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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 6791: An Old, Large Open
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| Title |
NGC 6791: An Old, Large Open Cluster |
| Explanation |
NGC 6791 is one of the oldest and largest open clusters of stars [ http://antwrp.gsfc.nasa.gov/apod/ap970128.html ] known. But how did it get so dirty? Open star clusters [ http://www.seds.org/messier/open.html ] usually contain a few hundred stars each less than a billion years old. Open star cluster [ http://antwrp.gsfc.nasa.gov/apod/lib/open_clusters.html ] NGC 6791 [ http://xxx.lanl.gov/ps/astro-ph/9812097 ], however, contains thousands of stars recently measured to be about 8 billion years old. What's really confusing, though, is that the stars of NGC 6791 [ http://xxx.lanl.gov/abs/astro-ph/9503065 ] are relatively dirty - the minuscule amounts of heavy elements [ http://pearl1.lanl.gov/periodic/ ] (generically called metals) are high relative to most other star clusters [ http://antwrp.gsfc.nasa.gov/apod/ap981025.html ]. Older stars are supposed to be metal poor, since metals have only been slowly accumulating in our Milky Way Galaxy [ http://www.damtp.cam.ac.uk/user/gr/public/gal_milky.html ]. This enigma makes NGC 6791, pictured above [ http://www.astrouw.edu.pl/~mochejsk/gallery.html ], one of the most studied open clusters [ http://cfa-www.harvard.edu/~stauffer/opencl/ ] and a possible example of how stars might evolve in the centers of galaxies. |
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NGC 246 and the Dying Star
| Title |
NGC 246 and the Dying Star |
| Explanation |
Appropriately nicknamed [ http://www.gemini.edu/ngc246image ]"the Skull Nebula", planetary nebula NGC 246 really does surround a dying star some 1,600 light-years away in the constellation Cetus [ http://hawastsoc.org/deepsky/cet/index.html ]. Expelled over a period of thousands of years, the lovely, intricate nebula is the outer atmosphere of a once sun-like star [ http://www.spitzer.caltech.edu/Media/releases/ ssc2004-13/release.shtml ]. The expanding outer atmosphere [ http://antwrp.gsfc.nasa.gov/apod/ap040424.html ] is interacting with the gas and dust in the interstellar [ http://www-ssg.sr.unh.edu/ism/what1.html ] medium, while the star itself, the fainter member of the binary star system seen at the nebula's center, is entering its final phase [ http://hubblesite.org/newscenter/newsdesk/archive/ releases/1997/38/astrofile/ ] of evolution, becoming a dense, hot white dwarf [ http://chandra.harvard.edu/xray_sources/ white_dwarfs.html ]. Star and nebula are moving rapidly toward the top of the detailed view, as suggested by the nebula's brighter, upper, leading edge. The sharp image spans just over 2.5 light-years at the estimated distance of NGC 246 [ http://x.astrogeek.org/observations/log.php?object_id=187 ] and also reveals distant background galaxies, some visible right through the nebula along the bottom. |
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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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NGC 7635: Bubble in a Cosmic
…
| Title |
NGC 7635: Bubble in a Cosmic Sea |
| Explanation |
Seemingly adrift in a cosmic sea [ http://www.skyfactory.org/ngc7635/ngc7635.htm ] of stars and glowing gas, the delicate, floating apparition near the center (next to a blue tinted star) of this widefield view is cataloged as NGC 7635 - The Bubble Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap040716.html ]. A mere 10 light-years wide, the tiny Bubble Nebula and the larger complex of interstellar gas and dust [ http://www-ssg.sr.unh.edu/ism/what1.html ] clouds are found about 11,000 light-years [ http://en.wikipedia.org/wiki/Light_year ] distant, straddling the boundary between the parental constellations Cepheus [ http://www.hawastsoc.org/deepsky/cep/ ] and Cassiopeia [ http://www.hawastsoc.org/deepsky/cas/ ]. Also included in the breathtaking vista is open star cluster M52 [ http://www.seds.org/messier/m/m052.html ] (upper left), some 5,000 light-years away. The digital [ http://www.skyfactory.org/ngc7635/ngc7635_int.htm ] color picture is based on photographic plates taken at the Palomar Observatory [ http://www.astro.caltech.edu/palomarnew/sot.html ] between 1992 and 1997. This cropped version spans about 2.7 degrees on the sky corresponding to a width of just over 500 light-years at the estimated distance of the Bubble Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap051107.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 4696: Energy from a Blac
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| Title |
NGC 4696: Energy from a Black Hole |
| Explanation |
In many cosmic environments [ http://antwrp.gsfc.nasa.gov/apod/ap031128.html ], when material falls toward a black hole energy is produced as some of the matter is blasted back out in jets [ http://antwrp.gsfc.nasa.gov/apod/ap000706.html ]. In fact, such black hole "engines" appear to be the most efficient in the Universe, at least on a galactic scale. This composite image [ http://chandra.harvard.edu/photo/2006/bhcen/ ] illustrates one example of an elliptical galaxy with an efficient black hole engine, NGC 4696 [ http://chandra.harvard.edu/photo/2006/bhcen/ animations.html ]. The large galaxy is the brightest member of the Centaurus [ http://www.angelfire.com/id/jsredshift/centaur.htm ] galaxy cluster, some 150 million light-years away. Exploring NGC 4696 [ http://www.arxiv.org/abs/astro-ph?papernum=0602549 ] in x-rays (red) astronomers can measure the rate at which infalling matter fuels the supermassive black hole [ http://chandra.harvard.edu/xray_sources/ blackholes_sm.html ] and compare it to the energy output in the jets to produce giant radio [ http://antwrp.gsfc.nasa.gov/apod/ap050628.html ] emitting bubbles. The bubbles, shown here in blue, are about 10,000 light-years across. The results confirm [ http://chandra.harvard.edu/press/06_releases/ press_042406.html ] that the process is much more efficient than producing energy through nuclear reactions [ http://fusedweb.pppl.gov/CPEP/Chart.html ] - not to mention using fossil fuels. Astronomers also suggest that as the black hole pumps out energy and heats the surrounding gas, star formation is ultimately shut off, limiting the size of large galaxies like NGC 4696. |
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NGC 253: Dusty Island Univer
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| Title |
NGC 253: Dusty Island Universe |
| Explanation |
