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Comets Kick up Dust in Helix
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| Title |
Comets Kick up Dust in Helix Nebula |
| Description |
This infrared image from NASA's Spitzer Space Telescope shows the Helix nebula, a cosmic starlet often photographed by amateur astronomers for its vivid colors and eerie resemblance to a giant eye. The nebula, located about 700 light-years away in the constellation Aquarius, belongs to a class of objects called planetary nebulae. Discovered in the 18th century, these colorful beauties were named for their resemblance to gas-giant planets like Jupiter. Planetary nebulae are the remains of stars that once looked a lot like our sun. When sun-like stars die, they puff out their outer gaseous layers. These layers are heated by the hot core of the dead star, called a white dwarf, and shine with infrared and visible colors. Our own sun will blossom into a planetary nebula when it dies in about five billion years. In Spitzer's infrared view of the Helix nebula, the eye looks more like that of a green monster's. Infrared light from the outer gaseous layers is represented in blues and greens. The white dwarf is visible as a tiny white dot in the center of the picture. The red color in the middle of the eye denotes the final layers of gas blown out when the star died. The brighter red circle in the very center is the glow of a dusty disk circling the white dwarf (the disk itself is too small to be resolved). This dust, discovered by Spitzer's infrared heat-seeking vision, was most likely kicked up by comets that survived the death of their star. Before the star died, its comets and possibly planets would have orbited the star in an orderly fashion. But when the star blew off its outer layers, the icy bodies and outer planets would have been tossed about and into each other, resulting in an ongoing cosmic dust storm. Any inner planets in the system would have burned up or been swallowed as their dying star expanded. So far, the Helix nebula is one of only a few dead-star systems in which evidence for comet survivors has been found. This image is made up of data from Spitzer's infrared array camera and multiband imaging photometer. Blue shows infrared light of 3.6 to 4.5 microns, green shows infrared light of 5.8 to 8 microns, and red shows infrared light of 24 microns. |
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Comets Kick up Dust in Helix
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| Title |
Comets Kick up Dust in Helix Nebula |
| Description |
This infrared image from NASA's Spitzer Space Telescope shows the Helix nebula, a cosmic starlet often photographed by amateur astronomers for its vivid colors and eerie resemblance to a giant eye. The nebula, located about 700 light-years away in the constellation Aquarius, belongs to a class of objects called planetary nebulae. Discovered in the 18th century, these colorful beauties were named for their resemblance to gas-giant planets like Jupiter. Planetary nebulae are the remains of stars that once looked a lot like our sun. When sun-like stars die, they puff out their outer gaseous layers. These layers are heated by the hot core of the dead star, called a white dwarf, and shine with infrared and visible colors. Our own sun will blossom into a planetary nebula when it dies in about five billion years. In Spitzer's infrared view of the Helix nebula, the eye looks more like that of a green monster's. Infrared light from the outer gaseous layers is represented in blues and greens. The white dwarf is visible as a tiny white dot in the center of the picture. The red color in the middle of the eye denotes the final layers of gas blown out when the star died. The brighter red circle in the very center is the glow of a dusty disk circling the white dwarf (the disk itself is too small to be resolved). This dust, discovered by Spitzer's infrared heat-seeking vision, was most likely kicked up by comets that survived the death of their star. Before the star died, its comets and possibly planets would have orbited the star in an orderly fashion. But when the star blew off its outer layers, the icy bodies and outer planets would have been tossed about and into each other, resulting in an ongoing cosmic dust storm. Any inner planets in the system would have burned up or been swallowed as their dying star expanded. So far, the Helix nebula is one of only a few dead-star systems in which evidence for comet survivors has been found. This image is made up of data from Spitzer's infrared array camera and multiband imaging photometer. Blue shows infrared light of 3.6 to 4.5 microns, green shows infrared light of 5.8 to 8 microns, and red shows infrared light of 24 microns. |
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The Tarantula Nebula
| Title |
The Tarantula Nebula |
| Description |
NASA's new Spitzer Space Telescope, formerly known as the Space Infrared Telescope Facility, has captured in stunning detail the spidery filaments and newborn stars of the Tarantula Nebula, a rich star-forming region also known as 30 Doradus. This cloud of glowing dust and gas is located in the Large Magellanic Cloud, the nearest galaxy to our own Milky Way, and is visible primarily from the Southern Hemisphere. This image of an interstellar cauldron provides a snapshot of the complex physical processes and chemistry that govern the birth -- and death -- of stars. At the heart of the nebula is a compact cluster of stars, known as R136, which contains very massive and young stars. The brightest of these blue supergiant stars are up to 100 times more massive than the Sun, and are at least 100,000 times more luminous. These stars will live fast and die young, at least by astronomical standards, exhausting their nuclear fuel in a few million years. The Spitzer Space Telescope image was obtained with an infrared array camera that is sensitive to invisible infrared light at wavelengths that are about ten times longer than visible light. In this four-color composite, emission at 3.6 microns is depicted in blue, 4.5 microns in green, 5.8 microns in orange, and 8.0 microns in red. The image covers a region that is three-quarters the size of the full moon. The Spitzer observations penetrate the dust clouds throughout the Tarantula to reveal previously hidden sites of star formation. Within the luminescent nebula, many holes are also apparent. These voids are produced by highly energetic winds originating from the massive stars in the central star cluster. The structures at the edges of these voids are particularly interesting. Dense pillars of gas and dust, sculpted by the stellar radiation, denote the birthplace of future generations of stars. The Spitzer image provides information about the composition of the material at the edges of the voids. The surface layers closest to the massive stars are subject to the most intense stellar radiation. Here, the atoms are stripped of their electrons, and the green color of these regions is indicative of the radiation from this highly excited, or 'ionized,' material. The ubiquitous red filaments seen throughout the image reveal the presence of molecular material thought to be rich in hydrocarbons. The Tarantula Nebula is the nearest example of a 'starburst' phenomenon, in which intense episodes of star formation occur on massive scales. Most starbursts, however, are associated with dusty and distant galaxies. Spitzer infrared observations of the Tarantula provide astronomers with an unprecedented view of the lifecycle of massive stars and their vital role in regulating the birth of future stellar and planetary systems. |
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The Eskimo Nebula from the N
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| Title |
The Eskimo Nebula from the Newly Fixed Hubble |
| Explanation |
In 1787, astronomer William Herschel [ http://www.windows.umich.edu/cgi-bin/tour_def/people/enlightenment/herschel.html ] discovered the Eskimo Nebula [ http://www.seds.org/billa/twn/n2392x.html ]. From the ground, NGC 2392 resembles a person's head surrounded by a parka [ http://www.oregonlink.com/arctic/cormorant_parka.html ] hood. In 2000, just after being fixed [ http://antwrp.gsfc.nasa.gov/apod/ap000105.html ], the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap970306.html ] imaged the Eskimo Nebula. From space, the nebula displays gas clouds so complex they are not fully understood. The Eskimo Nebula [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1990ApJ...362..226O ] is clearly a planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ], and the gas seen above composed the outer layers of a Sun-like star only 10,000 years ago. The inner filaments visible above [ http://oposite.stsci.edu/pubinfo/pr/2000/07/pr-photos.html ] are being ejected by strong wind [ http://www-istp.gsfc.nasa.gov/Education/wsolwind.html ] of particles from the central star. The outer disk contains unusual light-year long orange filaments. The Eskimo Nebula lies about 5000 light-year [ http://www.treasure-troves.com/astro/Light-Year.html ]s away and is visible with a small telescope in the constellation [ http://www.emufarm.org/~cmbell/myth/myth.html ] of Gemini [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Gemini.html ]. |
