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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 ].
NGC 1999: Reflection Nebula …
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 ].
NGC 6164: A Bipolar Emission …
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 ].
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 ].
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 ].
NGC 2174: Emission Nebula in …
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.
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://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 ].
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.
Stars, Dust and Nebula in NG …
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.
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 ].
In the Center of Reflection …
Title In the Center of Reflection Nebula NGC 1333
Explanation The dust is so thick in the center of NGC 1333 that you can hardly see the stars forming. Conversely, the very dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] clouds that hide the stars also reflects their optical light [ http://fuse.pha.jhu.edu/~wpb/spectroscopy/em_spec.html ], giving NGC 1333 [ http://www.robgendlerastropics.com/NGC1333text.html ]'s predominantly blue glow the general designation of a reflection nebula [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ]. A highly detailed image of the nebula, shown above [ http://www.noao.edu/image_gallery/html/im1037.html ], was taken recently by the Mayall 4-meter telescope [ http://www.noao.edu/outreach/kptour/mayall.html ] on Kitt Peak [ http://www.noao.edu/kpno/ ] in Arizona [ http://en.wikipedia.org/wiki/Arizona ], USA [ http://en.wikipedia.org/wiki/United_States ] and released to honor astronomer Stephen Strom [ http://www.noao.edu/outreach/press/pr07/pr0706.html ] on his retirement. Visible near the image top are vast blue regions of dust [ http://antwrp.gsfc.nasa.gov/apod/ap061211.html ] predominantly reflecting the light from bright massive stars [ http://antwrp.gsfc.nasa.gov/apod/ap060109.html ]. Visible in the thick central dust are not only newly formed stars but red jets [ http://antwrp.gsfc.nasa.gov/apod/ap070430.html ] and red-glowing gas energized by the light and winds [ http://www-spof.gsfc.nasa.gov/Education/wsolwind.html ] from recently formed young stars. The NGC 1333 [ http://adsabs.harvard.edu/abs/2002ApJ...580..959N ] nebula contains [ http://antwrp.gsfc.nasa.gov/apod/ap061006.html ] hundreds of newly formed stars that are less than one million years old. Reflection nebula [ http://en.wikipedia.org/wiki/Reflection_nebula ] NGC 1333 lies about 1,000 light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away toward the constellation of Perseus [ http://chandra.harvard.edu/photo/constellations/perseus.html ].
NGC 7293: The Helix Nebula
Title NGC 7293: The Helix Nebula
Explanation A mere seven hundred light years from Earth, in the constellation Aquarius [ http://hawastsoc.org/deepsky/aqr/index.html ], a sun-like star is dying. Its last few thousand years have produced the Helix Nebula [ http://www.seds.org/messier/xtra/ngc/n7293.html ] (NGC 7293), a well studied and nearby example of a Planetary Nebula [ http://en.wikipedia.org/wiki/Planetary_nebula ], typical of this final phase of stellar evolution. Nearly 11 hours [ http://www.astronomie.be/hambsch/namibia07/ n7293-halrgb_50f3.htm ] of exposure time have gone in to creating this remarkably deep view of the nebula. It shows details of the Helix's brighter inner region [ http://antwrp.gsfc.nasa.gov/apod/ap030510.html ], about 3 light-years across, but also follows fainter outer halo [ http://www.ing.iac.es/~rcorradi/HALOES/ ] features that give the nebula a span of well over six light-years. The white dot at the Helix's center is this Planetary Nebula's hot, central star [ http://hubblesite.org/newscenter/archive/releases/1997/ 38/astrofile/ ]. A simple looking nebula at first glance, the Helix is now understood to have a surprisingly complex geometry [ http://hubblesite.org/newscenter/archive/releases/2004/ 32/image/e/ ].
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.
NGC 1977: Blue Reflection Ne …
Title NGC 1977: Blue Reflection Nebula in Orion
Explanation The Orion Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap980127.html ] is visible to the unaided eye as a fuzzy patch near the famous belt of three stars [ http://antwrp.gsfc.nasa.gov/apod/ap970820.html ] in the
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 ] 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.
