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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.
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! 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 ].
Celebrating Hubble With NGC …
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 ].
NGC 6888: A Tricolor Starfie …
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 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 ].
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 ].
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.
NGC 3603: X-Rays From A Star …
Title NGC 3603: X-Rays From A Starburst Cluster
Explanation A mere 20,000 light-years from the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap000412.html ] lies the NGC 3603 [ http://chandra.harvard.edu/photo/cycle1/1123/ index.html ] star cluster, a resident of the nearby Carina [ http://www.astronomical.org/constellations/car.html ] spiral arm of our Milky Way galaxy [ http://www.seds.org/messier/more/mw.html ]. Seen here in this recent false-color x-ray image from [ http://chandra.harvard.edu/photo/cycle1/1123/ 1123_hand.html ] the Chandra Observatory, NGC 3603 is well known [ http://www.mpia-hd.mpg.de/STARS/NGC3603/NGC3603.html ] to astronomers as a young cluster in a large galactic star-forming region. [ http://www.ipac.caltech.edu/2mass/gallery/ images_hii.html#ngc3603 ] The image colors were chosen to show the relative x-ray brightness of the many individual sources present, where green are faint and red to purple hues are bright sources of x-rays. The stars in the cluster were formed in a single "burst" of star formation only one or two million years ago, so the x-rays are believed to come from the massive young stars themselves or from their energetic stellar winds. Since other common galactic sources of x-rays [ http://chandra.harvard.edu/xray_sources/index.html ] such as supernova remnants and neutron stars [ http://antwrp.gsfc.nasa.gov/apod/ap001215.html ] represent final stages in the life of a massive star, they are unlikely to be present in such a young cluster. Nearby NGC 3603 [ http://antwrp.gsfc.nasa.gov/apod/ap991018.html ] is thought to be a convenient example of the star clusters that populate distant starburst galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap980701.html ].
NGC 5139: Omega Centauri
Title NGC 5139: Omega Centauri
Explanation Centaurus [ http://hawastsoc.org/deepsky/cen/index.html ] is one of the most striking constellations in the southern sky. The Milky Way flows through this celestial expanse [ http://www.astro.wisc.edu/~dolan/constellations/extra/ Centaurus.html ] whose wonders also include the closest star system to the Sun, Alpha Centauri [ http://antwrp.gsfc.nasa.gov/apod/ap030323.html ], and the largest globular star cluster in our galaxy, Omega Centauri [ http://seds.org/messier/xtra/ngc/n5139.html ] (aka NGC 5139). This sharp [ http://www.martinpughastrophotography.id.au/Star_Clusters/ NGC5139.htm ] telescopic view of Omega Centauri shows off the central regions of the cluster of about 10 million stars. Omega Cen itself is about 15,000 light-years away and 150 light-years in diameter - the largest of 150 or so known globular [ http://seds.lpl.arizona.edu/messier/xtra/supp/mw_gc.html ] star clusters that roam the halo of our galaxy [ http://cassfos02.ucsd.edu/public/tutorial/MW.html ]. Though most star clusters consist of stars with the same age and composition, the enigmatic Omega Cen exhibits [ http://arxiv.org/abs/astro-ph/0402144 ] the presence of different stellar populations with a spread of ages and chemical abundances. In [ http://antwrp.gsfc.nasa.gov/apod/ap031213.html ] fact, Omega Cen may be the remnant core of a small galaxy merging [ http://arxiv.org/abs/astro-ph/0402144 ] with the Milky Way.
NGC 6826: The Blinking Eye
Title NGC 6826: The Blinking Eye
Explanation The colorful planetary nebula phase [ http://www.astro.washington.edu/balick/WFPC2/ ] of a sun-like star's life is brief [ http://oposite.stsci.edu/pubinfo/PR/97/38/astrofile1.html ]. Almost in the "blink of an eye" - cosmically speaking - the star's outer layers are cast off, forming an expanding emission nebula. This nebula lasts perhaps 10 thousand years compared to a 10 billion year stellar life span. Spectacular planetary nebulae [ http://oposite.stsci.edu/pubinfo/PR/97/38.html ] are familiar objects to both professional and amateur astronomers, but they still contain a few surprises. For instance, the lovely nebula NGC 6826 [ http://www.astro.washington.edu/balick/WFPC2/n6826.caption.html ], also known as the Blinking Eye Nebula, has mysterious red FLIERS [ http://antwrp.gsfc.nasa.gov/apod/ap961122.html ] seen on either side of the Hubble Space Telescope image above. Are they also expanding outward from the central star? If so, their "bow shocks" [ http://antwrp.gsfc.nasa.gov/apod/ap971203.html ] point in the wrong direction!
