|
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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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Emerging Planetary Nebula CR
…
| 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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M2-9: Wings of a Butterfly N
…
| 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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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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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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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 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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M2-9: Wings of a Butterfly N
…
| 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 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 ]. |
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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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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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The Snake Nebula in Ophiuchu
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| Title |
The Snake Nebula in Ophiuchus |
| Explanation |
What slithers there? The dark curly lanes visible in part of the constellation Ophiuchus [ http://galileo.gmu.edu/constellation/OPH.html ] belong to the Snake Nebula. The Snake Nebula is a series of dark absorption clouds [ http://antwrp.gsfc.nasa.gov/apod/lib/dark.html ]. Interstellar dust grains [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#dust ] - composed predominantly of carbon - absorb visible starlight and reradiate much of it in the infrared [ http://www.astro.washington.edu/strobel/lightnotes/lightnotes.html ]. Infrared is a band of light so red humans can't see it. This absorption causes stars in the background to be blocked from our view - and hence the appearance of noticeable voids on the sky. |
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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://antwrp.gsfc.nasa.gov/apod/ap020618.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://www.seds.org/billa/twn/n6720x.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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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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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/ap010319.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 Red Spider Planetary Neb
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| Title |
The Red Spider Planetary Nebula |
| Explanation |
Oh what a tangled web [ http://www.columbia.edu/acis/bartleby/bartlett/338.html#25 ] a planetary nebula [ http://www.seds.org/messier/planetar.html ] can weave. The Red Spider Planetary Nebula [ http://www.astro.washington.edu/balick/WFPC2/n6537.caption.html ] shows the complex structure that can result when a normal star ejects its outer gases and becomes a white dwarf star [ http://antwrp.gsfc.nasa.gov/apod/ap971102.html ]. Officially tagged NGC 6537, this two-lobed symmetric nebula houses one of the hottest white dwarfs [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1988ApJ%2E%2E%2E331%2E%2E532A&db_key=AST&nosetcookie=1 ] ever observed, probably as part of binary star [ http://antwrp.gsfc.nasa.gov/apod/ap970219.html ] system [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A%26A%2E%2E%2E269%2E%2E462C&db_key=AST&nosetcookie=1 ]. Internal winds [ http://antwrp.gsfc.nasa.gov/apod/ap970217.html ] emanating from the central stars, shown in the central inset, have been measured in excess of 300 kilometers per second. These hot winds expand the nebula, flow along the nebula's walls, and cause gas and dust to collide. Atoms caught in these colliding shocks radiate light shown in the above [ http://www.astro.washington.edu/balick/WFPC2/n6537.caption.html ] representative-light picture. |
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NGC 7009: The Saturn Nebula
| Title |
NGC 7009: The Saturn Nebula |
| Explanation |
The layers of the Saturn Nebula [ http://oposite.stsci.edu/pubinfo/PR/97/38/b5.html ] give a complex picture of how this planetary nebula [ http://www.seds.org/messier/planetar.html ] was created. The above picture [ http://oposite.stsci.edu/pubinfo/PR/97/38/b-js.html ], taken in April 1996 and released last week, allows a better understanding of the mysterious process that transformed a low-mass star into a white dwarf star [ http://antwrp.gsfc.nasa.gov/apod/ap971102.html ]. A computer model indicates that the central star of NGC 7009 [ http://www.astro.washington.edu/balick/WFPC2/n7009.caption.html ] first expelled the green gas that now appears barrel shaped. This green gas now confines stellar winds flowing from the central star, creating a jet which forms the ansae [ http://antwrp.gsfc.nasa.gov/apod/ap961122.html ] that appear in red at the tips. Much remains unknown, including why the gas has not become turbulent [ http://jcbmac.chem.brown.edu/scissorsHtml/liquids/turbulence.html ]. |
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The Hubble 5 Planetary Nebul
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| Title |
The Hubble 5 Planetary Nebula |
| Explanation |
The Hubble Double Bubble Planetary Nebula is bubbling over with excitement. More mundanely known as Hubble 5 [ http://www.astro.washington.edu/balick/WFPC2/hb5.caption.html ], this bipolar planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap971223.html ] is being created by a hot wind [ http://antwrp.gsfc.nasa.gov/apod/ap970217.html ] of particles streaming away from the central star system. The hot gas expands into the surrounding interstellar medium [ http://pegasus.phast.umass.edu/a100/handouts/ism.html ] in a fashion similar to the inflation of hot air balloons [ http://www-vrl.umich.edu/People/saha/photos.html ]. A supersonic shock-wave [ http://inuit.phys.ualberta.ca/~trpk/phys100/waves/waves.html ] can form at the boundary, causing newly excited gas there to shine as electrons [ http://pburton.maps.susx.ac.uk/scoap/physwrld/physwrld.htm ] recombine with resident elements [ http://CST.lanl.gov/CST/imagemap/periodic/periodic.html ]. In the above picture [ http://www.astro.washington.edu/balick/WFPC2/ ], colors are assigned according to the energy of the recombinant radiation. This star system lies about 2200 light-years from Earth [ http://antwrp.gsfc.nasa.gov/apod/ap970717.html ], and likely includes a Sun-like star slowly transforming itself into a white dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap971102.html ]. |
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Hen-1357: New Born Nebula
| Title |
Hen-1357: New Born Nebula |
| Explanation |
