Stephan's Quintet

[alan4908]

Stephan's Quintet is located in the constellation of Pegasus and was discovered in 1876 by Edouard Stephan using a 80cm reflector. Originally, he perceived the close pair (NGC 7318 A/B) as a single galaxy, so originally it was perceived as a quartet.  One of the galaxies (NGC 7320) is actually much closer to Earth (45m light years) than the rest which are much further away (287m to 310m light years). 

I thought a good challenge to have a go at the object since a search revealed that their are relatively few amateur images, probably because it is so tiny. The resultant LRGB image represents just over 12hours integration and was taken with my Esprit 150. 

I've also captured a few other galaxies in the image below which Pixinsight has annotated.  The one near the top right wasn't picked up,  however, a quick search on the free program Aladin informs me it is 2MFGC 17021.

 

Alan

LIGHTS: L:30, R:13, G:11, B:19 x 600s; DARKS:30, FLATS:40: BIAS: 100

 

Annotated version

[Rodd]

Nice colors--well done

Rodd

[ollypenrice]

A tempting and famous five, nicely done. 👋 We're working on this at the moment, not too far from where Edouard Stephan discovered the objects from Marseille. (You wouldn't discover too much from there these days!) The distance to NGC7320, according to redshift, is about the same as to the nearby NGC7331 but Halton Arp didn't accept this and used it as an example to challenge the redshift as a reliable distance measurement. An intriguing controversy. Both your data and ours shows an arc of tidal extension from NGC7320 which is parallel with a similar arc from NGC7319. You have to say that Arp has a valid question if he he asks why there should be two parallel tidal extensions from galaxies at radically different distances from NGC7331, if that is the attractor.

Olly

 

[alan4908]

6 hours ago, Rodd said:

Nice colors--well done

Rodd

Thanks Rodd ! 

 

2 hours ago, ollypenrice said:

A tempting and famous five, nicely done. 👋 We're working on this at the moment, not too far from where Edouard Stephan discovered the objects from Marseille. (You wouldn't discover too much from there these days!) The distance to NGC7320, according to redshift, is about the same as to the nearby NGC7331 but Halton Arp didn't accept this and used it as an example to challenge the redshift as a reliable distance measurement. An intriguing controversy. Both your data and ours shows an arc of tidal extension from NGC7320 which is parallel with a similar arc from NGC7319. You have to say that Arp has a valid question if he he asks why there should be two parallel tidal extensions from galaxies at radically different distances from NGC7331, if that is the attractor.

Olly

Thanks for the comment Olly. 

Yes, you can definitely see what appears to be a tidal tail emanating from NGC7320. However, I found this article on the subject from c10 years ago (http://chandra.harvard.edu/blog/node/150) which suggests it is an optical illusion. It states: Radio observations prove that the tail is unrelated to NGC7320 and is actually connected to the X-ray mission and the two spiral galaxies on the right (NGC7318a/b). The radio lets us see cold neutral hydrogen gas in the tails and trace the southern tail even where it passes behind NGC7320; there is no sign of disturbance in the gas or a connection to NGC7320, and the hydrogen is at the redshift of the other galaxies.

Alan

Edited August 4, 2019 by alan4908

[ollypenrice]

10 hours ago, alan4908 said:

Thanks Rodd ! 

 

Thanks for the comment Olly. 

Yes, you can definitely see what appears to be a tidal tail emanating from NGC7320. However, I found this article on the subject from c10 years ago (http://chandra.harvard.edu/blog/node/150) which suggests it is an optical illusion. It states: Radio observations prove that the tail is unrelated to NGC7320 and is actually connected to the X-ray mission and the two spiral galaxies on the right (NGC7318a/b). The radio lets us see cold neutral hydrogen gas in the tails and trace the southern tail even where it passes behind NGC7320; there is no sign of disturbance in the gas or a connection to NGC7320, and the hydrogen is at the redshift of the other galaxies.

Alan

Excellent link. Thanks for that. It really does look like a tidal extension from NG7320 but appearances can be deceptive...

Olly

[maw lod qan]

A amazing image. 

Thanks for posting it along with the information. It's like back to school here on the forum. Except I enjoy this learning.

[alan4908]

On 05/08/2019 at 08:58, maw lod qan said:

A amazing image. 

Thanks for posting it along with the information. It's like back to school here on the forum. Except I enjoy this learning.

Thanks. Yes, it's interesting what you can learn from this hobby. 

Alan