30 to 50 AU from the Sun containing many small icy bodies.
	www.seds.org /nineplanets/nineplanets/kboc.html (858 words)

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