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New General Catalogue (NGC) and Hubble Space Telescope (HST)
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NGC 4214: Star Forming Galax
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| Title |
NGC 4214: Star Forming Galaxy |
| Explanation |
Dazzling displays of star formation abound across the face of galaxy NGC 4214, a mere 13 million light-years away in the northern constellation Canes Venatici [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Canes_Venatici.html ]. While this 1997 Hubble Space Telescope image [ http://oposite.stsci.edu/pubinfo/pr/2000/01/pr-photos.html ] shows the numerous faint, older stars of NGC 4214 [ http://heritage.stsci.edu/public/2000jan6/ngc4214table.html ], the most eye-catching features are the galaxy's bright young star clusters surrounded by fluorescent gas clouds. Sculpted [ http://antwrp.gsfc.nasa.gov/apod/ap990930.html ] into bubbles and filamentary shapes by energetic explosions [ http://antwrp.gsfc.nasa.gov/apod/ap990515.html ] and stellar winds [ http://antwrp.gsfc.nasa.gov/apod/ap991130.html ] from massive cluster stars, the clouds fluoresce in the intense stellar ultraviolet radiation. The colorful [ http://www.c3.lanl.gov/mega-math/workbk/map/map.html ] spectacle of massive young star forming clusters and distinguished presence of a fainter, older stellar population indicate that NGC 4214 has experienced star formation [ http://observe.ivv.nasa.gov/nasa/exhibits/stellarbirth/ Star_index.html ] episodes spanning billions of years. |
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NGC 7635: The Bubble Nebula
| Title |
NGC 7635: The Bubble Nebula |
| Explanation |
What created this huge space bubble? A massive star [ http://antwrp.gsfc.nasa.gov/apod/ap971008.html ] that is not only bright and blue, but also emitting a fast stellar wind [ http://www-spof.gsfc.nasa.gov/Education/wsolwind.html ] of ionized gas [ http://www.unm.edu/~sgoold/Plasma.html ]. The Bubble Nebula [ http://heritage.stsci.edu/public/Oct22/bubble/NGC7635table.html ] is actually the smallest of three bubbles surrounding massive star BD+602522, and part of gigantic bubble network S162 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1995A%26A...295..509C ] created with the help of other massive stars. As fast moving gas expands off BD+602522, it pushes surrounding sparse gas into a shell [ http://antwrp.gsfc.nasa.gov/apod/ap990626.html ]. The energetic starlight then ionizes the shell, causing it to glow. The above picture [ http://oposite.stsci.edu/pubinfo/pr/2000/04/index.html ] taken with the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap970306.html ] and released [ http://oposite.stsci.edu/pubinfo/pr/2000/04/content/prc0004.txt ] last week shows many details of the Bubble Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap981118.html ] never seen before and many still not understood. The nebula, also known as NGC 7635 [ http://www.aao.gov.au/AAO/local/www/dfm/int010.html ], is about six light-years across and visible with a small telescope towards the constellation of Cassiopeia [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Cassiopeia.html ]. |
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NGC 1999: Reflection Nebula
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| Title |
NGC 1999: Reflection Nebula in Orion |
| Explanation |
A dusty bright nebula [ http://home.wxs.nl/~geldo006/brigneb.html ] contrasts dramatically with a dusty dark nebula in this Hubble Space Telescope image [ http://oposite.stsci.edu/pubinfo/pr/2000/10/index.html ] recorded shortly after December's orbital servicing mission [ http://hubble.gsfc.nasa.gov/ ]. The nebula [ http://oposite.stsci.edu/pubinfo/pr/2000/10/faq.html ], cataloged as NGC [ http://antwrp.gsfc.nasa.gov/apod/ap990429.html ] 1999, is a reflection nebula [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ], which shines by reflecting light from a nearby star. Unlike emission nebulae [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ], whose reddish glow [ http://antwrp.gsfc.nasa.gov/apod/ap980828.html ] comes from excited atoms of gas, reflection nebulae have a bluish cast [ http://www.physics.muni.cz/~ondra/mix/mix.html ] as their interstellar dust grains [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] preferentially reflect blue starlight. While perhaps the most famous reflection nebulae surround the bright young stars of the Pleiades [ http://antwrp.gsfc.nasa.gov/apod/ap000227.html ] star cluster, NGC 1999's stellar illumination is provided by the embedded variable star V380 [ http://donald.phast.umass.edu/research/comap/V380sm.html ] Orionis, seen here just left of center. Extending right of center, the ominous [ http://antwrp.gsfc.nasa.gov/apod/ap990226.html ] dark nebula [ http://antwrp.gsfc.nasa.gov/apod/dark_nebulae.html ] is actually a condensation of cold molecular gas and dust so thick and dense that it blocks light. From our perspective it lies in front of the bright nebula, silhouetted against the ghostly nebular glow. New stars [ http://dsnra.jpl.nasa.gov/origins/nyt.html ] will likely form within the dark cloud, called a Bok globule [ http://antwrp.gsfc.nasa.gov/apod/ap961229.html ], as self-gravity continues to compress its dense gas and dust. Reflection nebula NGC 1999 [ http://heritage.stsci.edu/public/ 2000mar2/ngc1999table.html ] lies about 1500 light-years away in the constellation Orion [ http://www.seds.org/messier/more/oricloud.html ], just south of Orion's well known emission nebula, M42 [ http://antwrp.gsfc.nasa.gov/apod/ap990522.html ]. |
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Open Cluster NGC 290: A Stel
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| Title |
Open Cluster NGC 290: A Stellar Jewel Box |
| Explanation |
Jewels don't shine this bright -- only stars do. Like gems in a jewel box, though, the stars of open cluster [ http://en.wikipedia.org/wiki/Open_cluster ] NGC 290 glitter in a beautiful display [ http://antwrp.gsfc.nasa.gov/apod/ap010618.html ] of brightness and color. The photogenic cluster, pictured above [ http://hubblesite.org/newscenter/newsdesk/archive/releases/2006/17/image/a ], was captured recently by the orbiting Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap021124.html ]. Open clusters of stars are younger, contain few stars, and contain a much higher fraction of blue stars than do globular clusters [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ] of stars. NGC 290 lies about 200,000 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] distant in a neighboring galaxy called the Small Cloud of Magellan [ http://antwrp.gsfc.nasa.gov/apod/ap050617.html ] (SMC). The open cluster [ http://antwrp.gsfc.nasa.gov/apod/ap060109.html ] contains hundreds of stars and spans about 65 light years across. NGC 290 and other open clusters are good laboratories for studying how stars of different masses evolve [ http://en.wikipedia.org/wiki/Stellar_evolution ], since all the open cluster's stars were born at about the same time. |
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NGC 2440: Cocoon of a New Wh
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| Title |
NGC 2440: Cocoon of a New White Dwarf |
| Explanation |
Like a butterfly, a white dwarf star begins its life by casting off a cocoon that enclosed its former self. In this analogy, however, the Sun would be a caterpillar and the ejected shell of gas would become the prettiest of all! In the above cocoon [ http://hubblesite.org/newscenter/newsdesk/archive/releases/1999/35/image/e ], the planetary nebula designated NGC 2440, contains one of the hottest white dwarf stars known. The white dwarf [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/dwarfs.html ] can be seen as the bright dot near the photo's center. Our Sun will eventually become a "white dwarf butterfly", but not for another 5 billion years. The above false color image [ http://heritage.stsci.edu/1999/38/ ] was post-processed by Forrest Hamilton [ http://heritage.stsci.edu/commonpages/infoindex/ourproject/f_hamilton.html ]. |
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Celebrating Hubble With NGC
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| Title |
Celebrating Hubble With NGC 6751 |
| Explanation |
Planetary nebulae do [ http://antwrp.gsfc.nasa.gov/apod/ap991023.html ] look simple, round, and planet-like in small telescopes. But images from the orbiting Hubble Space Telescope [ http://hubble.stsci.edu/ ] have become well known for showing these fluorescent gas shrouds [ http://antwrp.gsfc.nasa.gov/apod/ap991031.html ] of dying Sun-like stars to possess a staggering variety [ http://oposite.stsci.edu/pubinfo/pr/97/pn/index.html ] of detailed symmetries and shapes. This composite color Hubble image of NGC 6751 [ http://oposite.stsci.edu/pubinfo/pr/2000/12/index.html ] is a beautiful example of a classic planetary nebula with complex features and was selected to commemorate the tenth anniversary [ http://pao.gsfc.nasa.gov/gsfc/spacesci/hst10/hst_main.htm ] of Hubble in orbit. The colors were chosen to represent the relative temperature of the gas - blue, orange, and red indicating the hottest to coolest gas. Winds and radiation from the intensely hot central star [ http://antwrp.gsfc.nasa.gov/apod/ap990703.html ] (140,000 degrees [ http://www.unidata.ucar.edu/staff/ blynds/tmp.html ] Celsius [ http://www.cchem.berkeley.edu/ChemResources/ temperature.html ]) have apparently created the nebula's streamer-like features. The nebula's [ http://heritage.stsci.edu/public/2000apr6/ ngc6751table.html ] actual diameter is approximately 0.8 light-years or about 600 times the size [ http://antwrp.gsfc.nasa.gov/apod/ap990916.html ] of our solar system. NGC 6751 is 6,500 light-years distant in the constellation Aquila [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Aquila.html ]. |
