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Object of the Week November 14th, 2021 - NGC680
NGC 680 (and friends)
UGC 1286
Galaxy
Aries
R.A. 01h49m47.3s
Dec. +21°58'15" (2000)
Magnitude: 12.90 B
Size: 1.7' x 1.5'
For this OOTW I have chosen the nice galaxy pair NGC 678 and NGC 680 in Aries. I apologise
that this piece may not be up to the usual standards but I am recovering from Covid. Perhaps
not unsurprisingly for such a bright pair they were both discovered by William Herschel in 1784.
There is a third, very much fainter, galaxy in the field designated as IC 1730 which was discovered
by Javelle using a 30” refractor in 1896. I am slightly surprised that the pair did not make either the Arp
or VV lists as they are obviously interacting. NGC 680 is classified as an E2 with a disturbed envelope
and this is easily seen on the SDSS images which shows signs of shells. NGC 678 is an edge on
showing a strong dust lane and a prominent nucleus. The edge of the spiral arms appears to be
distorted. The pair is perhaps better known as being part of the NGC 691 group which consists of
9 galaxies being NGC 678, 680, 691, 694, 695 and NGC 695 along with IC 1730 and IC 167.
The group is also known as WBL 52. The group is spread over quite a wide area of sky with almost
a degree spanning NGC 691 and 695. The core of the group is centred around NGC 691, 678, 680
and NGC 694. NGC 678 and 680 were discovered in William Herschel in 1784 but it was two years
later in 1786 before he found 691. Heinrich d’Arrest found NGC 694 in 1861 as it is much fainter
than the others. Perhaps unusually for an IC object Bigourdan found IC 167 using a 12” refractor
in 1889. The whole group is spread around the bright double star 1 Ari. This may make it more
difficult to see than it should be. The group is about 122 million light years from us which is relatively close
by and explains the large angular spread of the group on the sky. NGC691 was home to SN 2005W,
although it only reached magnitude 15.2. Both NGC 691 and NGC 678 feature in the WSDSOH Vol 4
where both are described as brightish in a 16” telescope. NSOG reports the two brighter members as
easy in 22cm and the others as more challenging. Interestingly most of the galaxies in the group are
spirals or lenticulars with only NGC 680 as a confirmed elliptical, NGC 680 has also been classified as
a cD pec which would make it the main galaxy in the group. NGC 680 also appears to be interacting
with NGC 678 as well, although there is some debate as the RC suggests it may be interacting with
IC 1730. There is an interesting amateur image of the whole group at http://www.alsonwongastro.com/ngc691.htm.
Split away from the main group on the other side of 1 Ari are NGC 697 and 695. NGC 697 is a nice bright
spiral but NGC 695 is much fainter and although catalogued as a double galaxy its faintness suggests it
might not actually be a member of the group. Its recession velocity from NED, if correct, is 3 times
greater than the others in the group. It certainly appears in front of a field of much fainter galaxies.
There also appears to be some confusion over the identity of NGC 697 with Harold Corwin suggesting
it is actually NGC 674 and d’Arrest was confused and saw the same object twice.
Attachment 4519
