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	WFPC2/PC Imagery of the Extended Circumstellar Disk of Beta Pictoris. (Site not responding. Last check: 2007-10-01)
		WFPC2/PC Imagery of the Extended Circumstellar Disk of Beta Pictoris.
		We have observed the extensive circumstellar disk (Kuiper Belt) of \beta Pictoris using the WFPC2/PC aboard the Hubble Space Telescope.
		The final images clearly reveal the circumstellar disk of \beta Pic extending the full width of the PC (34 arcseconds), sampling a disk radius \geq 750 A.U. The disk shows clear evidence of asymmetric flaring at larger distances from the star.
	www.aas.org /publications/baas/v29n5/aas191/abs/S047003.html (234 words)

	CIRCUMSTELLAR DISK REVEALS SIGNS OF YOUNG PLANETS (Site not responding. Last check: 2007-10-01)
		The clumps in AU Mic's disk lie at separations of 25 to 40 Astronomical Units away from the central star (where one Astronomical Unit is the distance from the Earth to the Sun), or about 2 to 4 billion miles.
		However, many structures in the AU Mic disk are observed to be elliptical (non-circular), indicating that the planetary orbits are elliptical.
		The resulting infrared images are the sharpest ever obtained of a circumstellar disk, with an angular resolution of 1/25 of an arcsecond, about 1/500,000 the diameter of the full moon.
	www.keckobservatory.org /news/science/disk/disk.html (916 words)

	Circumstellar disk (Site not responding. Last check: 2007-10-01)
		A protoplanetary disc (also protoplanetary disk, proplyd) is a disc of dust and gas which orbits a protostar, within a solarnebula.
		As the cloud shrinks, conservation of angular momentum causes the random motions originally present in the cloudto become one coherent rotation.
		Further gravitational interactions may cause the dust and gas in the disk to condense into planetesimals.
	www.therfcc.org /circumstellar-disk-32258.html (160 words)

	[2.09] Evolutionary Timescales for Circumstellar Accretion Disks (Site not responding. Last check: 2007-10-01)
		It is fairly common consensus that circumstellar disks are near-ubiquitously present around stars at birth.
		These disks are the sites of planetary formation, and with detection of exo-solar planets now occurring routinely, understanding of the evolutionary link between young circumstellar disks and planets is more critical than ever.
		Dimunition of accretion disk activity and transition from optically thick accretion disks to optically thin post-planet-building disks occurs during the early pre-main sequence phase.
	www.aas.org /publications/baas/v31n5/aas195/649.htm (232 words)

	Universe Today - Massive Stars Have Protoplanetary Disks Too
		This discovery is the most concrete evidence for a disk around a massive young star and shows that massive stars like the BN object (which is about seven times the mass of the Sun) form the same way as lower-mass stars like the Sun.
		By contrast, the disk and the envelope are relatively opaque to light.
		The group’s success in detecting evidence for a disk and outflow around the BN object through high-resolution infrared polarimetry suggests that the same technique can be applied to other forming stars.
	www.universetoday.com /am/publish/printer_circumstellar_disk_cradles_massive_star.html (654 words)

	CAS astronomers find a circumstellar disk around a massive star
		In the other scenario, such star is formed by accretion from a circumstellar disk, which is a flattened system of dust and gas surrounding a protostar at the center, in the same way as its low-mass cousins are formed.
		And one of the critical evidence for the judgement is the existance of the circumstellar disks.
		However, it is difficult to spot such disks because high-mass stars are relatively rare and usually distant, and the luminance of disks is always dwarfed by that of protostars.
	www.chinaembassy.org.ro /rom/kjwh/t211345.htm (459 words)

	index
		There is little doubt that this object is indeed the infrared image of a circumstellar disk, viewed at an angle.
		Moreover, the dust disk in which the hot star is embedded, absorbs the stellar ultraviolet light extremely efficiently, thereby re-emitting this energy in the infrared.
		In view of the extremely high luminosity of such massive stars, any surrounding disks are subject to a fierce attack by the enormous flux of light to which they are exposed.
	www.eso.org /outreach/press-rel/pr-1998/pr-08-98.html (927 words)