Shiny NGC 253 [ http://seds.lpl.arizona.edu/messier/xtra/ngc/n0253.html ], sometimes called the Silver Dollar Galaxy, is one of the brightest spiral galaxies visible - and also one of the dustiest. First swept up [ http://antwrp.gsfc.nasa.gov/apod/ap991016.html ] in 1783 by mathematician and astronomer Caroline Herschel [ http://www.scottlan.edu/LRIDDLE/WOMEN/ herschel.htm ], the dusty island universe lies a mere 10 million light-years away in the southern constellation [ http://www.astronomy.org.nz/aas/Journal/Oct2004/ GreatGalaxyGrab.asp ] Sculptor. About 70 thousand light-years across, NGC 253 is the largest member of the Sculptor Group of Galaxies [ http://seds.lpl.arizona.edu/messier/xtra/ngc/ sclgr.html ], the nearest to our own Local Group of Galaxies [ http://seds.lpl.arizona.edu/messier/more/ local.html ]. In addition to its spiral dust lanes, striking tendrils of dust seem to be rising [ http://antwrp.gsfc.nasa.gov/apod/ap060414.html ] from the galactic disk in this gorgeous view [ http://ccd.cosmotography.com/images/small_ngc253.html ]. The high dust content accompanies frantic star formation, giving [ http://www.arxiv.org/abs/astro-ph/0509430 ] NGC 253 the designation of a starburst galaxy. NGC 253 is also known to be a strong source of high-energy [ http://antwrp.gsfc.nasa.gov/apod/ap010607.html ] x-rays and gamma rays, likely due to massive black holes near the galaxy's center. |
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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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Reflections on NGC 6188
| Title |
Reflections on NGC 6188 |
| Explanation |
NGC 6188 is an interstellar carnival of young blue stars [ http://antwrp.gsfc.nasa.gov/apod/ap980803.html ], hot red gas [ http://antwrp.gsfc.nasa.gov/apod/ap020317.html ], and cool dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap041219.html ]. Located 4,000 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away in the disk [ http://antwrp.gsfc.nasa.gov/apod/ap060113.html ] of our Galaxy, NGC 6188 [ http://www.robgendlerastropics.com/NGC6188text.html ] is home to the Ara OB1 association [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1994A%26A...289..922R ], a group of bright young stars whose nucleus forms the open cluster NGC 6193 [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1988PASP..100.1076A ]. These stars are so bright that some of their blue light reflects off of interstellar dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] forming the diffuse blue glow surrounding the stars in the above photograph [ http://www.robgendlerastropics.com/NGC6188MP.html ]. Open cluster [ http://en.wikipedia.org/wiki/Open_cluster ] NGC 6193 formed about three million years ago from the surrounding gas, and appears unusually rich in close binary stars. The red glow visible throughout the photograph arises from hydrogen [ http://www.chemicalelements.com/elements/h.html ] gas heated by the bright stars in Ara OB1. The dark dust [ http://en.wikipedia.org/wiki/Interstellar_dust ] that blocks much of NGC 6188's light was likely formed in the outer atmospheres of cooler stars [ http://antwrp.gsfc.nasa.gov/apod/ap990605.html ] and in supernovae ejecta [ http://antwrp.gsfc.nasa.gov/apod/ap971002.html ]. |
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NGC 6164: A Bipolar Emission
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| Title |
NGC 6164: A Bipolar Emission Nebula |
| Explanation |
How did a star form this beautiful nebula? In the middle of emission nebula [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] NGC 6164-5 is an unusually massive star nearing the end of its life. The star, visible in the center of the above image [ http://www.gemini.edu/dualneb ] and catalogued as HD 148937, is so hot that the ultraviolet light [ http://imagers.gsfc.nasa.gov/ems/uv.html ] it emits heats up gas that surrounds it. That gas was likely thrown off from the star, possibly by its fast rotation, like a rotating lawn sprinkler. Expelled material might have been further channeled by the magnetic field [ http://antwrp.gsfc.nasa.gov/apod/ap980629.html ] of the star, creating the symmetric shape [ http://antwrp.gsfc.nasa.gov/apod/ap060326.html ] of the bipolar nebula [ http://antwrp.gsfc.nasa.gov/apod/ap030113.html ]. Several cometary knots [ http://antwrp.gsfc.nasa.gov/apod/ap960416.html ] of gas are also visible on the lower left. NGC 6164-5 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1985PASP...97..780F&] spans about four light years [ http://en.wikipedia.org/wiki/Light_years ] and is located about 4,000 light years away toward the southern constellation Norma [ http://www.seds.org/Maps/Stars_en/Fig/norma.html ]. |
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NGC 1579: Trifid of the Nort
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| Title |
NGC 1579: Trifid of the North |
| Explanation |
Colorful NGC 1579 [ http://www.cosmotography.com/images/ small_ngc1579.html ] resembles the better known Trifid Nebula, but lies much farther north in planet Earth's sky, in the heroic constellation Perseus [ http://www.hawastsoc.org/deepsky/per/index.html ]. About 2,100 light-years away and 3 light-years across, NGC 1579 is [ http://www.noao.edu/outreach/aop/observers/ n1579.html ] a captivating study in color. Like the Trifid [ http://antwrp.gsfc.nasa.gov/apod/ap020424.html ], NGC 1579 is a dusty star forming region providing contrasting emission and reflection nebulae [ http://www.seasky.org/cosmic/sky7a05.html ] in the same field - the characteristic red glow of hydrogen gas and the blue of reflected starlight. Also like the Trifid [ http://antwrp.gsfc.nasa.gov/apod/ap020626.html ], dark dust lanes are prominent in the nebula's central regions. In fact, obscuring dust is pervasive in NGC 1579 [ http://www.seds.org/~spider/ngc/ngc.cgi?NGC1579 ], drastically dimming the visible light from the massive, young, hot stars still embedded in [ http://adsabs.harvard.edu/abs/1956PASP...68..353H ] the cosmic cloud. |
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Spiral Galaxy NGC 2403 from
…
| Title |
Spiral Galaxy NGC 2403 from Subaru |
| Explanation |