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Eta and Keyhole in the Carin
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| Title |
Eta and Keyhole in the Carina Nebula |
| Explanation |
South is toward the top in this colorful close-up [ http://www.southern-astro.com.au/gallery.php?PhotoID=13 ] view of the Great Carina Nebula [ http://www.seds.org/Messier/xtra/ngc/n3372.html ] (NGC 3372), famous star-forming region of the southern sky. Covering an area surrounding the dusty Keyhole Nebula [ http://heritage.stsci.edu/2000/06/index.html ] (NGC 3324) near picture center, the image spans about 40 light-years within the larger Carina Nebula [ http://etacar.umn.edu/etainfo/images/index.html#wide ] at an estimated distance of 7,500 light-years. Like the more northerly Orion Nebula, the bright Carina Nebula [ http://www.noao.edu/image_gallery/html/im0667.html ] is easily visible to the naked-eye. But the dramatic colors in this telescopic picture are mapped colors [ http://hubblesite.org/sci.d.tech/ behind_the_pictures/meaning_of_color/eagle.shtml ], based on three exposures through narrow filters each intended to record the light emitted by specific atoms in the gaseous nebula. Sulfur is shown in blue, hydrogen in green and oxygen in red hues. The Carina Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap051015.html ] is home to young, extremely massive stars, including the still enigmatic [ http://arxiv.org/abs/astro-ph/0603168 ] variable Eta Carinae [ http://www.seds.org/messier/xtra/ngc/etacar.html ], a star with well over 100 times the mass of the Sun. Highlighted by diffraction [ http://antwrp.gsfc.nasa.gov/apod/ap010415.html ] spikes, Eta is just above [ http://etacar.umn.edu/etainfo/basic/ ] and right (east) of the Keyhole. |
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The Eskimo Nebula from Hubbl
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| Title |
The Eskimo Nebula from Hubble |
| Explanation |
In 1787, astronomer William Herschel [ http://www.windows.ucar.edu/cgi-bin/tour_def/people/enlightenment/herschel.html ] discovered the Eskimo Nebula [ http://www.seds.org/billa/twn/n2392x.html ]. From the ground, NGC 2392 resembles a person's head surrounded by a parka [ http://www.oregonlink.com/arctic/cormorant_parka.html ] hood. In 2000, the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap021124.html ] imaged the Eskimo Nebula [ http://www.noao.edu/outreach/aop/observers/n2392.html ]. From space, the nebula displays gas clouds so complex they are not fully understood. The Eskimo Nebula [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1990ApJ...362..226O ] is clearly a planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ], and the gas seen above composed the outer layers of a Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ]-like star only 10,000 years ago. The inner filaments visible above [ http://hubblesite.org/newscenter/newsdesk/archive/releases/2000/07/image/a ] are being ejected by strong wind [ http://www-istp.gsfc.nasa.gov/Education/wsolwind.html ] of particles from the central star. The outer disk contains unusual light-year [ http://en.wikipedia.org/wiki/Light_year ] long orange filaments. |
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MyCn18: An Hourglass Nebula
| Title |
MyCn18: An Hourglass Nebula |
| Explanation |
The sands of time are running out for the central star of this hourglass-shaped planetary nebula [ http://fusedweb.pppl.gov/CPEP/ Chart_Pages/5.Plasmas/Nebula/Planetary.html ]. With its nuclear fuel [ http://fusedweb.pppl.gov/default.html ] exhausted, this brief, spectacular, closing phase of a Sun-like star's life [ http://observe.ivv.nasa.gov/nasa/space/stellardeath/stellardeath_contents.html ] occurs as its outer layers are ejected - its core becoming a cooling, fading White Dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap971102.html ]. Astronomers have recently used the Hubble Space Telescope [ http://hubble.stsci.edu/ ] (HST) to make a series of images of planetary nebulae [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ], including the one above [ http://www.stsci.edu/pubinfo/PR/96/07.html ]. Here, delicate rings of colorful glowing gas (nitrogen-red, hydrogen-green, and oxygen-blue) outline the tenuous walls of the "hourglass". The unprecedented sharpness of the HST images has revealed surprising details [ http://www.stsci.edu/pubinfo/gif/Hourgls.txt ] of the nebula ejection process [ http://antwrp.gsfc.nasa.gov/apod/ap960117.html ] and may help resolve the outstanding mystery of the variety of complex shapes and symmetries of planetary nebulae [ http://www.astro.washington.edu/balick/WFPC2/index.html ]. |
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The Crab Nebula in Blue and
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| Title |
The Crab Nebula in Blue and White |
| Explanation |
The Crab Nebula is a complex shell of expanding gas. The Crab Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap991122.html ] formed from a star that was seen to explode in a supernova [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html ] about 1000 years ago. This two color composite image [ http://www.noao.edu/image_gallery/html/im0466.html ] taken with the WIYN 3.5-meter telescope [ http://www.noao.edu/wiyn/wiynis.html ] shows in great detail filamentary structure of the glowing hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] gas. Also known as M [ http://www.seds.org/messier/xtra/history/CMessier.html ]1, the center is home to a dense neutron star [ http://www.astro.umd.edu/~miller/nstar.html ], a star as massive as our Sun [ http://www.seds.org/nineplanets/nineplanets/sol.html ] but only the size of a city [ http://antwrp.gsfc.nasa.gov/apod/ap970408.html ]. The neutron star [ http://antwrp.gsfc.nasa.gov/apod/neutron_stars.html ] is a pulsar [ http://lheawww.gsfc.nasa.gov/users/padi/Pulse/crab.html ] that spins thirty times a second and spits out energy that powers the nebula. The nebula [ http://nineplanets.org/twn/n1952x.html ] is named from its likeness to a crab [ http://www.clever.net/kerry/creature/helmet.htm ] in an early drawing. The Crab Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap981122.html ] still presents mysteries [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1995ApJ...454L.129F ] today as the total mass of the nebula and pulsar [ http://www.jb.man.ac.uk/~pulsar/Education/Sounds/sounds.html ] appears much less than the mass of the original pre-supernova star [ http://antwrp.gsfc.nasa.gov/apod/ap970812.html ]! |
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Light from the Heart Nebula
| Title |
Light from the Heart Nebula |
| Explanation |
What powers the Heart Nebula? The large emission nebula [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] dubbed IC 1805 [ http://antwrp.gsfc.nasa.gov/apod/ap040917.html ] looks, in whole, like a human heart [ http://www.pbs.org/wgbh/nova/heart/heartmap.html ]. The nebula glows brightly in red light emitted by its most prominent element: hydrogen [ http://en.wikipedia.org/wiki/Hydrogen ]. The red glow and the larger shape are all created by a small group of stars near the nebula's center [ http://antwrp.gsfc.nasa.gov/apod/ap060922.html ]. A close up spanning about 30 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] contains many of these stars is shown above [ http://www.telescopes.cc/ic1805large.htm ] . This open cluster [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] of stars contains a few bright stars [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2006A%26A...456.1121D ] nearly 50 times the mass of our Sun, many dim stars only a fraction of the mass of our Sun, and an absent microquasar [ http://antwrp.gsfc.nasa.gov/apod/ap040916.html ] that was expelled millions of years ago. The Heart Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap031022.html ] is located about 7,500 light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away toward the constellation [ http://www.mallorcaweb.net/masm/descon1.htm ] of Cassiopeia [ http://www.seds.org/Maps/Stars_en/Fig/cassiopeia.html ]. |
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NGC 1499: The California Neb
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| 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 ]. |
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At the Edge of the Crescent
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| Title |
At the Edge of the Crescent Nebula |
| Explanation |
