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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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NGC 7635: The Bubble Nebula
| Title |
NGC 7635: The Bubble Nebula |
| Explanation |
What created this huge space bubble? A massive star [ http://antwrp.gsfc.nasa.gov/apod/ap971008.html ] that is not only bright and blue, but also emitting a fast stellar wind [ http://www-spof.gsfc.nasa.gov/Education/wsolwind.html ] of ionized gas [ http://www.unm.edu/~sgoold/Plasma.html ]. The Bubble Nebula [ http://heritage.stsci.edu/public/Oct22/bubble/NGC7635table.html ] is actually the smallest of three bubbles surrounding massive star BD+602522, and part of gigantic bubble network S162 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1995A%26A...295..509C ] created with the help of other massive stars. As fast moving gas expands off BD+602522, it pushes surrounding sparse gas into a shell [ http://antwrp.gsfc.nasa.gov/apod/ap990626.html ]. The energetic starlight then ionizes the shell, causing it to glow. The above picture [ http://oposite.stsci.edu/pubinfo/pr/2000/04/index.html ] taken with the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap970306.html ] and released [ http://oposite.stsci.edu/pubinfo/pr/2000/04/content/prc0004.txt ] last week shows many details of the Bubble Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap981118.html ] never seen before and many still not understood. The nebula, also known as NGC 7635 [ http://www.aao.gov.au/AAO/local/www/dfm/int010.html ], is about six light-years across and visible with a small telescope towards the constellation of Cassiopeia [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Cassiopeia.html ]. |
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NGC 1999: Reflection Nebula
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| Title |
NGC 1999: Reflection Nebula in Orion |
| Explanation |
A dusty bright nebula [ http://home.wxs.nl/~geldo006/brigneb.html ] contrasts dramatically with a dusty dark nebula in this Hubble Space Telescope image [ http://oposite.stsci.edu/pubinfo/pr/2000/10/index.html ] recorded shortly after December's orbital servicing mission [ http://hubble.gsfc.nasa.gov/ ]. The nebula [ http://oposite.stsci.edu/pubinfo/pr/2000/10/faq.html ], cataloged as NGC [ http://antwrp.gsfc.nasa.gov/apod/ap990429.html ] 1999, is a reflection nebula [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ], which shines by reflecting light from a nearby star. Unlike emission nebulae [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ], whose reddish glow [ http://antwrp.gsfc.nasa.gov/apod/ap980828.html ] comes from excited atoms of gas, reflection nebulae have a bluish cast [ http://www.physics.muni.cz/~ondra/mix/mix.html ] as their interstellar dust grains [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] preferentially reflect blue starlight. While perhaps the most famous reflection nebulae surround the bright young stars of the Pleiades [ http://antwrp.gsfc.nasa.gov/apod/ap000227.html ] star cluster, NGC 1999's stellar illumination is provided by the embedded variable star V380 [ http://donald.phast.umass.edu/research/comap/V380sm.html ] Orionis, seen here just left of center. Extending right of center, the ominous [ http://antwrp.gsfc.nasa.gov/apod/ap990226.html ] dark nebula [ http://antwrp.gsfc.nasa.gov/apod/dark_nebulae.html ] is actually a condensation of cold molecular gas and dust so thick and dense that it blocks light. From our perspective it lies in front of the bright nebula, silhouetted against the ghostly nebular glow. New stars [ http://dsnra.jpl.nasa.gov/origins/nyt.html ] will likely form within the dark cloud, called a Bok globule [ http://antwrp.gsfc.nasa.gov/apod/ap961229.html ], as self-gravity continues to compress its dense gas and dust. Reflection nebula NGC 1999 [ http://heritage.stsci.edu/public/ 2000mar2/ngc1999table.html ] lies about 1500 light-years away in the constellation Orion [ http://www.seds.org/messier/more/oricloud.html ], just south of Orion's well known emission nebula, M42 [ http://antwrp.gsfc.nasa.gov/apod/ap990522.html ]. |
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IC 4406: A Seemingly Square
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| Title |
IC 4406: A Seemingly Square Nebula |
| Explanation |
How can a round star make a square nebula? This conundrum came to light with the discovery of planetary nebulae [ http://zebu.uoregon.edu/~imamura/208/feb22/feb22.html ] like IC 4406. IC 4406 [ http://www.astro.psu.edu/users/rbc/IC4406.html ] is most probably cylindrical, with its square appearance the result of our vantage point in viewing the cylinder. Hot gas is known [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1991A%26A...251..560S ] to be flowing out the ends of the cylinder, while filaments of dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] and molecular gas [ http://antwrp.gsfc.nasa.gov/apod/ap970430.html ] lace the bounding walls. The star primarily responsible for this interstellar sculpture [ http://oposite.stsci.edu/pubinfo/pr/97/pn/ ] can be found in the planetary nebula's center. In a few million years, the only thing left visible in IC 4406 [ http://www.iras.ucalgary.ca/cgi-bin/zhang/webpn?IC4406 ] will be a fading white dwarf star [ http://antwrp.gsfc.nasa.gov/apod/ap971102.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/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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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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Star EGGs in the Eagle Nebul
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| Title |
Star EGGs in the Eagle Nebula |
| Explanation |