Sprawling spiral arms dotted with bright red emission nebulas [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] highlight this new and detailed image of nearby spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] NGC 2403. Also visible in the photogenic spiral galaxy [ http://en.wikipedia.org/wiki/Spiral_galaxy ] are blue open clusters [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ], dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] lanes [ http://antwrp.gsfc.nasa.gov/apod/ap020620.html ], and a bright but relatively small central nucleus [ http://antwrp.gsfc.nasa.gov/apod/ap001220.html ]. NGC 2403 is located just beyond the Local Group of Galaxies [ http://en.wikipedia.org/wiki/Local_group ], at a relatively close 10 million light years away toward the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of the Giraffe [ http://www.kidsplanet.org/factsheets/giraffe.html ] (Camelopardalis [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=11 ]). NGC 2403 has a designated Hubble type [ http://en.wikipedia.org/wiki/Hubble_sequence ] of Sc. In 2004, NGC 2403 was home to one of the brightest supernovas [ http://antwrp.gsfc.nasa.gov/apod/ap040907.html ] of modern times. The above image [ http://subarutelescope.org/Pressrelease/2005/10/13/index.html ], the highest resolution complete image of NGC 2403 ever completed, was taken by the Japan [ http://www.cia.gov/cia/publications/factbook/geos/ja.html ]'s 8.3-meter Subaru telescope [ http://www.schoolsobservatory.org.uk/astro/textb/tele/world/subaru.htm ] located on Mauna Kea [ http://antwrp.gsfc.nasa.gov/apod/ap051220.html ], Hawaii [ http://en.wikipedia.org/wiki/Hawaii ], USA [ http://www.cdc.noaa.gov/USclimate/states.fast.html ]. |
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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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NGC 6888: A Tricolor Starfie
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| Title |
NGC 6888: A Tricolor Starfield |
| Explanation |
NGC 6888 [ http://www.noao.edu/image_gallery/html/im0834.html ], also known as the Crescent Nebula, is a cosmic bubble [ http://arxiv.org/abs/astro-ph/0310311 ] about 25 light-years across, blown by winds [ http://www.sdsc.edu/GatherScatter/GSwinter97/owocki.html ] from its central, bright, massive star. Near the center of this intriguing widefield view of interstellar gas clouds and rich star fields [ http://antwrp.gsfc.nasa.gov/apod/ap031023.html ] of the constellation Cygnus, NGC 6888 is about 5,000 light-years away. The three color composite [ http://dg-imaging.astrodon.com/gallery/ display.cfm?imgID=56 ] image was created by stacking exposures through narrow band filters that transmit the light [ http://hubblesite.org/sci.d.tech/behind_the_pictures/ meaning_of_color/eagle.shtml ] from atoms in the clouds. Hydrogen is shown as green, sulfur as red, and oxygen as blue. NGC 6888's central star is classified as a Wolf-Rayet star [ http://www.peripatus.gen.nz/Astronomy/WolRaySta.html ] (WR 136) and is shedding its outer envelope in a strong stellar wind, ejecting the equivalent of our Sun's mass every 10,000 years. Burning fuel at a prodigious rate and near the end of its stellar life [ http://heasarc.gsfc.nasa.gov/docs/xmm_lc/edu/lessons/ background-lifecycles.html ], this star should ultimately go out with a bang in a spectacular supernova explosion [ http://antwrp.gsfc.nasa.gov/apod/ap060430.html ]. |
|
NGC 7331 and Beyond
| Title |
NGC 7331 and Beyond |
| Explanation |
Spiral galaxy NGC 7331 [ http://www.seds.org/messier/Xtra/ngc/n7331.html ] is often touted as an analog to our own Milky Way [ http://cassfos02.ucsd.edu/public/tutorial/MW.html ]. About 50 million light-years distant in the northern constellation Pegasus [ http://hawastsoc.org/deepsky/peg/index.html ], NGC 7331 was recognized early on as a spiral nebula [ http://www.seds.org/messier/Xtra/Bios/rosse.html ] and is actually one of the brighter galaxies [ http://www.seasky.org/cosmic/sky7a07.html ] not included in Charles Messier's famous [ http://antwrp.gsfc.nasa.gov/apod/ap060302.html ] 18th century catalog. Since the galaxy's disk is inclined [ http://antwrp.gsfc.nasa.gov/apod/ap040701.html ] to our line-of-sight, long telescopic exposures often result in an image that evokes a strong sense of depth. The effect is further enhanced in this well-framed view by the galaxies that lie beyond this beautiful island universe [ http://www.astr.ua.edu/goodies/data_resources/ galaxies.text ]. The background galaxies are about one tenth the apparent size [ http://chandra.harvard.edu/photo/scale.html ] of NGC 7331 and so lie roughly ten times farther away. |
|
Still Life with NGC 2170
| Title |
Still Life with NGC 2170 |
| Explanation |
In this beautiful celestial still life [ http://www.photomeeting.de/astromeeting/nebulae/ 050208ngc2170a_d.htm ] composed with a cosmic brush, dusty nebula NGC 2170 [ http://www.seds.org/~spider/ngc/ngcic.cgi?NGC2170 ] shines at the upper left. Reflecting the light of nearby hot stars, NGC 2170 is joined by other bluish reflection [ http://antwrp.gsfc.nasa.gov/apod/ap041204.html ] nebulae and a compact red emission [ http://antwrp.gsfc.nasa.gov/apod/ap040629.html ] region against a backdrop of stars. Like the common household items still life painters [ http://www.artlex.com/ArtLex/s/still-life/ 1701-1850.html ] often choose for their subjects, the clouds of gas, dust, and hot stars pictured here are also commonly found in this setting - a massive, star-forming molecular cloud in the constellation Monoceros [ http://www.hawastsoc.org/deepsky/mon/index.html ]. The giant molecular cloud [ http://archive.ncsa.uiuc.edu/Cyberia/Bima/GMC.html ], Mon R2, is impressively close, estimated [ http://cdsads.u-strasbg.fr/cgi-bin/ nph-bib_query?2005A%26A...430..523W&db_key=AST&nosetcookie=1 ] to be only 2,400 light-years or so away. At that distance, this canvas would be about 15 light-years across. |
|
IC 410 and NGC 1893
| Title |
IC 410 and NGC 1893 |
| Explanation |
A faint, dusty rose of the northern sky, emission nebula IC 410 lies about 12,000 light-years away in the constellation Auriga [ http://hawastsoc.org/deepsky/aur/index.html ]. The cloud of glowing hydrogen gas is over 100 light-years across, sculpted [ http://antwrp.gsfc.nasa.gov/apod/ap051111.html ] by stellar winds [ http://www.peripatus.gen.nz/Astronomy/SteWin.html ] and radiation from embedded open star cluster NGC 1893. Formed in [ http://abyss.uoregon.edu/~js/ast122/lectures/lec13.html ] the interstellar cloud a mere [ http://www.arxiv.org/abs/astro-ph9909065 ] 4 million years ago, bright cluster stars are seen just below the prominent dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap030816.html ] cloud near picture center. Notable near the 7 o'clock position in this wide, detailed view are two relatively dense streamers of material trailing away from the nebula's central regions. Potentially sites of ongoing star formation, these cosmic tadpole [ http://antwrp.gsfc.nasa.gov/apod/ap060111.html ] shapes are about 10 light-years long. |