The Crescent Nebula is a rapidly expanding shell of gas surrounding a dying star. In this recently released image [ http://oposite.stsci.edu/pubinfo/PR/2000/23/pr-photos.html ] by the Hubble Space Telescope [ http://oposite.stsci.edu/pubinfo/HSToverview.html ], a bright dynamic part of the nebula three light-years across is shown in representative color. The Crescent Nebula [ http://www.ne.jp/asahi/stellar/scenes/object_e/ngc6888.htm ] began to form about 250,000 years ago as central Wolf-Rayet [ http://antwrp.gsfc.nasa.gov/apod/ap970928.html ] star WR 136 began to shed its outer envelope in a strong stellar wind [ http://www-istp.gsfc.nasa.gov/Education/wsolwind.html ], expelling the equivalent of our Sun's mass every 10,000 years. This wind [ http://science.msfc.nasa.gov/ssl/pad/solar/sun_wind.htm ] has been impacting surrounding interstellar gas [ http://antwrp.gsfc.nasa.gov/apod/ap000412.html ], compacting it into a series of complex shells, and lighting it up. The Crescent Nebula [ http://www.astro.uni-bonn.de/~maltmann/n6888colinfo.html ], also known as NGC 6888, lies about 4,700 light-years [ http://www.howstuffworks.com/question94.htm ] away in the constellation [ http://www.eaglequest.net/~bondono/iconst.html ] of Cygnus [ http://www.seds.org/Maps/Stars_en/Fig/cygnus.html ] and can only be seen through a telescope. Star WR 136 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1996A%26A...316..133G ] will probably undergo a supernova [ http://antwrp.gsfc.nasa.gov/apod/supernova_remnants.html ] explosion sometime in the next million years. |
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The Helix Nebula from CFHT
| Title |
The Helix Nebula from CFHT |
| Explanation |
One day our Sun may look like this. The Helix Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap960417.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://snoopy.gsfc.nasa.gov/~orfeus2/ultraviolet.html ] it causes the previously expelled gas to fluoresce [ http://www.exploratorium.edu/xref/exhibits/fluorescent_tube.html ]. The Helix Nebula [ http://www-personal.umich.edu/~jstys/nebulae/ngc7293.html ], given a technical designation of NGC 7293 [ http://www.seds.org/messier/xtra/ngc/n7293.html ], lies 450 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 1.5 light-years. The above image was taken with the Canada-France-Hawaii Telescope [ http://www.cfht.hawaii.edu/ ] (CFHT) located atop a dormant volcano in Hawaii [ http://www.state.hi.us/ ], USA. A close-up of the inner edge [ http://antwrp.gsfc.nasa.gov/apod/ap970720.html ] of the Helix Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap970901.html ] shows unusual gas knots of unknown origin [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998ApJ...503..792B ]. |
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M42: Wisps of the Orion Nebu
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| Title |
M42: Wisps of the Orion Nebula |
| Explanation |
The Great Nebula in Orion [ http://www.seds.org/billa/twn/n1976x.html ], an immense, nearby starbirth region [ http://antwrp.gsfc.nasa.gov/apod/stellar_nurseries.html ], is probably the most famous of all astronomical nebulas [ http://www.seds.org/billa/twn/ ]. Here, glowing gas [ http://fusedweb.pppl.gov/CPEP/Chart_Pages/5.Plasmas/Nebula/Emission.html ] surrounds hot young stars at the edge of an immense [ http://antwrp.gsfc.nasa.gov/apod/ap971201.html ] interstellar molecular cloud [ http://antwrp.gsfc.nasa.gov/apod/ap030202.html ] only 1500 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away. In the above deep image [ http://christensenastroimages.com/nebula/m42_2005.htm ], faint wisps and sheets of dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] and gas are particularly evident. The Great Nebula in Orion [ http://www.seds.org/messier/m/m042.html ] can be found with the unaided eye just below and to the left of the easily identifiable [ http://antwrp.gsfc.nasa.gov/apod/ap021225.html ] belt of three stars in the popular constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] Orion [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=60 ]. In addition to housing a bright open cluster [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] of stars known as the Trapezium [ http://antwrp.gsfc.nasa.gov/apod/ap971118.html ], the Orion Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap061120.html http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?Orion+Nebula ] contains many stellar nurseries [ http://archive.ncsa.uiuc.edu/Cyberia/Bima/StarForm.html ]. These nurseries contain hydrogen [ http://periodic.lanl.gov/elements/1.html ] gas, hot young stars, proplyds [ http://antwrp.gsfc.nasa.gov/apod/ap961017.html ], and stellar jets [ http://antwrp.gsfc.nasa.gov/apod/ap991129.html ] spewing material at high speeds. Also known as M42 [ http://antwrp.gsfc.nasa.gov/apod/ap020213.html ], the Orion Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap980421.html ] spans about 40 light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] and is located in the same spiral arm [ http://www.anzwers.org/free/universe/5000lys.html ] of our Galaxy [ http://adc.gsfc.nasa.gov/mw/mmw_images.html ] as the Sun [ http://www.nineplanets.org/sol.html ]. |
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IC 418: The Spirograph Nebul
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| Title |
IC 418: The Spirograph Nebula |
| Explanation |
What is creating the strange texture of IC 418? Dubbed the Spirograph Nebula [ http://heritage.stsci.edu/public/2000sept7/ic418table.html ] for its resemblance to drawings from a cyclical drawing tool [ http://www.wordsmith.org/~anu/java/spirograph.html ], planetary nebula [ http://www.noao.edu/jacoby/pn_gallery.html ] IC 418 shows patterns [ http://mathworld.wolfram.com/Spirograph.html ] that are not well understood. Perhaps they are related to chaotic winds [ http://www-spof.gsfc.nasa.gov/Education/wsolwind.html ] from the variable central star, which changes brightness unpredictably [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997A%26A...320..125H ] in just a few hours. By contrast, evidence indicates that only a few million years ago, IC 418 [ http://www.skyhound.com/sh/archive/jan/IC_418.html ] was probably a well-understood star similar to our Sun [ http://www.seds.org/nineplanets/nineplanets/sol.html ]. Only a few thousand years ago, IC 418 was probably a common red giant [ http://www.historyoftheuniverse.com/starold.html ] star. Since running out of nuclear fuel [ http://csep10.phys.utk.edu/astr162/lect/energy/ppchain.html ], though, the outer envelope has begun expanding outward leaving a hot remnant core destined to become a white-dwarf star [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/dwarfs.html ], visible in the image [ http://heritage.stsci.edu/public/2000sept7/displayic418.html ] center. The light from the central core excites surrounding atoms [ http://www.pbs.org/wgbh/aso/tryit/atom/ ] in the nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ] causing them to glow. IC 418 lies about 2000 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away and spans 0.3 light-years across. This recently released false-color image [ http://heritage.stsci.edu/public/2000sept7/ic418table.html ] taken from the Hubble Space Telescope [ http://www.stsci.edu/hst/ ] reveals the unusual details. |
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The Nebula And The Neutron S
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| Title |
The Nebula And The Neutron Star |
| Explanation |
The lonely RX J1856.5-3754 [ http://www.eso.org/outreach/press-rel/pr-2000/pr-19-00.html ] was formed from the collapsed core of an exploding star. At a distance of 180 light-years it is the closest known [ http://arXiv.org/abs/astro-ph/?0009031 ] neutron star. More massive than the Sun but only 20 kilometers across, this tiny stellar juggernaut plows through the hydrogen gas and dust clouds of interstellar space at about 200 kilometers per second. The surface of the neutron star [ http://www.astro.umd.edu/~miller/nstar.html ] is fantastically hot, around 700,000 degrees Celsius, making it detectable with orbiting x-ray telescopes. But optical astronomers were recently surprised to discover that RX J1856.5-3754 is also surrounded by a cone-shaped nebula. Indicated in this deep image from the European Southern Observatory's Kueyen telescope [ http://antwrp.gsfc.nasa.gov/apod/ap000707.html ], the nebula glows in the red light of ionized hydrogen atoms recombining with [ http://csep10.phys.utk.edu/astr162/lect/light/ absorption.html ] electrons. Its cone shape is analogous [ http://antwrp.gsfc.nasa.gov/apod/ap991127.html ] to the bow wave of a ship plowing through water. A faint blue dot near the tip of the cone is the neutron star itself. The nebula appears to have formed very near the surface [ http://antwrp.gsfc.nasa.gov/htmltest/rjn_bht.html ] of the neutron star and astronomers are trying to determine if the observed densities and temperatures can indeed explain the nebula's appearance. |
