Clear Skies
October 17th, 2021, 11:26 AM
At DSF we like galaxies. We like obscure ones. Interacting pairs, distortion. The skies of autumn provide us with plenty.
One such pair, in the constellation of Andromeda, consists of the galaxies NGC218 and MCG+06-02-017 (PGC2726). They go by Vorontsov-Vel'yaminov 527. Karachentsev listed these two as nr. 16 on his list of northern interacting pairs (KPG). The position is 00:46:35 +36d20m00s. That's exactly 3 degrees due southwest of Mu Andromeda, shining bright at mag. 3.9, and 5 degrees south of Messier 31.
Interaction and distortion is clear in both galaxies but the western one, NGC218, accounts for most of the spectacle. It was discovered on this day, October 17 in the year 1876 by French astronomer Édouard Stephan (https://en.wikipedia.org/wiki/Édouard_Stephan). Arp 319, "Stephan's Quintet" is named after him.
Both the POSS2 Blue (https://archive.stsci.edu/cgi-bin/dss_search?v=poss2ukstu_blue&r=00+46+35.35&d=%2B36+19+42.6&e=J2000&h=10&w=10&f=gif&c=none&fov=NONE&v3=) plate and the SDSS (http://skyserver.sdss.org/dr16/SkyServerWS/ImgCutout/getjpeg?TaskName=Skyserver.Chart.Image&ra=11.64729&dec=36.3285&scale=0.294&width=2041&height=2041&opt=&query=) image (we're in luck, as its right on the edge of the survey's coverage) reveal ragged structure and twisted arms, with bifurcation on the northern edge of the western arm. The small core is clearly offset, with a small, curved, brighter arm directly southeast.
4497 4498
Here's the pair in a PanSTARRS image (http://aladin.unistra.fr/AladinLite/?target=00%2046%2035.350%2B36%2019%2042.60&fov=0.1668&survey=P%2FPanSTARRS%2FDR1%2Fcolor-z-zg-g), through Aladin.
The smaller and fainter eastern galaxy, MCG+06-02-017, unmistakably shows distortion, too, but it's details will be tough to grab. It's elongated with a faint outer halo that has an extension on the south-southeastern side. It sports a faint nucleus. A mag. 15.4 star is on the southeastern edge.
Boris Vorontsov-Vel'yaminov (https://en.wikipedia.org/wiki/Boris_Vorontsov-Velyaminov) categorized the pair (page 26 (http://articles.adsabs.harvard.edu/pdf/1977A%26AS...28....1V)) as an evident and possible nest, describing NGC218 as Several coalescent galaxies of various dimensions. Strong perturbations. The MCG notes describe the pair as a Nest with clear pair.
Igor Karachentsev (https://www.iau.org/administration/membership/individual/3989/) described two spirals (https://ned.ipac.caltech.edu/level5/Sept02/Keel/Keel_contents.html): Disturbances in the spiral structure or general form of both components and added the note, for NGC218: Large internal motions, emissions not from the core.
Ten days..... ten nights ago, just before midnight, I observed these galaxies from the French Alps, about 125 km. north of Marseille Observatory (website (https://en.wikipedia.org/wiki/Marseille_Observatory) / Wikipedia (https://www.lam.fr/le-laboratoire/article/presentation?lang=en)) where Stephan worked over a century ago. My instrument was my 14" SCT:
NGC218 (KPG 16A) is an irregular, round glow without AV, with AV it is clearly flattened on the eastern side on a line from NNE to SSW. Brightest SE of the middle and gradually fainter towards the NW. Clearly irregular with AV but arms can not be discerned and no nucleus is visible.
ENE of NGC218 is a very faint, slightly north to south elongated glow (MCG+06-02-017, KPG 16B), at the limit of visibility without AV. With AV gradually brighter in the middle, no nucleus visible. The star on the SE edge is not visible.
A nice view.
I rated it 6/10.
As always, the CSOG observing guide for the current DSF OOTW - click here (https://clearskies.eu/csog/downloads/dsfootw#42) - can be downloaded without registration.