|
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. |
|
X-Ray Wind From NGC 3783
| Title |
X-Ray Wind From NGC 3783 |
| Explanation |
A black hole [ http://www.ncsa.uiuc.edu/Cyberia/NumRel/BlackHoles.html ] is supposed to inexorably attract matter. But the intense radiation generated as material swirls and plunges into its high gravity field also heats up surrounding gas and drives it away. In fact, measurements made using this recent Chandra Observatory [ http://chandra.harvard.edu/press/00_releases/ press_052500.html ] X-ray spectrum of active galaxy NGC 3783 reveal a wind of highly ionized atoms blowing away from the galaxy's suspected central black hole [ http://chandra.harvard.edu/xray_sources/quasars.html ] at a million miles per hour. Displayed in false color, the bright central spot is the X-ray image [ http://imagine.gsfc.nasa.gov/docs/science/how_l2/ xtelescopes_systems.html ] of NGC 3783 while the lines radiating away represent an X-ray spectrum [ http://imagine.gsfc.nasa.gov/docs/teachers/lessons/ xray_spectra/background-spectroscopy.html ] of this source produced by Chandra's High Energy Transmission Grating [ http://chandra.harvard.edu/about/science_instruments.html ] (HETG). An X-ray spectrum is the analog to the rainbow spread of colors in a visible light spectrum. It represents a detailed, spread out image of X-ray colors or energies arising from the source. Ionized atoms of iron, magnesium, oxygen, nitrogen and other elements [ http://www.webelements.com/ ] produce patterns of absorption at known X-ray energies. These patterns have been identified in the spectrum of NGC 3783 [ http://xxx.lanl.gov/abs/astro-ph/0004050 ] at slightly shifted energies and the measured shifts indicate the hot wind's velocity. |
|
Barred Spiral Galaxy NGC 130
…
| 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/ ]. |
|
NGC 5905 and 5908
| Title |
NGC 5905 and 5908 |
| Explanation |
These two [ http://www.photomeeting.de/astromeeting/galaxies/ 060702ngc5908a_d.htm ] beautiful galaxies, NGC 5905 (left) and NGC 5908 lie about 140 million light-years distant in the northern constellation Draco [ http://en.wikipedia.org/wiki/Draco_(constellation) ]. Separated by about 500,000 light-years, the pair are actually both spiral galaxies [ http://cassfos02.ucsd.edu/public/tutorial/Galaxies.html ] and nicely illustrate the striking contrasts in appearance possible when viewing spirals [ http://www.noao.edu/image_gallery/ spiral_galaxies.html ] from different perspectives. Seen face-on [ http://antwrp.gsfc.nasa.gov/apod/ap040410.html ], NGC 5905 is clearly a spiral galaxy with bright star clusters tracing arms that wind outward from a prominent central bar [ http://antwrp.gsfc.nasa.gov/apod/ap050825.html ]. Oriented edge-on [ http://antwrp.gsfc.nasa.gov/apod/ap010510.html ] to our view, the spiral nature of NGC 5908 is revealed by a bright nucleus and dark band of obscuring dust characteristic of a spiral galaxy's disk. In fact, NGC 5908 is similar in appearance to the well studied edge-on spiral galaxy M104 - The Sombrero Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap060115.html ]. |
|
NGC 2440: Cocoon of a New Wh
…
| 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 ]. |
|
NGC 1499: The California Neb
…
| Title |
NGC 1499: The California Nebula |
| Explanation |
What's California doing in space? Drifting through the Orion Arm of the spiral Milky Way Galaxy, this cosmic cloud [ http://www.anzwers.org/free/universe/nebulae/ ngc1499.html ] by chance echoes the outline of California [ http://en.wikipedia.org/wiki/California ] on the west coast of the United States [ https://www.cia.gov/cia/publications/factbook/geos/us.html ]. Our own Sun also lies within the Milky Way's Orion Arm [ http://www.anzwers.org/free/universe/5000lys.html ], only about 1,500 light-years from the California Nebula [ http://en.wikipedia.org/wiki/California_Nebula ]. Also known as NGC 1499 [ http://www.seds.org/~spider/spider/ Misc/n1499.html ], the classic emission nebula is around 100 light-year [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ]s long. It glows with the red light characteristic of hydrogen atoms recombining with long lost [ http://antwrp.gsfc.nasa.gov/apod/lib/lament.html ] electrons, stripped away (ionized [ http://csep10.phys.utk.edu/ astr162/lect/light/ionization.html ]) by energetic starlight. In this case, the star most likely providing the energetic starlight is the bright, hot, bluish Xi Persei, just right of the nebula and above picture center. Fittingly, this composite [ http://www.astro.caltech.edu/~wsk/ngc1499.html ] picture was made with images from a telescope in California - the 48-inch (1.2-meter) Samuel Oschin Telescope [ http://www.astro.caltech.edu/~wsk/sot.html ] - taken as a part of the second National Geographic Palomar [ http://antwrp.gsfc.nasa.gov/apod/ap030807.html ] Observatory Sky Survey [ http://www.astro.caltech.edu/~wws/poss2.html ]. |
|
Dusty NGC 1333
| Title |
Dusty NGC 1333 |
| Explanation |
Dusty NGC 1333 [ http://www.noao.edu/outreach/aop/observers/ n1333.html ] is seen in visible light as a reflection nebula [ http://antwrp.gsfc.nasa.gov/apod/ap031229.html ], dominated by bluish hues characteristic of starlight reflected by dust. But at longer infrared wavelengths, the interstellar [ http://www-ssg.sr.unh.edu/ism/what1.html ] dust itself glows. Moving your cursor over the picture will match up a visible light view [ http://www.starrywonders.com/ngc1333cm10.html ] with a false-color infrared image of the region from the Spitzer Space Telescope [ http://www.spitzer.caltech.edu/Media/releases/ssc2005-24/ release.shtml ]. The penetrating infrared view [ http://coolcosmos.ipac.caltech.edu//main_html/ index.html ] unmasks youthful stars that are otherwise obscured by the dusty [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] clouds that formed them. Also revealed are greenish streaks and splotches that seem to litter the region. The structures trace the glow of cosmic jets [ http://antwrp.gsfc.nasa.gov/apod/ap060203.html ] blasting away from emerging young stellar objects and plowing into the cold cloud material. In all, the chaotic [ http://www.quotedb.com/quotes/3885 ] environment likely resembles one in which our own Sun formed over 4.5 billion years ago. NGC 1333 [ http://www.robgendlerastropics.com/NGC1333text.html ] is a mere 1,000 light-years distant in the constellation Perseus [ http://www.hawastsoc.org/deepsky/per/index.html ]. |
|
