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Topic: Ring Nebula

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Planetary nebula

Helix Nebula

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	planetary nebula
		Planetary nebulae have nothing to do with planets other than their name, which was coined by William Herschel, in the 1780s, because their appearance suggested to him the greenish disk of Uranus.
		The first planetary nebulae to be discovered, and the only ones to be recorded in the Messier Catalogue are the Dumbbell Nebula (M27) in 1764, the Ring Nebula (M57) in 1779, the Little Dumbbell Nebula (M76) in 1780, and the Owl Nebula (M97) in 1781.
		Infant planetary nebulae sometimes show evidence of a bipolar flow, as in the case of the Butterfly Nebula or Ant Nebula.
	www.daviddarling.info /encyclopedia/P/planneb.html (898 words)

	M57 The Ring Nebula (Site not responding. Last check: 2007-11-03)
		This beautiful ring nebula is actually an expanding shell of gas thrown off explosively by a dying star, which is barely visible at the center of the ring.
		For example, the center of the ring appears blue from emissions of helium close to the star, because helium requires higher-energy photons to ionize than hydrogen or oxygen, and the conditions for emission by helium primarily occur near the star.
		Nebula of this type were named planetary nebula in the 18th century because these nebula resembled the disk of a planet in the telescopes of the time, and the name has stuck to this day.
	members.cox.net /sidleach/m57.htm (251 words)

	Ring Nebula - Wikipedia, the free encyclopedia
		The Ring Nebula (also known as the Messier 57 or NGC 6720) is located in the constellation Lyra.
		The nebula is located at 0.7 kpc (2300 light-years) from Earth and was discovered by Antoine Darquier de Pellepoix in 1779.
		The nebula has a visual magnitude of 8.8, and a photographic magnitude of 9.7.
	en.wikipedia.org /wiki/Ring_Nebula (441 words)

	Nebulae - Zoom Astronomy
		A reflection nebula is a nebula that glows as the dust in it reflects the light of nearby stars.
		The Cygnus loop is a nebula, a supernova remnant in the constellation Cygnus.
		The Orion Nebula is roughly 30 light-years in diameter.
	www.enchantedlearning.com /subjects/astronomy/stars/nebulae.shtml (638 words)

	Calvin College Observatory: Images--M57, the Ring Nebula
		Contents: This colorful loop is known as the Ring Nebula (also M57, being the 57th object listed in Messier's famous catalog.) It is estimated to be 1000 to 2000 light-years distant, so that the linear size of the 1.7 arcminute loop we see is almost 1000 times that of the orbit of Neptune.
		The Ring Nebula is found in the constellation of Lyra, which in turn is dominated by the bright star Vega.
		The celestial coordinates of the Ring Nebula are 18h53m36s,+33deg2' (epoch 2000).
	www.calvin.edu /academic/phys/observatory/images/ring (483 words)

	Palomar Observatory Ring Nebula (M57) planetary nebula
		The Ring Nebula is a classic example of a planetary nebula - an expanding cloud of gas given off by a dying star.
		The Ring Nebula lies within the constellation of Lyra, the harp, but too faint to be seen with the unaided eye.
		Ring Nebula (M57) photographed by Tom Jarrett with the 200-inch at Prime Focus IR Camera @ 1.3-2.17 microns.
	www.astro.caltech.edu /observatories/palomar/m57.html (314 words)

	Ring Nebula (M57, NGC 6720)
		One of the best known planetary nebulae and the second to be discovered, by the French astronomer Antoine Darquier (1718-1802) in 1779 (15 years after the first one, the Dumbbell Nebula).
		Although appearing as a flattened ring, M75 is actually toroidal or possibly even cylindrical in shape; we simply happen to be looking more or less down one of its poles.
		Sensitive observations have also shown that the toroid or cylinder has lobe-shaped extensions in polar directions, and also a halo of material extending to over 3.5' (2.4 light-years) –; remnants of the central star’s earlier stellar winds before the nebula itself was ejected.
	www.daviddarling.info /encyclopedia/R/Ring_Nebula.html (363 words)

	SPACE.com -- Sky Surprises: The Ghostly Ring
		As for the true nature of the ring, it is generally believed that sometime in the distant past, a star nearing the end of its life and having used up all of its nuclear fuel hurled great masses of gas out into space in a gaseous shell.
		The Ring Nebula is the most famous and among the brightest examples of what astronomers refer to as planetary nebulae.
		The ring shape might just begin to become evident to most eyes in small telescopes using a magnification of 100-power, although at least a 6-inch telescope is recommended to see the ring clearly.
	www.space.com /spacewatch/surprise_ring_021009.html (1217 words)

	Nebulae
		Planetary nebulae are shells of gas thrown out by stars nearing the end of their lives and are mainly circular in appearance.
		These nebulae are usually red because the predominant emission line of hydrogen happens to be red (other colors are produced by other atoms, but hydrogen is by far the most abundant).
		Reflection nebulae are clouds of dust which are simply reflecting the light of a nearby star or stars.
	www.geocities.com /the_150mm_reflector/nebula.htm (976 words)