Where do stars form? One place, star forming regions known as "EGGs", are uncovered at the end of this giant pillar [ http://antwrp.gsfc.nasa.gov/apod/ap050424.html ] of gas and dust [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#dust ] in the Eagle Nebula [ http://en.wikipedia.org/wiki/Eagle_Nebula ] (M [ http://antwrp.gsfc.nasa.gov/apod/messier.html ]16). EGGs, short for evaporating gaseous globules [ http://antwrp.gsfc.nasa.gov/apod/ap030816.html ], are dense regions of mostly molecular hydrogen [ http://periodic.lanl.gov/elements/1.html ] gas that fragment and gravitationally collapse to form stars [ http://antwrp.gsfc.nasa.gov/apod/ap060403.html ]. Light from the hottest and brightest of these new stars [ http://antwrp.gsfc.nasa.gov/apod/ap060109.html ] heats the end of the pillar and causes further evaporation of gas - revealing yet more EGGs [ ftp://ftp.hq.nasa.gov/pub/pao/pressrel/1995/95-190.txt ] and more young stars. This picture [ http://hubblesite.org/newscenter/newsdesk/archive/releases/1995/44/image/b ] was taken by the Wide Field and Planetary Camera [ http://www.stsci.edu/instruments/wfpc2/wfpc2_top.html ] on board the Hubble Space Telescope [ http://www.stsci.edu/hst/HST_overview/ ]. |
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Emerging Planetary Nebula CR
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| Title |
Emerging Planetary Nebula CRL 618 |
| Explanation |
CRL 618 may look to some like an Olympian [ http://www.olympics.com/ ] declaring victory. Only a few hundred years ago, however, CRL 618 [ http://hubble.esa.int/hubble/news/index.cfm?oid=24527 ] appeared as a relatively modest red giant star [ http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/971016.html ]. Since then it has run out of core material to fuse [ http://fusedweb.pppl.gov/CPEP/Chart.html ] and so has started to become a planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ]. In its current proto-planetary nebula [ http://www.astro.washington.edu/palen/Research/nsf/intro.html ] phase, CRL 618 [ http://hubble.esa.int/content/news/index.cfm?aid=18&cid=599&oid=12850 ] is evolving quickly, expelling hot gasses in complex jets [ http://antwrp.gsfc.nasa.gov/apod/ap960129.html ] and rings moving outwards faster than 700,000 kilometers per hour. In a few thousand years, the glowing core of the cool red giant [ http://www.historyoftheuniverse.com/starold.html ] will be bare, revealing a hot white dwarf star [ http://antwrp.gsfc.nasa.gov/apod/ap971102.html ]. Much remains unknown about planetary nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap990321.html ] formation, including details of how geometries like this form. Perhaps one day some part of this nebula will be able to declare victory - CRL 618 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1999ESASP.427..285C ] has an extraordinary abundance of carbon-chain molecules [ http://www.ifa.hawaii.edu/~wynnwill/110/16_life.htm ]. |
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The Cat's Eye Nebula
| Title |
The Cat's Eye Nebula |
| Explanation |
Three thousand light-years away, a dying star throws off shells of glowing gas. This image [ http://hubblesite.org/newscenter/archive/releases/1995/01/image/a/ ] from the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] reveals the Cat's Eye Nebula [ http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula ] to be one of the most complex [ http://www.astro.washington.edu/balick/WFPC2/ ] planetary nebulae [ http://en.wikipedia.org/wiki/Planetary_nebula ] known. In fact [ http://antwrp.gsfc.nasa.gov/apod/ap990916.html ], the features seen in the Cat's Eye [ http://antwrp.gsfc.nasa.gov/apod/ap010111.html ] are so complex that astronomers suspect the bright central object may actually be a binary star system [ http://antwrp.gsfc.nasa.gov/apod/ap970219.html ]. The term planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap010805.html ], used to describe this general class of objects, is misleading. Although these objects may appear round and planet-like in small telescopes, high resolution images [ http://www.noao.edu/jacoby/pn_gallery.html ] reveal them to be stars surrounded by cocoons of gas blown off in the late stages of stellar evolution [ http://instruct1.cit.cornell.edu/courses/astro101/java/evolve/evolve.htm ]. |
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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 Orion Nebula in Hydrogen
| Title |
The Orion Nebula in Hydrogen |
| Explanation |
The Great Nebula in Orion [ http://nineplanets.org/twn/n1976x.html ] can be found just below and to the left of the easily identifiable belt of three stars in the popular constellation Orion [ http://www.seds.org/Maps/Stars_en/Fig/orion.html ]. This fuzzy patch, visible to the unaided eye [ http://antwrp.gsfc.nasa.gov/apod/ap970825.html ], contains one of the closest stellar nurseries [ http://antwrp.gsfc.nasa.gov/apod/stellar_nurseries.html ], lying at a distance of about 1500 light years [ http://www.howstuffworks.com/question94.htm ]. The above picture [ http://robgendler.astrodigitals.com/Nebulas.html ] highlights red light emitted by the nebula's hydrogen [ http://school.discovery.com/homeworkhelp/worldbook/atozscience/h/268980.html ] gas. Dark dust [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#dust ] filaments punctuate regions of this glowing hydrogen gas and reflect light from the nebula's brightest stars [ http://antwrp.gsfc.nasa.gov/apod/ap971118.html ]. Recent observations of the Orion Nebula [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?m42 ] by the Hubble Space Telescope [ http://www.stsci.edu/hst/ ] have located solar-system sized regions [ http://antwrp.gsfc.nasa.gov/apod/ap990228.html ] that are thought to be planet-forming circumstellar disks. |