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A Dust Cloud in NGC 281
| Title |
A Dust Cloud in NGC 281 |
| Explanation |
Stars themselves can create huge and intricate dust sculptures [ http://antwrp.gsfc.nasa.gov/apod/ap050425.html ] from the dense and dark molecular cloud [ http://antwrp.gsfc.nasa.gov/apod/ap060409.html ]s from which they are born. The tools the stars use to carve their detailed works are high energy light [ http://imagers.gsfc.nasa.gov/ems/uv.html ] and fast stellar winds [ http://antwrp.gsfc.nasa.gov/apod/ap000318.html ]. The heat they generate evaporates the dark molecular dust [ http://en.wikipedia.org/wiki/Interstellar_dust ] as well as causing ambient hydrogen [ http://periodic.lanl.gov/elements/1.html ] gas to disperse and glow [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] red. Pictured above [ http://hubblesite.org/newscenter/newsdesk/archive/releases/2006/13/image/a ], a new open cluster of stars designated IC 1590 is nearing completion around the intricate interstellar mountain [ http://antwrp.gsfc.nasa.gov/apod/ap050424.html ] named NGC 281 [ http://heritage.stsci.edu/2006/13/caption.html ]. The dust cloud NGC 281, dubbed the Pacman [ http://en.wikipedia.org/wiki/Pacman ] nebula because of its overall shape [ http://antwrp.gsfc.nasa.gov/apod/ap050823.html ], is classified as a dense Bok Globule [ http://antwrp.gsfc.nasa.gov/apod/ap030127.html ] that lies about 10,000 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] distant. |
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NGC 3314: When Galaxies Over
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| Title |
NGC 3314: When Galaxies Overlap |
| Explanation |
Can this be a spiral galaxy? In fact, NGC 3314 [ http://oposite.stsci.edu/pubinfo/pr/2000/14/index.html ] consists of two large spiral galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap980314.html ] which just happen to almost exactly line-up. The foreground spiral is viewed nearly face-on, its pinwheel shape defined by young bright star clusters. But against the glow of the background galaxy, dark swirling lanes of interstellar dust [ http://antwrp.gsfc.nasa.gov/apod/ap980116.html ] are also seen [ http://antwrp.gsfc.nasa.gov/apod/ap971205.html ] to echo the face-on spiral's structure. The dust lanes [ http://antwrp.gsfc.nasa.gov/apod/ap990821.html ] are surprisingly pervasive, and this remarkable pair of [ http://www.astr.ua.edu/white/pairs/individual.html ] overlapping galaxies is one of a small number of systems in which absorption of visible light can be used to directly explore the distribution [ http://www.astr.ua.edu/white/pairs/thickthin.html ] of dust in distant spirals. NGC 3314 is [ http://heritage.stsci.edu/public/2000may11/about3314.html ] about 140 million light-years away in the southern constellation of Hydra [ http://www.astronomical.org/constellations/ hya.html ]. Just released [ http://heritage.stsci.edu/ ], this color composite was constructed from Hubble Space Telescope images made in 1999 and 2000. |
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Blue Stragglers In NGC 6397
| Title |
Blue Stragglers In NGC 6397 |
| Explanation |
In our neck of the Galaxy [ http://www.limber.org/globs.html ] stars are too far apart [ http://antwrp.gsfc.nasa.gov/apod/ap991211.html ] to be in danger of colliding, but in the dense cores of globular star clusters [ http://antwrp.gsfc.nasa.gov/apod/ap990312.html ] star collisions may be relatively common. In fact, researchers have evidence [ http://www.aas.org/publications/baas/v32n2/aas196/ 265.htm ] that the row of six closely spaced blue stars just below the label in this Hubble Space Telescope [ http://hubble.stsci.edu/ ] image were formed when stars directly collided. Pictured is the central region of NGC 6397 [ http://www.seds.org/messier/xtra/ngc/n6397.html ], a globular cluster [ http://www.seds.org/messier/glob.html ] about 6,000 light-years distant, whose stars [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/ stars.html ] all formed at about the same time. NGC 6397's [ http://dibonsmith.com/ngc6397.htm ] massive stars have long since evolved off the main sequence, exhausting their central supplies of nuclear fuel [ http://fusedweb.pppl.gov/default.html ]. This should leave the cluster with only old low mass stars, faint red main sequence stars and brighter blue and red giants [ http://plabpc.csustan.edu/astro/stars/giant.htm ]. However, spectroscopic data show that the indicated stars, descriptively dubbed blue stragglers [ http://antwrp.gsfc.nasa.gov/apod/ap971104.html ], are clearly main sequence stars which are too blue and too massive to still be there. Suggestively the stragglers appear to be two and occasionally three times as massive as the lower mass cluster stars otherwise present, supporting evidence [ http://www.boston.com/dailyglobe2/165/science/ Taking_measure_of_the_stars+.shtml ] for their formation from two and even three star collisions. |
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Barred Spiral Galaxy NGC 130
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| Title |
Barred Spiral Galaxy NGC 1300 |
| Explanation |
Big, beautiful, barred spiral galaxy NGC 1300 [ http://heritage.stsci.edu/2005/01/ supplemental.html ] lies some 70 million light-years away on the banks of the constellation Eridanus [ http://www.hawastsoc.org/deepsky/eri/index.html ]. This Hubble Space Telescope composite view [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2005/01/ ] of the gorgeous island universe is one of the largest Hubble images [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2005/01/image/a+warn ] ever made of a complete galaxy. NGC 1300 [ http://heritage.stsci.edu/2005/01/fast_facts.html ] spans over 100,000 light-years and the Hubble [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] image reveals striking details of the galaxy's dominant central bar and majestic spiral arms. In fact, on close inspection the nucleus of this classic barred [ http://csep10.phys.utk.edu/ astr162/lect/galaxies/hubble.html ] spiral itself shows a remarkable region of spiral structure [ http://antwrp.gsfc.nasa.gov/apod/ap030925.html ] about 3,000 light-years across. Unlike other spiral galaxies [ http://en.wikipedia.org/wiki/Spiral_galaxies ], including our own Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap050825.html ], NGC 1300 is not presently known to have a massive central black hole [ http://hubblesite.org/newscenter/newsdesk/archive/ releases/1997/01/text/ ]. |
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NGC 2440: Cocoon of a New Wh
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| Title |
NGC 2440: Cocoon of a New White Dwarf |
| Explanation |
Like a butterfly, a white dwarf star begins its life by casting off a cocoon that enclosed its former self. In this analogy, however, the Sun would be a caterpillar and the ejected shell of gas would become the prettiest of all! The above cocoon, the planetary nebula designated NGC 2440, contains one of the hottest white dwarf stars known. The white dwarf [ http://www.sciencenet.org.uk/database/Physics/Stars/p01158c.html ] can be seen as the bright dot near the photo's center. Our Sun will eventually become a "white dwarf butterfly", but not for another 5 billion years. The above false color image [ http://presto.stsci.edu/apsb/doc/pep/public-proposals/6119.pro ] and was post-processed by Forrest Hamilton [ http://heritage.stsci.edu/public/commonpages/heritagebios.html#forrest ]. |
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A Galaxy Collision in NGC 67
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| Title |
A Galaxy Collision in NGC 6745 |
| Explanation |
Galaxies don't normally look like this. NGC 6745 [ http://heritage.stsci.edu/public/2000nov2/ngc6745story.html ] actually shows the results of two galaxies that have been colliding [ http://antwrp.gsfc.nasa.gov/apod/ap990722.html ] for only hundreds of millions of years. Just off the above photograph [ http://hubblesite.org/newscenter/archive/releases/2000/2000/34/image/a/ ] to the lower right is the smaller galaxy, moving away. The larger galaxy, pictured above [ http://heritage.stsci.edu/public/2000nov2/ngc6745table.html ], used to be a spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] but now is damaged and appears peculiar [ http://antwrp.gsfc.nasa.gov/apod/ap980315.html ]. Gravity has distorted the shapes of the galaxies. Although it is likely that no stars in the two galaxies directly collided [ http://antwrp.gsfc.nasa.gov/apod/ap061024.html ], the gas, dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ], and ambient magnetic fields [ http://www-spof.gsfc.nasa.gov/Education/Imagnet.html ] do interact directly. In fact, a knot [ http://www.mckinnonsc.vic.edu.au/school/ties/ties.htm ] of gas pulled off the larger galaxy on the lower right has now begun to form stars. NGC 6745 [ http://en.wikipedia.org/wiki/NGC_6745 ] spans about 80 thousand light-years across and is located about 200 million light-years [ http://www.howstuffworks.com/question94.htm ] away. |
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A Galaxy Collision in NGC 67
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| Title |
A Galaxy Collision in NGC 6745 |
| Explanation |