This Hubble Space Telescope picture [ http://oposite.stsci.edu/pubinfo/pr/1998/15/ ] shows Hen-1357, the youngest known planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap980325.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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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?1991A%26A%2E%2E%2E251%2E%2E560S&db_key=AST&high=33613e8e5801093&nosetcookie=1 ] to be flowing out the ends of the cylinder, while filaments of dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap980104.html ] and molecular gas [ http://antwrp.gsfc.nasa.gov/apod/ap970430.html ] lace the bounding walls. The star primarily responsible [ http://www.astro.washington.edu/jalex/PNN_paper/GW_paper2.html ] for this interstellar sculpture can be found in the 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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Tentacles of the Tarantula N
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| Title |
Tentacles of the Tarantula Nebula |
| Explanation |
The Tarantula Nebula [ http://www.seds.org/messier/xtra/ngc/n2070.html ] is a giant emission nebula [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] within our neighboring galaxy the Large Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap040902.html ]. Inside this cosmic arachnid [ http://www.washington.edu/burkemuseum/spidermyth/myths/arachnid.html ] lies a huge central young cluster of massive stars, cataloged as R136 [ http://antwrp.gsfc.nasa.gov/apod/ap010730.html ] and partially visible on the upper right. The energetic light [ http://imagers.gsfc.nasa.gov/ems/uv.html ] and winds [ http://www-istp.gsfc.nasa.gov/Education/wsolwind.html ] from this cluster light up the nebula and sculpt the surrounding gas and dust into vast complex filaments [ http://antwrp.gsfc.nasa.gov/apod/ap030118.html ]. These "tentacles" give the Tarantula [ http://www.desertusa.com/july96/du_taran.html ] Nebula its name. In this impressive color image [ http://www.eso.org/outreach/press-rel/pr-2004/phot-34-04.html ] from the Wide-Field Imager [ http://www.ls.eso.org/lasilla/Telescopes/2p2T/E2p2M/WFI/ ] camera on ESO's 2.2-meter telescope [ http://www.astr.ua.edu/keel/telescopes/eso.html ] at La Silla Observatory [ http://www.ls.eso.org/index.html ], intricacies of the nebula's complex array of dust and gas [ http://www-ssg.sr.unh.edu/ism/what1.html ] are visible. A 300 light-year [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] portion of the Tarantula Nebula is imaged. The Tarantula Nebula [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?tarantula ], also dubbed 30 Doradus, lies 170,000 light years away toward the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Dorado [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=33 ]. |
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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://www.astro.washington.edu/balick/WFPC2/index.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/ap010319.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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Denizen of the Tarantula Neb
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| Title |
Denizen of the Tarantula Nebula |
| Explanation |
The star cluster at lower right, cataloged as Hodge 301 [ http://heritage.stsci.edu/public/apr1/h301table.html#facts ], is a denizen of the Tarantula Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap970604.html ]. An evocative nebula in the southern sky, the sprawling cosmic Tarantula is an energetic star forming region [ http://www.astro.washington.edu/grebel/sfh_lmc.html ] some 168,000 light-years distant in our neighboring galaxy the Large Magellanic Cloud. The stars within Hodge 301 formed together tens of millions of years ago and as the massive ones quickly exhaust their nuclear fuel they explode. In fact, the red giant stars of Hodge 301 are rapidly approaching this violent final phase of stellar evolution - known as a supernova [ http://antwrp.gsfc.nasa.gov/apod/ap951027.html ]. These supernova blasts send material and shock waves back [ http://oposite.stsci.edu/pubinfo/pr/1998/08/ ] into the nebular gas to create the Tarantula's glowing filaments also visible in this Hubble Space Telescope Heritage image [ http://oposite.stsci.edu/pubinfo/pr/1999/12/index.html ]. But these spectacular stellar death explosions signal star birth as well, as the blast waves condense gas and dust to ultimately form the next generation of stars inside the Tarantula Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap990221.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.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/ap971102.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?1997A%26A%2E%2E%2E319%2E%2E267S&db_key=AST&nosetcookie=1 ], a butterfly planetary nebula 2100 light-years 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 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/ap971021.html ]. Much remains unknown about the physical processes that cause planetary nebulae [ http://www.noao.edu/jacoby/pn_gallery.html ]. |
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Halos Around the Ring Nebula
| Title |
Halos Around the Ring Nebula |
| Explanation |
What's happened to the Ring Nebula? The familiar Ring that can be seen with a small back-yard telescope takes on a new look when viewed in dim light. The above recently-released, false-color image [ http://www.subaru.naoj.org/outreach/press_releases/990916/index.html#No1 ] taken by the giant Subaru Telescope [ http://www.subaru.naoj.org ] shows details of giant halos [ http://www.seds.org/messier/more/m057_jac.html ] of diffuse gas that are seen to envelop the entire structure. The Ring Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap990107.html ], also known as M [ http://antwrp.gsfc.nasa.gov/apod/ap960626.html ]57, is an elongated [ http://antwrp.gsfc.nasa.gov/apod/ap980504.html ] planetary nebula [ http://www.astro.washington.edu/balick/WFPC2/ ], a type of nebula that is created when a Sun-like star evolves to throw off its outer atmosphere and becomes a white dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap990703.html ]. The Ring Nebula [ http://heritage.stsci.edu/public/jan6/ringtable.html ] is about 2000 light-years away, and the main ring [ http://antwrp.gsfc.nasa.gov/apod/ap980504.html ] spans about one light-year. The origin and future evolution of the Ring Nebula [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997ApJ...487..328G ]'s outer halos is still being investigated. |
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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://www.stsci.edu/EPA/PR/95/01.html ] from the Hubble Space Telescope 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 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/ap990703.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 ]. On planet Earth, of course, cats and other creatures [ http://www.cccoe.k12.ca.us/bats/welcome.html ] may be on the prowl tonight. Keep "your" eyes peeled and have a safe and happy Halloween [ http://www.bestweb.net/~wallnut/halloween/index.html ]! |
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