NGC 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 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 ].
Starburst Cluster in NGC 360 …
Title Starburst Cluster in NGC 3603
Explanation A mere 20,000 light-years from the Sun lies NGC 3603 [ http://www.univie.ac.at/webda/cgi-bin/ ocl_page.cgi?cluster=NGC+3603 ], a resident of the nearby Carina spiral arm of our Milky Way Galaxy [ http://www.atlasoftheuniverse.com/milkyway.html ]. NGC 3603 is [ http://antwrp.gsfc.nasa.gov/apod/ap020814.html ] well known to astronomers as one of the Milky Way's largest star-forming regions. The central open star cluster contains thousands of stars more massive than our Sun, stars that likely formed only one or two million years ago in a single burst of star formation. In fact, nearby NGC 3603 [ http://hubblesite.org/newscenter/archive/releases/2007/34/image/ a/format/zoom/ ] is thought to contain a convenient example of the massive star clusters that populate much more distant starburst galaxies [ http://casswww.ucsd.edu/public/tutorial/Starbursts.html ]. Surrounding the cluster [ http://heritage.stsci.edu/2007/34/supplemental.html ] are natal clouds of glowing interstellar gas and obscuring dust, sculpted by energetic stellar radiation and winds. Recorded by [ http://heritage.stsci.edu/2007/34/fast_facts.html ] the Hubble's Advanced Camera for Surveys, the image spans about 17 light-years.
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 3293: A Bright Young Ope …
Title NGC 3293: A Bright Young Open Cluster
Explanation Hot blue stars [ http://antwrp.gsfc.nasa.gov/apod/ap010506.html ] shine brightly in this beautiful, recently formed galactic or "open" star cluster [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ]. Open cluster NGC 3293 [ http://www.seds.org/messier/xtra/ngc/n3293.html ] is located in the constellation Carina [ http://chandra.harvard.edu/photo/constellations/carina.html ], lies at a distance of about 8000 light years [ http://csep10.phys.utk.edu/guidry/violence/distances.html ], and has a particularly high abundance of these young bright stars. A study [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1982AJ.....87.1478H ] of NGC 3293 [ http://www.aao.gov.au/images/captions/aat010.html ] implies that the blue stars are only about 6 million years old, whereas the cluster's dimmer, redder stars [ http://antwrp.gsfc.nasa.gov/apod/ap010520.html ] appear to be about 20 million years old. If true, star formation [ http://archive.ncsa.uiuc.edu/Cyberia/Bima/StarForm.html ] in this open cluster [ http://www.seds.org/messier/open.html ] took at least 15 million years. Even this amount of time is short, however, when compared with the billions of years stars like our Sun [ http://www.nineplanets.org/sol.html ] live, and the over-ten billion year lifetimes of many galaxies [ http://www.astr.ua.edu/keel/galaxies/history.html ] and our universe [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/debate20.html ]. NGC 3293 appears just in front of a dense dust lane [ http://antwrp.gsfc.nasa.gov/apod/ap990919.html ] emanating from the Carina Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap990719.html ].
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 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 2440 Nucleus: The Hottes …
Title NGC 2440 Nucleus: The Hottest Star?
Explanation In the center of the above photograph [ http://pao.gsfc.nasa.gov/gsfc/lithos/hst/ngc2440/ngc2440.htm ] lies a star [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#star ] with one of the hottest surface temperatures yet confirmed. This bright white dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap950910.html ] star's surface has been measured at greater than 200,000 degrees Celsius - more than 30 times hotter than that of our own Sun [ http://antwrp.gsfc.nasa.gov/apod/ap950813.html ]. The white dwarf [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#wd ]'s extreme heat makes it glow extraordinarily bright: intrinsically more than 250 times brighter than the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap951004.html ]. The star is at the center of the planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap950628.html ] titled NGC 2440, which lies inside our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950908.html ]. The above computer sharpened image was taken by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ].
