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View Full Version : Object of the week 16th October 2022 - NGC 7679 - Arp 216



obrazell
October 16th, 2022, 08:28 AM
NGC 7679
Arp 216
VV 329

Galaxy
Class SB0 pec

Pisces

R.A. 23h28m46.7s
Dec. +03°30'41" (2000)

Magnitude: 13.40 B

Size: 1.2' x 0.8'



The starburst galaxy NGC 7679 in Pisces was first discovered by Heinrich d’Arrest in 1864 using an 11” refractor.
Classified as a barred lenticular galaxy it is also classed as a luminous infra-red galaxy or LIRG. It has an AGN
in the form of a Seyfert type but it is odd enough that it cannot be classified as a Type 1 or 2. It has been
classified as both but most recently it is suggested to be a Seyfert Type 2. It is associated with the spiral
galaxy NGC 7682, also discovered by d’Arrest, but two years earlier in 1862, although some sources suggest
they were both discovered in 1864. The two galaxies are interacting and were included both in Arp’s catalogue
as Arp 216 and Vorontsov-Velyaminov’s catalogue as VV 329. The Arp classification falls into the group
galaxies with adjacent loops. The two galaxies have a neutral hydrogen bridge connecting them. The star
burst in NGC 7679 takes place in the circumnuclear region and it is unusual as lenticular galaxies do not
usually contain enough gas for star formation to take place. In this case the star formation is thought to
have taken place about 10 million years ago.


4898

Image credit SDSS

The gravitational tides raised by the interaction have dragged
two plumes of material out of NGC 7679. The two galaxies probably had a close pass, perhaps 500 million
years ago and are currently separated by perhaps 97kpc. In comparison NGC 7682 does not appear to show
much disturbance. It is possible that the star plumes seen in NGC 7692 maybe the remnants of a merger with
another galaxy rather than as a result of the interaction with NGC 7682. NGC 7682 is also classified as a type
2 Seyfert.

4899

HST image credit, NASA/ESA and Judy Schmidt

The pair are thought to be about 190 million light years away. The galaxy seen in the arms of
NGC 7679 is a background object. There is a third galaxy in the field, UGC 12628, which given its redshift
may be part of the same group. There is also a tight 10th magnitude double star Bu 1222, discovered by
S.W. Burnham, about 5’ NW of NGC 7679.

The pair is pretty close so a high power eyepiece will be best when observing them. They should not be that
difficult in 40cm (16") telescopes and both galaxies should show a faint stellar core. It maybe that the plumes
will be visible in the very largest telescopes in amateur hands


As always, give it a go and let us know!!

Clear Skies
October 16th, 2022, 10:26 AM
A nice pair!

One observation in my log, just before midnight on 5 October 2018 in the French Ardennes. Galaxy MCG+00-59-048 (PGC71578, UGC12628) to the southeast was picked up, too. 14" SCT @ 168x/29':


NGC7679

A round glow with an extremely bright nucleus that is clearly visible without AV. With AV slightly larger and gradually brighter in the middle.

To the WNW is a mag. 11 star, slightly farther to the NNE is a mag. 12. To the ENE, just over twice the distance to the mag. 12 star, is the galaxy NGC7682 together with which this galaxy forms Arp 216.



NGC7682

A NNW-SSE elongated glow, gradually brighter in the middle. With AV the nucleus is visible and the core (the bar) is slightly more elongated NNW to SSE.
To the WSW is the galaxy NGC7679 together with which this galaxy forms Arp 216.
1/4 FoV to the SE is a very faint, east-west elongated glow, even in brightness, no detail visible, only visible with AV but clearly larger than NGC7679 and NGC7682 are (= galaxy MCG+00-59-048 / PGC71578). To the west thereof is a crooked shape of four mag. 11 and fainter stars of which three are aligned NNE to SSW.



4900 4901 4902

Click here (https://clearskies.eu/csog/downloads/dsfootw2022#42) to download the guide.

Steve Gottlieb
October 16th, 2022, 06:07 PM
All of my observations -- from a C-8 in 1982 to my 24" in 2016 -- mention a small intense nucleus in NGC 7679 with a stellar peak. I wasn't on the look out for the outer tidal feature, but it should be visible in the larger aperture.

Bu 1222, a mag 10.2/10.4 pair at 1.4" separation was cleanly resolved at 375x. Also, I could detect a central bar running through NGC 7682 from SW to NE.

Uwe Glahn
November 4th, 2022, 06:52 PM
Nice pair. The plume of 7679 is much easier and one of the brighter ones in the sky.

sketch: 27", 419x, Seeing III, NELM 6m0+
4913
home (http://www.deepsky-visuell.de/Zeichnungen/NGC7679_NGC7682.htm)

FaintFuzzies
November 27th, 2022, 12:17 AM
This is what I picked up about 15-20 years ago.

22” @305, 327 and 458x
NGC 7679 - Very bright, round disk with a much brighter middle. Well defined edge. About 1’ across. The brightest clump of the adjacent loop,
MAC 2328+0330, is barely visible as a small round patch just off the ENE edge.