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Topic: Emission nebula

	Emission nebula - Wikipedia, the free encyclopedia
		An emission nebula is a cloud of ionized gas (i.e.
		Among the several different types of emission nebula are H II regions, in which star formation is taking place and young, massive stars are the source of the ionising photons; and planetary nebulae, in which a dying star has thrown off its outer layers, with the exposed hot core then ionizing them.
		Emission nebulae often have dark spots in them which result from clouds of dust which block the light.
	en.wikipedia.org /wiki/Emission_nebula (345 words)

	Nebula - Wikipedia, the free encyclopedia
		A nebula (Latin: "mist"; pl. nebulae) is an interstellar cloud of dust, gas and plasma.
		Emission nebulae are internally illuminated clouds of ionized gas.
		Other nebulae are formed by the death of stars; a star that undergoes the transition to a white dwarf blows off its outer layer to form a planetary nebula.
	en.wikipedia.org /wiki/Nebula (387 words)

	Sea and Sky's Cosmic Wonders: Nebulae
		Indeed, a nebula is a cosmic cloud of gas and dust floating in space.
		Emission nebulae tend to be red in color because of the abundance of hydrogen.
		The nebula is illuminated by a group of stars at its center known as the trapezium.
	www.seasky.org /cosmic/sky7a05.html (1150 words)

	Nebulae - Zoom Astronomy
		Emission nebulae are formed when energetic ultraviolet light from a very hot star excites a cloud of hydrogen gas; the UV radiation ionizes the hydrogen (it strips electrons from the hydrogen atoms).
		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)

	Nebula
		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.
		Reflection nebulae and emission nebulae are often seen together and are sometimes b oth referred to as diffuse nebulae.
	www.crystalinks.com /crabnebula.html (620 words)

	B33, The Horsehead Nebula
		The Horsehead Nebula, B33, is the dark nebula in front of the bright red emission nebula IC 434.
		Along with the Orion Nebula, M42, it is part of a very large complex that is a stellar nursery where stars are forming out of the dust and gas.
		The Flame Nebula, NGC 2024, is to the lower left of Alnitak, Zeta Orionis, the easternmost star in the three distinctive stars in the Hunter's belt of Orion, and the brightest star in this photo.
	www.astropix.com /HTML/B_WINTER/B33.HTM (249 words)

	APOD Index - Nebulae: Emission Nebulae
		This emission nebula is famous partly because it resembles Earth's
		The two emission nebula are located about 1500 light years away and are separated by a dark absorption cloud.
		This image of the nebula was taken using a filter to select only light near the H-alpha wavelength.
	antwrp.gsfc.nasa.gov /apod/emission_nebulae.html (301 words)

	SUMMER SKIES NEBULAE
		The “COCOON” Nebula is a Magnitude 9.6 H-II Emission Nebula, at RA 21hr 51m 3s, DEC 47o 02', in the Constellation CYGNUS.
		The nebula clouds are suggestive to me of a large bird, head down with wings spread and tail fanned out to catch and sail the thermals of the brilliant night skies.
		As with most of the large southern sky emission nebulae, an open star cluster is also embedded in the nebula structure.
	pages.prodigy.net /fmewalt/_import/pages.prodigy.net/fmewalt/index5.html (1095 words)

	Fred's Astronomy Stuff - Nebulae, Galaxies, Clusters
		Nebulae (singular is nebula) are generally great clouds of dust or gas that intrinsically glow (emission nebulae), or reflect light from a nearby star (reflection nebulae).
		The Eagle Nebula (M16): Recently made famous by a Hubble Space Telescope image of the Eagle's head, this emission nebula is quite interesting with many tendrils of dust and gas that are working to form new stars.
		M8, the Lagoon Nebula: this is an emission nebula located approximately 4,500 light years away in the constellation Sagittarius.
	www.moonglow.net /ccd/pictures/neb (839 words)

	emission nebula
		A nebula that displays an emission spectrum because of energy that has been absorbed from one or more hot, luminous stars and reemitted by the nebular gas at specific wavelengths.
		This is different from a reflection nebula, where the light from the nebula is simply reflected light from the central star.
		The main categories of emission nebulas are H II regions, planetary nebulae, and supernova remnants.
	www.daviddarling.info /encyclopedia/E/emisneb.html (195 words)