	Subaru seminars
		The circumstellar environment within 10 AU of young stars is of particular interest for studies of star and planet formation.
		In this region, the star accretes the material from the circumstellar disk, and drives an energetic jet/wind.
		In the circumstellar disk, planets may be growing and tidally interacting with the circumstellar environment.
	www.naoj.org /Science/seminar.20030811.html (236 words)

	Dave Jewitt: Beta Pictoris Star (Site not responding. Last check: 2007-10-01)
		The models are used to constrain the range of disk parameters (inclination, radial gradient, vertical scale height, flare factor, phase function) in Beta Pictoris.
		From the Figure, we conclude that highly inclined (face-on) disks are difficult to distinguish from the circular halo of light scattered from the central star.
		The perpendicular spike (due to forward scattering from the near-side of the disk) seen in the middle column could easily be confused with a stellar jet.
	www.ifa.hawaii.edu /faculty/jewitt/beta.html (288 words)

	Circumstellar Disk Formation by Radiatively Driven Orbital Mass Ejection
		The link here shows an animation of such an outflow from a spot that is factor 10 brighter than the ambient star, and covering a circle approximately 10 degrees radius located at the equator of a star rotating at 350 km/s, with orbital speed 500 km/s.
		While this RDOME scenario thus demonstrates that radiative driving can, in principle, expel surface material into a circumstellar disk, I caution that the conditions assumed in these simulations are quite extreme, with brightness variations that are far stronger than have typically been thought to be possible on such stars.
		This research has not yet been published in any journal, but I have given several talks on the general probem of forming Be disks, with the somewhat whimsical title "The Rocket Science of Launching Stellar Disks", which you can access here in the original Powerpoint, or as a PDF document.
	www.bartol.udel.edu /%7Eowocki/RDOME/index.html (875 words)

	Press Release
		The team's results show the disks of dust and gas, which can be several billion kilometers across, are initially similar to the disk which is believed to have formed the planets in our own Solar system, but quickly evaporate in the glare of bright massive neighboring stars in the Trapezium.
		Evaporation of the circumstellar disk erodes approximately three moon masses of material per year according to the theoretical model, a number which is verified by the HST observations.
		The exact evaporation rate from the circumstellar disk is directly related to the size of the disk and thus, as the disk evaporates and shrinks, the erosion rate decreases.
	oposite.stsci.edu /pubinfo/pr/1997/orion/orion/pr.html (857 words)

	A layered edge-on circumstellar disk around HK Tau B
		The contributions of both components are well disentangled at 1.4 mm and the star previously known to host an edge-on circumstellar disk, HK Tau B, is elongated along the disk's major axis.
		We model the millimeter thermal emission from the circumstellar disk surrounding HK Tau B. We show that the disk mass derived from scattered light images cannot reproduce the 1.4 mm emission using opacities of the same population of submicron dust grains.
		We propose that this disk contains three separate layers: two thin outer surfaces which contain dust grains that are very similar to those of the ISM, and a disk interior which is relatively massive and/or has experienced limited grain growth with the largest grains significantly smaller than 1 mm.
	www.edpsciences.org /articles/aa/abs/2003/11/aa2849/aa2849.html (322 words)

	Hubble & Astronomy--Stars--Protoplanetary Disk--Protoplanetary Disk--Circumstellar Disk Around Beta (Site not responding. Last check: 2007-10-01)
		These two Hubble Space Telescope visible-light views of the edge- on disk of dust around the star Beta Pictoris yield telltale evidence for the existence of planets, and possibly the gravitational tug of a companion brown dwarf or bypassing star.
		Both views reveal warps in the disk that might be caused by the gravitational pull of one or more unseen companions.
		Because the disk is tilted nearly edge-on to Earth the images show a sharp, bright, straight ridge extending over the entire length of the disk.(in our solar system this feature is seen as zodiacal light, where sunlight is reflected by a concentration of dust in the ecliptic plane).
	www.usmkb.com /ImageDetail.php?iImageUnq=21068&sSort=&iGalleryUnq=161 (331 words)