NGC 7027: A Dying Star's Neb …
Title NGC 7027: A Dying Star's Nebula
Explanation This pseudo-color composite [ http://www.stsci.edu/pubinfo/gif/NGC7027.txt ] of two recent Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ] images is a picture of a Sun-like star nearing the end of its lifetime [ http://plabpc.csustan.edu/astro/stars/stars.htm ]. The exquisite details [ http://www.stsci.edu/pubinfo/PR/96/05.html ] visible in this planetary nebula [ http://fusedweb.pppl.gov/ CPEP/Chart_Pages/5.Plasmas/Nebula/Planetary.html ] indicate that when the star passed through its Red Giant phase [ http://plabpc.csustan.edu/astro/stars/giant.htm ] it initially shrugged off its outer atmosphere [ http://antwrp.gsfc.nasa.gov/apod/ap950628.html ] gently and evenly producing the outer faint spherical shells. As the process continued, material was apparently ejected in dense clumps producing dust clouds in the bright inner regions. The whole ejection process was amazingly rapid, taking only a few thousand years compared to a 10 billion year lifetime typical for Solar type stars. In the end the hot stellar core, now a white dwarf star [ http://antwrp.gsfc.nasa.gov/apod/ap950910.html ], was left - seen here as a white dot at the center of the nebula. Our middle-aged Sun [ http://antwrp.gsfc.nasa.gov/apod/ap951004.html ] will experience a similar fate ... in about 5 billion years!
Spiral Galaxy NGC 2997 from …
Title Spiral Galaxy NGC 2997 from VLT
Explanation NGC 2997 is a grand design spiral galaxy [ http://www.seds.org/messier/spir.html ]. Its small nucleus and sprawling spiral arms give it a type Sc [ http://zebu.uoregon.edu/~js/ast123/lectures/lec13.html ] designation. NGC 2997, pictured above [ http://www.eso.org/outreach/press-rel/pr-1999/pr-06-99.html ], is speeding away [ http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/ExpandUni.html ] from us at about 1100 kilometers per second, which would place it at about 55 million light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] distant, given current estimates of the expansion rate [ http://csep1.phy.ornl.gov/guidry/violence/hubble_constant.html ] of our universe. NGC 2997 [ http://www.ast.cam.ac.uk/AAO/images/captions/aat017.html ] is thought to have a mass of about 100 billion times that of our Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ], but is probably less massive than our own Milky Way galaxy [ http://casswww.ucsd.edu/public/tutorial/MW.html ]. NGC 2997 is not seen face-on [ http://antwrp.gsfc.nasa.gov/apod/ap011004.html ] - it is thought tilted by about 45 degrees. NGC 2997 is particularly notable [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1989ApJ...341..722W ] for a nucleus [ http://antwrp.gsfc.nasa.gov/apod/ap020603.html ] surrounded by a chain of hot giant clouds of ionized [ http://csep10.phys.utk.edu/astr162/lect/light/ionization.html ] hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ].
NGC 1569: Heavy Elements fro …
Title NGC 1569: Heavy Elements from a Small Galaxy
Explanation For astronomers, elements other than hydrogen [ http://antwrp.gsfc.nasa.gov/apod/ap010113.html ] and helium [ http://antwrp.gsfc.nasa.gov/apod/ap010120.html ] are sometimes considered to be simply "heavy elements". It's understandable really, because even lumped all together heavy elements make up an exceedingly small fraction [ http://csep10.phys.utk.edu/astr162/lect/sun/ composition.html ] of the Universe. Still, heavy elements can profoundly influence galaxy and star formation ... not to mention [ http://www.europhysicsnews.com/full/14/article1/ article1.html ] the formation of planets and people. In this tantalizing [ http://chandra.harvard.edu/photo/2002/1060/index.html ] false-color x-ray image from the orbiting Chandra Observatory [ http://chandra.harvard.edu/about/whereis.html ], small dwarf galaxy NGC 1569 [ http://www.seds.org/~spider/ngc/ngc.cgi?1569 ] is surrounded by x-ray emitting [ http://chandra.harvard.edu/xray_astro/ ] clouds of gas thousands of light-years across. The gas has recently been observed [ http://arXiv.org/abs/astro-ph/0203513 ] to contain significant concentrations of astronomers' heavy elements such as oxygen, silicon, and magnesium, supporting the idea that dwarf galaxies, the most common type of galaxy in the Universe [ http://www.anzwers.org/free/ universe/galgrps.html ], are largely responsible for heavy elements in intergalactic space. A mere 7 million light-years distant toward the long-necked [ http://www.nature-wildlife.com/girtxt.htm ] constellation Camelopardalis [ http://www.dibonsmith.com/cam_con.htm ], NGC 1569 has undergone a recent burst of star formation and stellar supernova explosions [ http://curious.astro.cornell.edu/ supernovae.php ]. The furious cosmic activity [ http://heasarc.gsfc.nasa.gov/docs/xmm_lc/edu/ lessons/background-lifecycles.html ] has heated the expanding gas clouds to temperatures of millions of degrees while enriching them with newly synthesized [ http://antwrp.gsfc.nasa.gov/apod/ap011026.html ] heavy elements.