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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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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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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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Carina Nebula Panorama from
…
| Title |
Carina Nebula Panorama from Hubble |
| Explanation |
In one of the brightest parts of Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap050605.html ] lies a nebula where some of the oddest things occur. NGC 3372, known as the Great Nebula in Carina [ http://antwrp.gsfc.nasa.gov/apod/ap040517.html ], is home to massive stars and changing nebula. Eta Carinae [ http://antwrp.gsfc.nasa.gov/apod/ap060326.html ], the most energetic star in the nebula, was one of the brightest stars in the sky in the 1830s, but then faded dramatically. The Keyhole Nebula, visible left the center [ http://heritage.stsci.edu/2007/16/supplemental.html ], houses several of the most massive stars known and has also changed its appearance. The entire Carina Nebula [ http://en.wikipedia.org/wiki/Carina_Nebula ] spans over 300 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] and lies about 7,500 light-years away in the constellation [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=17 ] of Carina. Pictured above [ http://hubblesite.org/newscenter/archive/releases/2007/16/image/a/ ] is the most detailed image [ http://heritage.stsci.edu/2007/16/index.html ] of the Carina Nebula ever taken. The controlled color [ http://heritage.stsci.edu/2007/16/original.html ] image [ http://www.spacetelescope.org/images/html/heic0707a.html ] is a composite of 48 high-resolution frames taken by the Hubble Space Telescope [ http://www.stsci.edu/hst/HST_overview/ ] and released to honor its 17th anniversary. Wide-field annotated [ http://heritage.stsci.edu/2007/16/supplemental.html ] and zoomable [ http://hubblesite.org/newscenter/archive/releases/2007/16/image/a/format/zoom/ ] image versions are also available. |
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NGC 6302: Big, Bright, Bug N
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| Title |
NGC 6302: Big, Bright, Bug Nebula |
| Explanation |
The bright clusters and nebulae of planet Earth's night sky are often named [ http://antwrp.gsfc.nasa.gov/apod/ap010205.html ] for flowers [ http://antwrp.gsfc.nasa.gov/apod/ap011214.html ] or insects [ http://insects.org/ ], and NGC 6302 [ http://antwrp.gsfc.nasa.gov/apod/ap980602.html ] is no exception. With an estimated surface temperature of about 250,000 degrees C, the central star of this particular planetary [ http://antwrp.gsfc.nasa.gov/apod/ap040207.html ] nebula is exceptionally hot though -- shining brightly in ultraviolet light but hidden from direct view by a dense torus of dust. Above is a dramatically detailed close-up [ http://hubble.esa.int/science-e/www/object/ index.cfm?fobjectid=34998 ] of the dying star's nebula [ http://www.aao.gov.au/images/captions/aat011.html ] recorded by the Hubble Space Telescope. Cutting across a bright cavity of ionized gas, the dust torus surrounding the central star is in the upper right corner of this view, nearly edge-on to the line-of-sight. Molecular hydrogen has recently been detected [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005hris.conf..423M ] in this hot star's dusty cosmic shroud. NGC 6302 lies about 4,000 light-years away in the arachnologically [ http://www.arachnology.org/Arachnology/ Arachnology.html ] correct constellation Scorpius [ http://hawastsoc.org/deepsky/sco/index.html ]. |
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Dust Pillar of the Carina Ne
…
| Title |
Dust Pillar of the Carina Nebula |
| Explanation |
Inside the head of this interstellar monster is a star that is slowly destroying it. The monster, actually an inanimate pillar of gas [ http://periodic.lanl.gov/elements/1.html ] and dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ], measures over a light year [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] in length. The star, not itself visible through the opaque dust, is bursting out partly by ejecting energetic beams of particles [ http://en.wikipedia.org/wiki/Particle_beam_weapon ]. Similar epic battles are being waged all over the star-forming Carina Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap070425.html ]. The stars will win in the end, destroying their pillars of creation [ http://antwrp.gsfc.nasa.gov/apod/ap070218.html ] over the next 100,000 years, and resulting in a new open cluster [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] of stars. The pink dots are newly formed stars that have already been freed from their birth monster. The above image [ http://hubblesite.org/newscenter/archive/releases/2007/16/image/i/ ] is only a small part of a highly detailed panoramic mosaic [ http://hubblesite.org/newscenter/archive/releases/2007/16/image/a/format/zoom/ ] of the Carina Nebula [ http://heritage.stsci.edu/2007/16/supplemental.html ] taken by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] and released last week. The technical name for the stellar jets are Herbig-Haro objects [ http://en.wikipedia.org/wiki/Herbig-Haro_objects ]. How a star creates Herbig-Haro jet [ http://antwrp.gsfc.nasa.gov/apod/ap060203.html ]s is an ongoing topic of research [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2006MNRAS.369.1167L ], but it likely involves an accretion disk [ http://antwrp.gsfc.nasa.gov/apod/ap991219.html ] swirling around a central star. A second impressive Herbig-Haro jet [ http://antwrp.gsfc.nasa.gov/apod/ap991129.html ] is visible across the bottom of a larger image. |
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The Cat's Eye Nebula from Hu
…
| 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 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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The Red Spider Planetary Neb