NGC 6888: The Crescent Nebul …
Title NGC 6888: The Crescent Nebula
Explanation What caused the Crescent Nebula? Looking like an emerging space cocoon [ http://antwrp.gsfc.nasa.gov/apod/ap010805.html ], the Crescent Nebula, visible in the center of the above image [ http://astrobug.free.fr/Crescent%20Zoom%20Sept%202007.htm ], was created by the brightest star in its center. A leading progenitor hypothesis has the Crescent Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap000802.html ] beginning to form about 250,000 years ago. At that time, the massive central star had evolved to become a Wolf-Rayet star [ http://antwrp.gsfc.nasa.gov/apod/ap981109.html ] (WR 136), shedding its outer envelope in a strong stellar wind [ http://www.peripatus.gen.nz/Astronomy/SteWin.html ], ejecting the equivalent of our Sun's mass every 10,000 years. This wind impacted surrounding gas left over from a previous phase [ http://hyperphysics.phy-astr.gsu.edu/hbase/astro/redsup.html ], compacting it into a series of complex shells [ http://antwrp.gsfc.nasa.gov/apod/ap020324.html ], and lighting it up. The Crescent Nebula [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000AJ....119.2991M ], also known as NGC 6888, lies about 4,700 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away in the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Cygnus [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=31 ]. Star WR [ http://en.wikipedia.org/wiki/Wolf-Rayet_star ] 136 will probably undergo a supernova [ http://antwrp.gsfc.nasa.gov/apod/supernova_remnants.html ] explosion sometime in the next million years.
NGC 2346: A Butterfly-Shaped …
Title NGC 2346: A Butterfly-Shaped Planetary Nebula
Explanation It may look like a butterfly, but it's bigger than our Solar System [ http://www.seds.org/nineplanets/nineplanets/overview.html ]. NGC 2346 [ http://heritage.stsci.edu/public/99oct7/ngc2346/ngc2346table.html ] is a planetary nebula [ http://www.noao.edu/jacoby/pn_gallery.html ] made of gas and dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] that has evolved into a familiar shape [ http://www.aao.gov.au/images/captions/aat079.html ]. At the heart of the bipolar planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap001217.html ] is a pair of close stars orbiting each other once every sixteen days. The tale [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1985ApJ...297..245S ] of how the butterfly blossomed probably began millions of years ago, when the stars were farther apart. The more massive star expanded to encompass its binary [ http://antwrp.gsfc.nasa.gov/apod/ap991219.html ] companion, causing the two to spiral closer and expel rings [ http://antwrp.gsfc.nasa.gov/apod/ap010729.html ] of gas. Later, bubbles of hot gas emerged as the core of the massive red giant star [ http://plabpc.csustan.edu/astro/stars/giant.htm ] became uncovered. In billions of years, our Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ] will become a red giant [ http://antwrp.gsfc.nasa.gov/apod/ap010630.html ] and emit a planetary nebula [ http://www.blackskies.com/index1.html ] - but probably not in the shape of a butterfly [ http://www.si.edu/resource/faq/nmnh/buginfo/butterfly.htm ], because the Sun [ http://www.windows.ucar.edu/cgi-bin/tour.cgi?link=/sun/sun.html ] has no binary star [ http://astrosun.tn.cornell.edu/courses/astro201/binstar.htm ] companion.
NGC 7023: The Iris Nebula
Title NGC 7023: The Iris Nebula
Explanation Like delicate cosmic petals, these clouds of interstellar dust and gas have blossomed 1,300 light-years away in the fertile star fields of the constellation Cepheus [ http://www.astropix.com/HTML/E_SUM_N/ CEPHEUSO.HTM ]. Sometimes called the Iris Nebula and dutifully cataloged as NGC [ http://www.seds.org/billa/ngc.html ] 7023, this is not the only nebula in the sky to evoke the imagery of flowers [ http://antwrp.gsfc.nasa.gov/apod/ap010214.html ]. Still, the beautiful digital image [ http://www.heavensgloryobservatory.com/ ] shows off the Iris Nebula's range of colors and symmetries in impressive detail. Within the Iris, dusty nebular material surrounds a massive, hot, young star in its formative [ http://btc.montana.edu/ceres/html/ stars1.html#lessonplans ] years. Central filaments of cosmic dust glow with a reddish photoluminesence as some dust grains effectively convert [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query? bibcode=1989ApJ...347L..25W&db_key=AST&high=3bc4bede8e21358 ] the star's invisible ultraviolet [ http://imagers.gsfc.nasa.gov/ems/uv.html ] radiation to visible red light. Yet the dominant color of the nebula is blue, characteristic of dust [ http://www.physics.muni.cz/~ondra/mix/mix.html ] grains reflecting starlight. Dark, obscuring clouds of dust and cold molecular gas are also present and can lead the eye to see other convoluted [ http://antwrp.gsfc.nasa.gov/apod/ap010720.html ] and fantastic [ http://antwrp.gsfc.nasa.gov/apod/ap990829.html ] shapes. Infrared observations [ http://cdsads.u-strasbg.fr/cgi-bin/ nph-bib_query?2000A%26A...354L..17M&db_key=AST&nosetcookie=1 ] indicate that this nebula may contain complex carbon molecules known as PAHs [ http://www.chem.ucl.ac.uk/cosmicdust/pah.htm ]. As shown here, the Iris Nebula [ http://www.robgendlerastropics.com/ 7023.html ] is about 6 light-years across.