	Nebulae
		These nebulae quickly expand and fade while their matter is spread in the interstellar surroundings.
		Emission Nebulae: Emit light because the atoms in their gases are excited by high energy radiation of stars involved.
		Absorption Nebulae or Dark Nebulae: Absorb light: Their gas component can be seen as absorption spectra in the light of background stars, their dust component by absorbing and reddening background light.
	www.seds.org /messier/nebula.html (731 words)

	eSky: Emission Nebula (Site not responding. Last check: 2007-11-06)
		In a Reflection Nebula, the nebulous material is visible because of the reflect light from nearby stars.
		In an Emission Nebula, the material making up the nebula is also clearly visible, but because of radiation it produces itself.
		The nebula's energy is ultimately derived from stars often embedded within its own structure, whose radiation causes ionisation within the nebula, leading to a release of energy visible as light.
	www.glyphweb.com /esky/concepts/emissionnebula.html (68 words)

	Stars, Stellar Systems, and Nebulae
		These nebulae are usually red because the predominant emission line of hydrogen happens to be red (other colours are produced by other atoms, but hydrogen is by far the most abundant).
		Reflection nebulae and emission nebulae are often seen together and are sometimes both referred to as diffuse nebulae.
		The famous ring nebula M57 is often regarded as the prototype of a planetary nebula, and a showpiece in the northern hemisphere summer sky.
	www.ing.iac.es /PR/science/stars.html (3176 words)

	Volume Visualization of the Orion Nebula
		One of the closest is the Orion Nebula, which is 1500 light-years from Earth and measures several light-years across.
		Voxels within the glowing parts of the nebula are made opaque and given a color based upon specially color-corrected Hubble imagery (color correction removes the reddening effects of dust and gas between Earth and the nebula).
		The volumetric model was used to render images of the nebula as seen from the point of view of a spacecraft flying through the nebula.
	vis.sdsc.edu /research/orion.html (1182 words)

	Emission Nebulae
		The HII regions (emission nebulae) are so named because they are composed mostly of a plasma of ionized hydrogen (HII) and free electrons.
		An equilibrium is established in a typical emission nebula when the temperature equivalent of this kinetic motion is between 7000 K and 20,000 K. For a typical emission nebulae, the density of ions (and electrons) is 1.0E8 to 1.0E10 particles per m^3.
		Some of the most famous and beautiful of the emission nebulae visible from the Northern Hemisphere are the Orion Nebula (M42, the Messier catalog number), the Lagoon Nebula (M8), and the Trifid Nebula (M20).
	fusedweb.pppl.gov /CPEP/Chart_Pages/5.Plasmas/Nebula/Emission.html (459 words)

	M-17, Omega Nebula (Site not responding. Last check: 2007-11-06)
		It is known as the "Omega Nebula" or the "Swan Nebula".
		Sir William Huggins, in 1866, was the first to study the light of M-17 with the spectroscope; he announced that the cloud was truly a mass of glowing gas, and not merely an unresolved cluster of stars.
		It requires only the slightest use of the imagination to transform this pattern into the graceful figure of a celestial swan floating in a pool of stars.......The space enclosed by the neck of the swan is evidently an obscuring cloud of some sort, and looks quite dark when compared to the star-strewn sky beyond.
	www.kopernik.org /images/archive/m17.htm (368 words)

	Gary & Jake - Astronomical Glossary
		Stars are formed when diffuse nebulae collapse under the influence of gravity, compressing and heating until nuclear fusion begins, igniting a new-born star.
		Nebula -- Nebulae (plural of nebula) are large interstellar clouds of dust and gas.
		Reflection nebula -- Reflection nebulae are illuminated solely by reflecting the light of nearby stars.
	www.garyandjake.com /glossary.php (675 words)

	Nebulae - Crystalinks
		One of the most famous objects in the sky, the Horsehead Nebula is a dark nebula only seen because of the reflection nebula, IC 434, that shines brightly behind it.
		The other prominent nebula in the bottom center of the image is the Flame Nebula, NGC 2024.
		Sadr is the central star of the Northern Cross and is surrounded by tremendous amounts of emission nebulosity.
	www.crystalinks.com /nebula.html (899 words)