…
| Title |
The Red Spider Planetary Nebula |
| Explanation |
Oh what a tangled web [ http://www.bartleby.com/100/338.25.html ] a planetary nebula [ http://www.seds.org/messier/planetar.html ] can weave. The Red Spider Planetary Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap980106.html ] shows the complex structure that can result when a normal star [ http://antwrp.gsfc.nasa.gov/apod/ap000815.html ] ejects its outer gases and becomes a white dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap000910.html ] star. Officially tagged NGC [ http://www.encyclopedia.com/printablenew/33395.html ] 6537 [ http://www.astro.washington.edu/balick/WFPC2/n6537.caption.html ], this two-lobed symmetric planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ] houses one of the hottest white dwarfs [ http://antwrp.gsfc.nasa.gov/apod/ap000730.html ] ever observed, probably as part of binary star [ http://astrosun.tn.cornell.edu/courses/astro201/binstar.htm ] system. Internal winds [ http://www-spof.gsfc.nasa.gov/Education/wsolwind.html ] emanating from the central stars, visible in the center, have been measured in excess of 1000 kilometers per second. These winds [ http://antwrp.gsfc.nasa.gov/apod/ap000318.html ] expand the nebula, flow along the nebula's walls, and cause waves of hot gas [ http://pearl1.lanl.gov/periodic/elements/1.html ] and dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] to collide. Atoms [ http://education.jlab.org/atomtour/ ] caught in these colliding shocks radiate light shown in the above representative-color picture [ http://www.spacetelescope.org/pressroom/embargo/heic0109_embargo.html ]. The Red Spider Nebula [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000A%26A...362L..17P ] lies toward the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Sagittarius [ http://www.astronomical.org/constellations/sgr.html ]. It's distance is not well known but estimated by some [ http://cdsads.u-strasbg.fr/cgi-bin/bib_query?1986A&A...157..191G ] to be about 4000 light-years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ]. |
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M57: The Ring Nebula
| Title |
M57: The Ring Nebula |
| Explanation |
Except for the rings of Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap000212.html ], the Ring Nebula [ http://seds.lpl.arizona.edu/messier/m/m057.html ] (M57) is probably the most famous celestial band. This planetary nebula's [ http://www.astro.washington.edu/balick/WFPC2/ ] simple, graceful appearance is thought to be due to perspective -- our view from planet Earth [ http://antwrp.gsfc.nasa.gov/apod/earth.html ] looking straight into what is actually a barrel-shaped cloud [ http://www.seds.org/billa/twn/n6720x.html ] of gas shrugged off by a dying central star. Astronomers of the Hubble Heritage Project [ http://heritage.stsci.edu/ ] produced this strikingly sharp image [ http://heritage.stsci.edu/public/jan6/ringbond.html ] from Hubble Space Telescope [ http://www.stsci.edu/hst/ ] observations using natural appearing colors to indicate the temperature of the stellar gas shroud. Hot blue gas near the energizing central star gives way to progressively cooler green and yellow gas at greater distances [ http://antwrp.gsfc.nasa.gov/apod/ap990922.html ] with the coolest red gas along the outer boundary. Dark, elongated structures [ http://antwrp.gsfc.nasa.gov/apod/ap970720.html ] can also be seen near the nebula's edge. The Ring Nebula [ http://seds.lpl.arizona.edu/messier/more/m057_jac.html ] is about one light-year [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] across and 2,000 light-years away in the northern constellation Lyra [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Lyra.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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IC 5067 in the Pelican Nebul
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| Title |
IC 5067 in the Pelican Nebula |
| Explanation |
The prominent ridge of emission featured in this dramatic skyscape [ http://astrosurf.com/afernandez/gallery/deepsky/ ic5070/ic5070_hst_asa_33.htm ] is cataloged as IC 5067 [ http://antwrp.gsfc.nasa.gov/apod/ap061227.html ]. Part of a larger emission nebula [ http://www.noao.edu/image_gallery/emission_nebulae.html ] with a distinctive shape, popularly called The Pelican Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap061130.html ], the ridge spans about 10 light-years following the curve of the cosmic pelican's head and neck. This false color view also translates the pervasive glow of narrow emission lines [ http://astro.u-strasbg.fr/~koppen/discharge/ index.html ] from atoms in the nebula to a color palette [ http://hubblesite.org/gallery/behind_the_pictures/ meaning_of_color/eagle.php ] made popular in Hubble Space Telescope images of star forming regions. Fantastic, dark shapes inhabiting the 1/2 degree wide field are clouds of cool gas and dust sculpted by the winds and radiation from hot, massive stars. Close-ups [ http://astrosurf.com/afernandez/gallery/deepsky/ic5070/ ic5070_hst_asa_50.htm ] of some of the sculpted clouds show clear signs [ http://www.noao.edu/outreach/latest/ngc1999about.html ] of newly forming stars. The Pelican Nebula, itself cataloged as IC 5070, is about 2,000 light-years away. To find [ http://antwrp.gsfc.nasa.gov/apod/ap070702.html ] it, look northeast of bright star Deneb [ http://antwrp.gsfc.nasa.gov/apod/ap070920.html ] in the high flying constellation Cygnus. A new APOD RSS feed is available here [ http://antwrp.gsfc.nasa.gov/apod.rss ], or from the link line below. |
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The Making of the Rotten Egg
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| Title |
The Making of the Rotten Egg Nebula |
| Explanation |