Galaxies don't normally look like this. NGC 6745 [ http://heritage.stsci.edu/public/2000nov2/ngc6745story.html ] actually shows the results of two galaxies that have been colliding [ http://antwrp.gsfc.nasa.gov/apod/ap990722.html ] for only hundreds of millions of years. Just off the above photograph [ http://heritage.stsci.edu/public/2000nov2/displayngc6745.html ] to the lower right is the smaller galaxy, moving away. The larger galaxy, pictured above [ http://heritage.stsci.edu/public/2000nov2/ngc6745table.html ], used to be a spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] but now is damaged and appears peculiar [ http://antwrp.gsfc.nasa.gov/apod/ap980315.html ]. Gravity has distorted the shapes of the galaxies. Although it is likely that no stars in the two galaxies directly collided [ http://antwrp.gsfc.nasa.gov/apod/ap971022.html ], the gas, dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ], and ambient magnetic fields [ http://www-spof.gsfc.nasa.gov/Education/Imagnet.html ] do interact directly. In fact, a knot of gas pulled off the larger galaxy on the lower right has now begun to form stars. NGC 6745 [ http://heritage.stsci.edu/public/2000nov2/ngc6745table.html#facts ] spans about 80 thousand light-years across and is located about 200 million light-years [ http://www.howstuffworks.com/question94.htm ] away. |
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NGC 602 and Beyond
| Title |
NGC 602 and Beyond |
| Explanation |
Near the outskirts of the Small Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap050617.html ], a satellite galaxy some 200 thousand light-years distant, lies 5 million year young [ http://en.wikipedia.org/wiki/Stellar_evolution ] star cluster NGC 602. Surrounded by natal gas and dust, NGC 602 is featured in this stunning Hubble image [ http://hubblesite.org/newscenter/archive/releases/ 2007/04/ ] of the region. Fantastic [ http://antwrp.gsfc.nasa.gov/apod/ap061227.html ] ridges and swept back shapes strongly suggest that energetic radiation and shock waves from NGC 602's massive young stars have eroded the dusty material and triggered a progression of star formation [ http://heritage.stsci.edu/2007/04/supplemental.html ] moving away from the cluster's center. At the estimated distance of the Small Magellanic Cloud, the picture spans about 200 light-years, but a tantalizing [ http://hubblesite.org/newscenter/archive/releases/2007/04/ image/a/format/zoom ] assortment of background galaxies are also visible in the sharp Hubble view. The background galaxies [ http://www.noao.edu/outreach/aop/observers/ bggalaxies.html ] are hundreds of millions of light-years or more beyond NGC 602. |
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The Star Clusters of NGC 131
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| Title |
The Star Clusters of NGC 1313 |
| Explanation |
Like grains of sand [ http://astronomy.swin.edu.au/staff/gmackie/billions.html ] on a cosmic beach, individual stars of barred spiral galaxy NGC 1313 [ http://antwrp.gsfc.nasa.gov/apod/ap061128.html ] are resolved in this sharp composite [ http://hubblesite.org/newscenter/archive/releases/2007/05/ ] from the Hubble Space Telescope's Advanced Camera for Surveys (ACS [ http://hubblesite.org/sci.d.tech/nuts_.and._bolts/ instruments/acs/ ]). The inner region of the galaxy is pictured [ http://hubblesite.org/newscenter/archive/releases/2007/05/ fastfacts/ ], spanning about 10,000 light-years. Hubble's unique ability to distinguish individual stars in the 14 million light-year distant galaxy has been used to unravel the fate [ http://en.wikipedia.org/wiki/Open_cluster#Eventual_fate ] of star clusters whose bright young stars are spread through the disk of the galaxy as the clusters dissolve [ http://arxiv.org/abs/astro-ph/0610798 ]. The exploration [ http://hubblesite.org/newscenter/archive/releases/2007/05/ full/ ] of stars and clusters in external galaxy NGC 1313 offers clues to star formation and star cluster evolution [ http://antwrp.gsfc.nasa.gov/apod/ap051118.html ] in our own Milky Way. |
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Planetary Nebula NGC 2440
| Title |
Planetary Nebula NGC 2440 |
| Explanation |
Planetary nebula [ http://en.wikipedia.org/wiki/Planetary_nebula ] NGC 2440 has an intriguing bow-tie [ http://www.folds.net/bowtie/ ] shape in this stunning view [ http://hubblesite.org/newscenter/archive/releases/2007/09/ ] from space. The nebula is composed of material cast off by a dying sun-like star as it enters its white dwarf phase [ http://antwrp.gsfc.nasa.gov/apod/ap060507.html ] of evolution. Details of remarkably complex structures are revealed within [ http://adsabs.harvard.edu/abs/1998ApJ...493..803L ] NGC 2440, including dense ridges of material swept back from the nebula's central star. Near the center of the view, the star itself is one of the hottest known [ http://antwrp.gsfc.nasa.gov/apod/ap951130.html ], with a surface temperature of about 200,000 kelvins [ http://lamar.colostate.edu/~hillger/temps.htm ]. About 4,000 light-years from planet Earth toward the nautical constellation Puppis [ http://hawastsoc.org/deepsky/pup/index.html ], the nebula spans over a light-year and is energized by ultraviolet light from the central star. The false-color image [ http://archive.stsci.edu/prepds/heritage/ngc2440/index.html ] was recorded earlier this month using the Hubble's Wide-Field Planetary Camera 2(WFPC2), demonstrating still impressive imaging capabilities following the failure of the Advanced Camera for Surveys. |
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NGC 1410/1409: Intergalactic
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| Title |
NGC 1410/1409: Intergalactic Pipeline |
| Explanation |
These two galaxies [ http://oposite.stsci.edu/pubinfo/PR/2001/02/index.html ] are interacting in a surprising way, connected by a "pipeline" of obscuring material that runs between them over 20,000 light-years of intergalactic space. Silhouetted [ http://antwrp.gsfc.nasa.gov/apod/ap000511.html ] by starlight, the dark, dusty ribbon appears to stretch from NGC 1410 (the galaxy at the left) and wrap itself around NGC 1409 (at right). A mere 300 million light-years distant in the constellation of Taurus [ http://aibn47.astro.uni-bonn.de/~gallery/constellations/ taurus/ ], the pair's recent collision has likely drawn out this relatively thin lane of material which is only about 500 light-years wide. Though the Hubble Space Telescope image dramatically illustrates [ http://www.astr.ua.edu/keel/research/ngc1410.html ] how galaxies exchange matter when they collide, it also presents challenges to current pictures of galaxy evolution [ http://oposite.stsci.edu/pubinfo/PR/97/34/ af3.html ]. The titanic collision has [ http://antwrp.gsfc.nasa.gov/apod/ap981219.html ] triggered star formation in NGC 1410 as evidenced by its blue star forming regions, yet NGC 1409 remains devoid of hot, young blue stars [ http://oposite.stsci.edu/pubinfo/PR/97/34/af4.html ] even though observations indicate that material is flowing into it. Bound by gravity, these two [ http://www.astr.ua.edu/white/pairs/individual.html ] galaxies are doomed to future collisions, merging [ http://oposite.stsci.edu/pubinfo/PR/97/34/ index.html#Animations ] over time into one. |
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Spiral Galaxy NGC 3310 in Ul
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| Title |
Spiral Galaxy NGC 3310 in Ultraviolet |
| Explanation |
Why is NGC 3310 bursting with young stars? The brightest of these new stars are so hot that they light up this spiral galaxy not only in blue light, but in light so blue humans can't see it: ultraviolet [ http://snoopy.gsfc.nasa.gov/~orfeus2/ultraviolet.html ]. The Hubble Space Telescope [ http://www.stsci.edu/hst/ ] took the above photograph [ http://oposite.stsci.edu/pubinfo/PR/2001/04/index.html ] in different bands of ultraviolet light. Speculation holds that NGC 3310 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1996ApJ...473L..21S ] collided with one of its own dwarf companion galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap991003.html ] only about 50 million years previously. This merger sent density waves [ http://fuse.pha.jhu.edu/~danforth/spiral/ ] rippling around the spiral disk, causing many gas clouds to condense into star forming regions. Imaging nearby galaxies in ultraviolet light [ http://oposite.stsci.edu/pubinfo/PR/2001/04/fastfacts.html ] allows astronomers to better understand the images of distant highly redshift [ http://www.astro.virginia.edu/~jh8h/glossary/redshift.htm ]ed galaxies in visible light, and so to understand why many of these distant galaxies appear relatively fragmented [ http://antwrp.gsfc.nasa.gov/apod/ap000709.html ]. The unusually smooth NGC 3310 [ http://oposite.stsci.edu/pubinfo/PR/2001/04/content/prc0104.txt ] spans over 20 thousand light years [ http://www.howstuffworks.com/question94.htm ] and lies about 50 million light years away towards the constellation of Ursa Major [ http://www.astronomical.org/constellations/uma.html ]. |
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Barred Spiral Galaxy NGC 167
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| Title |
Barred Spiral Galaxy NGC 1672 |
| Explanation |
Many spiral galaxies have bars across their centers. Even our own Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap000130.html ] is thought to have a modest central bar [ http://antwrp.gsfc.nasa.gov/apod/ap050825.html ]. Prominently barred spiral galaxy NGC 1672, pictured above [ http://hubblesite.org/newscenter/archive/releases/2007/15/image/a/ ], was captured in spectacular detail in this recently released image taken by the orbiting Hubble Space Telescope [ http://en.wikipedia.org/wiki/Hubble_Space_Telescope ]. Visible are dark filamentary dust lanes [ http://antwrp.gsfc.nasa.gov/apod/ap060219.html ], young clusters [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] of bright blue stars, red emission nebulas [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] of glowing hydrogen gas, a long bright bar of stars across the center, and a bright active nucleus [ http://en.wikipedia.org/wiki/Active_galactic_nucleus ] that likely houses a supermassive black hole [ http://antwrp.gsfc.nasa.gov/htmltest/rjn_bht.html ]. Light takes about 60 million years to reach us from NGC 1672 [ http://heritage.stsci.edu/2007/15/caption.html ], which spans about 75,000 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] across. NGC 1672, which appears toward the constellation of the Swordfish (Dorado [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=33 ]), is being studied [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004hst..prop.6669J ] to find out how a spiral bar contributes to star formation in a galaxy's central regions. |