NGC 7635: The Bubble
| Title |
NGC 7635: The Bubble |
| Explanation |
What created this huge space bubble? Blown by the wind from a star, this tantalizing [ http://www.exploratorium.edu/ronh/bubbles/ bubbles.html ], ghostly apparition is cataloged as NGC 7635, but known simply as The Bubble Nebula [ http://heritage.stsci.edu/1998/31/index.html ]. Astronomer Eric Mouquet's striking view utilizes [ http://astrosurf.com/ericmouquet/galerie/neb_rc/bubble_halpha_AOL_600.htm ] a long exposure with hydrogen alpha [ http://en.wikipedia.org/wiki/Hydrogen_alpha ] light to reveal the intricate details of this cosmic bubble [ http://antwrp.gsfc.nasa.gov/apod/ap030617.html ] and its environment. Although it looks delicate, the 10 light-year [ http://chandra.harvard.edu/photo/cosmic_distance.html ] diameter bubble offers evidence of violent processes [ http://antwrp.gsfc.nasa.gov/apod/ap021205.html ] at work. Seen here above and right of the Bubble's center is a bright hot star embedded in reflecting dust. A fierce stellar wind [ http://en.wikipedia.org/wiki/Stellar_wind ] and intense radiation from the star, which likely has a mass 10 to 20 times that of the Sun [ http://www.sunblock99.org.uk/sb99/fact/heavy.html ], has blasted out the structure of glowing gas [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query? bibcode=1995A%26A...295..509C ] against denser material in a surrounding molecular cloud. The intriguing Bubble Nebula lies a mere 11,000 light-years away toward the boastful constellation Cassiopeia [ http://en.wikipedia.org/wiki/Cassiopeia_%28constellation%29 ]. |
|
Unusual Giant Galaxy NGC 131
…
| Title |
Unusual Giant Galaxy NGC 1316 |
| Explanation |
Can unusual giant galaxy NGC 1316 help calibrate the universe? Quite possibly -- if it turns out this atypical galaxy is composed of typical stars. NGC 1316, pictured above [ http://www.eso.org/outreach/press-rel/pr-2000/pr-17-00.html ], is most obviously strange because it has a size and shape common for an elliptical galaxy [ http://antwrp.gsfc.nasa.gov/apod/elliptical_galaxies.html ] but dust lanes [ http://antwrp.gsfc.nasa.gov/apod/ap980116.html ] and a disk more commonly found in a spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ]. These attributes could be caused by interactions [ http://antwrp.gsfc.nasa.gov/apod/ap980710.html ] with another galaxy over the past billion years. Most recently, NGC 1316 [ http://antwrp.gsfc.nasa.gov/apod/ap990222.html ] has been monitored to find novae [ http://antwrp.gsfc.nasa.gov/apod/ap991215.html ], explosions emanating from white dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap971102.html ] stars that should have a standard brightness [ http://www.suite101.com/article.cfm/astronomy/13217 ]. Again, NGC 1316 [ http://www.vuw.ac.nz/~mackie/atlas/index/n1316/n1316.html ] was found atypical in that the nova rate was unexpectedly high. If, however, the stars and white dwarfs [ http://antwrp.gsfc.nasa.gov/apod/white_dwarfs.html ] that compose NGC 1316 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998AJ....115..514M ] are typical, then the novae [ http://astrosun.tn.cornell.edu/courses/astro201/novae.htm ] observed should be just as bright as novae [ http://csep10.phys.utk.edu/astr162/lect/novae/novae.html ] in other galaxies so that astronomers can use them to compute an accurate distance [ http://www.sciam.com/specialissues/0398cosmos/0398freedman.html ]. This distance can then be used to calibrate other distance indicators [ http://www.astro.ucla.edu/~wright/distance.htm ] and result in a more accurate scale for distances [ http://antwrp.gsfc.nasa.gov/debate/debate98.html ] throughout the universe [ http://www.drscience.com/vault/981023.htm ]. |
|
NGC 6960: The Witch's Broom
…
| Title |
NGC 6960: The Witch's Broom Nebula |
| Explanation |
Ten thousand years ago, before the dawn of recorded human history [ http://news.bbc.co.uk/hi/english/sci/tech/newsid_334000/334517.stm ], a new light must suddenly have appeared in the night sky and faded after a few weeks. Today we know this light was an exploding star [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html ] and record the colorful expanding cloud as the Veil Nebula [ http://nineplanets.org/twn/cygnusx.html ]. Pictured above [ http://robgendler.astrodigitals.com/Nebulas.html ] is the west end of the Veil Nebula [ http://www.astropix.com/HTML/E_SUM_N/VEIL.HTM ] known technically as NGC [ http://www.ngcic.com/dss/dss_images.htm ] 6960 but less formally as the Witch's Broom Nebula. The rampaging gas gains its colors by impacting and exciting existing [ http://antwrp.gsfc.nasa.gov/apod/ap960307.html ] nearby gas. The supernova remnant [ http://antwrp.gsfc.nasa.gov/apod/supernova_remnants.html ] lies about 1400 light-years away towards the constellation of Cygnus [ http://www.multimania.com/cdadfs/constellation/cygne/cygnus.htm ]. This Witch's Broom actually spans over three times the angular size of the full Moon [ http://antwrp.gsfc.nasa.gov/apod/moon.html ]. The bright blue star 52 Cygnus [ http://www.seds.org/Maps/Stars_en/Fig/cygnus.html ] is visible with the unaided eye from a dark location but unrelated to the ancient supernova [ http://www.chapman.edu/oca/benet/intro_sn.htm ]. |
|
A Galaxy Collision in NGC 67
…
| 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. |
|
Gangly Spiral Galaxy NGC 318
…
| Title |
Gangly Spiral Galaxy NGC 3184 |
| Explanation |
NGC 3184 is a large spiral galaxy [ http://www.seds.org/messier/spir.html ] with a small nucleus and long sprawling spiral arms. Although NGC 3184 [ http://www.kopernik.org/images/archive/n3184.htm ] contains hundreds of billions of stars, the blue color of its spiral arms [ http://online.bc.cc.ca.us/sea/astronomy/ismnotesb/ismglxyc.htm ] comes mostly from relatively few bright young blue stars [ http://antwrp.gsfc.nasa.gov/apod/ap000227.html ]. The galaxy is not empty of matter between these spiral [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] arms -- the bright stars that highlight the arms were created in huge density waves [ http://fuse.pha.jhu.edu/~danforth/spiral/ ] that circle the center. Visible [ http://www.ghg.net/akelly/ ] with a small telescope towards the constellation [ http://www.att.virtualclassroom.org/vc99/vc_04/cons_stars/cons/hist_cons.html ] of Ursa Major [ http://www.astronomical.org/constellations/uma.html ], light takes about 25 million years to reach us from NGC 3184 [ http://home.cc.umanitoba.ca/~umgonza4/histobserv.html ], and about 50,000 years just to cross it. NGC 3184 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997A%26AS..124..129P ] (Hubble type [ http://www.seds.org/messier/xtra/supp/gal-ttab.html ] Sbc) is notable for its high abundance [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1982PhDT........35M ] of heavy elements [ http://casa.colorado.edu/~uvconf/white_final/node5.html ] and a supernova [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/supernovae.html ] that has occurred there recently [ http://cfa-www.harvard.edu/iauc/07300/07329.html#Item1 ]. |