Open Cluster NGC 6520 from C …
Title Open Cluster NGC 6520 from CFHT
Explanation Did you ever have a day when it felt like a dark cloud [ http://antwrp.gsfc.nasa.gov/apod/ap010923.html ] was following you around? For the open cluster [ http://www.seds.org/messier/open.html ] of stars NGC 6520, every day is like this. On the left of the above picture [ http://www.cfht.hawaii.edu/HawaiianStarlight/AIOM/English/CFHT-Coelum-AIOM.html ] are many of NGC 6520's bright blue stars. They formed only millions of years ago - much more recently than our ancient Sun which formed billions of years ago. On the right is an absorption nebula [ http://antwrp.gsfc.nasa.gov/apod/dark_nebulae.html ], molecular cloud [ http://origins.jpl.nasa.gov/poster/bigbang3.html ] Barnard 86 [ http://astro.uchicago.edu/yerkes/virtualmuseum/Barnard.html ], from which the stars of NGC 6520 surely formed. This nebula contains much opaque dust [ http://antwrp.gsfc.nasa.gov/apod/ap010813.html ] that blocks light from the many stars that would have been visible in the background. Surrounding NGC 6520 [ http://www.ast.cam.ac.uk/AAO/images/captions/aat092.html ] is part of the tremendously dense starscape in the bulge of our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap970315.html ], the extended halo of stars that surrounds the center [ http://antwrp.gsfc.nasa.gov/apod/ap010708.html ] of our Galaxy. NGC 6520 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1982S%26T....63..254M ] spans about 10 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] and lies about 5500 light years away toward the direction of Sagittarius [ http://www.astronomical.org/constellations/sgr.html ].
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 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 ].
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 1818: Pick A Star
Title NGC 1818: Pick A Star
Explanation This is NGC 1818 [ http://antwrp.gsfc.nasa.gov/apod/ap980307.html ], a youthful, glittering cluster of 20,000 stars residing in the Large Magellanic Cloud [ http://seds.lpl.arizona.edu/messier/xtra/ngc/lmc.html ], 180,000 light-years away. Pick a star. Any star. Astronomers might pick [ http://oposite.stsci.edu/pubinfo/pr/1998/16/ ] the unassuming bluish-white one (circled) which appears [ http://hubblesite.org/sci.d.tech/behind_the_pictures/ wacky_shape/index.shtml ] to be a hot newly formed white dwarf star. What makes it so interesting? The standard astronomical wisdom suggests that stars over 5 times as massive as the sun rapidly exhaust [ http://archive.ncsa.uiuc.edu/Cyberia/Bima/ StarDeath.html ] their nuclear fuel and end their lives in a spectacular supernova explosion [ http://antwrp.gsfc.nasa.gov/apod/ap030528.html ]. With less than this critical mass [ http://heasarc.gsfc.nasa.gov/docs/ xmm_lc/edu/lessons/background-lifecycles.html ] they evolve into red giants, pass through a relatively peaceful planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap020302.html ] phase, and calmly fade away as white dwarf stars [ http://antwrp.gsfc.nasa.gov/apod/ap000910.html ] like this one. Except that as a member of the NGC 1818 cluster, this new white dwarf would have evolved from a red giant star [ http://www.historyoftheuniverse.com/starold.html ] over 7.6 times as massive as the sun -- which should have exploded! Its discovery [ http://xxx.lanl.gov/abs/astro-ph/9802117 ] will likely force astronomers to revise the limiting mass estimate for supernovae upward.