NGC 2244: A Star Cluster in …
Title NGC 2244: A Star Cluster in the Rosette Nebula
Explanation In the heart of the Rosette Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap000111.html ] lies a bright open cluster [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] of stars that lights up the nebula. The stars of NGC 2244 [ http://www.seds.org/messier/xtra/ngc/n2244.html ] formed from the surrounding gas only four million years ago [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1993ApJ...414..664K ] and emit light and wind that define the nebula's appearance [ http://www.cfht.hawaii.edu/Science/Astros/Imageofweek/ciw310100.html ] today. High energy light from the bright young stars [ http://antwrp.gsfc.nasa.gov/apod/ap010506.html ] of NGC 2244 ionizes the surrounding hydrogen gas [ http://pearl1.lanl.gov/periodic/elements/1.html ] clouds to create the red emission nebula [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] appearance. The hot wind [ http://science.msfc.nasa.gov/ssl/pad/solar/sun_wind.htm ] of particles that streams away from the cluster stars contributes to an already complex menagerie of gas and dust [ http://antwrp.gsfc.nasa.gov/apod/ap010813.html ] filaments while slowly evacuating the cluster center. NGC 2244 [ http://antwrp.gsfc.nasa.gov/apod/ap980214.html ] measures about 50 light-years [ http://einstein.stcloudstate.edu/Dome/constellns/lightyear.html ] across, lies about 4500 light-years away [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000A%26A...358..553H ], and is visible with binoculars towards the constellation [ http://www.physics.csbsju.edu/astro/asp/constellation.faq.html ] of Monoceros [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Monoceros.html ].
NGC 5189: A Strange Planetar …
Title NGC 5189: A Strange Planetary Nebula
Explanation After a Sun [ http://antwrp.gsfc.nasa.gov/apod/ap950813.html ]-like star [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#star ] can no longer support fusion [ http://fusedweb.pppl.gov/default.html ] in its core, the center condenses into a white dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap950910.html ] while the outer atmospheric layers are expelled into space and appear as a planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap950628.html ]. This particular planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap951130.html ] has a quite strange and chaotic structure. The inner part of this nebula contains an unusual expanding ring of gas that we see nearly edge-on. The exact mechanism that expels the planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap950727.html ] gas is a current topic of astronomical speculation and research.
NGC 4361: Galaxy Shaped Plan …
Title NGC 4361: Galaxy Shaped Planetary Nebula
Explanation Glowing in the red light emitted by hydrogen atoms [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#hydrogen ], the planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap950727.html ] NGC 4361 [ http://crux.astr.ua.edu/goodies/misc_images/ngc4361h.html ] is pictured above. The nebula itself is formed by the outer layers of gas shrugged off by the central star visible in the image. The star's nuclear fuel almost exhausted, it is cooling and shrinking - entering the white dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap950910.html ] phase of its life. The curved tendrils of emission reaching out from the body of the nebula have a shape reminiscent of the arms of of a spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950912.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!
Giant Emission Nebula NGC 36 …
Title Giant Emission Nebula NGC 3603 in Infrared
Explanation NGC 3603 is the largest region of glowing gas in our Milky Way galaxy [ http://adc.gsfc.nasa.gov/mw/mmw_edu.html ]. Spanning over 20 light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] across, the giant emission nebula [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] (HII region) is home to a massive star cluster [ http://antwrp.gsfc.nasa.gov/apod/ap010124.html ], thick dust pillars [ http://antwrp.gsfc.nasa.gov/apod/ap990604.html ], and a star about to explode [ http://antwrp.gsfc.nasa.gov/apod/ap011027.html ]. NGC 3603 was captured above in infrared light [ http://www.ipac.caltech.edu/Outreach/Edu/infrared.html ] by a Two Micron All Sky Survey [ http://www.ipac.caltech.edu/2mass/overview/about2mass.html ] (2MASS) telescope. The young star cluster near the center heats the region's mostly hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] gas. Many stars in the cluster are estimated [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001RMxAA..37...39T ] to be about one million years old, much less than the five billion-year age of our Sun [ http://www.nineplanets.org/sol.html ]. NGC 3603 [ http://www.ipac.caltech.edu/2mass/gallery/powcap9.html#ngc3603 ] lies approximately 20,000 light years away toward the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Carina [ http://www.astronomical.org/constellations/car.html ].