|
Unusual Starburst Galaxy NGC
…
| Title |
Unusual Starburst Galaxy NGC 1313 |
| Explanation |
Why is this galaxy so discombobulated? Usually, galaxies this topsy-turvy [ http://video.google.com/videoplay?docid=5403974888855118935 ] result from a recent collision with a neighboring galaxy. Spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] NGC 1313, however, appears to be alone. Brightly lit with new and blue massive stars, star formation appears so rampant in NGC 1313 [ http://www.eso.org/outreach/press-rel/pr-2006/phot-43-06.html ] that it has been labeled a starburst galaxy [ http://en.wikipedia.org/wiki/Starburst_galaxy ]. Strange features of NGC 1313 [ http://www.aao.gov.au/images/deep_html/n1313_d.html ] include that its spiral arms are lopsided and its rotational axis is not at the center of the nuclear bar. Pictured above [ http://www.eso.org/outreach/press-rel/pr-2006/pr-43-06.html ], NGC 1313 spans about 50,000 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] and lies only about 15 million light years away toward the constellation [ http://en.wikipedia.org/wiki/Constellation ] of Reticulum [ http://en.wikipedia.org/wiki/Reticulum_constellation ]. Continued numerical modeling [ http://ifa.hawaii.edu/~barnes/transform.html ] of galaxies like NGC 1313 might shed some light on its unusual nature. |
|
In the Arms of NGC 1097 R. J
…
| Title |
In the Arms of NGC 1097 R. Jay GaBany [ http://www.cosmotography.com/images/biography.html ] (Cosmotography.com [ http://www.cosmotography.com/ ]) |
| Explanation |
A smaller companion seems wrapped in the spiral arms of enigmatic galaxy NGC 1097 [ http://weblore.com/richard/ngc_1097.htm ]. This amazingly deep image [ http://www.cosmotography.com/images/ small_ngc1097.html ] of the peculiar spiral system, also known as Arp [ http://nedwww.ipac.caltech.edu/level5/Arp/frames.html ] 77, actually combines data from two telescopes, one in the northern and one in the southern hemisphere of planet Earth. The faint details revealed include hints of a mysterious jet [ http://adsabs.harvard.edu/abs/2003ApJ...585..281H ] emerging toward the top of the view. Seen to be about 42,000 light-years from the larger galaxy's center, the companion galaxy is gravitationally interacting [ http://arxiv.org/abs/astro-ph/9908269 ] with the spiral and will ultimately merge [ http://antwrp.gsfc.nasa.gov/apod/ap031211.html ] with it. NGC 1097's center also harbors a massive black hole [ http://www.pparc.ac.uk/Nw/eso_monster.asp ]. NGC 1097 is located about 45 million light-years away in the chemical constellation Fornax [ http://www.hawastsoc.org/deepsky/for/index.html ]. |
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NGC 1055 and M77
| Title |
NGC 1055 and M77 |
| Explanation |
Large spiral galaxy NGC 1055 (top left) joins spiral M77 in this lovely cosmic view [ http://www.robgendlerastropics.com/M77MosaicNM.html ] toward the constellation Cetus [ http://hawastsoc.org/deepsky/cet/index.html ]. The narrowed, dusty appearance of edge-on spiral NGC 1055 contrasts nicely with the face-on view of M77's bright [ http://antwrp.gsfc.nasa.gov/apod/ap061207.html ] nucleus and spiral arms. Both over 100,000 light-years across, the pair are dominant members of a small galaxy group about 60 million light-years away. At that estimated distance, M77 is [ http://www.seds.org/messier/m/m077.html ] one of the most remote objects in Charles Messier's catalog [ http://en.wikipedia.org/wiki/List_of_Messier_objects ] and is separated from fellow island universe NGC 1055 by at least 500,000 light-years. The mosaicked field is about the size of the full Moon on the sky [ http://members.aol.com/billferris/m77hop.html ] and includes colorful foreground Milky Way stars (with diffraction spikes [ http://antwrp.gsfc.nasa.gov/apod/ap010415.html ]) along with more distant background galaxies. |
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Barred Spiral Galaxy NGC 130
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| Title |
Barred Spiral Galaxy NGC 1300 |
| Explanation |
NGC 1300 is a large spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] that appears as a flattened figure eight. A huge bar that spans over 150,000 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] across the galaxy center dominates its appearance. The picturesque galaxy [ http://www.aao.gov.au/images/captions/aatccd014.html ] lies about 75 million light-years distant, so that light that we see now left during the age [ http://www.austmus.gov.au/lostkingdoms/snapshots/cretaceous_late.htm ] of the dinosaurs [ http://pubs.usgs.gov/gip/dinosaurs/ ]. Although it is well known how fast different parts of NGC 1300 rotate [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1996ApJ...469..131E ], the specific orbits of many component stars -- including how they interact with the gigantic bar -- remains a topic of research [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997A%26A...317...36L ]. Our own Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap971229.html ] is a spiral galaxy [ http://www.seds.org/messier/galaxy.html ] with a less prominent bar. NGC 1300 [ http://www.starlightccd.com/funstuff/flic/1999-11/12_f33_mx512/ngc1300.htm ] can be seen with a small telescope towards the constellation [ http://www.att.virtualclassroom.org/vc99/vc_04/cons_stars/cons/hist_cons.html ] of Eridanus [ http://www.astronomical.org/constellations/eri.html ]. |
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Star Forming Region NGC 6357
| Title |
Star Forming Region NGC 6357 |
| Explanation |