4494 4495 4496
Give 'em a go, and let us know!
One such pair, in the constellation of Andromeda, consists of the galaxies NGC218 and MCG+06-02-017 (PGC2726). They go by Vorontsov-Vel'yaminov 527. Karachentsev listed these two as nr. 16 on his list of northern interacting pairs (KPG). The position is 00:46:35 +36d20m00s. That's exactly 3 degrees due southwest of Mu Andromeda, shining bright at mag. 3.9, and 5 degrees south of Messier 31.
Interaction and distortion is clear in both galaxies but the western one, NGC218, accounts for most of the spectacle. It was discovered on this day, October 17 in the year 1876 by French astronomer Édouard Stephan (https://en.wikipedia.org/wiki/Édouard_Stephan). Arp 319, "Stephan's Quintet" is named after him.
Both the POSS2 Blue (https://archive.stsci.edu/cgi-bin/dss_search?v=poss2ukstu_blue&r=00+46+35.35&d=%2B36+19+42.6&e=J2000&h=10&w=10&f=gif&c=none&fov=NONE&v3=) plate and the SDSS (http://skyserver.sdss.org/dr16/SkyServerWS/ImgCutout/getjpeg?TaskName=Skyserver.Chart.Image&ra=11.64729&dec=36.3285&scale=0.294&width=2041&height=2041&opt=&query=) image (we're in luck, as its right on the edge of the survey's coverage) reveal ragged structure and twisted arms, with bifurcation on the northern edge of the western arm. The small core is clearly offset, with a small, curved, brighter arm directly southeast.
4497 4498
Here's the pair in a PanSTARRS image (http://aladin.unistra.fr/AladinLite/?target=00%2046%2035.350%2B36%2019%2042.60&fov=0.1668&survey=P%2FPanSTARRS%2FDR1%2Fcolor-z-zg-g), through Aladin.
The smaller and fainter eastern galaxy, MCG+06-02-017, unmistakably shows distortion, too, but it's details will be tough to grab. It's elongated with a faint outer halo that has an extension on the south-southeastern side. It sports a faint nucleus. A mag. 15.4 star is on the southeastern edge.
Boris Vorontsov-Vel'yaminov (https://en.wikipedia.org/wiki/Boris_Vorontsov-Velyaminov) categorized the pair (page 26 (http://articles.adsabs.harvard.edu/pdf/1977A%26AS...28....1V)) as an evident and possible nest, describing NGC218 as Several coalescent galaxies of various dimensions. Strong perturbations. The MCG notes describe the pair as a Nest with clear pair.
Igor Karachentsev (https://www.iau.org/administration/membership/individual/3989/) described two spirals (https://ned.ipac.caltech.edu/level5/Sept02/Keel/Keel_contents.html): Disturbances in the spiral structure or general form of both components and added the note, for NGC218: Large internal motions, emissions not from the core.
Ten days..... ten nights ago, just before midnight, I observed these galaxies from the French Alps, about 125 km. north of Marseille Observatory (website (https://en.wikipedia.org/wiki/Marseille_Observatory) / Wikipedia (https://www.lam.fr/le-laboratoire/article/presentation?lang=en)) where Stephan worked over a century ago. My instrument was my 14" SCT:
NGC218 (KPG 16A) is an irregular, round glow without AV, with AV it is clearly flattened on the eastern side on a line from NNE to SSW. Brightest SE of the middle and gradually fainter towards the NW. Clearly irregular with AV but arms can not be discerned and no nucleus is visible.
ENE of NGC218 is a very faint, slightly north to south elongated glow (MCG+06-02-017, KPG 16B), at the limit of visibility without AV. With AV gradually brighter in the middle, no nucleus visible. The star on the SE edge is not visible.
A nice view.
I rated it 6/10.
As always, the CSOG observing guide for the current DSF OOTW - click here (https://clearskies.eu/csog/downloads/dsfootw#42) - can be downloaded without registration.
4494 4495 4496
Give 'em a go, and let us know!