|
Barred Spiral Galaxy NGC 290
…
| Title |
Barred Spiral Galaxy NGC 2903 |
| Explanation |
NGC 2903 is a spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] similar to our own Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ]. Similarities include its general size and a central bar [ http://antwrp.gsfc.nasa.gov/apod/ap001004.html ]. One striking difference, however, is the appearance of mysterious hot spots [ http://antwrp.gsfc.nasa.gov/apod/ap010321.html http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1991ApJ...375..105J ] in NGC 2903's core. Upon inspection of the above image [ http://hubble.esa.int/hubble/news/imagecollection.cfm?oid=26173 ] and similar images taken by the Hubble Space Telescope, these hot spots [ http://hubble.esa.int/hubble/news/newsrelease.cfm?oid=26173 ] were found to be bright young globular clusters [ http://antwrp.gsfc.nasa.gov/apod/ap010311.html ], in contrast to the uniformly old globular clusters [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ] found in our Milky Way Galaxy [ http://www.seds.org/messier/more/mw.html ]. Further investigation [ http://arXiv.org/abs/astro-ph/0010522 ] has indicated that current star formation [ http://www.sciam.com/exhibit/102797stellar/hall.html ] is most rampant in a 2000 light-year [ http://chandra.harvard.edu/photo/cosmic_distance.html ] wide circumnuclear ring [ http://antwrp.gsfc.nasa.gov/apod/ap991212.html ] surrounding NGC 2903's center. Astronomers hypothesize [ http://hubble.esa.int/hubble/news/newsrelease.cfm?oid=26173 ] that the gravity of the central bar expedites star formation in this ring. NGC 2903 [ http://www.astro.princeton.edu/~frei/Gcat_htm/Sub_sel/gal_2903.htm ] lies about 25 million light-years [ http://www.pa.msu.edu/sci_theatre/ask_st/012292.html ] away and is visible with a small telescope towards the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Leo [ http://www.astronomical.org/constellations/leo.html ]. |
|
NGC 6302: Big, Bright, Bug N
…
| Title |
NGC 6302: Big, Bright, Bug Nebula |
| Explanation |
The bright clusters and nebulae of planet Earth's night sky are often named [ http://antwrp.gsfc.nasa.gov/apod/ap010205.html ] for flowers [ http://antwrp.gsfc.nasa.gov/apod/ap011214.html ] or insects [ http://insects.org/ ], and NGC 6302 [ http://antwrp.gsfc.nasa.gov/apod/ap980602.html ] is no exception. With an estimated surface temperature of about 250,000 degrees C, the central star of this particular planetary [ http://antwrp.gsfc.nasa.gov/apod/ap040207.html ] nebula is exceptionally hot though -- shining brightly in ultraviolet light but hidden from direct view by a dense torus of dust. Above is a dramatically detailed close-up [ http://hubble.esa.int/science-e/www/object/ index.cfm?fobjectid=34998 ] of the dying star's nebula [ http://www.aao.gov.au/images/captions/aat011.html ] recorded by the Hubble Space Telescope. Cutting across a bright cavity of ionized gas, the dust torus surrounding the central star is in the upper right corner of this view, nearly edge-on to the line-of-sight. Molecular hydrogen has recently been detected [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005hris.conf..423M ] in this hot star's dusty cosmic shroud. NGC 6302 lies about 4,000 light-years away in the arachnologically [ http://www.arachnology.org/Arachnology/ Arachnology.html ] correct constellation Scorpius [ http://hawastsoc.org/deepsky/sco/index.html ]. |
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New Stars Destroying NGC 174
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| Title |
New Stars Destroying NGC 1748 |
| Explanation |
NGC 1748 cannot contain all the new stars it has formed. The young stars, the most massive of which are bright blue [ http://antwrp.gsfc.nasa.gov/apod/ap010207.html ], emit so much energy they are pushing out and dispersing the gas and dust [ http://eta.pha.jhu.edu/~danforth/superfit/superfit.html ] that comprise this star forming nebula [ http://oposite.stsci.edu/pubinfo/PR/2001/11/pr-photos.html ]. Within only the past hundred thousand years, these stars have altered the bubble-like shape [ http://antwrp.gsfc.nasa.gov/apod/ap981118.html ] of the nebula and will likely destroy the nebula over the next few million years. Of particular interest [ http://arXiv.org/abs/astro-ph/0103414 ] is a bright region surrounded by a pink ring of dust [ http://antwrp.gsfc.nasa.gov/apod/ap980104.html ] and gas visible on the left of the above recently released picture [ http://hubble.esa.int/hubble/news/index.cfm?oid=26615 ] by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap970306.html ]. The center of this region is being evacuated by the wind [ http://www-spof.gsfc.nasa.gov/Education/wsolwind.html ] of the brightest star in the nebula. A lane of cooler dust connects NGC 1748 to a larger more diffuse nebula seen on the right. NGC 1748 [ http://oposite.stsci.edu/pubinfo/PR/2001/11/fastfacts.html ] spans about 25 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] in diameter and can be found in our galactic neighbor: the Large Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap000222.html ]. |
|
NGC 4449: Close-Up of a Smal
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| Title |
NGC 4449: Close-Up of a Small Galaxy |
| Explanation |
Grand spiral galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap030524.html ] often seem to get all the glory. Their newly formed, bright, blue star clusters along beautiful, symmetric spiral arms [ http://antwrp.gsfc.nasa.gov/apod/ap070706.html ] are guaranteed to attract attention. But small irregular galaxies form stars too, like NGC 4449 [ http://www.seds.org/~spider/spider/Misc/n4449.html ], located about 12 million light-years away. In fact, this sharp Hubble [ http://heritage.stsci.edu/2007/26/ ] Space Telescope close-up of the well-studied [ http://arxiv.org/abs/astro-ph/0010515 ] galaxy clearly demonstrates that reddish star forming regions and young blue star clusters are widespread [ http://hubblesite.org/newscenter/archive/releases/2007/26/ image/a/format/zoom/ ]. Less than 20,000 light-years across, the small island universe is similar in size, and often compared [ http://heritage.stsci.edu/2007/26/supplemental.html ] to our Milky Way's satellite galaxy, the Large Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap060510.html ]. NGC 4449 is a member of a group of galaxies [ http://www.atlasoftheuniverse.com/galgrps/cvni.html ] found in the constellation Canes Venatici. |
|
NGC 6826: The Blinking Eye
| Title |
NGC 6826: The Blinking Eye |
| Explanation |
The colorful planetary nebula phase [ http://www.astro.washington.edu/balick/WFPC2/ ] of a sun-like star's life is brief [ http://oposite.stsci.edu/pubinfo/PR/97/38/astrofile1.html ]. Almost in the "blink of an eye" - cosmically speaking - the star's outer layers are cast off, forming an expanding emission nebula. This nebula lasts perhaps 10 thousand years compared to a 10 billion year stellar life span. Spectacular planetary nebulae [ http://oposite.stsci.edu/pubinfo/PR/97/38.html ] are familiar objects to both professional and amateur astronomers, but they still contain a few surprises. For instance, the lovely nebula NGC 6826 [ http://www.astro.washington.edu/balick/WFPC2/n6826.caption.html ], also known as the Blinking Eye Nebula, has mysterious red FLIERS [ http://antwrp.gsfc.nasa.gov/apod/ap961122.html ] seen on either side of the Hubble Space Telescope image above. Are they also expanding outward from the central star? If so, their "bow shocks" [ http://antwrp.gsfc.nasa.gov/apod/ap971203.html ] point in the wrong direction! |
|
NGC 1512: A Panchromatic Vie
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| Title |
NGC 1512: A Panchromatic View |
| Explanation |
This spectacular [ http://oposite.stsci.edu/pubinfo/PR/2001/16/index.html ] color picture of the core of barred spiral galaxy NGC 1512 [ http://oposite.stsci.edu/pubinfo/PR/2001/16/fastfacts.html ] (bottom panel) is a composite of the seven Hubble Space Telescope images arrayed along the top. Each top panel image [ http://oposite.stsci.edu/pubinfo/PR/2001/16/extra-photos.html ] was made with a filter and camera sensitive to a different wavelength band in the electromagnetic spectrum [ http://hubble.stsci.edu/sci.d.tech/nuts_.and._bolts/ spec101.shtml ]. Arranged by increasing wavelength, at the far left are two ultraviolet images from Hubble's Faint Object Camera [ http://hubble.stsci.edu/sci.d.tech/nuts_.and._bolts/ instruments/foc/ ]. Next are two visible light images from its Wide Field Planetary Camera 2 [ http://hubble.stsci.edu/sci.d.tech/nuts_.and._bolts/ instruments/wfpc2/ ], followed on the right by three infrared images from the Near Infrared Camera and Multi-Object Spectrograph [ http://hubble.stsci.edu/sci.d.tech/nuts_.and._bolts/ instruments/nicmos/index.shtml ]. To make a pleasing composite color image [ http://aibn47.astro.uni-bonn.de/~gallery/articles/ imagecolor.html#map ], blue tones were assigned to the invisible ultraviolet, greenish colors were used for the visible bands, and yellow/red for the invisible infrared band images. These images show that the center of NGC 1512 appears dramatically altered when viewed in different wavelength bands. In particular, the ultraviolet images highlight clusters of young, hot stars in a ring 2,400 light-years wide surrounding the core. What caused this cosmic starburst [ http://antwrp.gsfc.nasa.gov/apod/ap991212.html ] ring? |