Fast expanding gas clouds mark the end for a central star in the Rotten Egg Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap991101.html ]. The once-normal star has run out of nuclear fuel [ http://observe.ivv.nasa.gov/nasa/exhibits/stars/star_5.html ], causing the central regions to contract into a white dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap000910.html ]. Some of the liberated energy causes the outer envelope of the star to expand. In this case, the result is a photogenic proto- planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ]. As the million-kilometer per hour gas rams into the surrounding interstellar gas [ http://antwrp.gsfc.nasa.gov/apod/ap000412.html ], a supersonic [ http://antwrp.gsfc.nasa.gov/apod/ap010221.html ] shock front [ http://www.pbs.org/wgbh/nova/barrier/boom/concept3.html ] forms where ionized [ http://csep10.phys.utk.edu/astr162/lect/light/ionization.html ] hydrogen [ http://www.chemicalelements.com/elements/h.html ] and nitrogen [ http://www.webelements.com/webelements/elements/text/N/key.html ] glow blue. The complex shock front [ http://antwrp.gsfc.nasa.gov/apod/ap001128.html ] had been hypothesized previously [ http://hubble.esa.int/hubble/news/newsrelease.cfm?oid=28169 ] but never so clearly imaged. Thick gas and dust [ http://antwrp.gsfc.nasa.gov/apod/ap010813.html ] hide the dying central star. The Rotten Egg Nebula [ http://oposite.stsci.edu/pubinfo/pr/1999/39/ ], also known as the Calabash Nebula [ http://sci.esa.int/content/searchimage/searchresult.cfm?aid=1&cid=14&ooid=28184 ] and OH231.8+4.2, will likely develop into a full bipolar planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap001217.html ] over the next 1000 years. The nebula, pictured above [ http://hubble.esa.int/hubble/gallery/new_searchresult.cfm?ooid=28164&imgid=12318 ], is about 1.4 light-years in extent and located about 5000 light-years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away toward the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Puppis [ http://www.astronomical.org/constellations/pup.html ]. |
|
Halloween and the Ghost Head
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| Title |
Halloween and the Ghost Head Nebula |
| Explanation |
Halloween's origin [ http://www.historychannel.com/exhibits/halloween/holiday_origins1.html ] is ancient and astronomical. Since the fifth century BC, Halloween [ http://en.wikipedia.org/wiki/Halloween ] has been celebrated as a cross-quarter day [ http://www-astronomy.mps.ohio-state.edu/~pogge/Ast161/Unit2/time.html ], a day halfway between an equinox [ http://antwrp.gsfc.nasa.gov/apod/ap000923.html ] (equal day / equal night) and a solstice [ http://antwrp.gsfc.nasa.gov/apod/ap971221.html ] (minimum day / maximum night in the northern hemisphere). With our modern calendar [ http://webexhibits.org/calendars/year-countries.html ], however, the real cross-quarter day [ http://www.whyy.org/tv12/franklinfacts/oct3100ff.html ] will occur next week. Another cross-quarter day is Groundhog's Day [ http://www.noblenet.org/year/groundhog.htm ]. Halloween's [ http://www.census.gov/Press-Release/www/releases/archives/facts_for_features_special_editions/010511.html ] modern celebration retains historic roots [ http://www.neopagan.net/Halloween-Origins.html ] in dressing to scare away the spirits of the dead. Perhaps a fitting modern tribute to this ancient holiday is the above-pictured Ghost Head Nebula [ http://photojournal.jpl.nasa.gov/catalog/PIA04226 ] taken with the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ]. Appearing similar to the icon of a fictional [ http://en.wikipedia.org/wiki/Casper_the_Friendly_Ghost ] ghost [ http://en.wikipedia.org/wiki/Ghost ], NGC 2080 is actually a star forming region [ http://antwrp.gsfc.nasa.gov/apod/stellar_nurseries.html ] in the Large Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap010804.html ], a satellite galaxy of our own Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ]. The Ghost Head Nebula spans about 50 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] and is shown in representative colors. |
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Hen 1357: New Born Nebula
| Title |
Hen 1357: New Born Nebula |
| Explanation |
This Hubble Space Telescope [ http://oposite.stsci.edu/pubinfo/pr/1998/15/ ] snapshot shows Hen-1357, the youngest known planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap011003.html ]. Graceful, gentle curves and symmetry suggest its popular name [ http://greeceny.com/ls/grade4/sea1.htm#Stingray ] - The Stingray Nebula [ http://oposite.stsci.edu/pubinfo/pr/1998/15/pr.html ]. Observations in the 1970s detected no nebular material, but this image from March 1996 clearly shows the Stingray's emerging bubbles and rings of shocked and ionized gas [ http://oposite.stsci.edu/pubinfo/pr/1998/15/ content/prc9815.txt ]. The gas is energized by the hot central star as it nears the end of its life, evolving toward a final white dwarf phase [ http://antwrp.gsfc.nasa.gov/apod/ap961203.html ]. The image also shows a companion star (at about 10 o'clock) within the nebula. Astronomers suspect that such companions account for the complex shapes and rings [ http://www.astro.washington.edu/balick/WFPC2/ ] of this and many other planetary nebulae. This cosmic infant is about 130 times the size of our own solar system and growing. It is 18,000 light-years distant, in the southern constellation Ara [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Ara.html ]. |
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The Fairy of Eagle Nebula
| Title |
The Fairy of Eagle Nebula |
| Explanation |