	People's Daily Online -- Circumstellar disk associated with a massive protostellar object: astronomers
		A group of astronomers from China, Japan and the United Kingdom obtained very sharp near-infrared polarization images of a famous massive protostellar object Becklin-Neugebauer (BN), by using the coronagraphic imager for adaptive optics (CIAO) mounted on the SUBARU telescope.
		Though the discovery of the disk is an important step towards the understanding of the massive star formation, there is still much work to do.
		Fortunately, with the technique of high-resolution near-infrared imaging polarimetry, it becomes possible to reveal the circumstellar disks associated with massive stars even if they are hiding behind the luminous star lights.
	english.peopledaily.com.cn /200509/02/eng20050902_205987.html (292 words)

	HST/NICMOS images of circumstellar disks (Site not responding. Last check: 2007-10-01)
		In the optical and near-infrared circumstellar disks are almost entirely seen in scattered light.
		If the disk is seen close to edge-on (within 5 to 10 degrees), the disk itself effectively blocks the direct starlight.
		Note that disks are not flat, their surface looks like the inside of a giant bowl.
	spider.ipac.caltech.edu /staff/brandner/topics/disks/disks.html (367 words)

	Circumstellar Dust Disks in Taurus-Auriga: The Submillimeter Perspective - Everything Science
		The median disk to star mass ratio is 0.5%.
		In this sample, the only stellar property that is correlated with the outer disk is the presence of a companion.
		The fraction of objects detected in the submillimeter is essentially identical to the fraction with excess nearinfrared emission, suggesting that dust in the inner and outer disk are removed nearly simultaneously.
	www.everything-science.com /content/view/139/81 (342 words)

	Temporal evolution of the accretion disk in exors: ISO observations of EX Lupi (Site not responding. Last check: 2007-10-01)
		EXORs undergo large amplitude outbursts as a direct result of enhanced mass accretion from their circumstellar disk, where the energy liberated results in a brightening of 3-5 magnitudes in the UV and optical.
		The outbursts play a major role in modifying the circumstellar environment, and initiate the formation of winds, jets, H-H objects, and dispersal of the disk, and likely influence the formation and evolution of giant planets and brown dwarfs.
		Exactly how the disk replenishes itself between the outbursts and the underlying mechanism that triggers the outbursts remains a mystery.
	www.iso.vilspa.esa.es /meetings/paris/Paris_abstracts/node201.html (278 words)

	Sebastian Wolf: Topics of Research
		We present simulations of a circumstellar disk around a solar-type star with an embedded planet of 1 Jupiter mass.
		We investigate the possibility to detect giant planets that are still embedded in young circumstellar disks.
		The lower bright region is the inner ring of the disk.
	www.mpia.de /homes/swolf/homepage/html/public/alma/alma-simus.html (715 words)

	Astron. Astrophys. 348, 557-569 (1999) (Site not responding. Last check: 2007-10-01)
		We investigate in details the properties of the disk surrounding the 8 Myr old star HR 4796 A, one of the few stars bringing precious clues to better understand the scenario which lead to planetary system formation.
		Both dust populations are highly collisional and the grain size distribution in the cold annulus is found to be cut-off by radiation pressure.
		At 70 AU, bodies as large as a few meters are required to fit the data leading to a minimum disk mass of a few Earth masses and to a gas to dust ratio less than 1.
	aa.springer.de /bibs/9348002/2300557/small.htm (253 words)

	Planet Quest: Missions - Keck Interferometer
		Circumstellar disk detection with the Keck Nuller (Traub)
		Our survey is designed to resolve the mystery of the "large" near-IR disks uncovered by the current generation of interferometer (IOTA/PTI), by studying the fundamental physical properties of accretion disks and how they vary as a function of stellar luminosity, total disk mass, age, and multiplicity.
		Our goal is to establish confidence in the nuller's ability to detect circumstellar dust down to the level of 10 times the solar zodiacal cloud, seen at 10 pc, so that a large scale survey for exozodiacal dust can proceed.
	planetquest.jpl.nasa.gov /Navigator/keck_sharedrisk.cfm (658 words)

	Sharpest Image Ever Obtained of a Circumstellar Disk
		Irregularities in the shape of the disk indicate the presence of unseen planets in orbit around the star.
		Infrared image of the edge-on dust disk around the star AU Microscopii obtained with the Keck II Telescope.
		The disk is visible because its orbiting dust particles scatter the light of the star.
	www.ifa.hawaii.edu /info/press-releases/Liu0804.html (955 words)