	Iowa Robotic Telescope Facilities
		Nebulae are clouds of dust and gas, and come in nearby stars.
		emission nebula is formed of gas and shines because it is hot.
		Next choose a point at the edge of the nebula, and record the x and y coordinates of this point.
	phobos.physics.uiowa.edu /curriculum/orion.html (1111 words)

	Really Hot Stars (ESO Press Release 08/03)
		In three nebulae, they succeeded in identifying the sources of energetic radiation and to eludicate their exceptional properties: some of the hottest, most massive stars ever seen, some of which are double.
		Nebulae are huge clouds of gas and dust, the cosmic material from which stars and planets form, cf.
		Nebulae are huge clouds of gas and dust, the cosmic material from which stars and planets form.
	www.eso.org /outreach/press-rel/pr-2003/pr-08-03.html (3317 words)

	New frames inhoud
		Because the nuclear fuel of the star almost is exhausted, the delicate equilibrium between gravity - containing all mass to the star - and the 'outside push' of the nuclear fusion - is distorted to the disadvantage of the gravitational power.
		The nebula itself will last for a few tens of thousand years; it will then fade away, leaving its cooling progenitor star as a dead remnant dwarf star.
		The indication 'planetary nebula' stems from the 19th century, where this kind of nebulae, viewed in the telescopes of that time, ressembled planets, so they were called: 'planetary nebulae'.
	www.xs4all.nl /~acvwpcd/nebulae.htm (927 words)

	Diffuse Nebulae
		Note that many emission nebulae also have an additional reflection nebula component (as they usually also contain dust); a most impressive example for this is the Trifid Nebula M20.
		Diffuse nebulae were longly be considered as distant, unresolved star clusters or star clouds, until in the 1860s spectroscopy revealed their gaseous nature by showing line spectra, in particular due to the pioneering research of William Huggins.
		Of Messier's nebulae, M78 is the only pure reflection nebula, and the first of these objects to be discovered; its nature as a reflection nebula was revealed in 1919, again by V.M. Slipher.
	www.seds.org /messier/diffuse.html (547 words)

	Emission Nebulae (Site not responding. Last check: 2007-11-06)
		Emission nebulae are so named because their light is emitted from gas excited by energetic radiation from nearby hot stars.
		The nebulae in Orion feature extensively in this collection because, at 1500 light years distant, they are among the closest of the Galaxy's star-forming regions.
		The Cone Nebula in the NGC 2264 cluster
	triton.elk.itu.edu.tr /~batman/astronom/astro_img/emission.html (149 words)

	Horsehead Nebula (Site not responding. Last check: 2007-11-06)
		The dark nebula that forms the Horsehead itself is known as Barnard 33 (B 33).
		The red background is the emission nebula IC 434, the reflection nebula NGC 2023 and the emission nebula are NGC 2024 also visible.
		The dark lanes in NGC 2024 may be part of the same dark nebula that forms the Horsehead.
	astroa.physics.metu.edu.tr /twn/b33x.html (102 words)

	M-43, part of the Orion Nebula
		M-43 is a bright emission nebula that appears in a small telescope as the detached northern portion of the Great Orion Nebula (M-42).
		It is the raindrop shaped nebula in the center of the image above, and it surrounds a 9th magnitude star.
		M-43, and the rest of the Orion Nebula, is itself only a portion of a larger nebuar complex of glowing gas, dark molecular clouds, and thousands of newly forming stars.
	www.kopernik.org /images/archive/m43.htm (265 words)

	Multiwavelength Messier 17
		Messier 17 is a diffuse emission nebula in the constellation of Sagittarius, and is known by a variety of other names, including the Omega Nebula.
		H II regions are the signposts for active star formation, and the peak of the radio emission is clearly in the same relative location as the far-infrared peak.
		The modest peak seen near the image center could be due to weak emission from the gas within the Omega Nebula, or it could originate from an un-cataloged background quasar.
	coolcosmos.ipac.caltech.edu /cosmic_classroom/multiwavelength_astronomy/multiwavelength_museum/m17.html (739 words)

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