The dust sculptures of the Eagle Nebula are evaporating. As powerful starlight whittles away these cool cosmic mountains [ http://antwrp.gsfc.nasa.gov/apod/ap031228.html ], the statuesque pillars [ http://antwrp.gsfc.nasa.gov/apod/ap070218.html ] that remain might be imagined as mythical beasts [ http://www.pantheon.org/areas/bestiary/ ]. Pictured above [ http://hubblesite.org/newscenter/newsdesk/archive/releases/2005/12/ ] is one of several striking dust pillars [ http://antwrp.gsfc.nasa.gov/apod/ap061022.html ] of the Eagle Nebula [ http://en.wikipedia.org/wiki/Eagle_Nebula ] that might be described as a gigantic alien fairy [ http://en.wikipedia.org/wiki/Fairies ]. This fairy, however, is ten light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] tall and spews radiation much hotter than common fire [ http://antwrp.gsfc.nasa.gov/apod/ap001121.html ]. The greater Eagle Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap041024.html ], M16, is actually a giant evaporating shell of gas and dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] inside of which is a growing cavity [ http://kidshealth.org/kid/health_problems/teeth/cavity.html ] filled with a spectacular stellar nursery currently forming an open cluster [ http://www.seds.org/messier/open.html ] of stars. The above image [ http://www.spacetelescope.org/images/html/heic0506b.html ] in scientifically re-assigned colors was released [ http://heritage.stsci.edu/2005/12b/index.html ] as part of the fifteenth anniversary celebration [ http://www.spacetelescope.org/news/html/heic0506.html ] of the launch [ http://antwrp.gsfc.nasa.gov/apod/ap021124.html ] of the Hubble Space Telescope [ http://www.stsci.edu/hst/HST_overview/ ]. |
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Halloween and the Ghost Head
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| Title |
Halloween and the Ghost Head Nebula |
| Explanation |
Halloween's origin [ http://teacherlink.ed.usu.edu/TLresources/longterm/LessonPlans/Byrnes/halloween.html ] is ancient and astronomical. Since the fifth century BC, Halloween [ http://www.historychannel.com/exhibits/halloween/ ] has been celebrated as a cross-quarter day [ http://www-astronomy.mps.ohio-state.edu/~pogge/Ast161/Unit2/time.html ], a day halfway between an equinox [ http://antwrp.gsfc.nasa.gov/apod/ap000923.html ] (equal day / equal night) and a solstice [ http://antwrp.gsfc.nasa.gov/apod/ap971221.html ] (minimum day / maximum night in the northern hemisphere). With our modern calendar [ http://webexhibits.org/calendars/year-countries.html ], however, the real cross-quarter day [ http://www.whyy.org/tv12/franklinfacts/oct3100ff.html ] will occur next week. Another cross-quarter day is Groundhog's Day [ http://www.hansenplanetarium.net/CQGroundhog.html ]. Halloween's [ http://www.jpl.nasa.gov/proto/ halloween_sounds.html ] modern celebration retains historic roots [ http://www.utah.edu/planetarium/CQHalloween.html ] in dressing to scare away the spirits of the dead. A perhaps-fitting modern tribute to this ancient holiday is the above-pictured Ghost Head Nebula [ http://hubble.esa.int/hubble/news/image.cfm?oid=28749&ooid=28750 ] taken with the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ]. Appearing similar to the icon of a fictional ghost [ http://www.yesterdayland.com/popopedia/shows/saturday/sa1025.php ], NGC 2080 is actually a star forming region [ http://antwrp.gsfc.nasa.gov/apod/stellar_nurseries.html ] in the Large Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap010804.html ], a satellite galaxy of our own Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ]. The Ghost Head Nebula spans about 50 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] and is shown in representative colors. |
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A Beautiful Boomerang Nebula
| Title |
A Beautiful Boomerang Nebula |
| Explanation |
This symmetric cloud dubbed the Boomerang Nebula [ http://heritage.stsci.edu/2005/25/caption.html ] was created by a high-speed wind [ http://www-spof.gsfc.nasa.gov/Education/wsolwind.html ] of gas and dust blowing from an aging central star at speeds of nearly 600,000 kilometers per hour. The rapid expansion has cooled molecules in the nebular gas to about one degree above absolute zero [ http://eo.ucar.edu/skymath/tmp2.html ] - colder than even the cosmic background radiation [ http://www.astro.ubc.ca/people/scott/faq_basic.html ] - making it the coldest known region in the distant Universe. Shining with light from the central star reflected by dust, the frigid Boomerang Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap030220.html ] is believed to be a star or stellar system evolving toward the planetary nebula [ http://www.noao.edu/jacoby/pn_gallery.html ] phase. This Hubble image [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2005/25/image/a ] was recorded using polarizing [ http://acept.la.asu.edu/PiN/rdg/polarize/ polarize.shtml ] filters (analogous to polaroid sunglasses) and color coded by the angle associated with the polarized light [ http://en.wikipedia.org/wiki/Polarization ]. The gorgeous result traces the small dust particles responsible for polarizing and scattering the light. The Boomerang Nebula spans about one light year [ http://science.howstuffworks.com/question94.htm ] and lies about 5,000 light years away toward the constellation [ http://en.wikipedia.org/wiki/Constellation ] Centaurus [ http://www.seds.org/Maps/Stars_en/Fig/centaurus.html ]. |
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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 ]. |
|
The Cat's Eye Nebula
| Title |
The Cat's Eye Nebula |
| Explanation |
Three thousand light years away, a dying star throws off shells of glowing gas. This Hubble Space Telescope image reveals "The Cat's Eye Nebula" to be one of the most complex "planetary nebulae" known. In fact, the features seen in this image are so complex that astronomers suspect the visible central star may actually be a double star system. The term planetary nebula, used to describe this general class of objects, is misleading. Although these objects may appear round and planet-like in small telescopes, high resolution images reveal them to be stars surrounded by cocoons of gas blown off in the late stages of evolution. |