	[No title] (Site not responding. Last check: 2007-10-01)
		One of the major successes of modern star formation theory has been the prediction that the circumstellar disks are inevitable by-products of the star formation process.
		A detailed study of the disk evolution is critically important to our understanding of the planet formation and other disk dispersal mechanisms and their associated timescales.
		We have been trying to trace the evolution of circumstellar disks from the early PMS phase to the late main sequence phase, using several observational diagnostics (emission-line activity, infrared excesses, polarisation) of the disks and by following their evolution in time.
	www.astro.ncu.edu.tw /contents/seminar/colloquium/explor.php?id=80 (211 words)

	Future Gemini Instrumentation - Figure 8 (Site not responding. Last check: 2007-10-01)
		The opaque circumstellar disk surrounding HH30 appears in shadow against the bright, disk-like scattered-light region (the remnant infalling envelope) seen above and below the disk.
		Emerging from HH30 is a highly-collimated, ionized jet, believed to be driven by processes related to accretion of material through a magnetized disk.
		Critical to the success of these observations is coronagraphic and polarimetric capability; most objects lack the favorable geometry of HH30, in which the central object is obscured by a nearly edge-on disk.
	www.gemini.edu /science/future_inst/figure8.html (127 words)

	A White Dwarf Explodes Inside a Dense Circumstellar Disk
		Outside the disk the density of the circumstellar matter is lower (gray).
		Because of the way the hydrogen line had brightened long after the supernova was first observed, the astronomers deduced that the disk included dense clumps and had been in place well before the white dwarf exploded.
		A structure that may resemble the progenitor of SN 2002ic: the NGC 6302 butterfly nebula is the remnant of a star that shed most of its outer layers before contracting, and may be one member of a binary system.
	www.lbl.gov /Science-Articles/Archive/Phys-white-dwarf.html (1458 words)

	Other Planetary Systems
		Both conditions are believed to be characteristic of a hypothesized circumstellar disk around our own Sun, which was a necessary precursor to the planet-building phase of our Solar Systems, according to current theory.
		More recent HST observations have shown the disk to be slightly warped as might be expected from the gravitational influence of a planet.
		The phenomena observed matches the theory of the formation of the solar system -- that is, a large gas cloud collapsed to form a star with an attendant circumstellar disk in which, over time, planets accreted from the matter in the disk and orbited the Sun.
	www.nineplanets.org /other.html (1806 words)

	Circumstellar Disks
		The most important and exciting reason we study circumstellar disks is because they are believed to be the sight of planetary formation.
		Furthermore, by studying these disks, we are able to constrain theories of planetary formation and can develop timescales for the evolution of planetary development.
		The nebula itself is illuminated by the star but the dust of the disk, which is almost edge on to our field of view, absorbs all of the optical light from the star hiding it from our view.
	feps.as.arizona.edu /outreach/disks.html (759 words)

	Circumstellar disk (Site not responding. Last check: 2007-10-01)
		It uses material from the Wiktionary page "Disk".
		accretion disk (Astronomy) A structure formed by matter falling into a gravitational source such as a galaxy, fl hole, or protostar.
		It allows you to examine data from a live network or from a capture file on disk.
	www.serebella.com /encyclopedia/article-Circumstellar_disk.html (445 words)

	[49.12] Circumstellar Disk Diagnostics from Polarimetry and Infrared Excesses (Site not responding. Last check: 2007-10-01)
		The circumstellar disks of B-type emission line stars polarize the light emitted by the star and also cause excess infrared radiation.
		The observed polarization and infrared excess are affected by both the disk inclination and optical depth.
		We have modeled the effects of these two parameters on the predicted polarization and infrared excesses of Be stars over a range of stellar temperatures, with the disk temperature set to a value 75% of the stellar temperature.
	protostar.aas.org /publications/baas/v34n4/aas201/65.htm (301 words)

	Circumstellar Disk Cradles Young Massive Star (Forwarded)
		to the discovery of a disk surrounding this newly forming star.
		signature of a disk and an outflow structure near the newborn star.
		circumstellar disk, the envelope and the cavity walls formed by the
	www.air-space.us /sci.space.news/14/Circumstellar-Disk-Cradles-Young-Massive-Star-(Forwarded)-article761.htm (760 words)

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