NGC 2237: The Rosette Nebula
Title NGC 2237: The Rosette Nebula
Explanation Would the Rosette [ http://c.gp.cs.cmu.edu:5103/prog/webster?rosette ] nebula by any other name " look " as sweet [ http://the-tech.mit.edu/Shakespeare/Tragedy/romeoandjuliet/ romeoandjuliet.all.html ]? The bland New General Catalog [ http://www.physics.sfsu.edu/asp/ngc.html ] designation of NGC 2237 [ http://seds.lpl.arizona.edu/billa/twn/n2237x.html ] doesn't appear to diminish the appearance of the this flowery emission nebula [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#emis_neb ]. Inside the nebula lies an open cluster [ http://antwrp.gsfc.nasa.gov/apod/ap960116.html ] of bright young stars designated NGC 2244. These stars recently formed from the nebular material and their stellar "wind" has cleared a hole in the nebula's center, insulated by a layer of dust [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#dust ] and hot gas [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#hydrogen ]. Ultraviolet [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#uv ] light from the hot cluster stars causes the surrounding nebula to glow.
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 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://antwrp.gsfc.nasa.gov/apod/ap010928.html ]. Pictured above [ http://starryscapes.com/nebula/ngc6960.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://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/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 ].
NGC 5882: A Small Planetary …
Title NGC 5882: A Small Planetary Nebula
Explanation Will most stars one day look like this? Pictured above is the planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/lib/planetary.html ] NGC 5882, captured [ http://scivax.stsci.edu/~hamilton/nuggets/HST_NUGGETS.HTML ] by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ]. Although planetary nebulae [ http://zebu.uoregon.edu/~imamura/208/feb22/feb22.html ] can appear similar to planets like Uranus [ http://antwrp.gsfc.nasa.gov/apod/ap950816.html ] and Neptune [ http://antwrp.gsfc.nasa.gov/apod/ap950817.html ], they are actually gas [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#hydrogen ] clouds surrounding stars typically hundreds of light years away. Planetary nebula [ http://home.cc.umanitoba.ca/~umbole/pneb.html ] form when a typical star [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#star ] completes fusion [ http://fusedweb.pppl.gov/default.html ] in its core and ejects an outer envelope of gas - usually about 10 percent of the star's initial mass. This gas shell dims in about 50,000 years - short compared to the lifetimes of stars [ http://xalph.ast.cam.ac.uk/public/niel/scales.html ]. Therefore, although only about 1000 planetary nebula [ http://wonka.physics.ncsu.edu/www/Astro/Research/Plneb/ ] are known in our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap960213.html ], it is thought that most stars go through this phase. Green light is emitted when oxygen [ http://web.cetlink.net/~yinon/o.html ] ions acquire electrons from the surrounding gas.
Explanation: These two clust …
Title Explanation: These two clusters [ http://www.stsci.edu/pubinfo/PR/96/31.html ] of bright, newly formed stars surrounded by a glowing nebula lie 10 million light years away in the dim, irregular galaxy cataloged as NGC 2366. The Hubble Space Telescope image [ http://www.stsci.edu/pubinfo/PR/96/31/A.html ] shows that the youngest cluster, the bottom one at about 2 million years old, is still surrounded by the gas and dust cloud it condensed from, while powerful stellar winds [ http://antwrp.gsfc.nasa.gov/apod/ap960510.html ] from the stars in the older cluster at the top (4-5 million years old), have begun to clear away its central areas giving the entire nebula an apparent hook shape. Compared to the sun, the stars in these clusters are massive and short lived [ http://antwrp.gsfc.nasa.gov/apod/ap951027.html ]. The brightest one, near the tip of the hook, is a rare Luminous Blue Variable with 30 to 60 times the mass of the sun - similar to the erruptive Eta Carina variable [ http://antwrp.gsfc.nasa.gov/apod/ap960611.html ] in our own Milky Way. Stars this massive are extremely variable [ http://physics.umd.edu/rgroups/astro-metro/etacar/etacar.html ]. A comparison with ground based images indicates that in three years this star's brightness increased by about 40 times making it currently the brightest star in this dim galaxy [ http://www.stsci.edu/pubinfo/captions/96-31.txt ]. Studies of such distant and diverse galaxies yield clues to the relationships of star formation and galactic evolution [ http://astrosun.phy.ulaval.ca/astro/pub.html ].