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 ].
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 6826: The Blinking Eye
Title NGC 6826: The Blinking Eye
Explanation The colorful planetary nebula phase [ http://www.astro.washington.edu/balick/WFPC2/ ] of a sun-like star's life is brief [ http://oposite.stsci.edu/pubinfo/PR/97/38/astrofile1.html ]. Almost in the "blink of an eye" - cosmically speaking - the star's outer layers are cast off, forming an expanding emission nebula. This nebula lasts perhaps 10 thousand years compared to a 10 billion year stellar life span. Spectacular planetary nebulae [ http://oposite.stsci.edu/pubinfo/PR/97/38.html ] are familiar objects to both professional and amateur astronomers, but they still contain a few surprises. For instance, the lovely nebula NGC 6826 [ http://www.astro.washington.edu/balick/WFPC2/n6826.caption.html ], also known as the Blinking Eye Nebula, has mysterious red FLIERS [ http://antwrp.gsfc.nasa.gov/apod/ap961122.html ] seen on either side of the Hubble Space Telescope image above. Are they also expanding outward from the central star? If so, their "bow shocks" [ http://antwrp.gsfc.nasa.gov/apod/ap971203.html ] point in the wrong direction!
NGC 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 ].
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 3293: A Bright Young Ope …
Title NGC 3293: A Bright Young Open Cluster
Explanation Hot blue stars [ http://antwrp.gsfc.nasa.gov/apod/ap971018.html ] shine brightly in this beautiful, recently formed galactic or "open" star cluster. Open cluster [ http://antwrp.gsfc.nasa.gov/apod/index/OpenCluster.html ] NGC 3293 is located in the constellation Carina [ http://galileo.gmu.edu/constellation/CAR.html ], lies at a distance of about 8000 light years, and has a particularly high abundance of these young bright stars. A study of NGC 3293 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1982AJ%2E%2E%2E%2E%2E87%2E1478H&db_key=AST ] implies that the blue stars are only about 6 million years old, whereas the cluster's dimmer, redder stars appear to be about 20 million years old. If true, star formation in this open cluster took at least 15 million years. Even this amount of time is short, however, when compared with the billions of years stars like our Sun [ http://antwrp.gsfc.nasa.gov/apod/lib/sun.html ] live, and the over-ten billion year lifetimes of many galaxies [ http://antwrp.gsfc.nasa.gov/apod/lib/spirals.html ] and our universe. NGC 3293 appears just in front dense dust lane [ http://adsabs.harvard.edu/cgi-bin/nph-article_query?bibcode=1980AJ%2E%2E%2E%2E%2E85%2E1193T&page=1&plate_select=NO&type=GIF ] emanating from the Carina Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap980112.html ].
NGC 1818: Pick A Star
Title NGC 1818: Pick A Star
Explanation This is NGC 1818 [ http://antwrp.gsfc.nasa.gov/apod/ap980307.html ], a youthful, glittering cluster of 20,000 stars residing in the Large Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap980203.html ], 164,000 light-years away. Pick a star. Any star. Astronomers might pick [ http://oposite.stsci.edu/pubinfo/pr/1998/16/ ] the unassuming bluish-white one (circled) which appears to be a hot newly formed white dwarf star. What makes it so interesting? The standard astronomical wisdom [ http://the-tech.mit.edu/Shakespeare/Quotes/bart.LoveLost.html#3 ] suggests that stars over 5 times as massive as the sun rapidly exhaust their nuclear fuel and end their lives in a spectacular supernova explosion [ http://antwrp.gsfc.nasa.gov/apod/ap970225.html ]. With less than this critical mass they evolve into red giants, pass through a relatively peaceful planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap980403.html ] phase, and calmly fade away as white dwarf stars [ http://antwrp.gsfc.nasa.gov/apod/ap961203.html ] like this one. Except that as a member of the NGC 1818 cluster, this new white dwarf would have evolved from a red giant star [ http://antwrp.gsfc.nasa.gov/apod/ap970216.html ] over 7.6 times as massive as the sun - which should have exploded! Its discovery [ http://xxx.lanl.gov/abs/astro-ph/9802117 ] will likely force astronomers to revise the limiting mass estimate for supernovae upward.
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 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.