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Planetary Nebula NGC 2440
| Title |
Planetary Nebula NGC 2440 |
| Explanation |
Planetary nebula [ http://en.wikipedia.org/wiki/Planetary_nebula ] NGC 2440 has an intriguing bow-tie [ http://www.folds.net/bowtie/ ] shape in this stunning view [ http://hubblesite.org/newscenter/archive/releases/2007/09/ ] from space. The nebula is composed of material cast off by a dying sun-like star as it enters its white dwarf phase [ http://antwrp.gsfc.nasa.gov/apod/ap060507.html ] of evolution. Details of remarkably complex structures are revealed within [ http://adsabs.harvard.edu/abs/1998ApJ...493..803L ] NGC 2440, including dense ridges of material swept back from the nebula's central star. Near the center of the view, the star itself is one of the hottest known [ http://antwrp.gsfc.nasa.gov/apod/ap951130.html ], with a surface temperature of about 200,000 kelvins [ http://lamar.colostate.edu/~hillger/temps.htm ]. About 4,000 light-years from planet Earth toward the nautical constellation Puppis [ http://hawastsoc.org/deepsky/pup/index.html ], the nebula spans over a light-year and is energized by ultraviolet light from the central star. The false-color image [ http://archive.stsci.edu/prepds/heritage/ngc2440/index.html ] was recorded earlier this month using the Hubble's Wide-Field Planetary Camera 2(WFPC2), demonstrating still impressive imaging capabilities following the failure of the Advanced Camera for Surveys. |
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X-rays and the Eagle Nebula
| Title |
X-rays and the Eagle Nebula |
| Explanation |
The premier Chandra X-ray Observatory images of M16 [ http://chandra.harvard.edu/photo/2007/m16/ ], the Eagle Nebula, show many bright x-ray sources in the region. Most of the x-ray sources [ http://chandra.harvard.edu/xray_astro/medxray.html ] are energetic young stars. They are seen here as colored spots superimposed on the Hubble's well-known optical view of M16's light-year long Pillars of Creation [ http://antwrp.gsfc.nasa.gov/apod/ap070218.html ]. For example, a blue source near [ http://chandra.harvard.edu/photo/2007/m16/zoom.html ] the tip of the large pillar at the upper left is estimated to be an embedded young star 4 or 5 times as massive as the Sun [ http://www.sunblock99.org.uk/sb99/fact/ heavy.html ]. Still, most of the x-ray sources are not coincident with the pillars themselves, indicating that embedded stars are not common in the dusty structures. The mostly empty pillars are thought to be an indication [ http://arxiv.org/abs/astro-ph/0610279 ] that star formation actually peaked millions of years ago within [ http://arxiv.org/abs/astro-ph/0201292 ] the Eagle Nebula [ http://seds.lpl.arizona.edu/messier/m/m016.html ]. |
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Dust and the Helix Nebula
| Title |
Dust and the Helix Nebula |
| Explanation |
Dust makes this cosmic eye look red. The eerie Spitzer Space Telescope image [ http://www.spitzer.caltech.edu/Media/releases/ ssc2007-03/index.shtml ] shows infrared [ http://coolcosmos.ipac.caltech.edu// ] radiation from the well-studied Helix Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap060112.html ] (NGC 7293) a mere 700 light-years away in the constellation Aquarius [ http://www.seds.org/Maps/Stars_en/Fig/aquarius.html ]. The two light-year diameter shroud of dust and gas around a central white dwarf has long been considered an excellent example of a planetary nebula [ http://www.noao.edu/jacoby/pn_gallery.html ], representing the final stages in the evolution of a sun-like star. But the Spitzer data show the nebula's central star itself is immersed in a surprisingly bright infrared glow. Models [ http://arxiv.org/abs/astro-ph/0702296 ] suggest the glow is produced by a dust debris disk [ http://antwrp.gsfc.nasa.gov/apod/ap041210.html ]. Even though the nebular material was ejected from the star many thousands of years ago, the close-in dust could be generated by collisions in a reservoir of objects analogous to our own solar system's Kuiper Belt [ http://www.ifa.hawaii.edu/faculty/jewitt/kb/kb.con.html ] or cometary Oort cloud [ http://www.windows.ucar.edu/tour/ link=/comets/Oort_cloud.html&edu=high ]. Formed in the distant planetary system, the comet-like bodies have otherwise survived even the dramatic late stages of the star's evolution [ http://en.wikipedia.org/wiki/Stellar_evolution ]. |
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M2-9: Wings of a Butterfly N
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| Title |
M2-9: Wings of a Butterfly Nebula |
| Explanation |
Are stars better appreciated for their art after they die? Actually, stars usually create their most artistic displays "as" they die. In the case of low-mass stars like our Sun [ http://www.seds.org/nineplanets/nineplanets/sol.html ] and M2-9 pictured above [ http://oposite.stsci.edu/pubinfo/PR/97/38/a.html ], the stars transform themselves from normal stars to white dwarfs [ http://antwrp.gsfc.nasa.gov/apod/white_dwarfs.html ] by casting off their outer gaseous envelopes. The expended gas frequently forms an impressive display called a planetary nebula [ http://www.seds.org/messier/planetar.html ] that fades gradually over thousand of years. M2-9 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997A%26A...319..267S ], a butterfly planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ] 2100 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away shown in representative colors, has wings that tell a strange but incomplete tale [ http://oposite.stsci.edu/pubinfo/PR/97/38/pr.html ]. In the center, two stars [ http://antwrp.gsfc.nasa.gov/apod/ap970219.html ] orbit inside a gaseous disk 10 times the orbit of Pluto [ http://antwrp.gsfc.nasa.gov/apod/ap990213.html ]. The expelled envelope of the dying star breaks out from the disk creating the bipolar appearance [ http://antwrp.gsfc.nasa.gov/apod/ap991012.html ]. Much remains unknown about the physical processes that cause planetary nebulae [ http://www.noao.edu/jacoby/pn_gallery.html ]. |
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Spherical Planetary Nebula A
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| Title |
Spherical Planetary Nebula Abell 39 |
| Explanation |
One of the largest spheres in our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ] is giving valuable clues about the chemical composition of stars by its very shape. Planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ] Abell 39 [ http://www.noao.edu/image_gallery/html/im0636.html ], now six light-years across, was once a sun-like star's outer atmosphere expelled thousands of years ago. The nearly perfect spherical [ http://math.rice.edu/~pcmi/sphere/ ] nature of Abell 39 [ http://www.noao.edu/outreach/press/pr01/pr0102.html ] allows astronomers to accurately estimate how much relative material is actually absorbing [ http://csep10.phys.utk.edu/astr162/lect/light/absorption.html ] and emitting light. Observations indicate that Abell 39 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000AAS...197.0616J ] contains only about half of the oxygen [ http://pearl1.lanl.gov/periodic/elements/8.html ] found in the Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ], an intriguing but not surprising confirmation of the chemical differences between stars. The reason why the central star is slightly off center by 0.1 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] is currently unknown. Abell 39 [ http://www.astrsp-mrs.fr/private/nebulae/a39.html ] lies about 7000 light years away, although several galaxies [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] millions of light years away can be seen through and around the nebula. |
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Planetary Nebula Mz3: The An
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| Title |
Planetary Nebula Mz3: The Ant Nebula |
| Explanation |
Why isn't this ant a big sphere? Planetary nebula [ http://www.noao.edu/jacoby/pn_gallery.html ] Mz3 is being cast off by a star similar to our Sun [ http://www.nineplanets.org/sol.html ] that is, surely, round. Why then would the gas that is streaming away create an ant [ http://www.discovery.com/cams/ant/learn.html ]-shaped nebula that is distinctly not round? Clues might include [ http://hubble.esa.int/hubble/news/ index.cfm?oid=25994 ] the high 1000-kilometer per second speed of the expelled gas, the light-year [ http://starchild.gsfc.nasa.gov/docs/StarChild/ questions/question19.html ] long length of the structure, and the magnetism [ http://www.wondermagnet.com/dev/magfaq.html ] of the star visible above [ http://heritage.stsci.edu/public/2001feb/display.html ] at the nebula's center. One possible answer is that Mz3 [ http://heritage.stsci.edu/public/2001feb/table.html ] is hiding a second, dimmer star that orbits close [ http://antwrp.gsfc.nasa.gov/apod/ap991219.html ] in to the bright star. A competing hypothesis holds that the central star's own spin and magnetic field [ http://antwrp.gsfc.nasa.gov/apod/ap980629.html ] are channeling the gas. Since the central star appears to be so similar to our own Sun, astronomers [ http://www.aas.org/%7Eeducation/career.html ] hope that increased understanding of the history of this giant space ant [ http://www.ag.ohio-state.edu/~ohioline/hyg-fact/2000/2064.html ] can provide useful insight into the likely future of our own Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ] and Earth [ http://antwrp.gsfc.nasa.gov/apod/earth.html ]. |