|
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 ] |
|
The Cat's Eye Nebula
| Title |
The Cat's Eye Nebula |
| Explanation |
Three thousand light-years away, a dying star throws off shells of glowing gas. This image [ http://www.stsci.edu/EPA/PR/95/01.html ] from the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] reveals the Cat's Eye Nebula [ http://oposite.stsci.edu/pubinfo/background-text/phinterv.txt ] to be one of the most complex [ http://www.astro.washington.edu/balick/WFPC2/ ] planetary nebulae [ http://oposite.stsci.edu/pubinfo/pr/97/pn/ ] known. In fact [ http://antwrp.gsfc.nasa.gov/apod/ap990916.html ], the features seen in the Cat's Eye [ http://antwrp.gsfc.nasa.gov/apod/ap010111.html ] are so complex that astronomers suspect the bright central object may actually be a binary star system [ http://antwrp.gsfc.nasa.gov/apod/ap970219.html ]. The term planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap010805.html ], used to describe this general class of objects, is misleading. Although these objects may appear round and planet-like in small telescopes, high resolution images [ http://www.noao.edu/jacoby/pn_gallery.html ] reveal them to be stars surrounded by cocoons of gas blown off in the late stages of stellar evolution [ http://plabpc.csustan.edu/astro/stars/stars.htm ]. |
|
The Eskimo Nebula from Hubbl
…
| 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 ]. |
|
At the Edge of the Helix Neb
…
| 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 ]. |
|
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. |
|
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. |
|
Cone Nebula Infrared Close-U
…
| Title |
Cone Nebula Infrared Close-Up |
| Explanation |
After astronauts repaired NICMOS [ http://oposite.stsci.edu/pubinfo/pr/2002/13/ index.html ] - the Near Infrared Camera and Multi-Object Spectrometer - during the latest Hubble Space Telescope servicing mission [ http://antwrp.gsfc.nasa.gov/apod/ap020314.html ], astronomers were quick to turn the sophisticated instrument on the photogenic stellar nursery [ http://antwrp.gsfc.nasa.gov/apod/ap020503.html ] known as the Cone Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap020107.html ]. This remarkable NICMOS [ http://www.stsci.edu/hst/nicmos/ ] close-up of the Cone Nebula [ http://oposite.stsci.edu/pubinfo/pr/2002/13/ fastfacts.html#Cone ] dramatically confirms that the Hubble's infrared vision has been restored [ http://oposite.stsci.edu/pubinfo/pr/2002/13/faq.html ]. Gas and dust clouds at the blunted tip of the cone-shaped star-forming region are seen here [ http://oposite.stsci.edu/pubinfo/pr/2002/13/ pr-photos.html ] in false-color covering an area about half a light-year across. Toward the left hand side of the picture, the four bright stars with diffraction spikes [ http://antwrp.gsfc.nasa.gov/apod/ap010415.html ] are also present in visible light images and are in front of the Cone Nebula, itself 2,500 light-years away. But the fainter stars to their right are embedded in or behind the nebula's obscuring dust clouds and are revealed [ http://oposite.stsci.edu/pubinfo/pr/2002/13/prc/ 0213aw.jpg ] only in this penetrating infrared view [ http://www.ipac.caltech.edu/Outreach/Edu/Regions/ irregions.html ]. |
|
IC 4406: A Seemingly Square
…
| Title |
IC 4406: A Seemingly Square Nebula |
| Explanation |
How can a round star make a square nebula? This conundrum comes to light when studying planetary nebulae [ http://zebu.uoregon.edu/~imamura/208/feb22/feb22.html ] like IC 4406. Evidence indicates that IC 4406 [ http://www.astro.psu.edu/users/rbc/IC4406.html ] is likely a hollow cylinder, with its square appearance the result of our vantage point in viewing the cylinder [ http://www.mathleague.com/help/geometry/3space.htm#cylinder ] from the side. Were IC 4406 [ http://heritage.stsci.edu/2002/14/table.html ] viewed from the top, it would likely look similar to the Ring Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap010729.html ]. This representative-color picture [ http://heritage.stsci.edu/2002/14/index.html ] is a composite [ http://heritage.stsci.edu/2002/14/supplemental.html ] made by combining images taken by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] last June and this January. Hot gas flows [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1991A%26A...251..560S ] out the ends of the cylinder, while filaments of dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] and molecular gas [ http://antwrp.gsfc.nasa.gov/apod/ap970430.html ] lace the bounding walls. The star primarily responsible for this interstellar sculpture [ http://antwrp.gsfc.nasa.gov/apod/ap000416.html ] can be found in the planetary nebula [ http://www.noao.edu/jacoby/pn_gallery.html ]'s center. In a few million years, the only thing left visible in IC 4406 [ http://www.iras.ucalgary.ca/cgi-bin/zhang/webpn?IC4406 ] will be a fading white dwarf star [ http://antwrp.gsfc.nasa.gov/apod/ap000910.html ]. |
|
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 ]. |
|
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 ]. |
|
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! |
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Gomez's Hamburger: A Proto-P
…
| 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
…
| 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 ]. |
|
The Eye of an Hourglass Nebu
…
| Title |
The Eye of an Hourglass Nebula |
| Explanation |