Celebrating Hubble With NGC …
Title Celebrating Hubble With NGC 6751
Explanation Planetary nebulae can [ http://antwrp.gsfc.nasa.gov/apod/ap040424.html ] look simple, round, and planet-like in small telescopes. But images from the orbiting Hubble Space Telescope [ http://hubblesite.org/reference_desk/faq/ category.php.cat=hst ] have become well known for showing these fluorescent gas shrouds [ http://antwrp.gsfc.nasa.gov/apod/ap050311.html ] of dying Sun-like stars to possess a staggering variety [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ image_category/nebula/planetary/ ] of detailed symmetries and shapes [ http://antwrp.gsfc.nasa.gov/apod/ap040910.html ]. This composite color Hubble image of NGC 6751 [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2000/12/ ] is a beautiful example of a classic planetary nebula with complex features. It was selected in April of 2000, to commemorate the tenth anniversary [ http://hubblesite.org/newscenter/newsdesk/future/ ] 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/ap050123.html ] (140,000 degrees [ http://www.unidata.ucar.edu/staff/ blynds/tmp.html ] Celsius [ http://www.astro.uu.se/history/Celsius_eng.html ]) have apparently created the nebula's streamer-like features. The nebula's [ http://heritage.stsci.edu/2000/12/fast_facts.html ] actual diameter is approximately 0.8 light-years or about 600 times the size of our solar system. NGC 6751 is 6,500 light-years distant in the high-flying constellation Aquila [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Aquila.html ].
Young Suns of NGC 7129
Title Young Suns of NGC 7129
Explanation Young suns still lie within dusty NGC 7129 [ http://coolcosmos.ipac.caltech.edu/image_galleries/ legacy/spitzer_n7129/index.html ], some 3,000 light-years away toward the royal constellation Cepheus [ http://www.astropix.com/HTML/E_SUM_N/CEPHEUSO.HTM ]. While these stars are at a relatively tender age, only about a million years old, it is likely that our own Sun formed in a similar stellar nursery some five "billion" years ago. Most noticeable in the striking image [ http://www.robgendlerastropics.com/NGC7129NM.html ] are the lovely bluish dust clouds that reflect [ http://antwrp.gsfc.nasa.gov/apod/ap011228.html ] the youthful starlight, but the smaller, deep red crescent shapes are also markers of energetic, young stellar objects. Known as Herbig-Haro [ http://www-astro.phast.umass.edu/catalogs/HHcat/ HHintro.html ] objects, their shape and color is characteristic of glowing hydrogen gas shocked by jets [ http://hubblesite.org/newscenter/newsdesk/archive/ releases/1995/24/image/a ] streaming away from newborn stars. Ultimately the natal gas and dust in the region will be dispersed, the stars drifting apart [ http://en.wikipedia.org/wiki/Open_cluster#Eventual_fate ] as the loose cluster orbits the center of the Galaxy. NGC 7129 is [ http://www.noao.edu/outreach/aop/observers/n7129.html ] about 10 light-years across.
NGC 7789: Galactic Star Clus …
Title NGC 7789: Galactic Star Cluster
Explanation At 1.6 billion years old, this cluster of stars [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.html ] is beginning to show its age. NGC [ http://antwrp.gsfc.nasa.gov/apod/ap990429.html ] 7789 is an open or galactic star cluster [ http://www.seds.org/messier/open.html ] about 8,000 light-years distant toward the constellation Cassiopeia [ http://www.seds.org/Maps/Stars_en/Fig/cassiopeia.html ] and lies near the plane of our Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap990224.html ] galaxy. All the stars in the cluster were likely born at the same time but the brighter and more massive ones have more rapidly exhausted [ http://antwrp.gsfc.nasa.gov/htmltest/gifcity/msblues.html ] the hydrogen fuel in their cores. These have evolved from main sequence [ http://plabpc.csustan.edu/astro/stars/main.htm ] stars like the sun into the gaggle of red giant stars apparent (with a reddish-yellow cast) in this lovely composite [ http://aibn47.astro.uni-bonn.de/~gallery/articles/ imagecolor.html#tri ] color image. Comparing computer models to observations of the red giants [ http://antwrp.gsfc.nasa.gov/apod/ap990312.html ] and main sequence stars astronomers can determine [ http://adsabs.harvard.edu/cgi-bin/ nph-bib_query?bibcode=1998PASP..110.1318G&db_key=AST&high=366dca0f3d29234 ] the mass and hence the age of the cluster stars just starting to "turn off" the main sequence [ http://ast.leeds.ac.uk/research/cmd.html ] to become red giants.