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M27: The Dumbbell Nebula
| Title |
M27: The Dumbbell Nebula |
| Explanation |
The first hint of what will become of our Sun [ http://www.nineplanets.org/sol.html ] was discovered inadvertently in 1764. At that time, Charles Messier [ http://www.seds.org/messier/xtra/history/biograph.html ] was compiling a list of "annoying" diffuse objects not to be confused with "interesting" comets. The 27th object on Messier's list [ http://antwrp.gsfc.nasa.gov/apod/ap960626.html ], now known as M27 [ http://www.seds.org/messier/m/m027.html ] or the Dumbbell Nebula, is a planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ], the type of nebula our Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ] will produce when nuclear fusion [ http://fusedweb.pppl.gov/ ] stops in its core. M27 [ http://antwrp.gsfc.nasa.gov/apod/ap981009.html ] is one of the brightest planetary nebulae [ http://www.seds.org/messier/planetar.html ] on the sky, and can be seen in the constellation [ http://www.att.virtualclassroom.org/vc99/vc_04/cons_stars/cons/hist_cons.html ] Vulpecula [ http://www.astronomical.org/constellations/vul.html ] with binoculars. It takes light about 1000 years to reach us from M27, shown above [ http://www.noao.edu/image_gallery/html/im0589.html ] in representative colors. Understanding the physics and significance of M27 [ http://www.seds.org/messier/twn/n6853x.html ] was well beyond 18th century science. Even today, many things remain mysterious about bipolar planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap001217.html ] like M27, including the physical mechanism that expels a low-mass star's gaseous outer-envelope, leaving an X-ray [ http://www.treasure-troves.com/physics/X-Ray.html ] hot white dwarf [ http://www.sciencenet.org.uk/database/Physics/Stars/p01158c.html ]. |
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The Cat's Eye Nebula from Hu
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| Title |
The Cat's Eye Nebula from Hubble |
| Explanation |
Staring across interstellar space, the alluring Cat's Eye [ http://heritage.stsci.edu/2004/27/] nebula lies three thousand light-years from Earth. A classic planetary nebula [ http://www.seds.org/messier/planetar.html ], the Cat's Eye (NGC 6543) represents a final, brief yet glorious phase [ http://www.astro.washington.edu/balick/WFPC2/ ] in the life of a sun-like star. This nebula's dying central star may have produced the simple, outer pattern of dusty concentric shells [ http://arxiv.org/abs/astro-ph/0401056 ] by shrugging [ http://antwrp.gsfc.nasa.gov/apod/ap011003.html ] off outer layers [ http://antwrp.gsfc.nasa.gov/apod/ap031101.html ] in a series of regular convulsions. But the formation of the beautiful, more complex inner structures is not well understood [ http://antwrp.gsfc.nasa.gov/apod/ap061112.html ]. Seen so clearly in this sharp Hubble [ http://hubblesite.org/newscenter/newsdesk/archive/ releases/2004/27/fastfacts/ ] Space Telescope image, the truly cosmic eye is over half a light-year across. Of course, gazing into the Cat's Eye [ http://antwrp.gsfc.nasa.gov/apod/ap031101.html ], astronomers may well be seeing the fate of our sun, destined to enter its own planetary nebula phase [ http://chandra.harvard.edu/xray_sources/ white_dwarfs.html ] of evolution ... in about 5 billion years [ http://hubblesite.org/newscenter/newsdesk/archive/ releases/1997/38/astrofile/ ]. |
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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/ ]. |
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NGC 3132: The Eight Burst Ne
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| Title |
NGC 3132: The Eight Burst Nebula |
| Explanation |
It's the dim star, not the bright one, near the center of NGC 3132 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997AAS...191.1508S&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. |
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Pulsar Wind in the Vela Nebu
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| Title |
Pulsar Wind in the Vela Nebula |
| Explanation |
The Vela pulsar was born [ http://antwrp.gsfc.nasa.gov/apod/ap980425.html ] 10,000 years ago at the center of a supernova -- an exploding star [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/ supernovae.html ]. In this Chandra Observatory x-ray image [ http://chandra.harvard.edu/photo/cycle1/velawv/ index.html ], the pulsar still produces a glowing nebula at the heart of the expanding cloud of stellar debris. The pulsar [ http://www.jb.man.ac.uk/~pulsar/Education/Sounds/ sounds.html ] itself is a neutron star [ http://heasarc.gsfc.nasa.gov/docs/objects/binaries/ neutron_star_structure.html ], formed as the stellar core was compacted [ http://observe.ivv.nasa.gov/nasa/space/stellardeath/ stellardeath_3a.html ] to nuclear densities. With a strong magnetic field, approximately the mass of the Sun, and a diameter of about 20 kilometers, the Vela pulsar rotates 11 times "a second". The sharp Chandra image aids astronomers [ http://xxx.lanl.gov/abs/astro-ph/0105128 ] in understanding such extreme systems as efficient high-voltage generators [ http://chandra.harvard.edu/chronicle/0201/vela.html ] which drive structured winds [ http://antwrp.gsfc.nasa.gov/apod/ap000609.html ] of electrically charged particles. An x-ray bright nebula is created as the pulsar winds slam into the surrounding material. This view spans about 6 light-years across the central region of the much larger Vela supernova remnant [ http://antwrp.gsfc.nasa.gov/apod/ap960612.html ]. |
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NGC 3132: The Eight Burst Ne
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| Title |
NGC 3132: The Eight Burst Nebula |
| Explanation |
It's the dim star, not the bright one, near the center of NGC 3132 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query? bibcode=1997AAS...191.1508S ] that created this odd but beautiful planetary nebula [ http://www.seds.org/messier/planetar.html ]. Nicknamed the Eight-Burst Nebula [ http://en.wikipedia.org/wiki/NGC_3132 ] and the Southern Ring Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap060625.html ], the glowing gas originated in the outer layers [ http://antwrp.gsfc.nasa.gov/apod/ap010301.html ] of a star like our Sun [ http://www.nineplanets.org/sol.html ]. In this representative color picture [ http://heritage.stsci.edu/1998/39/supplemental.html ], the hot blue pool of light seen surrounding this binary system [ http://antwrp.gsfc.nasa.gov/apod/ap970219.html ] is energized by the hot surface of the faint star. Although photographed to explore [ http://hubblesite.org/newscenter/archive/releases/1998/39/image/a/ ] unusual symmetries, it's the asymmetries that help make this planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ] so intriguing. Neither the unusual shape of the surrounding cooler shell nor the structure and placements of the cool filamentary dust lanes [ http://antwrp.gsfc.nasa.gov/apod/ap020703.html ] running across NGC 3132 [ http://heritage.stsci.edu/1998/39/index.html ] are well understood. |
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Cold Dust in the Eagle Nebul
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| Title |
Cold Dust in the Eagle Nebula |
| Explanation |
Stars are born in M16's Eagle Nebula [ http://seds.lpl.arizona.edu/messier/m/m016.html ], a stellar nursery 7,000 light-years from Earth toward the constellation Serpens [ http://www.astronomical.org/constellations/ser.html ]. The striking nebula's star forming pillars [ http://antwrp.gsfc.nasa.gov/apod/ap000924.html ] of gas and dust are familiar to astronomers [ http://antwrp.gsfc.nasa.gov/apod/ap970730.html ] from images at visible wavelengths, but this false-color picture [ http://sci.esa.int/content/news/ photorelease.cfm?aid=1&cid=1&oid=28114 ] shows off the nebula in infrared light [ http://imagers.gsfc.nasa.gov/ems/infrared.html ]. Data from ESA's Infrared Space Observatory [ http://www.iso.vilspa.esa.es/users/expl_lib/ mission.html ] satellite (ISO) was used to construct the detailed two color image [ http://www.iso.vilspa.esa.es/galleries/ism/eagle.htm ], dominated by infrared emission from clouds of interstellar material at temperatures below -100 degrees Celsius. Blue colors highlight emission thought to indicate the presence of complex carbon molecules [ http://www.sciam.com/explorations/1999/032299life/ ], known on planet Earth as PAHs [ http://www.chem.ucl.ac.uk/cosmicdust/pah.htm ], while red colors trace emission from cold, microscopic dust grains [ http://science.nasa.gov/headlines/y2000/ ast24apr_1.htm ]. Hot young stars are formed as this frigid material condenses under the influence of gravity [ http://hyperphysics.phy-astr.gsu.edu/hbase/astro/ gravc.html ]. Once begun, the process takes [ http://www.astro.psu.edu/users/carkner/ttauri/ star1.html ] only tens of thousands of years for truly massive stars and up to tens of millions of years for low mass stars like the Sun. |