NGC 7293: The Helix Nebula
Title NGC 7293: The Helix Nebula
Explanation Will our Sun [ http://www.nineplanets.org/sol.html ] look like this one day? The Helix Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap000828.html ] is the closest example of a planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ] created at the end of the life of a Sun-like star. The outer gasses of the star expelled into space [ http://www.seds.org/messier/planetar.html ] appear from our vantage point as if we are looking down a helix [ http://mathworld.wolfram.com/Helix.html ]. The remnant central stellar core, destined to become a white dwarf star [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/dwarfs.html ], glows in light so energetic [ http://imagers.gsfc.nasa.gov/ems/uv.html ] it causes the previously expelled gas to fluoresce [ http://www.exploratorium.edu/xref/exhibits/fluorescent_tube.html ]. The Helix Nebula [ http://www.seds.org/messier/xtra/ngc/n7293.html ], given a technical designation of NGC 7293 [ http://www.astro.uiuc.edu/~akspeck/evolved-stuff/nebulae/Helix/ ], lies about 650 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away towards the constellation [ http://www.emufarm.org/~cmbell/myth/myth.html ] of Aquarius [ http://www.astronomical.org/constellations/aqr.html ] and spans about 2.5 light-years. The above picture [ http://hubblesite.org/newscenter/archive/2003/11/ ] is a composite [ http://archive.stsci.edu/hst/helix/ ] of newly released images from the ACS [ http://acs.pha.jhu.edu/ ] instrument on the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] and wide-angle images from the Mosaic Camera on the WIYN [ http://www.noao.edu/wiyn/ ] 0.9-m Telescope [ http://www.noao.edu/dir/09m/description.html ] at Kitt Peak National Observatory [ http://www.noao.edu/kpno/ ]. A close-up [ http://antwrp.gsfc.nasa.gov/apod/ap020512.html ] of the inner edge of the Helix Nebula [ http://hubblesite.org/newscenter/archive/2003/11/fastfacts ] shows complex gas knots of unknown origin [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002ApJ...573L..55H ].
Tomorrow's picture: NGC 3242 …
Title Tomorrow's picture: NGC 3242: The 'Ghost of Jupiter' Planetary Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap970331.html ]
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 medicinal constellation Ophiucus [ http://www.hawastsoc.org/deepsky/oph/index.html ]. 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 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://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://www.ngcic.com/dss/dss_images.htm ] 6960 but less formally as the Witch [ http://antwrp.gsfc.nasa.gov/apod/ap031229.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://www.chapman.edu/oca/benet/intro_sn.htm ].
NGC 3372: The Great Nebula i …
Title NGC 3372: The Great Nebula in Carina
Explanation In one of the brightest parts of the Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap990224.html ] lies a nebula where some of the oddest things occur. NGC 3372, known as the Great Nebula in Carina [ http://www.ast.cam.ac.uk/AAO/images/captions/aat009.html ], is home to massive stars and changing nebula. Eta Carina [ http://antwrp.gsfc.nasa.gov/apod/ap020428.html ], the most energetic star in the nebula was one of the brightest stars [ http://www.astro.wisc.edu/%7Edolan/constellations/extra/brightest.html ] in the sky in the 1830s, but then faded dramatically. The Keyhole Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap000613.html ], visible near the center, houses several of the most massive stars known and has also changed its appearance. The Carina Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap031126.html ] spans over 300 light years and lies about 7000 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away in the constellation of Carina [ http://www.astro.wisc.edu/%7Edolan/constellations/constellations/Carina.html ]. The above image [ http://www.starryscapes.com/nebula/eta_carinae.html ] was taken from La Frontera in Alcohuaz, Chile [ http://sunsite.dcc.uchile.cl/chile/chile.html ]. Eta Carina [ http://antwrp.gsfc.nasa.gov/apod/ap971129.html ] might explode in a dramatic supernova [ http://heasarc.gsfc.nasa.gov/docs/snr.html ] within the next thousand years, and has even flared in brightness [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1999A%26A...346L..33S ] over just the past decade [ http://cfa-www.harvard.edu/iauc/07100/07146.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 left corner of this view, nearly edge-on to the line-of-sight. Surprisingly, minerals including water ice, along with complex hydrocarbon molecules have been detected [ http://iapetus.phy.umist.ac.uk/ NGC6302/ngc63202_paper_in_preparation.pdf ] 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 ].
NGC 7009: The Saturn Nebula
Title NGC 7009: The Saturn Nebula
Explanation The layers of the Saturn Nebula [ http://oposite.stsci.edu/pubinfo/PR/97/38/b5.html ] give a complex picture of how this planetary nebula [ http://www.seds.org/messier/planetar.html ] was created. The above picture [ http://oposite.stsci.edu/pubinfo/PR/97/38/b-js.html ], taken in April 1996 and released last week, allows a better understanding of the mysterious process that transformed a low-mass star into a white dwarf star [ http://antwrp.gsfc.nasa.gov/apod/ap971102.html ]. A computer model indicates that the central star of NGC 7009 [ http://www.astro.washington.edu/balick/WFPC2/n7009.caption.html ] first expelled the green gas that now appears barrel shaped. This green gas now confines stellar winds flowing from the central star, creating a jet which forms the ansae [ http://antwrp.gsfc.nasa.gov/apod/ap961122.html ] that appear in red at the tips. Much remains unknown, including why the gas has not become turbulent [ http://jcbmac.chem.brown.edu/scissorsHtml/liquids/turbulence.html ].