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NGC 3132: The Eight Burst Ne
…
| Title |
NGC 3132: The Eight Burst Nebula |
| Explanation |
It's the dim star, not the bright one, near the center of NGC 3132 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997AAS...191.1508S&db_key=AST&high=34f6e1de7f27502 ] that created this odd but beautiful planetary nebula [ http://www.seds.org/messier/planetar.html ]. Nicknamed the Eight-Burst Nebula and the Southern Ring Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap000716.html ], the glowing gas originated in the outer layers [ http://antwrp.gsfc.nasa.gov/apod/ap010301.html ] of a star like our Sun [ http://www.nineplanets.org/sol.html ]. In this representative color picture [ http://heritage.stsci.edu/public/Nov5/NGC3132table.html ], the hot blue pool of light seen surrounding this binary system [ http://antwrp.gsfc.nasa.gov/apod/ap970219.html ] is energized by the hot surface of the faint star. Although photographed to explore [ http://archive.stsci.edu/cgi-bin/prop_search?6221 ] unusual symmetries, it's the asymmetries that help make this planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ] so intriguing. Neither the unusual shape of the surrounding cooler shell nor the structure and placements of the cool filamentary dust lanes [ http://antwrp.gsfc.nasa.gov/apod/ap990919.html ] running across NGC 3132 [ http://heritage.stsci.edu/public/Nov5/n3132filters.html ] are well understood. |
|
Spiral Galaxy NGC 7742
| Title |
Spiral Galaxy NGC 7742 |
| Explanation |
This might resemble [ http://oposite.stsci.edu/pubinfo/pr/1998/28/index.html ] a fried egg you've had for breakfast [ http://antwrp.gsfc.nasa.gov/apod/ap980320.html ], but it's actually much larger. In fact, ringed by blue-tinted star forming [ http://antwrp.gsfc.nasa.gov/apod/ap980701.html ] regions and faintly visible spiral arms [ http://antwrp.gsfc.nasa.gov/apod/ap000920.html ], the yolk-yellow center of this face-on spiral galaxy, NGC 7742, is about 3,000 light-years across. About 72 million light-years [ http://www.treasure-troves.com/astro/Light-Year.html ] away in the constellation Pegasus [ http://www.seds.org/Maps/Stars_en/Fig/pegasus.html ], NGC 7742 is known to be a Seyfert galaxy [ http://www.astro.soton.ac.uk/PH308/AGN/Seyferts.html ] - a type of active spiral galaxy [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/active_galaxies.html ] with a center or nucleus which is very bright at visible wavelengths [ http://amazing-space.stsci.edu/light/index.html ]. Across the spectrum, the tremendous brightness [ http://seds.lpl.arizona.edu/messier/more/m077_hst.html ] of Seyferts [ http://www.seds.org/~spider/spider/ScholarX/seyferts.html ] can change over periods of just days to months and galaxies like NGC 7742 are suspected of harboring massive black holes at their cores [ http://oposite.stsci.edu/pubinfo/pr/97/18.html ]. This beautiful color picture is courtesy of the Hubble Space Telescope Heritage Project [ http://heritage.stsci.edu/public/commonpages/subjectindex.html ]. |
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Hot Gas Halo Detected Around
…
| Title |
Hot Gas Halo Detected Around Galaxy NGC 4631 |
| Explanation |
Is our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ] surrounded by a halo of hot gas? A step toward solving this long-standing mystery was taken recently with Chandra [ http://www1.msfc.nasa.gov/NEWSROOM/background/facts/cxoquick.htm ] X-ray observations of nearby galaxy NGC 4631 [ http://www.seds.org/messier/xtra/ngc/n4631.html ]. In the above composite picture [ http://chandra.harvard.edu/photo/cycle1/1138/index.html ], newly resolved diffuse X-ray [ http://chandra.harvard.edu/edu/chandra1012.html ] emission is shown in blue, superposed on an HST [ http://www.stsci.edu/hst/ ] image showing massive stars in red. Since NGC 4631 [ http://www.allthesky.com/galaxies/ngc4631.html ] is similar to the Milky Way [ http://www.seds.org/messier/more/mw.html ], this observation indicates [ http://xxx.lanl.gov/abs/astro-ph/0105541 ] that our own Galaxy is indeed surrounded by a halo of hot X-ray emitting gas, although we are too close to clearly differentiate it from more nearby [ http://antwrp.gsfc.nasa.gov/apod/ap000412.html ] extended X-ray sources. The clusters of massive stars [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] probably heat the halo [ http://antwrp.gsfc.nasa.gov/apod/ap971105.html ] gas. Exactly how this gas gets ejected into a halo is a topic of continuing research [ http://antwrp.gsfc.nasa.gov/apod/ap000207.html ]. |
|
NGC 1850: Not Found in the M
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| Title |
NGC 1850: Not Found in the Milky Way |
| Explanation |
A mere 168,000 light-years distant, this large, lovely cluster of stars, NGC 1850 [ http://antwrp.gsfc.nasa.gov/apod/ap000729.html ], is located near the outskirts of the central bar structure in our neighboring galaxy, the Large Magellanic Cloud [ http://www.seds.org/messier/xtra/ngc/lmc.html ]. A first glance at this [ http://oposite.stsci.edu/pubinfo/PR/2001/25/fastfacts.html ] Hubble Space Telescope composite image suggests [ http://oposite.stsci.edu/pubinfo/PR/2001/25/index.html ] that this cluster's size and shape are reminiscent of the ancient globular star clusters which roam our own Milky Way Galaxy's halo [ http://www.limber.org/globs.html ]. But NGC 1850's stars are young ... making it a type of star cluster [ http://csep10.phys.utk.edu/guidry/violence/ starclusters.html ] with no known counterpart in the Milky Way [ http://www.seds.org/messier/glob.html ]. NGC 1850 is also a double star cluster, with a second, compact cluster of stars visible here below and to the right of the large cluster's central region. Stars in the large cluster are estimated to be 50 million years young [ http://oposite.stsci.edu/pubinfo/PR/97/34/af4.html ], while stars in the compact cluster are younger still, with an age of about 4 million years. In fact, the smaller cluster contains T-Tauri stars [ http://xxx.lanl.gov/abs/astro-ph/0106321 ], thought to be low mass, solar-type stars still in the process [ http://etacha.as.arizona.edu/~eem/ttau/ ] of formation. The glowing nebula at the left, like the supernova remnants [ http://antwrp.gsfc.nasa.gov/apod/ap010623.html ] in our own galaxy, testifies to [ http://www.eso.org/outreach/press-rel/pr-1999/ phot-15-99.html ] violent stellar explosions, indicating short-lived massive stars [ http://antwrp.gsfc.nasa.gov/apod/ap991130.html ] were also present in NGC 1850 [ http://antwrp.gsfc.nasa.gov/apod/ap001224.html ]. |
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NGC 2440: Cocoon of a New Wh
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| Title |
NGC 2440: Cocoon of a New White Dwarf |
| Explanation |
Like a butterfly, a white dwarf star begins its life by casting off a cocoon that enclosed its former self. In this analogy, however, the Sun would be a caterpillar and the ejected shell of gas would become the prettiest of all! The above cocoon, the planetary nebula designated NGC 2440, contains one of the hottest white dwarf stars known. The white dwarf [ http://www.sciencenet.org.uk/database/Physics/Stars/p01158c.html ] can be seen as the bright dot near the photo's center. Our Sun will eventually become a "white dwarf butterfly", but not for another 5 billion years. The above false color image [ http://presto.stsci.edu/apsb/doc/pep/public-proposals/6119.pro ] and was post-processed by Forrest Hamilton [ http://heritage.stsci.edu/public/commonpages/heritagebios.html#forrest ]. |
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The Bubbling Cauldron of NGC
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| Title |
The Bubbling Cauldron of NGC 3079 |
| Explanation |
Edge-on [ http://antwrp.gsfc.nasa.gov/apod/ap010510.html ] spiral galaxy NGC 3079 is a mere 50 million light-years away toward the constellation Ursa Major. Shown in this [ http://oposite.stsci.edu/pubinfo/PR/2001/28/ index.html ] stunning false-color Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] image, the galaxy's disk - composed of spectacular star clusters in winding spiral arms and dramatic dark lanes of dust - spans some [ http://heasarc.gsfc.nasa.gov/docs/cosmic/cosmic.html ] 70,000 light-years. Still, NGC 3079's [ http://oposite.stsci.edu/pubinfo/PR/2001/28/ fastfacts.html ] most eye-catching features are the pillars of gas which tower above a swirling cosmic cauldron of activity at the galaxy's center. Seen in the close-up inset at lower right, the pillars rise to a height of about 2,000 light-years and seem to lie on the surface of an immense bubble rising from the galactic core. Measurements indicate that the gaseous pillars are streaming away from the core at 6 million kilometers per hour. What makes [ http://oposite.stsci.edu/pubinfo/PR/2001/28/ faq.html ] this galaxy's cauldron bubble [ http://tech-two.mit.edu/Shakespeare/macbeth/ macbeth.4.1.html ]? Astronomers are exploring [ http://xxx.lanl.gov/abs/astro-ph/0101010 ] the possibility that the superbubble [ http://antwrp.gsfc.nasa.gov/apod/ap991130.html ] is formed by winds [ http://www.physics.unc.edu/~cecil/science.html ] from massive stars. If so, these massive stars were likely born all at once as the galactic center underwent a sudden burst [ http://antwrp.gsfc.nasa.gov/apod/ap010124.html ] of star formation. |
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Starburst Cluster in NGC 360
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| Title |
Starburst Cluster in NGC 3603 |
| Explanation |