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NGC 6888: The Crescent Nebul
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| 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. |
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The Great Carina Nebula
| Title |
The Great Carina Nebula |
| Explanation |
A jewel of the southern sky [ http://antwrp.gsfc.nasa.gov/apod/ap070222.html ], the Great Carina Nebula [ http://seds.org/messier/xtra/ngc/n3372.html ], aka NGC 3372, spans over 300 light-years, one of our galaxy's [ http://antwrp.gsfc.nasa.gov/apod/ap071020.html ] largest star forming regions. Like the smaller, more northerly Orion Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap070106.html ], the Carina Nebula is easily visible to the naked eye, though at a distance of 7,500 light-years it is some 5 times farther away. This stunning telescopic view [ http://www.robgendlerastropics.com/EtacarinaeSG.html ] reveals remarkable details of the region's glowing filaments of interstellar gas and dark cosmic dust clouds. The Carina Nebula is home to young, extremely massive stars, including the still enigmatic variable Eta Carinae [ http://etacar.umn.edu/etainfo/images/index.html#wide ], a star with well over 100 times the mass of the Sun. Eta Carinae [ http://www.astro.uiuc.edu/~kaler/sow/etacar.html ] is the bright star left of the central dark notch in this field and just below the dusty Keyhole [ http://antwrp.gsfc.nasa.gov/apod/ap060316.html ] Nebula (NGC 3324). |
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The Planetary Nebula Show
| Title |
The Planetary Nebula Show |
| Explanation |
What do the Owl, the Cat's Eye, the Ghost of Jupiter, and Saturn have in common? They're all planetary nebulae [ http://ad.usno.navy.mil/pne/ ] of course(!), glowing gaseous shrouds shed by dying sun-like stars as they run out [ http://www.astro.washington.edu/balick/WFPC2/index.html ] of nuclear fuel. Beautiful to look at [ http://www.ucalgary.ca/~zhangc/pnimage.html ], the symmetric, planet-like shapes [ http://www.seds.org/messier/planetar.html ] of these cosmic clouds [ http://www.ipac.caltech.edu/2mass/gallery/ images_pne.html ], typically 1,000 times the size of our solar system [ http://www.cismall.com/deepsky/nebulae.html ], evoke their popular names. Flipping through [ http://www.noao.edu/outreach/aop/observers/ pn.html ] digital pictures made by participants in the Kitt Peak National Observatory Visitor Center's Advanced Observing Program [ http://www.noao.edu/outreach/aop/ ], astronomer Adam Block created [ http://antwrp.gsfc.nasa.gov/apod/ap010427.html ] this delightful animation. Ten different planetary nebula images are presented, each registered on the central star. In order, their catalog designations are NGC 1535 [ http://www.noao.edu/outreach/aop/observers/n1535.html ], NGC 3242 [ http://antwrp.gsfc.nasa.gov/apod/ap970331.html ] (Ghost of Jupiter), NGC 6543 [ http://home.achilles.net/~jtalbot/spectra/ Nebulium.html ] (Cat's Eye), NGC 7009 [ http://antwrp.gsfc.nasa.gov/apod/ap971230.html ] (Saturn Nebula), NGC 2438 [ http://antwrp.gsfc.nasa.gov/apod/ap990305.html ], NGC 6772 [ http://www.noao.edu/outreach/aop/observers/n6772.html ], Abell 39 [ http://antwrp.gsfc.nasa.gov/apod/ap010123.html ], NGC 7139 [ http://www.noao.edu/outreach/aop/observers/n7139.html ], NGC 6781 [ http://www.noao.edu/outreach/aop/observers/n6781.html ], and M97 [ http://www.noao.edu/outreach/aop/observers/ m97.html ] (Owl Nebula). This glorious final phase [ http://oposite.stsci.edu/pubinfo/PR/97/38/ astrofile1.html ] in the life of a star lasts only about 10,000 years. |
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The Medusa Nebula
| Title |
The Medusa Nebula |
| Explanation |
Braided, serpentine filaments of glowing gas suggest this nebula's popular name, The Medusa Nebula. Also known as Abell 21, this Medusa is an old planetary nebula [ http://www.seds.org/messier/planetar.html ] some 1,500 light-years away in the constellation Gemini [ http://en.wikipedia.org/wiki/Gemini_(constellation) ]. Like its mythological [ http://en.wikipedia.org/wiki/Medusa ] namesake, the nebula is associated with a dramatic transformation. The planetary nebula [ http://www.noao.edu/jacoby/pn_gallery.html ] phase represents a final stage in the evolution [ http://casswww.ucsd.edu/public/tutorial/StevI.html ] of low mass stars like the sun [ http://www.astro.washington.edu/balick/WFPC2/ ], as they transform themselves from red giants to hot white dwarf stars and in the process shrug off their outer layers. Ultraviolet radiation [ http://hyperphysics.phy-astr.gsu.edu/hbase/ems1.html ] from the hot star powers the nebular glow. The Medusa's transforming hot central star is visible in the detailed color image [ http://dg-imaging.astrodon.com/gallery/ display.cfm?imgID=106 ] as the small blue star within the upper half of the overall bright crescent shape [ http://www.noao.edu/outreach/aop/observers/medusa.html ]. Fainter filaments clearly extend above and to the left of the bright crescent region. The Medusa Nebula is estimated to be over 4 light-years across. |
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NGC 2346: A Butterfly-Shaped
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| 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. |
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T Tauri and Hind's Variable
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| Title |
T Tauri and Hind's Variable Nebula |
| Explanation |
The orange star centered in this remarkable telescopic skyview [ http://dg-imaging.astrodon.com/gallery/ display.cfm?imgID=109 ] is T Tauri, prototype of the class of T Tauri variable [ http://www.aavso.org/vstar/vsots/0201.shtml ] stars. Nearby it is a dusty yellow cosmic cloud historically known [ http://www.astro.umass.edu/catalogs/HHcat/abstracts/ herbigasp.html ] as Hind's Variable Nebula (NGC 1555/1554). Over 400 light-years away, at the edge of a molecular cloud, both star and nebula are seen [ http://mira.aavso.org/pipermail/aavso-discussion/ 2004-December/011285.html ] to vary significantly in brightness but not necessarily at the same time, adding to the mystery of the intriguing region. T Tauri stars are now generally recognized as young (less than a few million years old), sun-like stars still in the early [ http://hyperphysics.phy-astr.gsu.edu/hbase/astro/ gravc.html ] stages of formation [ http://archive.ncsa.uiuc.edu/Cyberia/Bima/ StarForm.html ]. To further [ http://fr.arxiv.org/abs/astro-ph/0406337 ] complicate the picture, infrared observations indicate that T Tauri itself is part of a multiple system and suggest that the associated Hind's [ http://www.daviddarling.info/encyclopedia/H/Hind.html ] Nebula may also contain a very young stellar object. The dramatic color image spans about 4 light-years at the estimated distance of T Tauri [ http://www.astronomy.com/asy/default.aspx?c=a&id=2765 ]. |
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M2-9: Wings of a Butterfly N
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| Title |
M2-9: Wings of a Butterfly Nebula |
| Explanation |
Are stars better appreciated for their art after they die? Actually, stars usually create their most artistic displays "as" they die. In the case of low-mass stars like our Sun [ http://www.nineplanets.org/sol.html ] and M2-9 pictured above [ http://oposite.stsci.edu/pubinfo/PR/97/38/a.html ], the stars transform themselves from normal stars to white dwarfs [ http://antwrp.gsfc.nasa.gov/apod/ap000910.html ] by casting off their outer gaseous envelopes. The expended gas frequently forms an impressive display called a planetary nebula [ http://www.seds.org/messier/planetar.html ] that fades gradually over thousand of years. M2-9 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997A%26A...319..267S ], a butterfly planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ] 2100 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away shown in representative colors, has wings that tell a strange but incomplete tale [ http://oposite.stsci.edu/pubinfo/PR/97/38/pr.html ]. In the center, two stars [ http://antwrp.gsfc.nasa.gov/apod/ap970219.html ] orbit inside a gaseous disk 10 times the orbit of Pluto [ http://antwrp.gsfc.nasa.gov/apod/ap990213.html ]. The expelled envelope of the dying star breaks out from the disk creating the bipolar appearance [ http://antwrp.gsfc.nasa.gov/apod/ap991012.html ]. Much remains unknown about the physical processes that cause planetary nebulae [ http://www.noao.edu/jacoby/pn_gallery.html ]. |