NGC 5307: A Symmetric Planet …
Title NGC 5307: A Symmetric Planetary Nebula
Explanation Some stellar nebulae are strangely symmetric. For example, every major blob of gas visible on the upper left of NGC 5307 [ http://oposite.stsci.edu/pubinfo/PR/97/38/b6.html ] appears to have a counterpart on the lower right. This picture taken by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap970306.html ] was released last week [ http://oposite.stsci.edu/pubinfo/PR/97/38/b-js.html ]. NGC 5307 is an example of a planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap971230.html ] with a spiral shape. Spiral planetary nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap951229.html ] are thought to be caused by a bright central white dwarf star [ http://antwrp.gsfc.nasa.gov/apod/ap961203.html ] expelling a symmetric wobbling jet [ http://oposite.stsci.edu/pubinfo/PR/97/38/b6.html ] of rapidly moving gas. It takes light about 10,000 years to reach us from NGC 5307 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AAS%2E%2E%2E187%2E8005B&db_key=AST&nosetcookie=1 ], and about 6 months just to go from one side to the other. In contrast, light takes only about 8 minutes to reach Earth [ http://antwrp.gsfc.nasa.gov/apod/ap971112.html ] from the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap960518.html ].
NGC 1977: Blue Reflection Ne …
Title NGC 1977: Blue Reflection Nebula in Orion
Explanation The Orion Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap980127.html ] is visible to the unaided eye as a fuzzy patch near the famous belt of three stars [ http://antwrp.gsfc.nasa.gov/apod/ap951114.html ] in the constellation [ http://galileo.gmu.edu/constellation/constellation.html ] Orion [ http://antwrp.gsfc.nasa.gov/apod/ap970523.html ]. The above picture captures a part of the Orion Nebula [ http://seds.lpl.arizona.edu/billa/twn/n1976x.html ] that primarily reflects light from bright Orion stars. This reflection nebula [ http://antwrp.gsfc.nasa.gov/apod/index/ReflectionNebulae.html ] appears blue because the blue light from the neighboring stars scatters more efficiently from nebula gas than does red light. The dark lanes are composed of mostly interstellar dust [ http://antwrp.gsfc.nasa.gov/apod/ap980116.html ] - fine needle-shaped carbon grains.
Planetary Nebula NGC 7027 in …
Title Planetary Nebula NGC 7027 in Infrared
Explanation NGC 7027 [ http://antwrp.gsfc.nasa.gov/apod/ap960117.html ] is one of the smallest known planetary nebulae [ http://www.seds.org/messier/planetar.html ]. Even so, NGC 7027 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997A%26A%2E%2E%2E323%2E%2E217P&db_key=AST&high=33613e8e5825712&nosetcookie=1 ] is 14,000 times larger than the Earth-Sun distance [ http://encarta.msn.com/index/concise/0VOL0E/01b40000.asp ]. Planetary nebula are so named [ http://antwrp.gsfc.nasa.gov/apod/ap980218.html ] because the first few discovered appeared similar to planets. Planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap971223.html ] are actually dying stars, though, that have recently run out of nuclear fuel. The outer gaseous shells are expelled by an unknown process, frequently creating spectacular displays [ http://antwrp.gsfc.nasa.gov/apod/ap961203.html ]. In the above picture [ http://oposite.stsci.edu/pubinfo/pr/1998/11/a.html ] in infrared light [ http://www.ipac.caltech.edu/Outreach/Edu/discovery.html ], the hot central star is visible. Our Sun [ http://antwrp.gsfc.nasa.gov/apod/ap960916.html ] will become a planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap970802.html ] in about 5 billion years.
NGC 6369: A Donut Shaped Neb …
Title NGC 6369: A Donut Shaped Nebula
Explanation Why isn't the star in the center of the nebula? NGC 6369 [ http://www.astro.psu.edu/users/rbc/NGC6369.html ] appears to be a fairly ordinary planetary nebula [ http://www.astro.lsa.umich.edu/OLDWWW/users/iotm/9612/nebula.html ]. It can be seen with a good telescope in the constellation of Ophiuchus [ http://galileo.gmu.edu/constellation/OPH.html ]. The gas expelled by the central star is bunched in the shape of a donut or cylinder. During the planetary nebula [ http://www.seds.org/messier/planetar.html ] phase, the central star sheds its outer atmosphere as it is evolving to become a white dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap971102.html ] star. The above image was taken with the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950811.html ]. A closer look at NGC 6369 indicates that the central star is closer to a dimmer edge of the nebula than to the opposing brighter edge.