A mere 20,000 light-years from the Sun lies NGC 3603 [ http://www.univie.ac.at/webda/cgi-bin/ ocl_page.cgi?cluster=NGC+3603 ], a resident of the nearby Carina spiral arm of our Milky Way Galaxy [ http://www.atlasoftheuniverse.com/milkyway.html ]. NGC 3603 is [ http://antwrp.gsfc.nasa.gov/apod/ap020814.html ] well known to astronomers as one of the Milky Way's largest star-forming regions. The central open star cluster contains thousands of stars more massive than our Sun, stars that likely formed only one or two million years ago in a single burst of star formation. In fact, nearby NGC 3603 [ http://hubblesite.org/newscenter/archive/releases/2007/34/image/ a/format/zoom/ ] is thought to contain a convenient example of the massive star clusters that populate much more distant starburst galaxies [ http://casswww.ucsd.edu/public/tutorial/Starbursts.html ]. Surrounding the cluster [ http://heritage.stsci.edu/2007/34/supplemental.html ] are natal clouds of glowing interstellar gas and obscuring dust, sculpted by energetic stellar radiation and winds. Recorded by [ http://heritage.stsci.edu/2007/34/fast_facts.html ] the Hubble's Advanced Camera for Surveys, the image spans about 17 light-years. |
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NGC 3132: The Eight Burst Ne
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| Title |
NGC 3132: The Eight Burst Nebula |
| Explanation |
It's the dim star, not the bright one, near the center of NGC 3132 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query? bibcode=1997AAS...191.1508S ] that created this odd but beautiful planetary nebula [ http://www.seds.org/messier/planetar.html ]. Nicknamed the Eight-Burst Nebula [ http://en.wikipedia.org/wiki/NGC_3132 ] and the Southern Ring Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap060625.html ], the glowing gas originated in the outer layers [ http://antwrp.gsfc.nasa.gov/apod/ap010301.html ] of a star like our Sun [ http://www.nineplanets.org/sol.html ]. In this representative color picture [ http://heritage.stsci.edu/1998/39/supplemental.html ], the hot blue pool of light seen surrounding this binary system [ http://antwrp.gsfc.nasa.gov/apod/ap970219.html ] is energized by the hot surface of the faint star. Although photographed to explore [ http://hubblesite.org/newscenter/archive/releases/1998/39/image/a/ ] unusual symmetries, it's the asymmetries that help make this planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ] so intriguing. Neither the unusual shape of the surrounding cooler shell nor the structure and placements of the cool filamentary dust lanes [ http://antwrp.gsfc.nasa.gov/apod/ap020703.html ] running across NGC 3132 [ http://heritage.stsci.edu/1998/39/index.html ] are well understood. |
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Spiral Galaxy NGC 3310 Acros
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| Title |
Spiral Galaxy NGC 3310 Across the Visible |
| Explanation |
The party is still going on in spiral galaxy NGC 3310. Roughly 100 million years ago, NGC 3310 [ http://antwrp.gsfc.nasa.gov/apod/ap010117.html ] likely collided with a smaller galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap001102.html ] causing the large spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] to light up with a tremendous burst of star formation [ http://archive.ncsa.uiuc.edu/Cyberia/Bima/StarForm.html ]. The changing gravity during the collision created density waves [ http://fuse.pha.jhu.edu/~danforth/spiral/ ] that compressed existing clouds of gas and triggered the star-forming party [ http://antwrp.gsfc.nasa.gov/apod/ap010812.html ]. The above image [ http://heritage.stsci.edu/public/2001sep/table.html ] composite by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] was used to find the ages of many of the resulting clusters [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] of stars. To the surprise of many, some of the clusters [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ] are quite young, indicating that starburst galaxies [ http://chandra.harvard.edu/xray_sources/starburst.html ] may remain in star-burst mode for quite some time. NGC 3310 [ http://home.cc.umanitoba.ca/~umnorri1/ngc3310intro.html ] spans about 50,000 light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ], lies about 50 million light years away, and is visible with a small telescope [ http://es.rice.edu/ES/humsoc/Galileo/Things/telescope.html ] towards the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Ursa Major [ http://www.astronomical.org/constellations/uma.html ]. |
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The Galactic Ring of NGC 678
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| Title |
The Galactic Ring of NGC 6782 |
| Explanation |
Do spiral galaxies [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] look the same in every color? NGC 6782 [ http://heritage.stsci.edu/public/2001nov/table.html ] demonstrates colorfully that they do not. In visible light [ http://imagers.gsfc.nasa.gov/ems/visible.html ], NGC 6782 appears [ http://heritage.stsci.edu/public/2001nov/original.html ] to be a normal spiral galaxy [ http://www.seds.org/messier/spir.html ] with a bright bar [ http://antwrp.gsfc.nasa.gov/apod/ap990624.html ] across its center. In ultraviolet light [ http://liftoff.msfc.nasa.gov/academy/universe/ultraviolet.html ], however, the central region blossoms into a spectacular and complex structure highlighted by a circumnuclear ring, as shown in the above [ http://heritage.stsci.edu/public/2001nov/display.html ] representative color [ http://heritage.stsci.edu/public/commonpages/imageconstruct.html ] Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] image. Many of the young stars that formed [ http://antwrp.gsfc.nasa.gov/apod/ap000924.html ] in a recent burst of star formation emit the ultraviolet light [ http://imagers.gsfc.nasa.gov/ems/uv.html ]. Astronomers are studying possible relationships between the central bar and the ring [ http://heritage.stsci.edu/public/2001nov/supplemental.html ]. Light we see today from NGC 6782 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997ApJ...487..603Q ] left about 180 million years ago, while dinosaurs [ http://www.ucmp.berkeley.edu/diapsids/dinosaur.html ] roamed the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap001127.html ]. The galaxy spans about 80,000 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] and can be seen with a telescope [ http://antwrp.gsfc.nasa.gov/apod/ap011014.html ] toward the constellation of Pavo [ http://www.astronomical.org/constellations/pav.html ]. |
|
The Spiral Arms of NGC 4622
| Title |
The Spiral Arms of NGC 4622 |
| Explanation |
While stirring a morning cup of coffee and thinking cosmic thoughts [ http://www.astr.ua.edu/goodies/data_resources/ galaxies.text ] many astronomers would [ http://bama.ua.edu/~rbuta/ngc4622/pr.html ] glance at this Hubble Space Telescope image of spiral galaxy NGC 4622 and assume that the galaxy was rotating [ http://www.owlnet.rice.edu/~spac250/elio/spac.html ] counterclockwise in the picture. One hundred million light-years away in the constellation Centaurus [ http://chandra.harvard.edu/photo/constellations/ centaurus.html ], NGC 4622's gorgeous outer spiral arms [ http://fuse.pha.jhu.edu/~danforth/spiral/ ], traced by bright bluish star clusters and dark dust lanes, should be winding up like ... well, like swirls in a cup of coffee [ http://www.sciam.com/askexpert/astronomy/ astronomy17.html ]. But a closer look [ http://bama.ua.edu/~rbuta/ngc4622/ ] at this galaxy reveals that a pronounced inner spiral arm winds in the opposite direction. So which way is this galaxy rotating? Recent evidence [ http://www.aas.org/publications/baas/v33n4/aas199/ 374.htm ] combining ground-based spectroscopy and the sharp Hubble image data surprisingly indicates that the galaxy is likely rotating "clockwise" in the picture, its outer spiral arms opening outward in the direction of rotation. There are further indications that a past collision with a smaller companion galaxy has contributed to this bizarre rotational arrangement of spiral arms, essentially unique among known large spiral galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap010427.html ], in NGC 4622 [ http://nedwww.ipac.caltech.edu/level5/Rings/ Rings17_1.html ]. |
|
Oddities of Star Cluster NGC
…
| Title |
Oddities of Star Cluster NGC 6397 |
| Explanation |
One of these stars is blinking. This star [ http://hubble.esa.int/hubble/gallery/new_searchresult.cfm?ooid=29458&imgid=12986 ], a member of globular cluster [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ] NGC 6397, is noteworthy not just because it blinks, but because it blinks so fast and because its companion star is so atypical. Speculation holds [ http://hubble.esa.int/hubble/news/newsrelease.cfm?oid=29454 ] that this might be a neutron star [ http://www.astro.umd.edu/~miller/nstar.html ] spun up to a rate of 274 rotations each second by the bloated red star [ http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/971016.html ] it orbits. Matter gravitationally pulled from the bloated star likely orbits [ http://antwrp.gsfc.nasa.gov/apod/ap010508.html ] the millisecond pulsar [ http://www.livingreviews.org/Articles/Volume1/1998-10lorimer/ ], making it spin faster when it crashes onto the surface. The odd system might have resulted when the neutron star [ http://antwrp.gsfc.nasa.gov/apod/ap981128.html ] captured a normal star after a near collision near the globular cluster [ http://www.seds.org/messier/glob.html ]'s dense center. Other collisions near the center of NGC 6397 [ http://antwrp.gsfc.nasa.gov/apod/ap000622.html ] are thought to have produced other oddities -- blue straggler stars [ http://antwrp.gsfc.nasa.gov/apod/ap971104.html ]. The Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] took the above image [ http://hubble.esa.int/hubble/gallery/new_searchresult.cfm?ooid=29460&imgid=12988 ] of the colorful globular cluster [ http://www.seds.org/messier/xtra/ngc/n6397.html ]. |