	Ring Nebula
		The Ring Nebula is a planetary nebula which is located in the constellation Lyra.
		The Ring Nebula is located at 18 53.6 right ascension and 33 02 declination.
		This Planetary Nebula has an apparent angular size of 1.4 x 1.0 and a visual brightness of 8.8.
	www.absoluteastronomy.com /nebulas/ring.htm (73 words)

	Best of AOP: M57- The Ring Nebula
		The ring nebula is probably one of the most famous deep sky objects in the sky.
		Generally when amatuers begin their telescopic journey, after the Orion Nebula, the Ring is one of the next objects on the list.
		Like others of its type, the Ring Nebula is the expelled outer envelope of a once aged star that has now reached its final stages of life.
	www.caelumobservatory.com /obs/m57.html (406 words)

	Messier Object 57
		The famous ring nebula M57 is often regarded as the prototype of a planetary nebula, and a showpiece in the northern hemisphere summer sky.
		Recent research has confirmed that it is, most probably, actually a ring (torus) of bright light-emitting material surrounding its central star, and not a spherical (or ellipsoidal) shell, thus coinciding with an early assumption by John Herschel.
		As most planetary nebulae, the Ring is much brighter visually at magnitude 8.8 than photographically at only 9.7 mag; a consequence of the fact that most light is emitted in very few particular spectral lines (see the discussion in our planetary nebulae page).
	www.seds.org /messier/m/m057.html (1351 words)

	Ring Nebula
		The Ring Nebula (or M 57) is the most famous of all the planetary nebulae.
		The Ring Nebula was first cataloged by the French astronomer Charles Messier (1730–1817) and is sometimes designated M 57.
		The Ring Nebula is about one light year in diameter and is about 2000 light years distant, toward the constellation Lyra.
	www.astrographics.com /GalleryPrintsIndex/GP0006.html (247 words)

	M57, Ring Nebula
		It's appearance as a tiny ring of smoke in a dark sky is a sight not soon forgotten.
		A planetary nebula is actually a large cloud of gas which was previously expelled from the central star.
		Even though the Ring is probably the most photographed object in the sky, it is so much brighter, that the galaxy is not visible in images optimized to bring out detail in M57.
	schmidling.com /m57.htm (778 words)

	HubbleSite - NewsCenter - Looking Down a Barrel of Gas at a Doomed Star (01/06/1999) - Introduction
		The pictures reveal that the "Ring" is actually a cylinder of gas seen almost end-on.
		Such elongated shapes are common among other planetary nebulae, because thick disks of gas and dust form a waist around a dying star.
		This photo reveals dark, elongated clumps of material embedded in the gas at the edge of the nebula; the dying central star is floating in a blue haze of hot gas.
	hubblesite.org /newscenter/archive/releases/1999/01 (166 words)

	Hubble Heritage
		Such elonged shapes are common among other planetary nebulae, because thick disks of gas and dust around the waist of the star slow down the expansion in that direction, leaving the gas free to flow out perpendicular to the disk.
		The Ring Nebula is about 2000 light years from Earth, and has a diameter of about one light year.
		Thus the Ring Nebula is in fact a non-spherical, axisymmetric planetary nebula (like many other PNe), which we happen to view from a direction close to its axis of symmetry.
	heritage.stsci.edu /1999/01/supplemental.html (1327 words)

	The Ring Nebula (Original) (Site not responding. Last check: 2007-11-03)
		Planetary nebulae are not so named because of an association with planets but because, in a telescope, their round shape resembles a planet.
		The nebula is lit by fluorescence caused by the large amount of ultraviolet radiation emitted by the central star.
		Planetary nebulae are not associated with novae, but are their own discreet phenomenon in the universe.
	spacefinder.tripod.com /pages/088o.htm (126 words)

	Cosmic Voyage-The Online Resource for Amateur Astronomers (Site not responding. Last check: 2007-11-03)
		M57 is the most observed planetary nebula in the night sky.
		The 15.2 magnitude central star of the Ring Nebula is a difficult detection unless conditions feature both good transparency and steady seeing.
		Magnitude 13.0 GSC 2642-0433, is visible near the eastern edge of the nebula.
	members.aol.com /billferris/m57.html (569 words)

	M57, The Ring Nebula
		Planetary nebula are shells of gas shed by stars late in their life cycles after using up all of their nuclear fuel.
		Observing with a 17 inch Dobsonian at the same time, the central star was not observed, either by myself, or the owner of the 17 inch, who does not have a lens in his eye, and claims to have seen the central star in an 8 inch SCT when he was much younger.
		As noted by Brian Skiff in his article on Photometry of M57 Field Stars, the two faint stars outside of the Ring Nebula, at magnitudes 14.1 and 14.7 must be visible if any hope of seeing the central star is to be realized.
	www.astropix.com /HTML/E_SUM_N/M57.HTM (739 words)