NGC 6302: The Butterfly Nebu …
Title NGC 6302: The Butterfly Nebula
Explanation The Butterfly Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap971021.html ] is only thousands of years old. As a central star of a binary system [ http://antwrp.gsfc.nasa.gov/apod/ap970219.html ] aged, it threw off its outer envelopes of gas in a strong stellar wind [ http://mars-hotel.ph.msstate.edu/~mhia/data/S/Stellarwind.html ]. The remaining stellar core is so hot it ionizes the previously ejected gas, causing it to glow. The different colors of this planetary nebula [ http://www.seds.org/messier/planetar.html ] are determined by small differences in its composition. This bipolar nebula [ http://antwrp.gsfc.nasa.gov/apod/ap971223.html ] will continue to shine brightly for only a few thousand more years, after which its central star will fade and become a white dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap971102.html ] star. The above picture [ http://www.hq.eso.org/outreach/info-events/ut1fl/pr-pictures/ut1fl-set3.html#04 ] is one of the first ever taken by the Very Large Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap960901.html ] (VLT), a new 8.2-meter telescope located in Chile [ http://sunsite.dcc.uchile.cl/chile/chile.html ].
NGC 7023: The Iris Nebula
Title NGC 7023: The Iris Nebula
Explanation Like delicate cosmic petals, these clouds of interstellar dust and gas have blossomed 1,300 light-years away in the fertile star fields of the constellation Cepheus [ http://www.astropix.com/HTML/E_SUM_N/ CEPHEUSO.HTM ]. Sometimes called the Iris Nebula and dutifully cataloged as NGC [ http://www.seds.org/billa/ngc.html ] 7023, this is not the only nebula in the sky to evoke the imagery of flowers [ http://antwrp.gsfc.nasa.gov/apod/ap010214.html ]. Still, the beautiful digital image [ http://www.robgendlerastropics.com/NGC7023.html ] shows off the Iris Nebula's range of colors and symmetries in impressive detail. Within the Iris, dusty nebular material surrounds a massive, hot, young star in its formative [ http://antwrp.gsfc.nasa.gov/apod/ap040315.html ] years. Central filaments of cosmic dust glow with a reddish photoluminesence as some dust grains effectively convert [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query? bibcode=1989ApJ...347L..25W&db_key=AST&high=3bc4bede8e21358 ] the star's invisible ultraviolet [ http://imagers.gsfc.nasa.gov/ems/uv.html ] radiation to visible red light. Yet the dominant color of the nebula is blue, characteristic of dust [ http://leo.astronomy.cz/mix/mix.html ] grains reflecting starlight. Dark, obscuring clouds of dust and cold molecular gas are also present and can lead the eye to see other convoluted [ http://antwrp.gsfc.nasa.gov/apod/ap010720.html ] and fantastic [ http://antwrp.gsfc.nasa.gov/apod/ap031229.html ] shapes. Infrared observations [ http://cdsads.u-strasbg.fr/cgi-bin/ nph-bib_query?2000A%26A...354L..17M&db_key=AST&nosetcookie=1 ] indicate that this nebula may contain complex carbon molecules known as PAHs [ http://www.chem.ucl.ac.uk/cosmicdust/pah.htm ]. As shown here, the Iris Nebula [ http://www.noao.edu/outreach/aop/observers/n7023.html ] is about 6 light-years across.
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/ap040704.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://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/ap020703.html ] running across NGC 3132 [ http://heritage.stsci.edu/1998/39/index.html ] are well understood.
NGC 6210: The "Turtle in Spa …
Title NGC 6210: The "Turtle in Space" Planetary Nebula
Explanation A Turtle in Space? Planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap980809.html ] NGC 6210 may look like a giant space turtle, but it is actually much more massive and violent. Fortunately, this gas cloud in Hercules [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Hercules.html ] lies about 6500 light years away. NGC 6210 [ http://oposite.stsci.edu/pubinfo/pr/1998/36/index.html ] was investigated [ http://presto.stsci.edu/cgi-bin/get-proposal-info?6792 ] with the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ] because it showed evidence of unusual relative abundances of nebular gas. The resulting detailed representative-color picture, above [ http://oposite.stsci.edu/pubinfo/pr/1998/36/pr-photos.html ], shows jets of hot gas streaming through holes in an older, cooler shell of gas. The central star that created the planetary nebula [ http://www.noao.edu/jacoby/pn_gallery.html ] is clearly visible in the center of the inset image. Analyses of data involving this recently released picture [ http://oposite.stsci.edu/pubinfo/pr/1998/36/pr-photos.html ] may help explain the origin of chemical abundances [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1993A%26A...280..581P&db_key=AST&high=34f6e1de7f27697 ] in this nebula and our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap971229.html ].