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The Great Nebula in Orion
| Title |
The Great Nebula in Orion |
| Explanation |
The Great Nebula in Orion, M42, can be found on the night sky just below and to the left of the easily identifiable belt of three stars in the popular constellation Orion. This nebula is one of the closest stellar nurseries - where young stars are being formed even now. Clumps of gas (mostly hydrogen and helium) and dust in the nebula are squeezed together by their own gravity until they collapse and form stars. Some stars we can see here partially obscured by the nebula, are only about 100,000 years old - just babies compared to the 5 billion (5,000,000,000) years of our Sun. For more information see NASA, Hubble Space Telescope Scientific Institute press release. [ http://www.stsci.edu/ftp/stsci/epa/gif/OrionFull.txt ] |
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M1: The Crab Nebula
| Title |
M1: The Crab Nebula |
| Explanation |
In the year 1054 a star in the constellation of Taurus exploded in a spectacular supernova [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#sn ] so bright it appeared to dominate the sky except for the Sun and Moon for many days. It left behind one of the most brilliant nebulae, listed first in Charles Messier's [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#messier ] list of nebulous sky objects. Today we know that the center of the nebula houses the remnant of the explosion: a spinning neutron star [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#ns ] called a pulsar. The Crab pulsar is visible in almost every part of the electromagnetic spectrum, and has been a useful astronomical tool. It is still unclear how the the pulsar emits the light that we see. For more information on M1 see The Electronic Universe Project's write-up. [ http://zebu.uoregon.edu/messier/m1.txt ] Many images of Messier objects can be found in The Electronic Universe Project's The Galaxy Gallery: Messier Objects. [ http://zebu.uoregon.edu/messier.html ] Tomorrow's picture: M15: A Great Globular Cluster |
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M57: The Ring Nebula
| Title |
M57: The Ring Nebula |
| Explanation |
A star with mass similar to that of our Sun will throw off its outer gasses after fusion has stopped in its core. Possibly the most visually spectacular of these planetary nebula is the pictured Ring Nebula. The appearance as a ring is really an illusion of projection - the nebula is actually a spherical shell. At the center a blue dot is visible which is the old core of the star, known as a white dwarf. [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#wd ] It is still not known exactly how the star throws off the gas that becomes the nebula. For more information on the Ring Nebula see The Electronic Universe Project's write-up. [ http://zebu.uoregon.edu/messier/m57.txt ] Many images of Messier objects can be found in The Electronic Universe Project's The Galaxy Gallery: Messier Objects. [ http://zebu.uoregon.edu/messier.html ] Tomorrow's picture: M82: An Irregular Galaxy |
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NGC 2244: A Star Cluster in
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| 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 ]. |
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The Eskimo Nebula from Hubbl
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| Title |
The Eskimo Nebula from Hubble |
| Explanation |
In 1787, astronomer William Herschel [ http://www.windows.ucar.edu/cgi-bin/tour_def/people/enlightenment/herschel.html] discovered the Eskimo Nebula [ http://www.seds.org/billa/twn/n2392x.html ]. From the ground, NGC 2392 resembles a person's head surrounded by a parka [ http://www.oregonlink.com/arctic/cormorant_parka.html ] hood. In 2000, the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap970306.html ] imaged the Eskimo Nebula. From space, the nebula displays gas clouds so complex they are not fully understood. The Eskimo Nebula [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1990ApJ...362..226O ] is clearly a planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ], and the gas seen above composed the outer layers of a Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ]-like star only 10,000 years ago. The inner filaments visible above [ http://oposite.stsci.edu/pubinfo/pr/2000/07/pr-photos.html ] are being ejected by strong wind [ http://www-istp.gsfc.nasa.gov/Education/wsolwind.html ] of particles from the central star. The outer disk contains unusual light-year long orange filaments. The Eskimo Nebula lies about 5000 light-year [ http://www.treasure-troves.com/astro/Light-Year.html ]s away and is visible with a small telescope in the constellation [ http://www.emufarm.org/~cmbell/myth/myth.html ] of Gemini [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Gemini.html ]. |
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At the Edge of the Helix Neb
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| Title |
At the Edge of the Helix Nebula |
| Explanation |
While exploring the inner edge of the Helix Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap000828.html ] with the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ]'s Wide Field Planetary Camera 2 [ http://www.stsci.edu/instruments/wfpc2/wfpc2_top.html ], astronomers were able to produce this striking image [ http://oposite.stsci.edu/pubinfo/PR/96/13.html ] - rich in details of an exotic environment. This planetary nebula [ http://www.noao.edu/jacoby/pn_gallery.html ], created near the final phase of a sun-like [ http://instruct1.cit.cornell.edu/courses/astro101/java/evolve/evolve.htm ] star's life [ http://antwrp.gsfc.nasa.gov/htmltest/gifcity/msblues.html ], is composed of tenuous shells of gas ejected by the hot central star. The atoms [ http://education.jlab.org/atomtour/ ] of gas, stripped of electrons [ http://www.aip.org/history/electron/ ] by ultraviolet radiation [ http://liftoff.msfc.nasa.gov/academy/universe/ultraviolet.html ] from the central star, radiate light at characteristic energies allowing specific chemical elements [ http://pearl1.lanl.gov/periodic/default.htm ] to be identified. In this image [ http://oposite.stsci.edu/pubinfo/PR/96/13.html ], emission from nitrogen [ http://pearl1.lanl.gov/periodic/elements/7.html ] is represented as red, hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] emission as green, and oxygen [ http://pearl1.lanl.gov/periodic/elements/8.html ] as blue. The inner edge of the Helix Nebula [ http://www.seds.org/messier/xtra/ngc/n7293.html ], also known as NGC 7293, is in the direction toward the central star, which is toward the upper right. Clearly visible near the inner edge are finger shaped cometary knots [ http://antwrp.gsfc.nasa.gov/apod/ap960416.html ]. |
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Cone Nebula Close-Up
| Title |
Cone Nebula Close-Up |
| Explanation |
Cones, pillars [ http://antwrp.gsfc.nasa.gov/apod/ap011125.html ], and majestic flowing shapes [ http://www.goodearthgraphics.com/virtcave/staltite/ staltite.html ] abound in stellar nurseries [ http://archive.ncsa.uiuc.edu/Cyberia/Bima/StarForm.html ] where natal clouds of gas and dust are buffeted by energetic winds from newborn stars. A well-known example, the Cone Nebula [ http://www.skyhound.com/sh/archive/jan/NGC_2264.html ] within the bright galactic star-forming region NGC 2264, was captured in this close-up view [ http://sites.stsci.edu/pubinfo/pr/2002/11/ pr-photos.html#b ] from the Hubble Space Telescope's newest camera [ http://www.ball.com/aerospace/acs.html ]. While the Cone Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap020107.html ], about 2,500 light-years away in Monoceros [ http://www.hawastsoc.org/deepsky/mon/index.html ], is around 7 light-years long, the region pictured here surrounding the cone's blunted head is a mere 2.5 light-years across. In our neck [ http://www.anzwers.org/free/universe/5000lys.html ] of the galaxy that distance is just [ http://www.anzwers.org/free/universe/12lys.html ] over half way from the Sun to its nearest stellar neighbor, Alpha Centauri [ http://antwrp.gsfc.nasa.gov/apod/ap020425.html ]. The massive star NGC 2264 IRS [ http://oposite.stsci.edu/pubinfo/PR/97/16.html ], seen by Hubble's infrared camera in 1997, is the likely source of the wind sculpting the Cone Nebula and lies off the top of the image. The Cone Nebula's reddish veil is produced by [ http://csep10.phys.utk.edu/astr162/lect/light/ absorption.html ] glowing hydrogen gas. |