	Universe Today - Astrophoto: The Ring Nebula by Stefan Heutz (Site not responding. Last check: 2007-11-03)
		Riding high in the northern sky near the bright white star Vega, the Ring Nebula is one of the most favorite deep sky objects targeted visually by backyard stargazers.
		The Ring Nebula was discovered about 200 years ago by French astronomer Charles Messier, an avid comet hunter, and made its way into his catalog used to keep track of false comets as item number 57.
		Recent imagery by the Hubble Space Telescope has confirmed that the Ring Nebula is not spherical in shape; it is more like a tube that is slightly constricted in the middle so that it resembles a stretched hourglass.
	www.universetoday.com /am/publish/m57_042506.html?2442006 (432 words)

	M57 - The Ring Nebula (Site not responding. Last check: 2007-11-03)
		The Ring Nebula (NGC6720, M57) is a planetary nebula in the constellation Lyra.
		It is the result of a star (visible in the center of the ring) which ejected its outer shell of gas into surrounding space.
		It is located at a distance of approximately 4000 light years and the ring itself is approximately 1/2 light year across.
	www.astroimages.org /ccd/m57.html (132 words)

	Helix Nebula - Wikipedia, the free encyclopedia
		The Helix Nebula (also known as NGC 7293) is a planetary nebula (PN) about 650 light-years away in the constellation Aquarius.
		The Helix Nebula is an example of a planetary nebula created at the end of the life of a Sun-like star.
		The outer-most ring is flattened on one side due to its colliding with the ambient interstellar medium.
	en.wikipedia.org /wiki/Helix_Nebula (409 words)

	NCKAS -Nebula
		NGC 3242 is such a planetary nebula, with the stellar remnant white dwarf star visible at the center.
		Nebula are some of the most striking and beautiful of all the objects in the sky and are considered "Deep Sky Objects" or DSO's because they tend be be very dim and diffuse.
		This complex is an emission nebula (clouds of gas, exited and glowing from the radiation of hot O and B stars) and an impressive open cluster.
	www.nckas.org /nebulae (2194 words)

	APOD: 2006 June 25 - M57: The Ring Nebula (Site not responding. Last check: 2007-11-03)
		Now known as M57 or NGC 6720, the gas cloud became popularly known as the Ring Nebula.
		It is now known to be a planetary nebula, a gas cloud emitted at the end of a Sun-like star's existence.
		This helps indicate that the Ring Nebula is not spherical, but cylindrical.
	antwrp.gsfc.nasa.gov /apod/ap060625.html (179 words)

	2MASS Atlas Image Gallery
		The nebula was spectacularly imaged in the optical in a number of bands by the Hubble Space Telescope.
		Planetary nebulae are formed as low-mass stars, like our Sun, reach the end of their lives and lose their outer envelopes (for this nebula, what are now the ring and halo structures) to the interstellar medium.
		The bright ring is the equatorial torus, from a high-density slow wind from the evolving star, whereas the fainter halo structures are the polar lobes and the remnants of a faster, low-density wind.
	www.ipac.caltech.edu /2mass/gallery/images_pne.html (2017 words)

	Star Facts - November 1995 Article (Site not responding. Last check: 2007-11-03)
		The famous Ring Nebula, also known as M57, is one of the strangest looking sights in the night time sky.
		The Ring Nebula is almost exactly in the middle of these two dim stars.
		The donut-like ring we see when looking at the Ring Nebula is the disconnected shell of gas from a sun that once was - a sun with approximately the mass of our own sun.
	home.comcast.net /~pharris125/sfa1195.html (587 words)

	Image ssc2005-07a
		A planetary nebula is a shell of material ejected from a dying star.
		Located about 2,000 light years from Earth in the constellation Lyra, the Ring Nebula is also known as Messier Object 57 and NGC 6720.
		The "ring" is a thick cylinder of glowing gas and dust around the doomed star.
	www.spitzer.caltech.edu /Media/releases/ssc2005-07/ssc2005-07a.shtml (303 words)

	APOD: 2001 July 29 - M57: The Ring Nebula (Site not responding. Last check: 2007-11-03)
		Explanation: Except for the rings of Saturn, the
		Ring Nebula (M57) is probably the most famous celestial band.
		Hot blue gas near the energizing central star gives way to progressively cooler green and yellow gas at greater distances with the coolest red gas along the outer boundary.
	antwrp.gsfc.nasa.gov /apod/ap010729.html (157 words)

	M57:The Ring Nebula (Site not responding. Last check: 2007-11-03)
		M57, the Ring Nebula, is one of the most beautiful objects in the Northern sky.
		M57 is believed to be a planetary nebula, similar in structure to M27.
		The Ring Nebula was probably formed when this central star exploded long ago.
	www.csupomona.edu /~jdu/cis311/tutorial05/m57.htm (89 words)

	The Ring Nebula (M57)
		The Ring Nebula is one of the most famous objects in the sky and perhaps the most spectacular example of a planetary nebula.
		The Ring is visible in a 3-inch telescope as an elongated hazy spot.
		In recent years evidence has accumulated that the real shape of the Ring nebula may be a cylinder and we are viewing it from one end.
	www.skyhound.com /sh/archive/jul/M_57.html (545 words)

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