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NGC 7331 and Beyond
| Title |
NGC 7331 and Beyond |
| Explanation |
Spiral galaxy NGC 7331 [ http://www.seds.org/messier/Xtra/ngc/n7331.html ] is often touted as an analog to our own Milky Way [ http://cassfos02.ucsd.edu/public/tutorial/MW.html ]. About 50 million light-years distant in the northern constellation Pegasus [ http://hawastsoc.org/deepsky/peg/index.html ], NGC 7331 was recognized early on as a spiral nebula [ http://www.seds.org/messier/Xtra/Bios/rosse.html ] and is actually one of the brighter galaxies [ http://www.seasky.org/cosmic/sky7a07.html ] not included in Charles Messier's famous [ http://antwrp.gsfc.nasa.gov/apod/ap060302.html ] 18th century catalog. Since the galaxy's disk is inclined [ http://antwrp.gsfc.nasa.gov/apod/ap040701.html ] to our line-of-sight, long telescopic exposures often result in an image that evokes a strong sense of depth. The effect is further enhanced in this well-framed view by the galaxies that lie beyond this beautiful island universe [ http://www.astr.ua.edu/goodies/data_resources/ galaxies.text ]. The background galaxies are about one tenth the apparent size [ http://chandra.harvard.edu/photo/scale.html ] of NGC 7331 and so lie roughly ten times farther away. |
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NGC 6369: The Little Ghost N
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| Title |
NGC 6369: The Little Ghost Nebula |
| Explanation |
This pretty planetary nebula, cataloged as NGC 6369 [ http://rao.150m.com/NGC6369.html ], was discovered by 18th century astronomer William Herschel [ http://www.bath-preservation-trust.org.uk/museums/ herschel/ ] as he used a telescope to explore the constellation Ophiucus [ http://www.corona_borealis.homestead.com/files/ pronouncing_the_stars.htm ]. Round and planet-shaped, the nebula is also relatively faint [ http://astro.isi.edu/reference/herschel.html ] and has acquired the popular moniker of Little Ghost Nebula. Planetary nebulae [ http://www.seds.org/messier/planetar.html ] in general are not [ http://antwrp.gsfc.nasa.gov/apod/ap020302.html ] at all related to planets, but instead are created at the end of a sun-like star's life as its outer layers expand [ http://antwrp.gsfc.nasa.gov/apod/ap010805.html ] into space while the star's core shrinks to become a white dwarf. The transformed white dwarf star [ http://antwrp.gsfc.nasa.gov/apod/ap000910.html ], seen near the center, radiates strongly at ultraviolet wavelengths and powers the expanding nebula's glow. Surprisingly complex details [ http://cdsads.u-strasbg.fr/cgi-bin/ nph-bib_query?1997ApJ...487..304H&db_key=AST&nosetcookie=1 ] and structures of NGC 6369 are revealed in this delightful color image [ http://heritage.stsci.edu/2002/25/index.html ] composed from Hubble Space Telescope data [ http://heritage.stsci.edu/2002/25/original.html ]. The nebula's main ring structure is about a light-year across and the glow from ionized oxygen, hydrogen, and nitrogen atoms are colored [ http://opostaff.stsci.edu/%7Elevay/process/ ] blue, green, and red respectively. Over 2,000 light-years away, the Little Ghost [ http://antwrp.gsfc.nasa.gov/apod/ap970331.html ] Nebula offers a glimpse of the fate of our Sun, which should produce its own pretty planetary nebula only about 5 billion years from now. |
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NGC 6369: The Little Ghost N
…
| Title |
NGC 6369: The Little Ghost Nebula |
| Explanation |
This pretty planetary nebula, cataloged as NGC 6369 [ http://rao.150m.com/NGC6369.html ], was discovered by 18th century astronomer William Herschel [ http://www.bath-preservation-trust.org.uk/museums/ herschel/ ] as he used a telescope to explore the medicinal constellation Ophiucus [ http://www.hawastsoc.org/deepsky/oph/index.html ]. Round and planet-shaped, the nebula is also relatively faint [ http://astro.isi.edu/reference/herschel.html ] and has acquired the popular moniker of Little Ghost Nebula. Planetary nebulae [ http://www.seds.org/messier/planetar.html ] in general are not [ http://antwrp.gsfc.nasa.gov/apod/ap020302.html ] at all related to planets, but instead are created at the end of a sun-like star's life as its outer layers expand [ http://antwrp.gsfc.nasa.gov/apod/ap010805.html ] into space while the star's core shrinks to become a white dwarf. The transformed white dwarf star [ http://antwrp.gsfc.nasa.gov/apod/ap000910.html ], seen near the center, radiates strongly at ultraviolet wavelengths and powers the expanding nebula's glow. Surprisingly complex details [ http://cdsads.u-strasbg.fr/cgi-bin/ nph-bib_query?1997ApJ...487..304H&db_key=AST&nosetcookie=1 ] and structures of NGC 6369 are revealed in this delightful color image [ http://heritage.stsci.edu/2002/25/index.html ] composed from Hubble Space Telescope data [ http://heritage.stsci.edu/2002/25/original.html ]. The nebula's main ring structure is about a light-year across and the glow from ionized oxygen, hydrogen, and nitrogen atoms are colored [ http://opostaff.stsci.edu/%7Elevay/process/ ] blue, green, and red respectively. Over 2,000 light-years away, the Little Ghost [ http://antwrp.gsfc.nasa.gov/apod/ap970331.html ] Nebula offers a glimpse of the fate of our Sun, which should produce its own pretty planetary nebula only about 5 billion years from now. |
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