|
NGC 4414: A Flocculent Spira
…
| Title |
NGC 4414: A Flocculent Spiral Galaxy |
| Explanation |
How much mass do flocculent [ http://www.bartleby.com/61/6/F0190600.html ] spirals hide? The above true color image of flocculent spiral galaxy [ http://www.star.le.ac.uk/edu/galaxies/spirals.html ] NGC 4414 was taken with the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] to help answer this question. Flocculent spirals [ http://nedwww.ipac.caltech.edu/level5/Elmegreen/Elm3.html ] -- galaxies without well defined spiral arms -- are a quite common form of galaxy, and NGC 4414 is one of the closest. Stars and gas near the visible edge of spiral galaxies [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] orbit the center so fast that the gravity from a large amount of unseen dark matter [ http://www.sciam.com/specialissues/0398cosmos/0398rubin.html ] must be present to hold them together. Pictured above is the photogenic center of NGC 4414. A bright foreground star from our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap000518.html ] shines in the foreground of the image. Although NGC 4414's center likely holds little dark matter [ http://chandra.harvard.edu/xray_astro/dark_matter.html ], understanding its matter distribution helps calibrate the rest of the galaxy and, by deduction, flocculent spirals in general. By determining a precise distance [ http://www.astro.virginia.edu/~jh8h/glossary/distanceladder.htm ] to NGC 4414 [ http://antwrp.gsfc.nasa.gov/apod/ap990609.html ], astronomers also hope to help calibrate the scale [ http://antwrp.gsfc.nasa.gov/debate/debate96.html ] to the more distant universe [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998ApJ...509...80S ]. |
|
NGC 2787: A Barred Lenticula
…
| Title |
NGC 2787: A Barred Lenticular Galaxy |
| Explanation |
Lenticular galaxies aren't supposed to be photogenic. Like spiral galaxies [ http://www.seds.org/messier/spir.html ], they contain a disk [ http://antwrp.gsfc.nasa.gov/apod/ap990919.html ], but like elliptical galaxies [ http://www.noao.edu/image_gallery/elliptical_galaxies.html ], they are usually short on dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ], gas, and pretty spiral [ http://antwrp.gsfc.nasa.gov/apod/ap011004.html ] arms. Lenticulars [ http://www.seds.org/messier/lenticul.html ] are relatively little studied [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1992ApJ...401L..79B ], possibly because of their seemingly benign nature. Famous galaxies historically classified as lenticular include M84 [ http://www.seds.org/messier/m/m084.html ], M85 [ http://www.seds.org/messier/m/m085.html ], and M86 [ http://www.seds.org/messier/m/m086.html ]. Recent pictures and evidence, however, indicate that lenticulars [ http://nedwww.ipac.caltech.edu/level5/CLASSIFICATION/lasog.html ] can be both photogenic and scientifically interesting. For example, the above image [ http://heritage.stsci.edu/2002/07/index.html ] of NGC 2787 [ http://heritage.stsci.edu/2002/07/supplemental.html ] taken with the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] shows that the center of this lenticular galaxy [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1987A%26A...175....4S ] has interesting structure. The image was taken to help determine how lenticular galaxies [ http://www-thphys.physics.ox.ac.uk/users/Galactic/layman/gal_types.html#lenticular ] formed, and what happens in their centers. The span of NGC 2787 [ http://heritage.stsci.edu/2002/07/table.html ] in the above image [ http://heritage.stsci.edu/2002/07/default.html ] is about 4500 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ], while the galaxy lies about 25 million light years away toward the constellation of Ursa Major [ http://www.astronomical.org/constellations/uma.html ]. |
|
NGC 4676: When Mice Collide
| Title |
NGC 4676: When Mice Collide |
| Explanation |
These two galaxies are pulling each other apart. Known as "The Mice [ http://sites.stsci.edu/pubinfo/pr/2002/11/prc/prc0211d.txt ]" because they have such long tails, each spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] has likely already passed through the other and will probably collide again and again until they coalesce. The long tails [ http://burro.astr.cwru.edu/NAS/NAS.html ] are created by the relative difference between gravitational pulls [ http://www.clupeid.demon.co.uk/tides/simple.html ] on the near and far parts of each galaxy. Scrolling right will show the very long tail of one of the galaxies. Because the distances are so large, the whole thing takes place in slow motion -- over hundreds of millions of years. NGC 4676 [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1974ApJ...187..219S ] lies about 300 million light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away toward the constellation of Coma Berenices [ http://www.astronomical.org/constellations/com.html ] and are likely members [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1961ApJ...133..726B ] of the Coma Cluster of Galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap020203.html ]. The above picture [ http://sites.stsci.edu/pubinfo/pr/2002/11/pr-photos.html#d ] was taken with the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ]'s new Advanced Camera for Surveys [ http://acs.pha.jhu.edu/ ] which is more sensitive and images a larger field than previous Hubble cameras. The camera's increased sensitivity has imaged, serendipitously, galaxies far [ http://antwrp.gsfc.nasa.gov/apod/ap000709.html ] in the distance scattered about the frame. |
|
The Swirling Center of NGC 4
…
| Title |
The Swirling Center of NGC 4261 |
| Explanation |
What evil lurks in the hearts of galaxies? The above picture [ http://www.stsci.edu/pubinfo/gif/NGC4261C.txt ] by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ] of the center of the nearby galaxy NGC 4261 tells us one dramatic tale [ http://www.stsci.edu/pubinfo/press-releases/95-47.txt ]. Here gas [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#hydrogen ] and dust [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#dust ] are seen swirling near this elliptical galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950913.html ]'s center into what is almost certainly a massive black hole [ http://antwrp.gsfc.nasa.gov/apod/ap951127.html ]. The disk is probably what remains of a smaller galaxy that fell in hundreds of millions of years ago. Collisions like this may be a common way of creating such active galactic nuclei as quasars [ http://antwrp.gsfc.nasa.gov/apod/ap951022.html ]. Strangely, the center of this fiery whirlpool is offset from the exact center of the galaxy - for a reason that for now remains an astronomical mystery. |
|
NGC 2440 Nucleus: The Hottes
…
| Title |
NGC 2440 Nucleus: The Hottest Star? |
| Explanation |
In the center of the above photograph [ http://pao.gsfc.nasa.gov/gsfc/lithos/hst/ngc2440/ngc2440.htm ] lies a star [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#star ] with one of the hottest surface temperatures yet confirmed. This bright white dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap950910.html ] star's surface has been measured at greater than 200,000 degrees Celsius - more than 30 times hotter than that of our own Sun [ http://antwrp.gsfc.nasa.gov/apod/ap950813.html ]. The white dwarf [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#wd ]'s extreme heat makes it glow extraordinarily bright: intrinsically more than 250 times brighter than the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap951004.html ]. The star is at the center of the planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap950628.html ] titled NGC 2440, which lies inside our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950908.html ]. The above computer sharpened image was taken by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ]. |
|
NGC 7027: A Dying Star's Neb
…
| Title |
NGC 7027: A Dying Star's Nebula |
| Explanation |
This pseudo-color composite [ http://www.stsci.edu/pubinfo/gif/NGC7027.txt ] of two recent Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ] images is a picture of a Sun-like star nearing the end of its lifetime [ http://plabpc.csustan.edu/astro/stars/stars.htm ]. The exquisite details [ http://www.stsci.edu/pubinfo/PR/96/05.html ] visible in this planetary nebula [ http://fusedweb.pppl.gov/ CPEP/Chart_Pages/5.Plasmas/Nebula/Planetary.html ] indicate that when the star passed through its Red Giant phase [ http://plabpc.csustan.edu/astro/stars/giant.htm ] it initially shrugged off its outer atmosphere [ http://antwrp.gsfc.nasa.gov/apod/ap950628.html ] gently and evenly producing the outer faint spherical shells. As the process continued, material was apparently ejected in dense clumps producing dust clouds in the bright inner regions. The whole ejection process was amazingly rapid, taking only a few thousand years compared to a 10 billion year lifetime typical for Solar type stars. In the end the hot stellar core, now a white dwarf star [ http://antwrp.gsfc.nasa.gov/apod/ap950910.html ], was left - seen here as a white dot at the center of the nebula. Our middle-aged Sun [ http://antwrp.gsfc.nasa.gov/apod/ap951004.html ] will experience a similar fate ... in about 5 billion years! |
|
NGC 6369: The Little Ghost N
…
| Title |
NGC 6369: The Little Ghost Nebula |
| Explanation |
