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Arp Peculiar Object Number 85 - Spiral Galaxy With Large High Surface Brightness Companion
NGC 5194 (= PGC 47404 = M51), The Whirlpool Galaxy
(also, with NGC 5195 = Arp 85), Discovered (Oct 13, 1773) by Charles Messier. An 8th-magnitude spiral galaxy (type SA(s)bc pec) in Canes Venatici (RA 13 29 52.6, Dec +47 11 44)
Historical Identification:
Physical Information: NGC 5194's recessional velocity of 465 km/sec is too small to provide a reliable distance indication, but happens to provide a relatively accurate result of 22 million light years. Redshift-independent distance estimates have ranged from 19 to 30 million light years, but observations of a 2005 supernova in NGC 5195 slightly lowered the estimated distance to 23 ± 4 million light years. Given that and its apparent size of 11.2 by 6.9 arcmin, the galaxy is about 70 thousand light years across. Its spectacular spiral structure is believed to be due to its interaction with NGC 5195, with which it forms Arp 85. (Note: The history of discovery implies that M51 should apply only to NGC 5195, but it is not uncommon for NGC 5194 to be referred to as M51A and for NGC 5195 to be referred to as M51B, as though they had both discovered by Messier.) NGC has a bright central nucleus, making it a Seyfert galaxy (type Sy 2). An extensive bridge of stars, gas and dust connects M51 with its smaller companion. Clusters of hot, bright young stars, and gases heated by their radiation illuminate the spiral arms, and clearly define them. Thick dust lanes straddle the arms, sweep across the "bridge" and partially obscure the companion. The Whirlpool Galaxy was the first nebula observed to have a spiral structure, by the 3rd Lord Rosse, using the 72-inch Leviathan (the largest telescope in the world for many decades) at Birr Castle in 1845.
"Excerpt courtesy of Courtney Seligman"
cseligman.com/text/atlas/ngc51a.htm#5194
Image... Cherryvalley Observatory (I83). Telescope: 0.2-m SCT & SBIG STL-1301E CCD Camera @f7.6. Image Scale 2.17 arcsec/pixel, Field of View 46 x 37 arcmins.
Flat field and dark subtract calibration frames. Combined Stack of two images of 210 seconds each unfiltered and unbinned. CCD operating temperature: -42 degrees. Image acquisition and processing: CCD Soft v5, TheSky6 Professional and Mira Pro v7. December 27th 2014.
Dr. Halton Arp originally compiled the Atlas of peculiar galaxies with photographs he made mainly using the Palomar 200-inch telescope and the 48-inch Schmidt telescope between the years 1961 to 1966. Original image can be found here: ned.ipac.caltech.edu/level5/Arp/Figures/big_arp85.jpeg
Arp Peculiar Object Number 85 - Spiral Galaxy With Large High Surface Brightness Companion
NGC 5194 (= PGC 47404 = M51), The Whirlpool Galaxy
(also, with NGC 5195 = Arp 85), Discovered (Oct 13, 1773) by Charles Messier. An 8th-magnitude spiral galaxy (type SA(s)bc pec) in Canes Venatici (RA 13 29 52.6, Dec +47 11 44)
Historical Identification:
Physical Information: NGC 5194's recessional velocity of 465 km/sec is too small to provide a reliable distance indication, but happens to provide a relatively accurate result of 22 million light years. Redshift-independent distance estimates have ranged from 19 to 30 million light years, but observations of a 2005 supernova in NGC 5195 slightly lowered the estimated distance to 23 ± 4 million light years. Given that and its apparent size of 11.2 by 6.9 arcmin, the galaxy is about 70 thousand light years across. Its spectacular spiral structure is believed to be due to its interaction with NGC 5195, with which it forms Arp 85. (Note: The history of discovery implies that M51 should apply only to NGC 5195, but it is not uncommon for NGC 5194 to be referred to as M51A and for NGC 5195 to be referred to as M51B, as though they had both discovered by Messier.) NGC has a bright central nucleus, making it a Seyfert galaxy (type Sy 2). An extensive bridge of stars, gas and dust connects M51 with its smaller companion. Clusters of hot, bright young stars, and gases heated by their radiation illuminate the spiral arms, and clearly define them. Thick dust lanes straddle the arms, sweep across the "bridge" and partially obscure the companion. The Whirlpool Galaxy was the first nebula observed to have a spiral structure, by the 3rd Lord Rosse, using the 72-inch Leviathan (the largest telescope in the world for many decades) at Birr Castle in 1845.
"Excerpt courtesy of Courtney Seligman"
cseligman.com/text/atlas/ngc51a.htm#5194
Image... Cherryvalley Observatory (I83). Telescope: 0.2-m SCT & SBIG STL-1301E CCD Camera @f7.6. Image Scale 2.17 arcsec/pixel, Field of View 46 x 37 arcmins.
Flat field and dark subtract calibration frames. Combined Stack of two images of 210 seconds each unfiltered and unbinned. CCD operating temperature: -42 degrees. Image acquisition and processing: CCD Soft v5, TheSky6 Professional and Mira Pro v7. December 27th 2014.
Dr. Halton Arp originally compiled the Atlas of peculiar galaxies with photographs he made mainly using the Palomar 200-inch telescope and the 48-inch Schmidt telescope between the years 1961 to 1966. Original image can be found here: ned.ipac.caltech.edu/level5/Arp/Figures/big_arp85.jpeg