What's happening in the eye-like center of this planetary nebula? [ http://www.noao.edu/jacoby/pn_gallery.html ] The geometry revealed in this Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap960128.html ] view of the central part of an "etched hourglass nebula [ http://antwrp.gsfc.nasa.gov/apod/ap960118.html ]" known as MyCn 18 [ http://www.stsci.edu/pubinfo/gif/Hourgls.txt ] presents a puzzle. First, the axis of this central region does not line up well with the outer hourglass structure. Next, the hot star (the white spot to the left of center) which ejected this gaseous nebula as it evolved towards its white dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap950910.html ] phase, is not exactly at the center of the "eye". These unexpected results leave astronomers looking for the missing pieces of the ejection process that created this unusual and beautiful structure. |
|
Searchlight Beams from the E
…
| Title |
Searchlight Beams from the Egg Nebula |
| Explanation |
The dramatic and mysterious looking object revealed in this Hubble Space Telescope image [ http://www.stsci.edu/pubinfo/gif/EggNeb.txt ] is known as the Egg Nebula [ http://www.stsci.edu/pubinfo/PR/96/03.html ]. It is an aging star about 3,000 lightyears distant, entering its Planetary Nebula [ http://fusedweb.pppl.gov/CPEP/Chart_Pages/5.Plasmas/ Nebula/Planetary.html ] phase of evolution. Surrounded by an expanding cloud of gas and dust, a dense cocoon of dust (seen as the dark band running diagonally across the center) encloses the star itself and blocks it from direct view. The searchlight appearance is created as light from the star shines more easily through the thinner parts of the cocoon. Dust particles in the expanding cloud scatter and reflect the starlight making the beams visible. The sharpness of the HST image reveals a wealth of detail which will help to understand this complex and spectacular part of the stellar lifecycle [ http://antwrp.gsfc.nasa.gov/apod/ap960118.html ]. |
|
Rampaging Fronts of the Veil
…
| Title |
Rampaging Fronts of the Veil Nebula |
| Explanation |
A supernova explosion [ http://www.ast.cam.ac.uk/RGO/leaflets/supernovae/supernovae.html ] of a high-mass star results in fast moving blast waves. At the front of the waves shown above, ionized gas in the Veil Supernova Remnant [ http://seds.lpl.arizona.edu/billa/twn/cygnusx.html ] rushes out from the explosion, sweeps up material, and breaks up many atoms into constituent ions and electrons. Observations [ file://stsci.edu/stsci/epa/tiff/cloop.txt ] with the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ] in 1993 indicate that the blue shock wave was catapult away from the stellar explosion after the red shock wave and has yet to catch up to it in some regions. The Veil supernova remnant's has a very large angular size - six times the diameter of the full moon - and different parts of it are known as the "Cygnus Loop [ http://antwrp.gsfc.nasa.gov/apod/ap950718.html ]" and catalog numbers NGC 6960, NGC 6979, NGC 6992, and NGC 6995. |
|
The Crab Nebula Pulsar Shrug
…
| Title |
The Crab Nebula Pulsar Shrugs |
| Explanation |
How does a city-sized neutron star power the vast Crab Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap020714.html ]? The expulsion of wisps of hot gas at high speeds appears to be at least part of the answer. Yesterday time-lapse movies [ http://chandra.harvard.edu/photo/2002/0052/movies.html ] taken from both the Chandra X-ray Observatory [ http://chandra.harvard.edu/about/ ] and the Hubble Space Telescope [ http://www.stsci.edu/hst/HST_overview/ ] were released [ http://chandra.harvard.edu/photo/2002/0052/index.html ] showing a wisp of gas moving out at about half the speed of light. Wisps like this [ http://www1.msfc.nasa.gov/NEWSROOM/news/releases/2002/02-233.html ] likely result from tremendous electric voltages [ http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elevol.html ] created by the central pulsar, a rapidly rotating, magnetized, central neutron star [ http://www.astro.umd.edu/~miller/nstar.html ]. The hot plasma [ http://www.plasmas.org/what-are-plasmas.htm ] strikes existing gas, causing it glow in colors across the electromagnetic spectrum [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ]. Pictured above [ http://chandra.harvard.edu/photo/2002/0052/more.html ] is a composite image of the center of the Crab Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap990929.html ] where red represents radio [ http://imagers.gsfc.nasa.gov/ems/radio.html ] emission, green represents visible [ http://imagers.gsfc.nasa.gov/ems/visible.html ] emission, and blue represents X-ray [ http://imagers.gsfc.nasa.gov/ems/xrays.html ] emission. The dot at the very center is the hot pulsar [ http://antwrp.gsfc.nasa.gov/apod/ap010719.html ] spinning 30 times per second. |
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The Keyhole Nebula Near Eta
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| Title |
The Keyhole Nebula Near Eta Carinae |
| Explanation |
The dark dusty Keyhole Nebula gets its name from its unusual shape. Designated NGC 3324, the Keyhole Nebula [ http://seds.lpl.arizona.edu/billa/twn/n3324x.html ] is a smaller region superposed on the bright Eta Carina Nebula [ http://seds.lpl.arizona.edu/billa/twn/n3372x.html ]. The Eta Carina Nebula is the largest nebula in angular extent on the sky, larger than the famous Orion Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap951121.html ], but its southerly location makes it less familiar to Northern Hemisphere skywatchers. The star Eta Carinae [ http://antwrp.gsfc.nasa.gov/apod/ap960111.html ] itself is extremely variable and has faded in a mere 150 years - formerly one of the brightest in the sky it is now invisible without a telescope. The nebula created [ http://antwrp.gsfc.nasa.gov/apod/ap950712.html ] by the star's 19th century outburst [ http://www.stsci.edu/pubinfo/gif/WFPCEtaCar.txt ] has been photographed by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ]. |
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