For reasons unknown, NGC 6357 is forming some of the most massive stars ever discovered. Near the more obvious Cat's Paw [ http://antwrp.gsfc.nasa.gov/apod/ap991207.html ] nebula, NGC 6357 houses the open star cluster Pismis 24 [ http://antwrp.gsfc.nasa.gov/apod/ap061219.html ], home to these tremendously bright and blue stars. The overall red glow near the inner star forming region results from the emission [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] of ionized [ http://csep10.phys.utk.edu/astr162/lect/light/ionization.html ] hydrogen [ http://en.wikipedia.org/wiki/Hydrogen ] gas. The surrounding nebula, shown above [ http://www.spacetelescope.org/images/html/heic0619e.html ], holds a complex tapestry of gas, dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap060409.html ], stars still forming, and newly born stars. The intricate patterns are caused by complex interactions between interstellar winds [ http://csep10.phys.utk.edu/astr162/lect/sun/wind.html ], radiation pressures [ http://en.wikipedia.org/wiki/Radiation_pressure ], magnetic fields [ http://www-spof.gsfc.nasa.gov/Education/whmfield.html ], and gravity [ http://www-scf.usc.edu/~kallos/gravity.htm ]. NGC 6357 spans about 400 light years and lies about 8,000 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away toward the constellation of the Scorpion [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=73 ]. |
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Dwarf Elliptical Galaxy NGC
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| Title |
Dwarf Elliptical Galaxy NGC 205 in the Local Group |
| Explanation |
Our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ] is not alone. It is part of a gathering of about 25 galaxies known as the Local Group [ http://www.seds.org/messier/more/local.html ]. Members include the Great Andromeda Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap991114.html ] (M31), M32 [ http://antwrp.gsfc.nasa.gov/apod/ap991103.html ], M33 [ http://antwrp.gsfc.nasa.gov/apod/ap980721.html ], the Large Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap000222.html ], the Small Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap000430.html ], Dwingeloo 1 [ http://antwrp.gsfc.nasa.gov/apod/ap000109.html ], several small irregular galaxies [ http://www.seds.org/messier/irre.html ], and many dwarf elliptical [ http://nedwww.ipac.caltech.edu/level5/Ferguson/frames.html ] and dwarf spheroidal galaxies [ http://www.astro.uu.se/~ns/review.html ]. Pictured [ http://www.cfht.hawaii.edu/Science/Astros/Imageofweek/ciw061299.html ] on the lower left is one of the many dwarf ellipticals [ http://www.astro.psu.edu/users/pdurrell/dE.html ]: NGC 205 [ http://www.seds.org/messier/m/m110.html ]. Like M32 [ http://www.seds.org/messier/m/m032.html ], NGC 205 [ http://nedwww.ipac.caltech.edu/level5/Hodge/Hodge5_5.html ] is a companion to the large M31, and can sometimes be seen to the south of M31 [ http://www.seds.org/messier/m/m031.html ]'s center in photographs. The above image [ http://www.cfht.hawaii.edu/Science/Astros/Imageofweek/ciw061299.html ] shows NGC 205 to be unusual [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998ApJ...499..209W ] for an elliptical galaxy [ http://antwrp.gsfc.nasa.gov/apod/elliptical_galaxies.html ] in that it contains at least two dust clouds [ http://antwrp.gsfc.nasa.gov/apod/ap990919.html ] (at 1 and 4 o'clock - they are visible but hard to spot) and signs of recent star formation [ http://antwrp.gsfc.nasa.gov/apod/stellar_nurseries.html ]. This galaxy is sometimes known as M110, although it was actually not part of Messier [ http://antwrp.gsfc.nasa.gov/apod/ap960626.html ]'s original catalog [ http://antwrp.gsfc.nasa.gov/apod/messier.html ]. |
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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 2174: Emission Nebula in
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| Title |
NGC 2174: Emission Nebula in Orion |
| Explanation |
A lesser known sight in the nebula-rich [ http://antwrp.gsfc.nasa.gov/apod/ap061015.html ] constellation Orion, NGC 2174 [ http://www.astropix.com/HTML/B_WINTER/NGC2174.HTM ] can be found with binoculars near the head of the celestial hunter [ http://www.windows.ucar.edu/tour/link=/the_universe/ Constellations/orion.html&edu=high ]. About 6,400 light-years distant, the glowing cosmic cloud surrounds loose clusters of young stars. Covering an area larger than the full Moon on the sky, this stunning narrow band image [ http://www.photonhunter.com/nebulae/NGC2174.html ] adopts a typical color mapping of the atomic emission from NGC 2174. The false-color mapping [ http://hubblesite.org/gallery/behind_the_pictures/ meaning_of_color/eagle.shtml ] shows otherwise red hydrogen emission in green hues and emphasizes sulfur emission in red and oxygen in blue. Placing your cursor on the image will reveal an alternative image of the nebula made through broad band filters [ http://hubblesite.org/gallery/behind_the_pictures/ meaning_of_color/filters.shtml ]. The broad band image combines filters in a closer analogy [ http://hubblesite.org/gallery/behind_the_pictures/ meaning_of_color/rgb.shtml ] to human vision, dominated by the red glow [ http://antwrp.gsfc.nasa.gov/apod/ap060324.html ] of hydrogen. |
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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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NGC 6960: The Witch's Broom
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| Title |
NGC 6960: The Witch's Broom Nebula |
| Explanation |
Ten thousand years ago, before the dawn of recorded human history [ http://news.bbc.co.uk/hi/english/sci/tech/newsid_334000/334517.stm ], a new light must suddenly have appeared in the night sky and faded after a few weeks. Today we know this light was an exploding star [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html ] and record the colorful expanding cloud as the Veil Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap010928.html ]. Pictured above [ http://www.noao.edu/image_gallery/html/im0852.html ] is the west end of the Veil Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap030204.html ] known technically as NGC [ http://en.wikipedia.org/wiki/New_General_Catalog ] 6960 but less formally as the Witch [ http://antwrp.gsfc.nasa.gov/apod/ap061211.html ]'s Broom [ http://www.broomshop.com/history/ ] Nebula. The rampaging gas gains its colors by impacting and exciting existing [ http://www.seds.org/billa/twn/cygnusx.html ] nearby gas. The supernova remnant [ http://antwrp.gsfc.nasa.gov/apod/supernova_remnants.html ] lies about 1400 light-years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away towards the constellation of Cygnus [ http://www.multimania.com/cdadfs/constellation/cygne/cygnus.htm ]. This Witch's Broom actually spans over three times the angular size [ http://imagine.gsfc.nasa.gov/YBA/HTCas-size/more-ang_size.html ] of the full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap030810.html ]. The bright star 52 Cygnus [ http://www.seds.org/Maps/Stars_en/Fig/cygnus.html ] is visible with the unaided eye from a dark location but unrelated to the ancient supernova [ http://en.wikipedia.org/wiki/Supernova ]. |