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 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.
NGC 3242: The Ghost of Jupit …
Title NGC 3242: The Ghost of Jupiter
Explanation After a star [ http://imagine.gsfc.nasa.gov/docs/teachers/lifecycles/ stars.html ] like the Sun completes fusion in its core, it throws off its outer layers in a brief, beautiful cosmic display called a planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap030614.html ]. NGC 3242 is [ http://www.seds.org/~spider/spider/Misc/ n3242.html ] such a planetary nebula, with the stellar remnant white dwarf star [ http://antwrp.gsfc.nasa.gov/apod/ap000910.html ] visible at the center. This nebula is sometimes called The Ghost of Jupiter for its faint [ http://antwrp.gsfc.nasa.gov/apod/ap050728.html ], but similar appearance to our solar system's ruling gas giant planet. NGC 3242 is [ http://www.astro.washington.edu/balick/W_F_P_C_2/N_3_2_4_2/ index.html ] light-years across however, and much farther away than the measly 40 light-minutes distance to Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ]. In fact, while watching this ghostly nebula expand over time, astronomers have estimated [ http://adsbit.harvard.edu/cgi-bin/ nph-article_query?1995AJ%2E%2E%2E%2E109%2E2600H ] the distance to NGC 3242 to be about 1,400 light-years. The red FLIERs [ http://www.astro.washington.edu/balick/ W_F_P_C_2/ ] visible near the edges of the nebula are still a bit mysterious, though.
Dusty NGC 1333
Title Dusty NGC 1333
Explanation Dusty NGC 1333 [ http://www.noao.edu/outreach/aop/observers/ n1333.html ] is seen as a reflection nebula [ http://antwrp.gsfc.nasa.gov/apod/ap031229.html ] in visible light images, sporting 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 - shown in red in this false-color Spitzer Space Telescope image [ http://www.spitzer.caltech.edu/Media/releases/ssc2005-24/ release.shtml ]. The penetrating infrared view [ http://coolcosmos.ipac.caltech.edu//main_html/ index.html ] also shows youthful stars that would otherwise still be obscured by the dusty [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] clouds which formed them. Notably, greenish streaks and splotches that seem to litter the region trace the glow of cosmic jets [ http://antwrp.gsfc.nasa.gov/apod/ap970619.html ] blasting away from emerging young stellar objects as the jets plow into the cold cloud material. In all, the chaotic scene [ http://www.quotedb.com/quotes/3885 ] 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 3603: An Active Star Clu …
Title NGC 3603: An Active Star Cluster
Explanation NGC 3603 [ http://www.astro.washington.edu/grebel/NGC3603.html ] is home to a massive star cluster, thick dust pillars, and a star about to explode [ http://antwrp.gsfc.nasa.gov/apod/ap970812.html ]. The central open cluster [ http://antwrp.gsfc.nasa.gov/apod/ap960116.html ] contains about 2000 bright stars, each of which is much brighter and more massive than our Sun [ http://www.seds.org/nineplanets/nineplanets/sol.html ]. Together, radiation [ http://snoopy.gsfc.nasa.gov/~orfeus2/ultraviolet.html ]s [ http://antwrp.gsfc.nasa.gov/apod/ap970217.html ] from these stars [ http://antwrp.gsfc.nasa.gov/apod/ap990604.html ] are energizing and pushing away surrounding material, making NGC 3603 [ http://antwrp.gsfc.nasa.gov/cgi-bin/cossc/apod_search?NGC+3603 ] one of the most interesting HII regions [ http://www.treasure-troves.com/astro/HIIRegion.html ] known. NGC 3603 [ http://www.ozemail.com.au/~lmacdonald/universe/12970198/3603-df.htm ] is about 20,000 light-years away, and the region shown is about 20 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] across. Possibly most interesting about this recently released, representative-color picture [ http://www.eso.org/outreach/press-rel/pr-1999/pr-16-99.html ] are the large number of dim stars visible. These stars are less massive than our Sun, demonstrating that great numbers of low-mass stars also form in active starburst regions [ http://antwrp.gsfc.nasa.gov/apod/ap990502.html ].
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