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/ap971004.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://aibn47.astro.uni-bonn.de/~gallery/nebulae/n7635.html ] is actually the smallest of three bubbles surrounding massive star BD+602522 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1995A%26A...295..509C&db_key=AST&high=34f6e1de7f22312 ], and part of gigantic bubble network S162 created with the help of other massive stars. As fast moving gas expands off BD+602522, it pushes surrounding sparse gas into a shell. The energetic starlight then ionizes the shell, causing it to glow. The Bubble Nebula [ http://heritage.stsci.edu/public/Oct22/bubble/NGC7635table.html ], also known as NGC 7635, is about 10 light-years across and visible with a small telescope towards the constellation of Cassiopeia [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Cassiopeia.html ].
NGC 1499: California Nebula
Title NGC 1499: California Nebula
Explanation 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 on the west coast of the United States. 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. Also known as NGC 1499 [ http://www.seds.org/~spider/spider/ Misc/n1499.html ], the classic emission nebula is around 100 light-years 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 ].
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, the glowing gas originated in the outer layers of a star like our Sun [ http://www.hawastsoc.org/solar/eng/sun.htm ]. In this representative color picture [ http://oposite.stsci.edu/pubinfo/pr/1998/39/index.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 NGC 3132 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/ap980318.html ] running across NGC 3132 [ http://oposite.stsci.edu/pubinfo/pr/1998/39/content/prc9839.txt ] are well understood.
Stars, Dust and Nebula in NG …
Title Stars, Dust and Nebula in NGC 6559
Explanation When stars form, pandemonium reigns. A textbook [ http://zebu.uoregon.edu/text.html ] case is the star forming region NGC 6559 [ http://antwrp.gsfc.nasa.gov/apod/ap040629.html ]. Visible above 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 ] can be 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.
Reflection Nebula NGC 1435
Title Reflection Nebula NGC 1435
Explanation Reflection nebulae [ http://www.aao.gov.au/local/www/dfm/reflection.html ] reflect light from a nearby star. Many small carbon [ http://mwanal.lanl.gov/julie/imagemap/periodic/6.html ] grains in the nebula reflect the light. The blue color typical of reflection nebula [ http://fusedweb.pppl.gov/CPEP/Chart_Pages/5.Plasmas/Nebula/Reflection.html ] is caused by blue light being more efficiently scattered [ http://math.ucr.edu/home/baez/physics/blue_sky.html ] by the carbon dust [ http://antwrp.gsfc.nasa.gov/apod/ap980104.html ] than red light. The brightness of the nebula is determined by the size and density of the reflecting grains, and by the color and brightness of the neighboring star(s). NGC 1435 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1979ApJ...231..732J ], pictured above [ http://www.janis.or.jp/users/kitahara/e-m45-95.jpg.html ], surrounds Merope (23 Tau) [ http://www.seds.org/messier/more/m045_tab.html ], one of the brightest stars in the Pleiades [ http://antwrp.gsfc.nasa.gov/apod/ap981025.html ] (M45). The Pleiades [ http://www.seds.org/messier/m/m045.html ] nebulosity is caused by a chance encounter between an open cluster [ http://antwrp.gsfc.nasa.gov/apod/ap980803.html ] of stars and a molecular cloud [ http://antwrp.gsfc.nasa.gov/apod/ap970430.html ]. The unusual area on the far left, known as Bernard's Merope Nebula [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1996AJ....111.1241H ] (IC 349), reflects visible light with unusually high efficiency.
NGC 6334: The Bear Claw Nebu …
Title NGC 6334: The Bear Claw Nebula
Explanation NGC 6334 is a cloud of gas and dust that appears to be forming massive stars. At 5500 light-years away, the Bear Claw Nebula [ http://slime.bu.edu/~kraemer/pics.html ], as it has also been dubbed, is more than three times as distant as the Orion Nebula [ http://www.seds.org/billa/twn/n1976x.html ], but still close enough for detailed study. The Bear Claw Nebula can be found towards the constellation of Scorpius [ http://astro.gmu.edu/classes/a113/constellations/SCO1.HTM ]. In visible light, ionized gas makes NGC 6334 look quite red [ http://www.aao.gov.au/local/www/dfm/uks011.html ]. The above false-color photograph, however, was taken in infrared light [ http://www.ipac.caltech.edu/Outreach/Edu/discovery.html ]. There, the glow of starlight absorbing dust [ http://www.pha.jhu.edu/~danforth/superfit/superfit.html ] is more apparent (depicted in blue). Current research [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1999ApJ...512..260J ] indicates that the bright sources are very young and massive stars. These stars emit light so energetic and intense that it destroys fine grains of dust [ http://antwrp.gsfc.nasa.gov/apod/ap980104.html ] in their immediate vicinity, creating an abundance of ionized gas [ http://www.unm.edu/~sgoold/Plasma.html ] (depicted in red).
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