This pretty planetary nebula, cataloged as NGC 6369 [ http://rao.150m.com/NGC6369.html ], was discovered by 18th century astronomer William Herschel [ http://www.bath-preservation-trust.org.uk/museums/ herschel/ ] as he used a telescope to explore the constellation Ophiucus [ http://www.corona_borealis.homestead.com/files/ pronouncing_the_stars.htm ]. Round and planet-shaped, the nebula is also relatively faint [ http://astro.isi.edu/reference/herschel.html ] and has acquired the popular moniker of Little Ghost Nebula. Planetary nebulae [ http://www.seds.org/messier/planetar.html ] in general are not [ http://antwrp.gsfc.nasa.gov/apod/ap020302.html ] at all related to planets, but instead are created at the end of a sun-like star's life as its outer layers expand [ http://antwrp.gsfc.nasa.gov/apod/ap010805.html ] into space while the star's core shrinks to become a white dwarf. The transformed white dwarf star [ http://antwrp.gsfc.nasa.gov/apod/ap000910.html ], seen near the center, radiates strongly at ultraviolet wavelengths and powers the expanding nebula's glow. Surprisingly complex details [ http://cdsads.u-strasbg.fr/cgi-bin/ nph-bib_query?1997ApJ...487..304H&db_key=AST&nosetcookie=1 ] and structures of NGC 6369 are revealed in this delightful color image [ http://heritage.stsci.edu/2002/25/index.html ] composed from Hubble Space Telescope data [ http://heritage.stsci.edu/2002/25/original.html ]. The nebula's main ring structure is about a light-year across and the glow from ionized oxygen, hydrogen, and nitrogen atoms are colored [ http://opostaff.stsci.edu/%7Elevay/process/ ] blue, green, and red respectively. Over 2,000 light-years away, the Little Ghost [ http://antwrp.gsfc.nasa.gov/apod/ap970331.html ] Nebula offers a glimpse of the fate of our Sun, which should produce its own pretty planetary nebula only about 5 billion years from now. |
|
NGC 7293: The Helix Nebula
| Title |
NGC 7293: The Helix Nebula |
| Explanation |
The Helix nebula (New General Catalog number 7293) is estimated to be a mere 450 light-years from the Sun, in the direction of the constellation Aquarius [ http://bradley.bradley.edu/~dware/aquarius.html ]. At that distance it may well be the closest planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/lib/planetary.html ], offering a dramatic snapshot of a brief final evolutionary stage [ http://fusedweb.pppl.gov/CPEP/Chart_Pages/ 5.Plasmas/Nebula/Planetary.html ] in the life of a solar-type star. In this color image the nebula glows red in the light of nitrogen and hydrogen atoms energized by the ultraviolet radiation [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#uv ] from the central star [ http://antwrp.gsfc.nasa.gov/apod/ap960209.html ]. The main rings themselves, though faint, have an angular size about half that of the full moon and span about 1.5 light-years. Because it is so close, it is a prime subject for study by astronomers [ http://blackhole.aas.org/meetings/aas186/program/abs/S3804.html ]. When the Hubble Space Telescope was focused near the inner edge of the main ring, at about the 12 o'clock position in the above image, it resolved some of the spoke like radial structures visible into intriguing cometary knots [ http://antwrp.gsfc.nasa.gov/apod/ap960416.html ]. |
|
NGC 604: Giant Stellar Nurse
…
| Title |
NGC 604: Giant Stellar Nursery |
| Explanation |
Scattered within this cavernous nebula [ http://oposite.stsci.edu/pubinfo/pr/96/27.html ], cataloged as NGC 604 [ http://www.seds.org/messier/more/m033_n604.html ], are over 200 newly formed hot, massive, stars. At 1,500 light-years across, this expansive cloud of interstellar gas and dust is effectively a giant stellar nursery located some three million light-years distant in the spiral galaxy, M33 [ http://antwrp.gsfc.nasa.gov/apod/ap960708.html ]. The newborn stars irradiate the gas with energetic ultraviolet light [ http://trifle.gsfc.nasa.gov/UIT/Astro1/ Astro1_pictures.html ] stripping electrons from atoms and producing a characteristic nebular glow [ http://vis.sdsc.edu/research/hayden2.html ]. The details [ http://adsbit.harvard.edu/cgi-bin/ nph-iarticle_query?1996ApJ%2E%2E%2E456%2E%2E174H ] of the nebula's structure hold clues to the mysteries of star formation and galaxy evolution. |
|
NGC 1818: A Young Globular C
…
| Title |
NGC 1818: A Young Globular Cluster |
| Explanation |
Globular clusters [ http://antwrp.gsfc.nasa.gov/apod/ap020416.html ] once ruled the Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap980523.html ]. Back in the old days [ http://antwrp.gsfc.nasa.gov/apod/ap001029.html ], back when our Galaxy first formed, perhaps thousands of globular clusters roamed our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ]. Today, there are perhaps 200 left [ http://www.faqs.org/faqs/astronomy/faq/part8/section-5.html ]. Many globular clusters were destroyed [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997ApJ...474..223G ] over the eons by repeated fateful encounters with each other or the Galactic center [ http://antwrp.gsfc.nasa.gov/apod/ap010708.html ]. Surviving relics are older than any Earth fossil [ http://craton.geol.brocku.ca/faculty/rc/teaching/1F90/history/shorthistory2.html ], older than any other structures in our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap990224.html ], and limit the universe [ http://liftoff.msfc.nasa.gov/academy/universe/age.html ] itself in raw age. There are few, if any, young globular clusters [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ] in our Milky Way Galaxy [ http://www.seds.org/messier/more/mw.html ] because conditions are not ripe for more to form. Things are different next door, however, in the neighboring LMC galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap010804.html ]. Pictured above is a "young" globular cluster residing there: NGC 1818 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1995A%26A...295...54W ]. Observations show it formed only about 40 million years ago - just yesterday compared to the 12 billion year ages of globular clusters [ http://www.seds.org/messier/glob.html ] in our own Milky Way [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_ts?milky+way ] |
|
NGC 3393: A Super Spiral?
| Title |
NGC 3393: A Super Spiral? |
| Explanation |
A bird? A plane? No, but pictured here is something physically much larger, flying much higher, and moving much faster than either of these. It is, in fact, a Seyfert type 2 spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/lib/spirals.html ]. The "S" is actually a lane of stars, gas and dust [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#dust ] circling the core. Designated NGC 3393, the bright core makes this galaxy a Seyfert [ http://msowww.anu.edu.au/~mga/seyfert.html ] and the infrared glow of central dust help distinguish it as "type 2." Seyfert galaxies [ http://praxis.pha.jhu.edu/papers/papers/afdscirev_b/node9.html ] have extremely energetic nuclei similar to more powerful quasars [ http://www.ph.unimelb.edu.au/~bholman/qso/qso1.html ]. Seyferts [ http://www-astronomy.mps.ohio-state.edu/~pogge/agn.html ] are thought to have black holes [ http://cossc.gsfc.nasa.gov/htmltest/rjn_bht.html ] in their centers. Most of the lines and small spots in this image are due to cosmic rays [ http://www.ngdc.noaa.gov/stp/SOLAR/COSMIC_RAYS/cosmic.html ] striking the imager and are unrelated to structure in the galaxy. |
|
NGC 604: Giant Stellar Nurse
…
| Title |
NGC 604: Giant Stellar Nursery in M33 |
| Explanation |
The nebula cataloged as NGC 604 is a giant star forming region, 1500 light years across, in the nearby spiral galaxy, M33 [ http://antwrp.gsfc.nasa.gov/apod/ap960708.html ]. Seen here in a snapshot [ http://www.stsci.edu/pubinfo/PR/96/27.html ] by the Hubble Space Telescope, over 200 newly formed, hot, massive, stars are scattered within a cavern-like, gaseous, interstellar cloud. The stars irradiate the gas with energetic ultraviolet light [ http://fondue.gsfc.nasa.gov/UIT/Astro1/Astro1_pictures.html ] stripping electrons from atoms and exciting them - producing a characteristic nebular glow [ http://antwrp.gsfc.nasa.gov/apod/lib/emission.html ]. The details [ http://adsabs.harvard.edu/cgi-bin/ nph-bib_query?1996ApJ%2E%2E%2E456%2E%2E174H&db_key=AST ] of the nebula's structure hold clues to the mysteries of star formation [ http://antwrp.gsfc.nasa.gov/apod/ap960510.html ] and its effect on the evolution of galaxies [ ftp://crux.astr.ua.edu/web/goodies/data_resources/galaxies.text ]. |
|
NGC 253: The Sculptor Galaxy
| Title |
NGC 253: The Sculptor Galaxy |
| Explanation |
NGC 253 [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?ngc+253 ] is not only one of the brightest spiral galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap980922.html ] visible, it is also one of the dustiest [ http://antwrp.gsfc.nasa.gov/apod/ap980116.html ]. Discovered in 1783 by Caroline Herschel [ http://history.math.csusb.edu/Mathematicians/Herschel_Caroline.html ] in the constellation of Sculptor [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sculptor.html ], NGC 253 [ http://astro.nmsu.edu/~choopes/research.html ] lies only about ten million light-years distant. NGC 253 [ http://seds.lpl.arizona.edu/messier/xtra/ngc/n0253.html ] is the largest member of the Sculptor Group of Galaxies [ http://seds.lpl.arizona.edu/messier/xtra/ngc/sclgr.html ], the nearest group to our own Local Group of Galaxies [ http://seds.lpl.arizona.edu/messier/more/local.html ]. The dense dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] accompanies a high star formation [ http://antwrp.gsfc.nasa.gov/apod/ap020717.html ] rate, giving NGC 253 [ http://antwrp.gsfc.nasa.gov/apod/ap990121.html ] the designation of starburst galaxy [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998ApJ...505..639E ]. Visible in the above photograph [ http://oposite.stsci.edu/pubinfo/pr/1998/42/a.html ] from the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] is the active central nucleus [ http://www.astr.ua.edu/keel/agn/text.html ], also known to be a bright source of X-rays [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#X-ray ] and gamma rays [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ]. |
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