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M42: Orion Nebula Mosaic
| Title |
M42: Orion Nebula Mosaic |
| Explanation |
The Great Nebula in Orion [ http://www.stsci.edu/pubinfo/gif/OrionMos.txt ] is one of the most interesting of all astronomical nebulae known. Here fifteen pictures [ http://www.stsci.edu/pubinfo/PR/95/45.html ] from the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ] have been merged to show the great expanse and diverse nature of the nebula. In addition to housing a bright open cluster [ http://antwrp.gsfc.nasa.gov/apod/ap951101.html ] of stars known as the Trapezium, the Orion Nebula contains many stellar nurseries [ http://antwrp.gsfc.nasa.gov/apod/ap951106.html ]. These nurseries contain hydrogen [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#hydrogen ] gas, hot young stars [ http://antwrp.gsfc.nasa.gov/apod/ap950620.html ], proplyds [ http://antwrp.gsfc.nasa.gov/apod/ap950911.html ], and stellar jets [ http://antwrp.gsfc.nasa.gov/apod/ap951012.html ] spewing material at high speeds. Much of the filamentary structure visible in this image are actually shock waves - fronts where fast moving material encounters slow moving gas. Some shock waves are visible near one of the bright stars in the lower left of the picture. The Orion Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap950703.html ] is located in the same spiral arm of our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950908.html ] as is our Sun [ http://antwrp.gsfc.nasa.gov/apod/ap951004.html ]. It takes light about 1500 years to reach us from there. |
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MyCn18: An Hourglass Nebula
| Title |
MyCn18: An Hourglass Nebula |
| Explanation |
The sands of time are running out for the central star of this hourglass-shaped planetary nebula [ http://fusedweb.pppl.gov/CPEP/ Chart_Pages/5.Plasmas/Nebula/Planetary.html ]. With its nuclear fuel [ http://fusedweb.pppl.gov/default.html ] exhausted, this brief, spectacular, closing phase of a Sun-like star's life [ http://www.astro.virginia.edu/class/hawley/astr124/starbirth.html ] occurs as its outer layers are ejected - its core becoming a cooling, fading white dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap000910.html ]. In 1995, astronomers used the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] (HST) to make a series of images of planetary nebulae [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ], including the one above [ http://www.stsci.edu/pubinfo/PR/96/07.html ]. Here, delicate rings of colorful glowing gas (nitrogen [ http://pearl1.lanl.gov/periodic/elements/7.html ]-red, hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ]-green, and oxygen [ http://pearl1.lanl.gov/periodic/elements/8.html ]-blue) outline the tenuous walls of the "hourglass". The unprecedented sharpness of the HST images has revealed surprising details [ http://www.stsci.edu/pubinfo/gif/Hourgls.txt ] of the nebula ejection process [ http://antwrp.gsfc.nasa.gov/apod/ap960117.html ] and may help resolve the outstanding mystery of the variety of complex shapes and symmetries of planetary nebulae [ http://www.astro.washington.edu/balick/WFPC2/index.html ]. |
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NGC 5189: A Strange Planetar
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| 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. |
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MyCn18: An Hourglass Nebula
| Title |
MyCn18: An Hourglass Nebula |
| Explanation |
The sands of time are running out for the central star of this hourglass-shaped planetary nebula [ http://fusedweb.pppl.gov/CPEP/ Chart_Pages/5.Plasmas/Nebula/Planetary.html ]. With its nuclear fuel [ http://fusedweb.pppl.gov/default.html ] exhausted, this brief, spectacular, closing phase of a Sun-like star's life [ http://plabpc.csustan.edu/astro/stars/stars.htm ] occurs as its outer layers are ejected - its core becoming a cooling, fading White Dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap950910.html ]. Astronomers have recently used the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ] (HST) to make a series of images of planetary nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap950729.html ], including the one above [ http://www.stsci.edu/pubinfo/PR/96/07.html ]. Here, delicate rings of colorful glowing gas (nitrogen-red, hydrogen-green, and oxygen-blue) outline the tenuous walls of the "hourglass". The unprecedented sharpness of the HST images has revealed surprising details [ http://www.stsci.edu/pubinfo/gif/Hourgls.txt ] of the nebula ejection process [ http://antwrp.gsfc.nasa.gov/apod/ap960117.html ] and may help resolve the outstanding mystery of the variety of complex shapes and symmetries of planetary nebulae [ http://antwrp.gsfc.nasa.gov/apod/lib/planetary.html ]. |
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NGC 7027: A Dying Star's Neb
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| 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! |
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Gomez's Hamburger: A Proto-P
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| Title |
Gomez's Hamburger: A Proto-Planetary Nebula |
| Explanation |
What, in heaven, is that? Sometimes astronomers [ http://www.aas.org/education/career.html ] see things on the sky they don't immediately understand [ http://antwrp.gsfc.nasa.gov/apod/ap990928.html ]. In 1985 this happened to Arturo Gomez [ http://heritage.stsci.edu/2002/19/bio/bio_gomez_english.html ], and the object became known as Gomez's Hamburger [ http://www.lib.ucdavis.edu/exhibits/food/panel6.html ] for its distinctive yet familiar shape. After some investigation, the object was identified as a proto-planetary nebula [ http://www.astro.washington.edu/palen/Research/nsf/intro.html ], a gas cloud emitted by a Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ]-like star just after its central hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] fuel has all been fused [ http://casswww.ucsd.edu/physics/ph7/StevI.html ] to helium [ http://pearl1.lanl.gov/periodic/elements/2.html ]. Gomez's Hamburger is on its way [ http://instruct1.cit.cornell.edu/courses/astro101/java/evolve/evolve.htm ] to becoming a full-fledged planetary nebula [ http://www.seds.org/messier/planetar.html ] in a few thousand years. The light seen (the bun) is reflected [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ] by dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] from the central star, although the star itself is obscured by a thick dust disk [ http://antwrp.gsfc.nasa.gov/apod/ap000208.html ] that runs across the middle (the patty). Gomez's Hamburger [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1987ApJ...316L..21R ], pictured above [ http://heritage.stsci.edu/2002/19/table.html ] in a recent image from the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ], is only a fraction of a light year [ http://www.howstuffworks.com/question94.htm ] across but located approximately 10,000 light years away towards the constellation of Sagittarius [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sagittarius.html ]. |
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Henize 3-401: An Elongated P
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| Title |
Henize 3-401: An Elongated Planetary Nebula |
| Explanation |
How do dying stars eject their outer layers? Stars that create elegant planetary nebulas [ http://www.noao.edu/jacoby/pn_gallery.html ] like Henize 3-401, pictured above [ http://hubble.esa.int/hubble/news/image.cfm?oid=30272&ooid=30277 ], are not unusual, causing speculation that, one day, our own Sun [ http://www.nineplanets.org/sol.html ] may look like this. Henize 3-401 is one of the most elongated planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap020106.html ]s yet discovered, a particularly odd feat [ http://antwrp.gsfc.nasa.gov/apod/ap020618.html ] for a seemingly round star. Perhaps, some astronomers hypothesize, the elongated shape gives a clue to the expulsion mechanism. Genesis hypotheses include that the outer layers of gas are funneled out by the star's own magnetic field [ http://www-istp.gsfc.nasa.gov/Education/Imagnet.html ], and that a second unseen star is somehow involved. After the gas disperses in a few thousand years, only a white dwarf star [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/dwarfs.html ] will remain. Henize 3-401 lies about 10,000 light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away toward the constellation [ http://www.emufarm.org/~cmbell/myth/myth.html ] of Carina [ http://www.astronomical.org/constellations/car.html ]. |
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Giant Emission Nebula NGC 36
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| 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 ]. |
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