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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 1850: Gas Clouds and Sta
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| Title |
NGC 1850: Gas Clouds and Star Clusters |
| Explanation |
There's nothing like it in our own Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap000130.html ]. Globular clusters as young as NGC 1850 [ http://antwrp.gsfc.nasa.gov/apod/ap000729.html ] don't exist here. Globular clusters [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ] only 40 millions of years old can still be found in the neighboring LMC [ http://antwrp.gsfc.nasa.gov/apod/ap000222.html ] galaxy, though, but perhaps none so unusual as NGC 1850 [ http://oposite.stsci.edu/pubinfo/press-releases/94-40.txt ]. Close inspection of the above photograph [ http://www.eso.org/outreach/press-rel/pr-1999/phot-15-99.html ] will reveal two clusters. Below and right of the main group of stars known as NGC 1850 [ http://www.mso.anu.edu.au/~kim/thesis/node6.html ]A is a smaller, still younger group dubbed NGC 1850B [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1994ApJ...435L..43G ]. This cluster is made of stars only about four million years old. The large red cloud of gas surrounding the clusters may have been predominantly created by supernovae explosions [ http://heasarc.gsfc.nasa.gov/docs/snr.html ] of stars in the younger cluster. The red supernova remnant [ http://antwrp.gsfc.nasa.gov/apod/supernova_remnants.html ] N57D is visible on the upper left. |
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Polar Ring Galaxy NGC 2685
| Title |
Polar Ring Galaxy NGC 2685 |
| Explanation |
NGC 2685 is [ http://www.seds.org/~spider/Spider/Misc/n2685.html ] a confirmed polar ring galaxy - a rare type of galaxy [ http://www.seds.org/messier/galaxy.html ] with stars, gas and dust orbiting in rings perpendicular to the plane of a flat galactic disk. The bizarre [ http://antwrp.gsfc.nasa.gov/apod/ap990510.html ] configuration could be caused by the chance capture of material [ http://www.astro.spbu.ru/EducTech/prg.html ] from another galaxy by a disk galaxy, with the captured debris strung out in a rotating ring. Still, observed [ http://arxiv.org/abs/astro-ph0209004 ] properties of NGC 2685 suggest that the rotating ring structure is remarkably old and stable. In this fascinating [ http://www.rdelsol.com/Galaxy/NGC2685.html ] view of the peculiar system also known as Arp [ http://nedwww.ipac.caltech.edu/level5/Arp/frames.html ] 336 or the Helix galaxy, the strange, perpendicular rings [ http://www.obspm.fr/actual/nouvelle/ apr03/prg.en.shtml ] are easy to trace as they pass in front of the galactic disk, along with other disturbed outer structures. NGC 2685 is about 50,000 light-years across and 40 million light-years away in the constellation Ursa Major [ http://www.wikisky.org/?object=Ursa+Major&zoom=2 ]. |
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Stars, Dust and Nebula in NG
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| Title |
Stars, Dust and Nebula in NGC 2170 |
| Explanation |
When stars form, pandemonium reigns. A textbook [ http://zebu.uoregon.edu/text.html ] case is the star forming region NGC 2170 [ http://antwrp.gsfc.nasa.gov/apod/ap060805.html ]. Visible above [ http://www.rc-astro.com/photo/id1178.html ] are red glowing emission nebulas [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] of hydrogen [ http://periodic.lanl.gov/elements/1.html ], blue reflection nebulas [ http://en.wikipedia.org/wiki/Reflection_nebula ] of dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ], dark absorption nebulas [ http://www.glyphweb.com/esky/concepts/absorptionnebula.html ] of dust, and the stars that formed from them. The first massive stars formed from the dense gas will emit energetic light [ http://imagers.gsfc.nasa.gov/ems/uv.html ] and winds [ http://www.peripatus.gen.nz/Astronomy/SteWin.html ] that erode, fragment, and sculpt [ http://antwrp.gsfc.nasa.gov/apod/ap050425.html ] their birthplace. And then they explode [ http://heasarc.gsfc.nasa.gov/docs/snr.html ]. The resulting morass [ http://antwrp.gsfc.nasa.gov/apod/ap020424.html ] is often as beautiful as it is complex. After tens of millions of years, the dust boils away, the gas gets swept away, and all that is left is a naked open cluster [ http://antwrp.gsfc.nasa.gov/apod/ap040222.html ] of stars. |
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NGC 1410/1409: Intergalactic
…
| 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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NGC 2442: Galaxy in Volans
| Title |
NGC 2442: Galaxy in Volans |
| Explanation |
Distorted galaxy [ http://burro.cwru.edu/JavaLab/GalCrashWeb/main.html ] NGC 2442 can be found in the southern constellation of the flying fish [ http://oceanlink.island.net/oinfo/biodiversity/flyingfish/ flyingfish.html ], (Piscis) Volans [ http://www.dibonsmith.com/vol_con.htm ]. Located about 50 million light-years away, the galaxy's two spiral arms [ http://curious.astro.cornell.edu/question.php?number=199 ] extending from a pronounced central bar give it an ominous [ http://en.wikipedia.org/wiki/Ides_of_March ] hook-shaped appearance. This striking color image [ http://www.starshadows.com/gallery/ display.cfm?imgID=132 ] also shows obscuring dust lanes, young blue star clusters and reddish star forming [ http://antwrp.gsfc.nasa.gov/apod/ap061123.html ] regions surrounding a core of yellowish light from an older population of stars. But the star forming regions seem more concentrated along the drawn-out northern (top) spiral arm. The distorted structure is likely the result of a close encounter [ http://arxiv.org/abs/astro-ph/9701015 ] with a smaller galaxy located just outside this telescopic field of view. The picture spans [ http://chandra.harvard.edu/photo/scale.html ] about 1/6 of a degree, or 150,000 light years at the estimated distance of NGC 2442 [ http://www.aao.gov.au/images/captions/aat098.html ]. |
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![In the Arms of NGC 1097 R. Jay GaBany [ http://www.cosmotography.com/images/biography.html ] (Cosmotography.com [ http://www.cosmotography.com/ ])](http://mm04.nasaimages.org/MediaManager/srvr?mediafile=/Size1/NVA2-4-NA/7232/ngc1097_gabany_f.jpg&userid=1&username=admin&resolution=1&servertype=JVA&cid=4&iid=NVA2&vcid=NA&usergroup=NASA_Astronomy_Picture_of_the_Day_Collecti-4-Admin&profileid=16)
